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HM Fire Service Inspectorate Publications Section London: The Stationery Office

• Hydraulics, Pumps and Water Supplies

Crown Copyright 200 I Published with the permission of the Home Office Preface on behalf of the Controller of Her Majesty's Stationery Office

Applications for reproduction should be made in writing to The Copyright Unit, Her Majesty's Stationery Office, SI. Clements House, 2-16 Co]egate, olwich, R3 IBQ

ISBNO 113412169 This new Fire Service Manual, 'Hydraulics, which, in turn, have created problems Pumps and Water Supplies', is designed to replace regarding water for firefighting. Book 7 of the Manual of Firemanship, 'Hydraulics, pumps and pump operation' and (ii) The increasing use made by brigades of Cover photograph: Shropshire Fire and Rescue Service much of the text is taken from that publication large diameter hose and the means to because it remains relevant today. However, the deploy and retrieve it. Half-title page photograph: Shropshire Fire and Rescue Service format of this new Manual differs significantly from that of its predecessor. (iii) Initiatives regarding the development of flowmetering and of automatic pump and The hydraulics theory has been condensed to that tank fill controls have come to fruition, which is considered necessary for firefighters to: though not all brigades are taking advantage of such equipment. understand the behaviour of water and the • firefighting equipment which controls it. (iv) A greater emphasis on safe working practices. • make informed decisions regarding the supply and management of water both on (v) The substantial replacement of the type the fireground and when pre-planning. "A" branch with more modern, adjustable branches. Reference to the former has, In order to maintain the flow of the main text, however, been retained in this publication. derivations of the hydraulics formulae have been removed from it, but those readers who wish to This new publication has been written giving due study them in detail will find them in the appen­ regard to these developments. dices section. Home Office, 2001 Additionally, there is no longer a requirement for a knowledge of logarithms and, following consul­ tation with brigades, it became clear that the mate­ rial in the appendices on graphs and on powers and roots could, if required, best be studied in a mathematics text book. Consequently these sec­ tions have been removed.

Some of the most significant developments since Book 7 was published have been:

(i) The obligations placed upon the privatised water undertakers to reduce leakage have Printed in the United Kingdom by The Stationery Office TJ45195/01 50019585 resulted in lower mains operating pressures

Hvdraulies, Pumps and Water Supplies 111 Hydraulics, Pumps and Water Supplies

Contents

Preface Hi Chapter 1 Elemental")' Principle of Hydraulic 1 Introduction 1 1.1 The properties of water 1 1.2 Principal characteristics of pressure 2 1.3 Relationship between pressure and head for water 3 1.4 Loss of pressure due to friction 4 1.5 Energy changes in water streams 6 1.6 Water power and efficiency 9 1.7 Jet reaction 10 1.8 Water hammer 10 Chapter 2 In truments 13 Introduction 13 2.1 Measurement of pressure 13 2.2 Measurement of f10wrate 18 Chapter 3 Atmo pheric Pre sure and Suction Lift 23 Introduction 23 3.1 Atmospheric pressure 23 3.2 Suction lift 24 3.3 Siphons 26 Chapter 4 Water Supplie and Hydrants 27 Introduction 27 4.1 Legislation concerning mains water supplies 27 4.2 Distribution of water supplies 28 4.3 Water supplies for firefighting 32 4.4 Pressure and flow in mains 34 4.5 Special fire mains 35 4.6 Hydrants 35 4.7 Types of hydrant 37 4.8 Hydrant gear and characteristics 38 4.9 Hydrant marking 39 4.10 Inspection and testing of hydrants 40 4.11 New Roads and Street Works Act 1991 44

Chapter 5 Pumps and Primers 45 Introduction 45 5.1 Operating principles of non-centrifugal pumps 45

Hydraulics, Pumps and Water Supplies V 5.2 Operating principles of centrifugal pumps 48 5.3 Vehicle mounted fire pumps 52 5.4 Portable pumps 59 5.5 Safety 63 Chapter 6 Pump Operation and the Distribution ofWat r on the Fireground 65

Introduction 65 6.1 Getting to work from a hydrant 65 6.2 Getting to work from open water 66 6.3 Cooling systems 69 6.4 Instrumentation 70 6.5 Estimation of required pump pressures 72 6.6 Identification of faults 73 6.7 Maintenance and testing 74 6.8 Assisted pump and automatic tank fill controls 75 Chapter 7 Pre-planning 77

Introduction 77 7.1 Estimation of water requirements 77 7.2 Assessment of additional water supplies 79 7.3 Supplying water to the fireground 80 7.4 Water carrying 80 7.5 Water relaying 82 7.6 Practical considerations 85 7.7 Special equipment 88 Glossary of hydraulics terms 95 Appendices 99 Appendix 1 ymboIs and unit 100 Appendix 2 Transposition of formulae 101 Appendix 3 l\tleasurement of area and volume 107 Appendi 4 Derivation of hydraulics formulae 115 Appendix 5 Summary of formulae and other data 123 Appendix 6 Sections 57 and 58 of the Water Indu try Act 1991 126 Appendix 7 Metrication 128

Acknowledgements 130 e

VI Fire Service Manual Hydraulics, Pumps and h per Water Supplies

Chapter 1 - Elementary Principles of Hydraulics

Introduction the earth but, to a close approximation, it is 9.81 metres per second per second (9.81 m/s2), so The term hydraulics refers to the study of the the weight of I kilogram of water is behaviour of water both when it is in motion and when it is at rest. A grasp of the elementary I x 9.81 = 9.8JN principles of the subject is necessary to enable firefighters to: A cubic metre of water therefore exerts a down­ ward force of 9810 N (1000 x 9.81), or 9.81 kilo­ (i) understand the behaviour of water in newtons (kN). relation to the operation of fire service equipment. For most practical purposes therefore:

(ii) make informed decisions concerning I litre of water weighs 10 newtons the supply and delivery of water in the 1 cubic metre of water weighs 10 000 newtons dynamic arena of the fireground. Although the density (see Fire Service Manual (iii) make effective arrangements for Volume I 'Chemistry and Physics for Fire­ the provision of water supplies at the fighters ') of water varies with the degree ofpurity, pre-planning stage. such variations are very small and may usually be ignored. Sea water, for example, has a density of 1.1 The Properties ofWater approximately 1.03 kg/litre

Water when pure is a colourless, odourless liquid Pure water has a freezing point of O°C and a boil­ with a molecular composition of two atoms of ing point of 100°C, both at normal atmospheric hydrogen combined with one atom of oxygen pressure (l bar approx.). Between these tempera­

(H20). A litre of water has a mass of tures at atmospheric pressure, therefore, water 1 kilogram (kg), and a cubic metre, which is for all exists as a liquid and exhibits all the characteristic practical purposes 1000 litres, therefore has a mass properties of a fluid. It is virtually incompressible, of 1000kg or I tonne. and an increase of I bar only causes a decrease in volume of 0.000 002 per cent. The weight (i.e. the downward force which gravity exerts) ofa body depends on its mass (m), and also As a fluid water has volume but is incapable of on how powerfully it is attracted by gravity. It is resisting change of shape, i.e. when poured into a shown in the Fire Service Manual Volume I container it will adjust itself irrespective of the 'Chemistry and Physics for Firefighters' that: shape of the latter, and will come to rest with a level surface. This is because there is very little weight = mg newtons (N) friction or cohesion between the individual mole­ cules of which water is composed. where g is the acceleration due to gravity. The Water, of the degree of purity likely to be used value of g varies very slightly over the surface of for firefighting purposes, is a reasonably good

Hydraulics. Pumps and Water Supplies 1 , conductor of electricity and therefore great care its orientation because the pressure exerted by the Figure 1.2 (d) should be taken to prevent firefighting streams fluid is the same in all directions. This is equally Downward pressure from coming into contact with live electrical true regardless ofwhether the pressure is due to the oj'afluid in an open equipment. (See Fire Service Manual Volume 2 height of the column of fluid itself or is externally vessel is proportional 'Fire Service Operations - Electricity'.) applied e.g. by a pump. to the density o/the fluid 1.2 Principal characteristic of (c) Downward pressure of a fluid in an open pressure vessel is proportional to its depth. Mercury Water

The S.l. unit of pressure is the newton per square Figure 1.1 shows three vertical containers, The metre (N/m2) another name for which is the depth of water in them is 10m, 20m and 30m. If Pascal. However, it has been decided that, pressure gauges were to be placed at the bottom of because this is a very small unit, the fire service each container they would show readings of unit of pressure will be the 'bar'. The relationship approximately I bar, 2 bar and 3 bar respectively between these units is: i.e. the pressure indications would be in the same 13.6 bar 1 bar ratio as the depths. 1 bar =100000 N/m2 or 105 N/m2 (d) The downward pressure of a fluid in an This last principle is illustrated in Figure 1.3, the head will be independent of the precise route which shows a number of containers of varying which the pipe or hose takes. However, once flow Normal atmospheric pressure = 1.013 bar. open vessel is proportional to the density of the fluid. shapes. The pressure at the bottom of each is is taking place, friction between the moving water There are a number of basic rules governing the exactly the same provided the depth of liquid (or and the inside surface of the pipe or hose becomes head) is the same in each case. a complicating factor which will be considered principal characteristics of pressure in liquids. In Figure 1.2 are shown two containers, one hold­ later in this chapter. These are: ing mercury and the other water. The depth of liq­ One practical consequence of this principle is that uid is the same in both containers. If pressure the static (i.e. no flow) pressure at the delivery end (a) The pressure exerted by a fluid at rest is gauges were to be placed at the bottom of each 1.3 Relation hip between Pressure of a pireline leading from an elevated storage tank always at right angles to the surface of container the pressure at the bottom ofthe mercury and Head for Water or reservoir is decided solely by the vertical dis­ the vessel which contains it. container would be found to be 13.6 times the pres­ tance between the water surface and the point It has already been stated that the pressure of a liq­ sure at the bottom of the water container because where the pressure is measured, because the head uid contained in an open vessel is proportional (b) The pressure at any point in a fluid at mercury is 13.6 times as dense as water. rest is the same in all directions. of water is the same no matter how convoluted the both to the depth of the liquid and to its density. The precise relationship for pressure is: (e) The downward pressure of a fluid on the route which the pipeline takes. Also, if water is A gauge connected onto a line ofpiping or hose, or bottom of a vessel is independent of the being pumped up to such a container, or to an p= Hpg (see Appendix 4 for derivation) to the bottom of a storage tank, containing a fluid shape of that vessel. elevated branch for firefighting purposes, the at rest will give the same reading no matter what amount of pump pressure required to overcome

Figure 1.3 (e) The downward \ pressure ofa fluid on \ the bottom afa vessel is independent afthe shape afthat vessel. 30m

20m Head

10m

1 bar 2 bar 3 bar j 2 Figure i.i(e) Downward pressure ofafluid in an open vessel is proportional to its depth. 1m

2 Fire Service Manual Hydraulics, Pumps and Water Supplies 3 where p is the pressure in newtons per square It is clear from these examples that the error intro­ situations listed above. Such practical considera­ (iii) Pr is directly proportional to the square of metre, H is the head (depth) of liquid in metres, p duced by using the approximate formulae is small tions are discussed in detail in later chapters. the flowrate (l). is the density of the liquid in kilograms per cubic and likely to be within the limits of accuracy of metre (kg/m3) and g is the acceleration due to grav­ most gauges. 1.4.1 Laws governing loss of pressure i.e. Pr ex L2 ity. Taking p as 1000 kg/m3 and g as 9.81 rnIs2 due to friction gIves Example 3 Thus, for example, if the flowrate through a line of Experiments on the flow ofwater through hose and hose is doubled, the pressure loss due to friction p H x 1000 x 9.81 N/m2 A pump pressure of 5 bar is required to operate a pipes show that, to a reasonably good approxima­ will be increased by a factor of four. branch when it is working at ground level. If the tion, the loss ofpressure (Pr) due to friction is gov­ P = 0.0981 x H bar branch is raised to a height of 25m above the erned by the following laws: (Since, for a given pipe diameter, velocity of flow ground what must be the pump pressure in order to is directly proportional to flowrate, an equivalent Transposing this formula to find H we have: maintain the same output? (i) Pr is directly proportional to the length (l) statement to this law is that friction loss is propor­ of hose through which the water flows. tional to the square of the velocity of the water.) P metres The additional pressure required to overcome the H = 0.0981 head of 25m is given by: i.e. Pr ex I (iv) Pr is inversely proportional to the fifth power of the hose diameter (d). or H = 10.19 x P metres H I.e. 25 Thus, if 0.5 bar pressure is lost when water flows P 10 10 through I hose length, then 5 bar will be lost if the 1 i.e. Pr ex - To a close approximation these two fonnulae same quantity of water flows through 10 lengths. dS simplify to: 2.5 bar (ii) Pr is directly proportional to a quantity Diameter is the most important single factor which H bar Thus the new pump pressure will need to be: called the friction factor (t) for the hose affects friction loss. Because of the fifth power P=­ 10 (determined largely by the roughness of law, a modest change in hose diameter produces a 5 + 2.5 = 7.5 bar its inside surface). dramatic change in friction loss. Taking what is H = 10 x P metres admittedly an extreme case, the friction loss in 1.4 Loss of Pressure due to Friction i.e. Pr ex f 45mm hose is approximately 32 (25) times greater Example 1 than the friction loss in 90mm hose with full flow When water flows through a hose or pipe there is a The friction factor is also affected by other influ­ couplings, for the same flowrate. This extreme A static water pressure of 6 bar is required at a cer­ gradual loss ofpressure resulting from the need to ences, in particular whether the couplings are change is largely due to the fact that, in the larger tain point from a supply to be obtained from an overcome the frictional resistance which exists smaller or larger than the hose itself, but the values hose, because the area of cross section is four elevated reservoir. At what vertical height above between the moving water stream and the internal quoted normally allow for these factors. times as great, the velocity of flow is only a quar­ this point must the water surface be? surface of the hose or pipe. The magnitude of this ter of that in the smaller hose. frictional resistance depends on the various factors Table 1.1 below gives the approximate friction fac­ H = 10 x P i.e. 10 x 6 discussed in paragraph 1.4.1. It is ofparticular sig­ tors for a variety of hose diameters, but it should 1.4.2 The Friction Loss Formula nificance: be appreciated that different samples of hose, = 60 metres head although ofnominally the same diameter, may take There are several formulae which may be used for (i) when water is drawn from hydrants on slightly different values. the calculation of friction loss and the greater the (The exact formula gives 61.14 metres head) small diameter mains; required degree of accuracy required the more complex the formula becomes. For firefighting sit­ Example 2 (ii) when pumping water over long distances Table 1.1 Friction factors for hose uations, where the highest accuracy is not required, by means of a relay; the most useful relationship brings together the The water level of a tank in a sprinkler installation Diameter of hose Friction four proportionality statements given above and is 40 metres above a pressure gauge. What pres­ (iii) on the fireground when small diameter factor can be shown to be: sure in bar should register on the gauge? hose is used. 38mm, 45mm, 64mm and 70mm 0.005 9000flU 90mm with standard instantaneous Pr H I.e. 40 The accurate estimation of friction loss by calcula­ dS P couplings 0.007 10 10 tion is notoriously difficult but, fortunately, this is seldom necessary. What is more important is to 90mm with full flow couplings 0.005 in which f is the friction factor, Pr the pressure loss = 4 bar appreciate which physical factors are most signifi­ 100mm and 125mm 0.004 in bars, I the length of hose in metres, L the cant in determining friction loss so that due flowrate in litres per minute and d the hose diam­ 150mm 0.003 (The exact formula gives 3.924 bar). allowance may be made for them in the types of eter in millimetres.

4 Fire Service Manual Hydraulics, Pumps and Water Supplies 5 Example 4 1.5 Energy Change in Water 1.5.1 Flow through Nozzles 1.5.2 Flow through a Venturi tream The flowrate in 50m of45mm diameter hose is 400 Figure 1.4 shows water flowing through a Figure 1.5 shows water flowing through a ven­ litres per minute (IImin). What is the loss of pres­ When water flows through channels of varying cross Type A nozzle. As the water flows from point A to turi, i.e. a section of pipe in which the diameter sure in the hose if the friction factor is 0.005? section, such as nozzles, couplings, venturi, and the point 8 its velocity, and hence its kinetic energy, gradually reduces from its initial value, at point volutes of pumps, changes in velocity and pressure increase but only at the expense of the pressure A, to a minimum, at the throat, B, before increas­ 9000flU occur. 8emoulli's equation, which is derived in which decreases from a few bar at point A to ing again. 8ecause the changes in diameter are Pr d5 Appendix 4, gives the precise quantitative relation­ atmospheric at point 8. There are no significant gradual, little turbulence is created in the water ship between these variables, but an understanding of changes in the other types of energy. stream. 9000 X 0.005 X 50 X 400 X 400 the observed behaviour ofthe water may be achieved I.e. Pr 45 X 45 X 45 X 45 X 45 by consideling the changes in the various forms of energy which occur as the water flows through the i.e. the loss channel. These forms of energy, most of which are of pressure 2.0 bars (or I bar per length) explained in the Fire Service Manual Volume J­ ~ 'Physics and Chemistry for Firefighters' are: A B Example 5 A (i) Kinetic - energy which the water has ~ Calculate the pressure loss due to friction if: because of its velocity

(i) 90mm hose with a friction factor of 0.007 (ii) Potential - energy which the water has Figure 1.4 1--Vater flowing through a Type A nozzle. Figure 1.5 Water flowing through a venturi. because of its height above a fixed (ii) twin lines of 45mm hose reference point such as an outlet or pump were to be substituted for the 45mm hose in Example 4. (iii) Pressure It is shown in Appendix 4 that the relationship As the water flows from A to 8 its velocity, and between the velocity of the jet, v, and the original hence its kinetic energy, increases to a maximum at (i) for the 90rnm hose: (iv) Heat pressure, P, is: the expense of pressure which falls to a minimum value at B. At point C the kinetic energy has 9000 X 0.007 X 50 x 400 x 400 Application of the Principle ofthe Conservation of v = 14.14 vP decreased to its initial value (if the diameters at A Pr 90 x 90 x 90 x 90 x 90 Energy, which dictates that energy cannot be creat­ and C are the same) and the pressure recovers to ed or destroyed but only transformed from one and that the number of litres per minute (IImin) close to its former value. If the pressure at C is not i.e. the loss form into another, implies that if one form ofener­ discharged, L, is given by: too high, it is possible for the pressure at the throat of pressure = 0.09 bar (approximately 0.05 bar gy is increased then that increase will be reflected of the venturi to fall to below that of the atmos­ per length) by a decrease in one or more of the other forms. 2 d 2vP phere with the result that air, water or any other L This principle applies to water flowing in the types - 3 fluid outside the device will be drawn (induced) (ii) for the twinned 45mm hose the flowrate in of channel mentioned in the following paragraphs. into the stream through any opening which may each line is 200 IImin so: Example 6 exist at the throat. This is the principle underlying Because of friction, heat energy is created at the the operation ofsome types offlowmeter, the foam 9000 X 0.005 X 50 x 200 x 200 expense of pressure when water flows through a Calcu late the f]owrate from a 15mm type A nozzle inductor and of the ejector pump which is Pr 45 X 45 X 45 X 45 X 45 line of hose, though it would be difficult to detect when working at a pressure of 4 bar. described in Chapter 5. any increase in the temperature of the water. Once = 0.5 bar (or 0.25 bar per length) heat energy has been produced it cannot easily be 2 d2vP 1.5.3 Flow through Sudden Reductions L converted back to any of the other forms. Heat - 3 in Diameter The advantage of using large diameter hose in energy is also created at any points in a water relay and fireground situations is clearly illustrat­ stream where turbulence is caused by sudden 2xl5x15xv4 Figure 1.6 shows water flowing through a channel flowrate ed by these examples, though in the latter case, changes in cross section or the direction of flow. - 3 in which the diameter abruptly reduces from its ease of handling and manoeuvrability ofhose lines For most practical purposes temperature changes initial value, at point A, to a smaller value, at point may be more important. in water streams may be ignored though when a 300 litres per minute B before abruptly increasing again. centrifugal pump is running against a closed, or Table 6.1 in Chapter 6 gives approximate pressure very restricted, delivery the water gets noticeably N.B. this formula cannot be applied to diffuser and losses due to friction for various hose diameters hot because much of the energy supplied to the jet/spray type nozzles because the water is not dis­ and flowrates. pump is wasted in the creation of turbulence. charged through a simple circular section.

6 Fire Service Manual Hydraulics. Pumps and Water Supplies 7 •• occur as water is pumped, through a single stage 1.6 Water Power and Efficiency Because it is more convenient to express efficien­ pump, from an open source to a jet on the fire­ cy, E, in percentage terms, this formula is usually ground. When water passes through a pump its total ener­ written as: gy is increased because energy is supplied from an Tracing the velocity line from (I) to (6) it will be A external source, i.e. the engine which drives the E = WP x 100 seen that the velocity through the suction hose pump. As the kinetic energy of the water is small, BP from (I) to (2) is constant and comparatively low both on entering and leaving the pump, the newly Turbulence because of the large diameter, but there is a small acquired energy is almost entirely in the form of It is important, when using the formula, to appre­ loss of pressure energy mainly to compensate for Figure 1.6 Water flowing through a channel having a pressure. It is shown in Appendix 4 that the water ciate that WP and BP should be measured in the the increase in potential energy as the water is lift­ sudden change in diameter power (i.e. the energy created per second) pro­ same units, i.e. both in watts or both in kilowatts. ed. After reaching the entry to the impeller at (2) duced by a pump is given by the formula: the velocity and pressure both increase until the Example 8 As with the venturi, there is an increase in kinetic water leaves the impeller at (3). This apparent con­ wp = 100LP energy as the water is forced through the reduced tradiction of the principle of the conservation of 60 The manufacturer's technical data for the portable cross section and a consequential reduction in energy can occur because, at this stage, energy is pump in Example 7 indicates that the rated power pressure. However, although the kinetic energy fed into the system from an external source (the where WP is the water power measured in watts, L of the engine is 37 kW. What is the efficiency of reduces to its initial value as the water stream l engine). From (3) to (4) the water is passing t the flowrate measured in litres per minute (l/min) the pump? returns to its original diameter, at point C, there is through the volute or diffuser, gradually decreas­ and P the increase in pressure, between inlet and by no means a complete recovery in pressure. This ing in velocity until it reaches (4) the outlet of the outlet, measured in bar. E = 24 x 100 is because the sudden change in diameter causes pump casing and the inlet ofthe delivery hose. The 37 turbulence, particularly on the downstream side of decrease in kinetic energy is accompanied by a Example 7 the restriction, and some of the pressure energy is corresponding increase in pressure. From (4) to (5) i.e. efficiency = 65% approximately irrecoverably converted to heat energy. the water is passing through the delivery hose and Calculate the water power of a portable pump maintains a constant velocity though there is a which, at full power, delivers 1600 J1min when Example 9 Standard instantaneous couplings used with gradual reduction of pressure due to friction loss. increasing the pressure by 9 bar. any hose diameter above 640101, kinks in a line Between (5), the end of the delivery hose and the A pump is required to deliver 2700 IImin at lObar. of hose, and mains water meters of smaller entry to the branch, and (6), the outlet of the noz­ lOO x 1600 x 9 watts Assuming an efficiency of 65%, calculate the diameter than the pipes in which they are WP zle, the kinetic energy increases at the expense of 60 brake power required to drive it. installed, all cause turbulence and a corre­ pressure energy as explained previously. sponding overall loss of pressure. The more dra­ 24000 watts matic the change in cross section, the greater wp = 100 x 2700 x 10 The energy changes which take place when a two 60 will be the penalty in terms of pressure loss. stage pump is used are similar to those described I.e. Water Power = 24 kilowatts (kW) above except that stages (2) to (4) are repeated i.e. Water Power = 45 000 watts or 45 kW 1.5.4 Flow through a Single Stage Pump because of the two impellers. Some of the energy supplied to drive the pump will, because of internal turbulence, be converted Transposing the formula for E to make BP the sub­ Figure 1.7 shows the changes in pressure and to heat so it is therefore not 100% efficient in its ject gives: velocity (and therefore kinetic energy) which ability to convert the brake power, BP, supplied by the engine or motor, into water power. WP x lOO BP E The efficiency of any machine is defined as: 45 x 100 efficiency 65 useful power delivered by the machine i.e. Brake Power = 69 kW approximately Velocity ....---- ..... power required to drive the machine Pressure ..r- ..iiiiiiili -IIII]r---i,-:A~tm..:..:.:.o.:.s::.Ph:.:.e.:..r:.:.i..:..c..:p-r-e-ss-u-r-e-T--~I i.e., for a pump: It should be appreciated that the efficiency of a pump is by no means a fixed quantity but varies Suction hose Impeller Volute Delivery hose Nozzle efficiency widely according to the operating conditions. For 5 6 234 example, if the pump is operating against a closed wp delivery, the efficiency is zero because all the Figure 1.7 Changes in pressure and velocity as water is pumpedfrom a supply to the nozzle. BP energy supplied is converted to heat. It is usually

8 Fire Service Manual Hydraulics. Pumps and Water Supplies 9 •

•• highest when the pump is operating at, or close to, (a) With 25mm nozzle: where F is measured in newtons, m in kilograms, v Some pumps have a small pressure relief channel its quoted duty point. in metres per second and t in seconds. The product in the non-return valve on the suction side of the R = 0.157 x 7 x 25 2 In x v is known as the momentum of the moving pump which is designed to give protection to the 1.7 Jet Reaction object and the force, F, is therefore equal to the collecting head against water hammer. = 687 newtons. change of momentum per second. When water is projected from a nozzle, a reaction (ii) the rapid closure of the hydrant to tank equal and opposite to the force required to dis­ (b) With 12.5mm nozzle: One of the most important implications of the for­ valve or the hydrant valve itself charge the jet takes place at the nozzle which tends mula is that the force required to bring an object to to recoil in the opposite direction to the flow. Thus R = 0.157 x 7 x 12.52 rest depends inversely on the braking time - the This may cause the main on which the hydrant is the firefighter(s), or whatever is supporting the shorter the time the greater the force exerted. Thus, situated to fracture. Damage is most likely to occur branch, must be prepared for and be capable of = 172 newtons. if a vehicle is brought to rest in 0.1 seconds as the when the main is of small diameter with a conse­ absorbing this reaction. result of a collision the braking force will be quent high velocity of flow. The difference between the two reactions is there­ 100 times greater than if it is brought to rest in, say, At least one fatality and many fore approx. 515 newtons. 10 seconds as a result of normal braking, and the injuries have been caused by effect of this large force on the vehicle (and on the These examples indicate the Advantage can be taken of jet reaction to drive a object with which it collides) will be only too evi­ necessity for slowly closing hydrants, firefighters' inability to cope with fireboat without propelling machinery, solely by dent! unexpectedly large jet reactions. jets fixed at the rear of the vessel. Water from the shut-off type branches and other fire pumps can be by-passed through these jets, There are a number of fireground situations where valves in order to a\'oid wate.­ The whole of the reaction takes place as the water and the reaction of the water leaving the nozzles the time taken to terminate the flow of a substan­ hamme.- which might burst hose and leaves the nozzle, and whether or not the jet strikes propels the boat in the opposite direction to the tial mass of water, moving with considerable damage couplings, pumps, collecting a nearby object has no effect on the reaction, reaction from the jets. No increase in the speed of velocity, may be very short and where, as a conse­ though the object itself will experience a force of the vessel is gained by the jets striking the surface quence, damage to equipment may result from the heads, tanks and water mains. similar magnitude. Thus, whether or not a jet held of the water, or by their being placed under water; very large forces involved. Such situations include: by a firefighter on a ladder strikes a wall is the reaction causing the propulsion of the boat immaterial to his stability on the ladder, which is takes place entirely at the nozzle. This can be (i) shutting down a branch rapidly governed solely by the reaction at the nozzle. demonstrated by diverting the water from under­ water propelling jets to the monitor, when the boat Even though fire service hose is flexible and there­ It is shown in Appendix 4 that, for a Type A nozzle, will travel at approximately the same speed. fore able to absorb much of the kinetic energy of the reaction, R, measured in newtons, is given by: the water, damage to couplings through too rapid 1.8 Water Hammer shut-down of branches is possible and there is evi­ R = 0.157 P d 2 dence that damage may also occur to pumps and This is a phenomenon with which most people will collecting heads. where P is the nozzle pressure in bars and d is its be familiar because it frequently occurs in domes­ diameter in millimetres tic situations such as when the flow of water • One particular activity where damage can occur is through a long run of metal pipe is stopped very through the very rapid operation of the on/off con­ Whilst it is often possible for one firefighter to quickly by the rapid closing of a tap. The conse­ trol ofhigh pressure hosereel diffuser branches, for hold a small jet, several may be required for a large quent metallic 'clunk' which may be heard is the instance, whilst adopting the "pulsing" technique jet, even though the operating pressure ofboth may consequence of 'water hammer'. as a firefighting tactic. This technique is designed be the same, because the reaction depends not only to deliver a controlled amount of water, in droplet on the velocity of the jet but also on the mass of When a moving object, such as a vehicle or a col­ form, to cool hot gases. A slower, measured, oper­ water discharged per second. For large jets some umn of water, undergoes a change in velocity the ation of the on/off control to create the desired form ofsupport, such as a branch holder, may well force (F) required to accelerate or decelerate it effect is preferred, so unnecessary damage to cou­ be required. depends on its mass (m), its velocity (v) and the plings etc. through water hammer should be time (t) in which the change in velocity takes reduced. (More information about using pulsing as Example 10 place. Appendix 4 shows that the relationship a firefighting tactic can be found on page 14 ofthe between these quantities is: Fire Service Manual, Volume 2 'Compartment What is the difference between the reaction of the Fires and Tactical Ventilation'.) water leaving a 25mm nozzle as compared with F = mv a 12.5mm nozzle if the pressure in both cases is t 7 bar?

10 Fire Service Manual Hydraulics, Pumps and mller Supplies 11 Hydraulics, Pumps and Ch pt Water Supp es

Chapter 2 - Instruments

Introduction 2.1 easurement of

An understanding of the measurement of pressure 2.1.1 Water gauges (manometers) is of obvious and fundamental importance in fire service work because the correct and safe use of Very small pressure differences, such as those pumps and comprehension of information on their existing between compartments in buildings performance and on the potential capacity of equipped with pressurisation systems. may conve­ hydrants, etc., depend upon it. Sometimes, for niently and accurately be measured by means of example in the case of pressurisation systems on a simple water gauge. This device (Figure 2.1) escape staircases, measurement of small pressure consists of a U-tube, one end ofwhich is open and differences is important. situated in one of the compartments whilst the other is connected, via flexible tubing to the other Flowrate measurements are another important compartment. The water level in the open limb aspect of hydrant testing. Also, in recent years, a lises or falls depending on whether the pressure number of firefighting appliances have been fitted there is below or above the pressure in the closed with flowmeters and, although they are not in limb and the vertical difference between the levels widespread use at present, it is appropriate that a in the two limbs, measured in mm, is a convenient limited amount of information on these is includ­ way of expressing the pressure difference. ed. The advantages of the use of flowmeters in fireground pumping operations are discussed in The device may be refined in a number of ways paragraph 6.4.7. aimed at increasing the accuracy with which it can

Figure 2.1 Diagrammatic arrangement ofa water gauge showing: (I) reading when pressure d[rference is zero; (2) reading when /pressurre pressure difference is applied. The scale is calibrated to indicate l the difference in height between the surface of the water in the 1>1'0 limbs. 1

Hvdraulics. PW11PS and Water Supplies 13 be read. For example, the graduated limb may be Gauges may be constructed to measure pressure the wall and the exact shape ofthe cross-section of lObar or more, the vacuum scale. reading down to inclined rather than vertical resulting in the water only, vacuum only, or may be arranged to read the tube being carefully chosen for the pressure -I bar (i.e. absolute vacuum), would only occupy surface having to travel much further along that both. The first is termed a pressure gauge, the sec­ range over which the gauge is designed to operate. one-tenth or less of the length of the pressure scale limb in order to achieve the same vertical differ­ ond a vacuum gauge, and the third a compound It is obvious that under no circumstances must the (Figure 2.3, right) and would be difTicult to read ence and so magnifying the separation between the gauge. The water pumping system on fire service tube be subjected to excessive pressures, otherwise accurately. To overcome this difficulty the graduations. appliances is normally fitted with both pressure it would take on a permanent 'set' and thus become diaphragm gauge was introduced. and compound gauges, whilst the engine lubricat­ inaccurate. Liquids other than water, e.g. mercury, may be ing system is equipped with a pressure gauge. The (ii) Diaphragm type gauge used depending on the range of pressure differ­ suction foam inductor is fitted with a vacuum The mechanism which connects the free end of the ences which it is required to measure. gauge. There are two main types ofgauge in use in Bourdon tube to the pointer is called the move­ This type of gauge depends for its operating prin­ the fire service, the Bourdon tube type and the ment. It usually consists of a pivoted toothed quad­ ciple on the movement of a corrugated metal cir­ For water, since the relationship between pressure diaphragm type. rant, one end of which is connected by a link to the cular diaphragm (Figure 2.4), which is secured at and head is: end ofthe tube, whilst the teeth mesh with a pinion its periphery but free to move at its centre. (i) Bourdon tube gauge on the pointer spindle. Attached to the spindle is a hair-spring, the function of which is to keep the When subjected to a positive pressure the p H 10 In this type of gauge (Figure 2.2) the pressure­ teeth of the pinion in close contact with those of diaphragm may move only over a limited propor­ responsive element consists of a tube (the Bourdon the quadrant and so eliminate any free movement. tion of its surface into the small diameter ca ity in a difference in level of 1 metre would mean a pres­ tube), oval in section, sealed at one end and formed The linkage can be arranged to magnify the scale the front housing, but, under reduced pressure, it sure differential of 0.1 bar so: in the shape of the greater part of the circumfer­ reading as required. The geared movement allows is free to move over its whole surface into the ence of a circle. When pressure is applied internal­ an almost full circular reading to be obtained at the large diameter cavity in the rear housing. The each millimetre equates to a pressure ly, this tube tends to straighten, and conversely maximum pressure which the particular instru­ effect of this arrangement is that the diaphragm differential of 0.0001 bar or 0.1 mbar. when air is exhausted it tends to curl up more tight­ ment is designed to measure. behaves much more flexibly under reduced pres­ ly. The amount of movement at the free end of the sure than it does under positive pressure and the 2.1.2 Pressure and compound gauges tube is approximately proportional to the pressure The pointer of a bourdon gauge will move in a resulting movement is correspondingly greater. or vacuum applied and, provided that movement is clockwise direction the same distance for a positive This movement is transmitted via a peg which is Most gauges used by the fire service indicate relatively small, the tube returns to its normal posi­ pressure of 1 bar as it will move in an anticlockwise attached to the diaphragm, a rocker bar, a quadrant "gauge pressure" i.e. the difference between the tion when the pressure or vacuum is released. A direction for a vacuum of l bar so, only if the pres­ and pinion to a pointer which moves over a grad­ true (absolute) pressure being measured and linkage at the free (sealed) end of the tube magni­ sure scale is graduated up to just I bar, will both uated scale. The stabiliser and hair spring ensure atmospheric pressure. They therefore register zero fies the movement and transmits it to a pointer positive and negative scales on the gauge occupy there is no back-lash in the mechanism. when exposed to atmospheric pressure but will moving over a suitably graduated dial. Gauges of the same length on the dial (Figure 2.3, left). Compound gauges of this type are specially give a positive indication when exposed to pres­ this type used on fire brigade appliances conform designed to have a long vacuum scale and a rela­ sures above atmospheric and a negative indication to British Standard 1780. Their Bourdon tubes are If, as is much more likely on fire pumps, the tively short pressure scale (Figure 2.5) and are when exposed to pressures below it. usually made of phosphor bronze, the thickness of instrument is required to measure pressures up to used on the inlet side of fire pumps where it is t· Figure 2.2 Diagrams Figure 2.3 Bourdon Bourdon showing ({rom behind) tube compound gauge tube the mechanism ofa dials. under pressure BOUl'don tube pressure or vacuum gauge.

Pointer •

14 Fire Service Manual Hydraulics, Pumps and Water Supplies 15 Figure 2.4 Figure 2.5 Hair Diagram showing Diaphragm type gauge Pad Pinion Spring the construction of dial showing the long Stabiliser a diaphragm type vacuum scale and Peg compound gauge. relatively short pressure scale. Pointer

Rocker __...... Bar

Glass Figure 2.6 Grey Line shows Diaphragm Diagrams showing: deflected under suction (I) the con"ect arrangement for the ® Glass coils on a gauge Small Cavity connection: (2) incorrect arrange­ To Pump ment leading to the formation ofpockets Large Cavity Rocker Bar ofwater etc. \J Diaphragm position Water trapped in Vertical Coils at normal pressure

of minor pressure fluctuations through the connec­ Other ways of dealing with the problem of rapid tion. The gauge thus shows a mean reading and fol­ pressure fluctuations are: lows the pressure variations more slowly than important to have a reasonably accurate measure the pipe or at least causing a blockage and render­ would be the case if the aperture were fully open. (1) the inclusion of a throttling device, such as a of the incoming water pressure (which will be ing the gauge inoperative. Under no circumstances should the cock be entire­ fine capillary tube, in the gauge connection. negative when pumping from an open supply ly closed in an endeavour to 'iron out' these fluc­ below the level of the pump). There is, however, (iv) Gauge cocks tuations. This merely isolates the gauge from the (2) filling the gauge with a viscous liquid, as no relevant British Standard covering their con­ pressure or vacuum which it is desired to measure shown in Figure 2.7, has the effect ofdamp­ struction. The connections of both pressure and compound and a false reading is obtained. ing fluctuations. gauges are sometimes fitted with a cock at the (iii) Connections point where they meet the pump casing. The func­ With the inclusion of one or other of these devices tions of this cock are twofold: first, so that the ff, prompted by a low or zero it is now quite usual to dispense with the gauge Gauges on pumps are usually connected by means pump can still be used if the gauge has been reading on a gauge which has cock. of copper piping to the point at which it is desired removed or the connecting piping has been dam­ to measure the pressure, or the vacuum as the case aged; and, second, to damp down the movement of mistakenly been isolated, the (v) Care of gauges may be. This piping usually has in it one or more the needle, where this is oscillating due to pulsa­ pump operator increases pump coils designed to accommodate small changes in It should be appreciated that gauges are sensitive tion. It should be appreciated that manipulation of pressure, a dangerous situation length due to vibration, expansion or contraction. the gauge cock will not cure an unsteady reading instruments and must be treated with care if they These coils should always be arranged so that they due to vibration of the gauge itself. Where the for branchholders may well are to give long and accurate service without main­ are horizontal (Figure 2.6(1 ». This prevents the reading fluctuates due to pulsation in the pressure result. tenance. Though failure of the pressure element is formation of an air lock and water cannot become to be measured, partially closing down the cock unlikely, shock resulting from sudden changes of trapped and freeze (Figure 2.6(2», thus splitting restricts the opening and retards the transmission pressure, should be avoided.

16 Fire Service Manual Hydraulics, Pumps and Water Supplies 17 Figure 2.7 Viscous for a standard size flow tube. However, to measure A pressure gauge graduated in metres head is also liquid damping 0/ LOW PRESSURE high flowrates, the manometer tube will need to be provided; this is attached to a male coupling so HIGH PRESSURE a pressure gauge. inconveniently long unless an alternative strategy, that the gauge can be connected to a standpipe (Counesy 0/ Fire Service such as using a closed tube, is employed. head in order that the static pressure in the main College) can be checked. A vent cock is provided in the The Yernon Morris instrument, intended for coupling to release the water pressure when the hydrant testing, is shown in Figure 2.9. gauge is disconnected.

It consists of a flow tube having a male connec­ The following gives a briefoutline of the operating tion at one end for attaching to a standpipe head, principle and procedure: and a swivel joint at the other end to which the manometer is connected. The manometer has Standard range (7.2 to 34 litres per second)

GREEN OPEN HOSE REEL three ranges of flow marked on it in red, black MANUAL REO CLOSED OFF ON and white: the standard range of 7.2 to 34 litres The vent plug is screwed tightly shut before flow per second (l/sec) (432 to 2040 l/min); a low commences. Because the air trapped in the range of 2.6 to 7.2 l/sec (156 to 432 l/min), and manometer tube is now being compressed as the a top range of 34 to 60 l/sec (2040 to 3600 l/min). water attempts to rise, the range of the instrument

2.2 Measurement of Flowrate The Pitot tube is a very simple device which is used to measure the velocity of flow of a stream of Figure 2.9 The Vernon It is sometimes necessary to be able to measure the liquid. It consists only of a small diameter tube Morris Flow Gauge jar flowrate (the number of litres per minute or per with a right angle bend in it fixed into the pipe testing hydrants. second) available from a pump or hydrant and, for which contains the flowing liquid as shown in Hexagon Cap ~ this reason, a limited number of the available Figure 2.8. The short limb of the tube is horizontal Air Chamber instruments are described briefly below. Probably and points along the axis of the pipe towards the the most widely used of these instruments is the oncoming liquid whilst the longer limb is vertical Yernon Morris hydrant testing gauge, but, in recent and effectively forms a manometer. / years, flowmeters have also been built into the Compensator Plug deliveries of pumping appliances. As the moving liquid attempts to flow into the Pitot tube it forces its way up the vertical limb to a 2.2.1 The Vernon Morris hydrant height which increases as the velocity increases. testing gauge Although the relationship between the height to 6 which the liquid rises in the manometer tube and Pressure The principle of operation of the instrument, the flowrate involves a number of factors, includ­ Gauge Manometer which incorporates a device called a Pitot tube, ing the flow pipe diameter, it is quite easy to cali­ 2 may be explained by reference to Figure 2.8. brate the manometer tube to read flowrate directly 5

4 Figure 2.8 The Pitot tube principle.

3 ~

Height of Column depends on the Velocity of Flow Compensator Chamber

.)

18 Fire Service Manual Hydraulics, Pumps and Water Supplies 19 - is effectively extended beyond that achieved with Figure 2.12 Principle the tube open. The flowrate reading is obtained ofthe electromagnetic from the red scale on the manometer housing but, flowmeter Magnetic Field at Right Angles ifthe water level does not rise far enough to be vis­ Flow to Direction of Flow Direction ible, the vent plug is removed and the reading ::::~: taken from the low range scale. Wheel 1 ;=:::::===~~e:======:=; Low range (2.6 to 7.2 litres per second)

With the vent plug removed the manometer tube is Small Voltage generated open to atmosphere and flowrate readings are Figure 2.10 Operating principle 0/ the paddle wheel across moving water may obtained from the black scale. type flowmeta be used to glive direct indication of Flowrate Top range (34 to 60 litres per second) designed as an alternative to the hydrant testing If, when using the standard range, the water level gauge described previously. It has a useful range of reasonably pure, is a sufficiently good conductor smooth reduction in diameter, to a point called the in the manometer tube goes off scale, then the 150 to 1800 l/min. to cause a small voltage, which may be measured throat, followed by an increase back to the normal flowrate exceeds 34 l/sec and the effective range of by a sensitive detector, to be generated and the diameter. As water, or any other fluid, flows through the instrument has to be further increased. In order 2.2.3 Other types of flowmeter flowrate, for a pipe of given diameter, may be the device its speed increases to a maximum at the to achieve this the hexagon cap is removed from indicated directly. throat and then decreases to its initial value when the top of the manometer and the compensator A number of other types of instrument, of which the normal diameter is resumed. plug inserted into the air chamber; the cap is then just two are described below, are available for the This type of instrument also IS In use as a flow replaced and screwed tightly down. Before the measurement of flow rates from hydrants and from measuring device on some pumping appliances. As explained in paragraph 1.5.2, because of the manometer is attached to the swivel joint connec­ pumps. Although they are not widely used in One of its advantages is that there is no discernible increase in kinetic energy at the throat, the pres­ tion, the compensator chamber has to be screwed brigades at the present time, their future use cannot pressure loss as water flows through it. sure P2 at that point is less than the pressure PI at into the bottom of the manometer, and the com­ be ruled out, so a brief outline of their operating the point just before the diameter starts to reduce. bined fitting then attached to the swivel joint con­ principles is appropriate. (b) Venturi type Oowmeters The pressure difference between the two points, nection. This has the effect of increasing the vol­ which may be measured by a suitable gauge, ume of air trapped in the manometer tube but (a) Electromagnetic type Oowmeters A typical venturi is shown in Figure 2.13. It consists depends on the flowrate and can be used to give a reducing the space into which it is compressed as of a section of a pipe in which there is a gradual direct indication of it. the water level rises. The reading ofthe rate offlow When a conductor of electricity moves through is taken from the white figures on the back of the a magnetic field which is at right angles to the manometer housing. After use, both the compen­ direction of motion a voltage, proportional to the Figure 2.13 The/low oj'water through a ~ sator plug and chamber should be removed. velocity of the conductor, is developed across it cqP1 venturi. as shown in Figure 2.12. Water, even when ::::::==:=------'-'--___=___ WP2 ~-==:::::====: 2.2.2 The paddle wheel type flowmeter

The instrument consists of a flow tube into which --====:=:::==---~ --==--==--===-- a paddle wheel is inserted so that the blades project partially into the stream of water as shown in Figure 2.14 Figure 2.10. It rotates at a speed which is directly Flowmeters on a proportional to the rate of flow of the water and pumping appliance. creates magnetic pulses, which are counted elec­ (COllrtesy 0/1-11'0 Service tronically, each time one ofthe blades passes a sen­ College) sor.

The instrument is calibrated to give a direct indi­ cation of flowrate and is sometimes fitted to the individual deliveries on firefighting pumps as shown in Figure 2.14. Figure 2.11 shows the Figure 2. JJ The paddle wheel type hydrant testing gauge Vernon Morris version of the instrument which is in use. (Photo: /lemon Morris & Co. Ltdt

20 Fire Service Manual Hydraulics. Pumps and Water Supplies 21 Hydraulics, Pumps an Water Supplies

Chapter 3 - Atmospheric Pressure and Suction Lift

Introduction rise. The behaviour of water in this way, when sub­ jected to a partial vacuum, is of fundamental The atmosphere which envelops the earth, importance in firefighting operations, since upon although gaseous, possesses definite weight. Since it depends the process of priming a pump from the weight is exerted, for all practical purposes, open water. uniformly all over the surface of the earth and through the cavities of the body as well as exter­ It will be convenient at this stage to study Figure nally, the human body is unaware of it and behaves 3.1. In the diagram AB is the surface of a sheet of as though such pressure did not exist. open water over part of which, CD, is inverted a long tube, sealed at the upper end, except for a con­ However, it is important to understand the signifi­ nection to a pump. If, initially, the pressure in the cance of atmospheric pressure because the height tube acting on the surface CD is normal atmos­ to which a pump can lift water under suction from pheric the system may be regarded as akin to a pair an open source, the performance of the pump and ofscales, the two pans ofwhich are equally weight­ the operation of a siphon are all dependent on it. ed, i.e. each is loaded with 1.013 bar. Ifthe pressure in the vertical tube is now reduced, the pressure 3.1 Atmospheric Pres ure bearing down on the portion CD is progressively

A column of air I metre square and extending to the upper limit of the atmosphere weighs, on aver­ age, 101 300 newtons at sea level, and, therefore: vacuum~

Atmospheric Pressure 101 300 N/m 2 or 1.013 bar

(remembering we must divide by 100 000 to con­ vert from N/m2 to bars)

For most practical purposes, therefore, we may Approx regard atmospheric pressure as having a value 10m of I bar Atmospheric Pressure Approx. Atmosphelic pressure acts on the surface of any 1bar (103 N/m2 ) open body of water just as on the other parts of the earth's surface. If, however, this atmospheric pres­ A C 0 B sure is removed from above a portion of the water, in other words, ifa vacuum is formed, then the sur­ face of the water is subjected to unequal pressures and, the water being resistant to compression but not to change of shape, that part of the surface Figure 3./ Diagram showing the principle oflifting which is relatively free from pressure will tend to waler by almospheric pressure.

Hydraulics, Pumps and WaleI' Supplies 23 • reduced in value. The atmospheric pressure outside This is precisely what happens when a pump is the water surface and the centre line of the vaporise (and so create an opposing vapour the tube does not change, and it will be seen, there­ primed. The suction hose takes the place of the impeller. Water has no tensile strength and cannot pressure) as it nears the impeller. This ten­ fore, that the system is now unbalanced. Water vertical tube and the primer is the device for therefore be pulled upward, and as we have already dency increases rapidly with Temperature. flows up the tube until the pressure exerted at the exhausting or removing the air from the suction. seen, it is the atmospheric pressure only which In fact the vapour pressure ofwater becomes base of the column of water in the tube is equal to As the pressure inside the suction is reduced, so the raises the water (see Figure 3.1). equal to atmospheric pressure at its boiling the pressure of the surrounding atmosphere. excess pressure ofthe air on the exposed surface of point so making it totally impossible to lift the water forces the latter up the suction until it The purpose of a priming device, when water is water at, or near, this temperature. At nor­ Theoretically if an absolute vacuum could be reaches the inlet of the pump. It follows. therefore, being lifted on the suction side of a pump, is to mal outdoor water temperatures the effect is formed in the tube, i.e. if the air could be com­ that even theoretically, when under perfect work­ create a partial vacuum within the pump chamber small, however. pletely exhausted, then the water would rise a ver­ ing conditions, at normal atmospheric pressure a and suction hose. The atmosphere exerts pressure tical distance sufficient to create a pressure of pump cannot lift water from a greater depth than on the open surface of the water and so forces the These five factors may conveniently be remem­ 1.013 bars at the level CD. IO.3m from its surface to the centre of the pump water up through the suction hose and into the bered by the mnemonic CREST. inlet. pump. The mechanical condition of the pump and Using the relationship, already established, hence its ability to create a partial vacuum also has Factors (i), (ii), (iii) and (iv) are each increased by between head and pressure: The value for atmospheric pressure quoted above, a bearing on the total height of the suction lift. increasing flowrate, and because the proportion of i.e. 1.013 bar, is the average value at sea level. 1t atmospheric pressure available to deal with them H = 10.19 x P changes, according to variations in meteorological 3.2.2 Practical Limitations decreases as lift increases, it follows that the out­ conditions, by as much as about 5% below or above put from the pump will also decrease with increas­ this vertical distance is seen to be: this figure, so the maximum suction lift achievable It has been shown that water cannot rise to a verti­ ing lift. Whilst suction lifts of 8.5m or more are when a region of high pressure is over the country cal height greater than approximately 10m in a sometimes obtained under very good conditions, I0.19 x 1.013 or 10.3m may be almost a metre more than when there is a completely evacuated tube, and that it does so 8m can be considered the approximate practical deep depression. There is also a significant varia­ because it is forced up by the atmospheric pressure maximum if a worthwhile output is to be obtained No amount of further effort, whether by endeav­ tion of atmospheric pressure with altitude. It acting on the water sUlface outside. from the pump. ouring to increase the vacuum (which is impossi­ reduces by approximately 10% (0.1 bar) for every ble) or by lengthening the tube, will induce the 1000m gain in height so that maximum theoretical When pumping from an open source it is the In order to appreciate the impact of lift on pump water to rise higher than I 0.3m. It has already been suction lift is correspondingly reduced - to about atmospheric pressure alone which can provide performance consider a pump working from open stated that sea water is slightly denser than fresh 9m at an altitude of 1000m. the lift necessary for the water to enter the water with a suction lift of 3m as shown in Figure water, so that a shorter column of sea water would pump. 3.2 left. (Note that when manufacturers give infor­ balance the atmospheric pressure. Because the It has already been shown that water will rise to a mation on pump performance, a subject discussed density of sea water is 1.03 kg/litre, it would height of 10.3m in a completely evacuated tube, However, the atmospheric pressure's ability to lift in Chapter 5, it is common to specify a lift of 3m.) require a column of length: and such a device could, in principle, be used as a water is reduced to below the theoretical capabili­ To do the work of raising the water to the pump a barometer to measure atmospheric pressure. ty of about 10m because it also has to: pressure equivalent to 3m head of water is 10.3 However the height of the instrument would make required. This, subtracted from a total available 1.03 it entirely unpractical for general use, so the length (i) Create flow i.e. to give the water kinetic pressure equivalent to 10m, leaves a pressure of the column necessary to counterbalance the air energy as it changes from its static state in equivalent to 7m head to overcome the various i.e. IO metres to balance the atmospheric pressure. pressure is reduced by using the densest conve­ the open supply to its moving state in the losses described above. nient liquid - mercury. As mercury is 13.6 times as suction hose; If, however, the air is not completely exhausted dense as water, atmospheric pressure will be capa­ If, however, the suction lift were 8m (Figure 3.2 from the tube, then the water will only rise to a ble of supporting a column of height 10.3/13.6 (ii) overcome frictional Resistance to flow In right), a pressure equivalent to 8m head of water height sufficient to balance the pressure difference metres, i.e. the suction hose and couplings; would be required to raise the water to the pump, existing between the inside and the outside of the leaving only 2m head to overcome the losses. tube. Thus, ifthere remains in the tube air at a pres­ atmospheric (iii) overcome pressure loss due to turbulence Consequently, for any given diameter of suction, sure equivalent to that exerted by a column of pressure = O.76m or 760mm of mercury and shock as the water enters the pump the quantity of water capable of being delivered water 3.3m high, then the water will only rise 7m. impeller. It is known as Entry loss and would be considerably less than that possible at a 3.2 Suction Lift varies with the design of the pump; 3m suction lift. 1t will be seen therefore that when a vacuum is formed in a long tube or pipe, water is driven up by 3.2.1 Basic facts (iv) overcome pressure loss as the water is The practical steps to be taken in order to ensure the external pressure of the air acting on the forced through the Strainer and changes its the best possible pump perfonnance when pumping exposed surface of the water although, in common A pump is said to lift water when the water is taken direction of flow after entering; from an open supply are discussed in Chapter 6. parlance, we say that it is sucked up by the from an open source below the inlet of the pump vacuum. and the suction lift is the vertical distance between (v) overcome any tendency for the water to

24 Fire Service Manual Hydraulics, Pumps and Water Supplies 25 - Hydra lies, Pumps and Ch P r Water Supplies

Figure 3.2 Sketch shoWing pump working from a lift of(left) 3m. and (right) 8m. Chapter 4 - Water Supplies and Hydrants 7m

2m

IntrOduction There are now many performance indicators used to report upon undertakers together with 3m This chapter discusses legislation concerning water mandatory targets for leakage and water quality for firefighting, the water authorities' methods of compliance. water distribution and water supplies especially for 8m firefighting purposes. This subject naturally leads The Environment Agency has a water resource on to hydrants, and related equipment, which give licensing authority in addition to pollution moni­ brigades the means to access these supplies. toring and control, which through abstraction licensing, can have an impact upon the amount of 4.1 Legislation concerning Mains water available in distribution systems. Water Supplies The Drinking Water Inspectorate has responsibility 4.1.1 The Water Industry Act 1991, Water for monitoring water quality and instigates prose­ Act 1989, Water (Scotland) Act 1980, cutions in such events as the supply of discoloured Northern Ireland water which is considered 'unwholesome'.

The Water Act 1989 (which applies only to Currently, the Water (Scotland) Act 1980, as 3.3 Siphons England and Wales) provided for the former water amended, is the primary legislation covering this authorities to be privatised and established the subject in Scotland. A siphon (Figure 3.3) consists of an inverted U­ appointment of a Director General of Water tube with legs of unequal length and is used to Services to ensure that the water companies are In Northern Ireland responsibility for water transfer liquid, e.g. over the edge of the vessel in able to finance their functions and to determine resources lies with the Department of the which it is contained, to a point at a lower level. and monitor levels of customer service. Enviroment (Northern Ireland). One leg of the siphon must be submerged in the Short Leg liquid which is to be lifted, and the point of dis­ Independent of the Director, Regional OFWAT 4.1.2 The Fire Services Act 1947 charge must lie at a lower level than the surface of Customer Service Committees were also set up, the liquid. Its operation may be compared to the comprised of appointed members, to promote the Sections 13, 14, 15 and 16 of the Fire Services Act behaviour of a chain suspended over a pulley with interests of customers. 1947 also contain provisions for the supply of unequal vertical lengths. The longer length, water for firefighting. because it is heavier, will pull up the shorter length The Act also set new standards for the supply and even if both ends are resting on horizontal sur­ quality of water. In 1991 the clauses of the 1989 Section 13 of the Act requires ~that: Water Long faces. However, the important difference between Leg Act which related to the provision ofwater for fire­ a chain and a column of liquid is that the latter has "A fire authority shall take all reasonable Tank fighting were included in the Water Industry Act of no tensile strength and maintains its integrity only that year. The statutory requirements of the 1991 measures for ensuring the provision of an because of atmospheric pressure. It follows that, Act will be discussed later in this chapter. adequate supply of water, and for securing that when using water, the siphon will only work so it will be available for use, in case of fire." long as the shorter limb is less than IOm. The pipe Water undertakers have a duty to provide a supply Figure 3.3 The principle ofa siphon. or hose used must be rigid because otherwise, the of water for 'domestic purposes' and an obligation Under Section 14 (1 and 2) of the Act, the fire pressure inside it being less than atmospheric, it to provide a supply of water for commercial or authority may enter into an agreement with statu­ will simply collapse under the atmospheric pres­ industrial purposes if it does not affect the domes­ tory water undertakers for the purpose of imple­ sure acting on the outside. tic supply of existing customers. menting Section 13 on such terms as to payment or

26 Fire Service Manual Hydraulics. Pumps and Water Supplies 27 - otherwise as may be specified in the agreement. normal consumers. Failure, without reasonable a network of trunk and distr-ibution location of which can be determined by closing No water undertakers shall unreasonably refuse to excuse, on the part of the undertaker to comply is • mains, service reservoirs and booster down different s ctions ofthe system until a reduc­ enter into any such agreement proposed by a fire an offence. pumps (where necessary) which supply tion to normal consumption resumes. authority. Section 14 (3) of the Act states that water to: undertakers are responsible, at the expense of the NB. Section 147 of the Water Industry Act 1991 The design of the public network, including diam­ fire authority, for the clear indication, by a notice stipulates that no charge may be made by any water a number of zones, sometimes referred to eters of pipes etc., is based on factors such as: or distinguishing mark which may be placed on a undertaker in respect of • as District Metered Areas (DMAs), in wall or fence adjoining a street or public place, of each of which the pressure is maintained • Maximum requirements at peak demand. the situation of every fire hydrant provided by (a) water taken for the purpose of the at a high enough value to satisfy normal • Minimum pressure requirements. them. extinguishing of fires or taken by a fire conSllmer demand. • Ag ing factors. authority for any other emergency purposes; • Estimat d future demands. The obligations of statutory water undertakers Each DMA (Figure 4.1) is supplied by one or two under subsections (I), (2) and (3) are enforceable, (b) water taken for the purpose of testing incoming mains, sometimes with pressure reduc­ Figure 4.2 shows typical daily variatIOns in under section 18 of the 1991 Water Industry Act. apparatus installed or equipment used for ing valves, and the entry point(s) metered so that demand for a week in the winter and for a week in Any complaints about a water undertaker not car­ extinguishing fires or for the purpose of the consumption of the DMA may be measured. If the summer. rying out these obligations should be directed to training persons for fire-fighting; or it is necessary to shut down the usual supply main the Secretary of State if they cannot be resolved. for maintenance or other reasons, water may be The D As are supplied by a system of trunk (c) the availability of water for any purpose imported from a neighbouring DMA via the zone mains (anything up to 1.2m in diameter) and A fire authority is empowered under Section 15 (1) mentioned in paragraph (a) or (b) above. valves. A sudden dramatic increase in consump­ distribution mains. Service mains, which supply of the Act to make agreements to secure the use, tion may well indicate that a burst has occurred, the the consumers within a DMA, are smaller and in case of fire, of water under the control of any However, Section 23 of the Water (Scotland) Act person other than water undertakers; to improve 1980 states only that: the access to any such water and to lay and main­ tain pipes and carry out other works in connection "the undertakers shall allow any person to - DMA Boundary with the use of such water in case of fire. Section take, without payment, water for extinguish­ - Main in Excess of 150mm -- Main less than 150mm ing fires from any pipe on which a hydrant 15 (2), however, indicates that the fire authority X Sluice Valve may be liable to pay reasonable compensation for is fixed." o Washout Hydrant this use. • Fire Hydrant 4.2 Distribution ofWater Supplies Section 16 of the Act provides that if a person is proposing to carry out works for the supply ofwater 4.2.1 General to any part of the area of a fire authority that person is required to give not less than six weeks notice in Water undertakers obtain their water from three writing to the fire authority prior to the commence­ mam sources: ment ofthe works. In the case ofworks affecting any fire hydrant the authority or person executing the (i) River intakes. work is normally required to give the fire authority (ii) Impounding reservoirs. These contain water written notice at least seven days before the work has collected from high ground, streams and begun. In an emergency, where it would be impracti­ general rainfall. cable for notice to be given in the time stipulated, (iii) Underground sources e.g. wells, boreholes notice is to be given as early as may be. and springs.

Section 30 of the Act establishes that, at any fire, About one-third of the total supply is drawn from the senior fire officer present has sole charge and each source but in each case the water is fed into control of all operations for the extinction of the main storage reservoirs, purified and then passed fire, including the use of any water supply, and into the distribution system. This system conveys 200 mm that the water undertaker, on being requested by water to the consumer and, in general, consists of Zone this officer to provide a greater supply and pres­ mains and pipes laid under public roads. There is Valve I~ ~I sure of water for firefighting, shall take all no standard pattern for an authority's distribution 100 metres necessary steps to comply with the request even network but it will often consist of: if this results in the interruption of supplies to Figure 4.1 Diagrammatic representation ala District Metered Area. The mains are normally laid under public roads.

28 Fire Service Manual Hydraulics. Pumps and Water Supplies 29

> usually of 75, 100 or 150mm diameter. Large con­ (ii) provide support to areas, particularly at sumers, whose demands may be too great for the times of peak demand, when gravity flows 18 . service mains, may sometimes be supplied by dis­ would be insufficient to maintain supplies; tribution mains. In rural areas even the distribution ...... 16 .; t ••••••••.•• l' ••••.••••• t •• _ •••••••• : ••••••••••• : ••••••••••• ! .•••••••••• r •••• mains may not exceed l50mm and could be only (iii) provide supplies to areas that lie close to, or 75mm. above, the level that water is physically able to flow under gravity alone. 14 .: : : : : : : a •••••• :••••• 4.2.2 Associated Features (d) Pressure reducing valves 12 .: : : : : : : : . (a) Sluice valves Except for those in which the pressure is already

•:•••• • I••••• ~ ••••••••• •• : ••••••••••• : ••••••••••• : •••••••• ••• : •••••••••••"•••••••••••"•••• Sluice valves are fixed at intervals along trunk and ~ 10 ...... low, because they lie close to reservoir level, typi­ distribution mains, and occasionally on service cal DMAs would, in order to minimise the amount mains if they are larger than usual. (Note: the term of water wasted through leakage, have pressure 8 'stop valve' is normally used for valves in domes­ reducing valves on each of the incoming mains to tic premises.) lower the operating pressure to the minimum need­ 6 ed to sustain normal requirements. Though section Valves that are normally closed are used to sepa­ 65( I) of the 1991 Act requires only that the pres­ 4 rate areas with differing pressure characteristics, sure be sufficient to cause water to reach the top of areas that fall into different water supply or water the top-most storey of every building within the 2'--+-----+------+------1-----+------+------1-----+-- quality zones, or that define District Metered undertaker's area, OFWAT, the regulatory body for Man 29 Tue 30 Wed 01 Thu 02 Fri 03 Sat 04 Sun 05 Mon 06 Areas. Most valves are normally open and are the water industry, sets the minimum pressure at placed on the system to enable areas of the net­ the boundary as 10 metres head at a flow of 9 work to be isolated for repair, maintenance or litres/minute. emergency works. 'Pressure Management' is increasingly being They are operated by water undertakers' officials employed using more sophisticated devices which 18 , . to control or isolate flows efficiently within the maintain a minimum pressure but open up in distribution system. They can also be used, in response to increases in flow, thus maintaining tar­ ...... some cases, to divert water where there is a get pressures. 16 '.' , , . .. '" '" .. shortage for firefighting. 4.2.3 Deterioration of Pipes 14 (b) Service reservoirs Cast iron or other ferrous metal pipes often devel­ 12 Service reservoirs serve the dual purpose of bal­ op tuberculation or corrosion internally, which ancing the distribution system and providing a increases the friction loss in the main and therefore reserve of water against the possibility of an inter­ reduces its carrying capacity (see Chapter I). The ~ 10 .. ,'. ,',.. ruption in supply due to a breakdown or excessive design of the distribution system may have to take demand. These often include large overhead tanks this into account, based on the calculated severity 8 and water towers. of the expected deterioration.

6 (c) Booster pumps Plastic pipes, which are not susceptible to tubercu­ lation and corrosion, are being increasingly 4 . - , _. Booster pumps are used to increase pressure in installed as also are special internal linings, similar trunk mains for transfer of supplies over long dis­ to fire hose, as a means of re-conditioning badly tances. corroded and leaky mains. 2L--+-----f-----+------1------+-----+-----+------f-- Sun 25 Mon 26 Tue27 Wed 28 Thu 29 Fri 30 Sat 31 Sun 01 And, in addition, to: Water undertakers maintain regular refurbish­ ment programmes to overcome these problems

Figure 4.2 Typical daily variations in water demand/or a winter week (above) and/or Cl summer week (below). (i) provide opportunities to reconfigure areas to and improve running pressures and the flow (Courtes)' ofWessex Water) balance pressures; carrying capacities of their networks.

30 Fire Service Manual Hydraulics, Pumps and Water Supplies 31 - 4.3 Water Supplies for Firefighting works in connection with the supply of water, it • Communication in respect of and during an (ii) In considering requests for additional mains should., therefore, be possible to keep these records emergency. capacity the optimum combination for the 4.3.1 General up to date. provision ofwater for firefighting should be • Review ofpre-planning and performance sought which minimises both the need for Section 13 of the Fire Services Act specifies the 4.3.2 Agreements between Fire Authorities following an incident. oversizing and the potentially adverse fire authorities' responsibility for securing ade­ and Water Undertakers impact on microbiological quality caused by quate supplies of water and ensuring that it is It also recommends the introduction of formal stagnation. Full consideration will need to available for firefighting. In the United Kingdom Many fire authorities have negotiated codes of training sessions, seminars and site visits, conduct­ be given to issues which relate to the testing most of this water is taken from water undertak­ practice (based on a model agreement drafted in ed by employees with appropriate expet1ise, in of hydrants, training and the design and ers' mains though water from private mains, e.g. 1993 by the Chief and Assistant Chief Fire order to build an awareness ofthe respective roles, maintenance requirements of any fire ser­ on factory premises, is also used., subject to agree­ Officers' Association) with the relevant water operating procedures and problems faced by those vice equipment which may have an impact ment. However the primary function of these undertakers to establish a working relationship involved. on water quality. mains is to provide water for domestic purposes between them and so to enable fire authorities to and this provision may not be adequate for fire­ meet their obligations under Section 13 of the Fire As a general principle there should be operational (iii) Fire services and water undertakers should fighting in a particular area. Services Act. These codes of practice cover areas cooperation between fire services and water under­ consider the value to be gained from the such as: takers to provide and secure water for firefighting. flow testing of hydrants and of other There is, at the present time, no legislation which Water undet1akers' expertise is central to the methodologies for establishing potential requires water undertakers to provide minimum • Hydrant installation, maintenance and process of assessing and predicting the extent to flowrates which do not involve the tisk of flowrates for firefighting purposes. testing. which the distribution system can provide water water discolouration and., as such, should for firefighting purposes. Such provision is there­ preferably be used. Mains supplies can be improved by increasing the • Provision of water for firefighting fore a joint process balancing what might be size of the mains but, if this is requested by a fire purposes. required with what may be available and then (iv) Service reservoirs are not used directly for authority, then that fire authority will have to pay. agreeing any actions necessary to fill the gap - if firefighting purposes. However, following Financial considerations will often limit the sort of • Liaison between the fire authority and one exists. Particular attention should be paid to risk assessment, it may be necessary to con­ improvement that is reasonable for a fire authority the water undertaker, particularly those potential incidents that carry the greatest risk sider the installation of a fire hydrant at the to ask for, so it may be necessary to negotiate a during emergencies. and might demand substantial water resources for boundary of the site. compromise with the water undertaker between firefighting. Careful pre-planning, both to deter­ firefighting requirements and what the undertaker • Charges to the fire authority for work on mine the likely water requirement and to identify (v) Cross contamination of mains water with would provide for domestic purposes. hydrant installations etc. available sources, is essential. These issues are contaminated water is avoided. It is, there­ considered in some detail in Chapter 7. fore, important that equipment is adequately To augment mains supplies, brigades should sur­ Problems regarding water for firefighting may still maintained, e.g. non-return valves on vey all sources ofwater, including open water, near occur and., in order to help resolve them, a A particular concern of the National Liaison pumps. enough to to be of use for fire risks in their area National Liaison Group was recently set up. This Group, which is addressed in the guidance docu­ (see Chapter 7 - Pre-planning). This has become had the brief of drafting a new Code of Practice to ment, is that of the possible effect on water quality (vi) Any actions which create sub atmospheric even more important in recent years as water "facilitate and promote liaison between Local of fire service operations. Any firefighting or test­ pressures in the mains should be prevented. authorities have lowered operating pressures, par­ Authority Fire Brigades and Water Companies by ing of apparatus has the potential to affect the ticularly at night when ordinary domestic require­ producing guidance which identifies the issues that chemical or microbiological quality of the water. The introduction of additional legislation, to estab­ ments are at a minimum, to reduce both the proba­ Water Companies and Fire Brigades should consid­ The causes include disturbing sediment in the lish and enforce the responsibilities of water bility of leaks occurring and the high proportion of er when preparing their own local agreements". main by changes in the rate of flow or flow rever­ undertakers with regard to the water requirements water which is wasted when they do. sal, and negative pressures in the main which could for firefighting purposes, is a possibility. The resulting "National guidance document on the suck in contaminated water from the surrounding Because of the possibility of contamination, water provision of water for firefighting" was published soil. It is essential therefore that: 4.3.3 Industrial Risks should never be taken directly from service reser­ jointly by the Local Government Association and voirs though it may be acceptable to the water Water UK in December 1998. It places particular (i) The liaison process should make the Local There may be isolated patches ofhigh risk in a pre­ undertaker for it to be taken from adjoining emphasis on improved local, district and national Fire Authority fully aware ofthe implications dominantly low-risk area. In these cases, fire washouts. liaison between the brigades and water undertakers of discoloured water incidents. A communi­ authorities usually advise the owners to install and recommends that local discussions should cation process should be agreed which some form of adequate water supply for firefight­ All brigades keep records of the water supplies in address the following areas: provides the water undertaker with the ing, e.g. reservoirs, underground tanks. their area and the access to them. As the Fire opportunity to consider whether anything can Services Act 1947, section 16, requires fire author­ • Facilitating the ongoing availability of be done operationally to minimise the risk of In many industrial premises large quantities of ities to be notified of any intention to carry out water for firefighting. supplying discoloured water to its customers. water will be required for processes carried on in

32 Fire Service Manual Hydraulics. Pumps and Water Supplies 33

> the plant. Fire authorities usually have discussions appropriate value for the friction factor of a cor­ 4.5 pecial Fire Mains not be liable for the cost of repairing or replacing with the owners and agree on the amounts they can roded main is of the order of 0.0 I, so the loss of the hydrant incurred as a result of the damage. take for firefighting. However, under Section 58 of pressure is given by: In some countries the system of special fire mains the Water Industry Act 1991, developers, at their is employed. Such a system has the advantage that Section 14(5) of the same Act makes it an offence own expense, may require water undertakers to 9000f/12 it can be planned solely to provide an adequate to use a fire hydrant without proper authority, or to Pr install and maintain hydrants specifically for fire­ d5 water supply for all fire risks at a suitable pressure damage or obstruct a hydrant otherwise than in fighting purposes. Whatever the situation in these and that untreated water may be used. Such mains consequence of using the hydrant with the consent cases, it should be made quite clear to the owners 9000 x 0.0 I x 200 x 1000 x 1000 are rare in this country, and only exist in special of the water undertaker. i.e. Pr that the fire authority cannot be expected to meet 100 x I00 x 100 x I00 x 100 cases such as a large factory in an area where the the expense ofproviding water supplies for special public supply is not adequate to cover the special 4.6.2 Siting and Fixing of Hydrants premises out of all proportion to the remainder of i.e. Loss of pressure risk, and in certain docks. Sometimes these mains the risk in the area. The fire authority should = 1.8 bar are fed from a river or canal or some other untreat­ When water mains are installed or changed, the advise such premises to install equipment in accor­ ed water source, and in such cases it is essential to plans submitted to the fire authority will show the dance with BS 5306: 1983 "Fire extinguishing Thus, even at the relatively modest flowrate of ensure that no cross connection is made during intended route and size of the mains. The fire installations and equipment on premises, Part I: 1000 l/min, it is quite possible that most of the firefighting operations between foul water mains authority should identify likely fire risks, estimate Hydrant systems, hose reels and foam inlets". available pressure in the main is used to overcome and potable water supplies. In other cases, special the water requirements and then specify the num­ friction in the main itself. On the other hand, pro­ fire mains use water from the undertakers' supply. ber and position of hydrants accordingly. The water 4.4 Pres ure and Flow in Main vided there is no constriction in it, a large main of undertakers should be able to state the approximate 200mm or more will probably be able to supply All special fire mains must be fitted with British flow of water from each proposed hydrant under It should be noted that, because of the variation in several pumps before the pressure falls substantial­ Standard hydrants. most conditions. The fire authority will then be the demands from customers, flow and pressure in ly (a similar calculation shows that, for the same able to decide whether the flow from the hydrants the mains will vary according to the time of day, flowrate, the pressure loss in a 200mm main is less 4.6 Hydrants near the fire risk is sufficient to cover the risk ade­ day of the week and the time of year (see Figure than 0.1 bar) and consequently the location of quately and, if not, to plan for additional supplies. 4.2) so that the quantity of water available for fire­ these larger mains, especially those upstream of 4.6.1 Statutory Requirements Existing hydrants are normally placed at intervals fighting may also vary. The standing pressure at a pressure reducing valves, and the hydrants on them of between 90 and 180 metres, but there are a num­ hydrant, i.e. the pressure in the main when water is is an important aspect of pre-planning. Section 57 of the Water Industry Act 1991 requires ber of current recommendations, regarding their being taken only for normal domestic purposes, is the water undertakers to allow water to be taken spacing, for different areas of risk. Discussions are not in itself an accurate guide to how much water Once the standing pressure is used to overcome from their mains, by any person, for firefighting currently taking place concerning the introduction will be available in an emergency situation. When friction in the main no further increase in flow purposes and (at the fire authority's expense) to pro­ of guidelines for hydrant spacing on new develop­ firefighting water is being drawn the flowrate, and will be possible no matter how many hydrants vide hydrants where the fire authority require them ments and on whether the developer should be hence the loss of pressure due to friction (see are opened. and maintain such hydrants in good working order. made responsible for meeting the cost of installa­ Chapter 1), may, particularly ifthe main is ofsmall tion, such a change would require new legislation. diameter, be considerably greater than normal with Tuberculation and corrosion in mains will reduce Section 58 ofthe Act requires water undertakers, at Any new spacing guidelines are likely to be decid­ the result that the pressure in the main will fall. their effective diameter and cause internal rough­ the request ofthe owner or occupier of a factory or ed on a risk assessment basis. The reduction in pressure depends on: ness which, together with the bends and fittings place of business and at their expense, to fix fire such as meters, will increase frictional loss. This is hydrants for the purpose of firefighting only. The water main is provided with a branch or (i) the diameter of the main. one ofthe main reasons why hydrants fitted on two T-piece to which the hydrant is attached either (ii) the condition of the main internally (which different mains of the same diameter in the same For Scotland similar provisions are made in the directly or with a short length of pipe inserted. The affects its diameter and roughness). pressure zone can give very different rates of Water(Scotland) Act 1980. hydrant is situated in a chamber or pit of brickwork (iii) the length of the main. flow. A knowledge of the capacity of every main or other suitable material which is covered with a (iv) the amount of water being drawn from is an important aspect of planning efficient fire Although, with the exception of specially request­ removable or hinged lid, usually of cast iron. The the main. protection of an area and consequently it may be ed hydrants, the cost of installing, maintaining and hydrant valve is generally contained in the same pit necessary to conduct flow tests from hydrants, par­ renewing them is borne by the fire authority, the but it is still possible to find old hydrant installa­ For a small diameter main the internal pressure ticularly those on long mains of small diameter. water undertaker is entitled to allow other individ­ tions where the valve is in a separate pit. Such may reduce to not much more than atmospheric, One proposal, under consideration at the time of uals or concerns to use fire hydrants, and occa­ installations, however, are being gradually replaced. even when only one hydrant is opened, so that writing, is for hydrant plates to give information sionally damage is caused in this way. Under attempts to obtain more water by opening neigh­ about the flowrates available from the main rather Section 14(3)(b) of the Fire Services Act 1947, The introduction of pillar hydrants with their bouring hydrants would be futile. To illustrate the than the main diameter. when damage is caused to a hydrant as the result of advantages of greater conspicuity and higher point let us calculate the loss of pressure due to any use made of it with the consent of the water delivery rates is a distinct possibility for the future. friction (Pr) when 1000 lImin (L) are drawn from a undertaker when not used for firefighting or other Fitting them with a Storz coupling would facilitate 100mm main (d) which is 200m in length (I). An purposes of a fire brigade, the fire authority shall direct connection to large diameter hose.

34 Fire Service Manual Hydraulics, Pumps and Water Supplies 35 ... Many old installations have the hydrant positioned their own patterns, but it specifies the more impor­ 4.7 Types of Hydrant wedge until it is clear of the waterway. The spindle on top of the T-piece on the main in the roadway tant features of sluice valve and screw-down passes through the valve cover by means of the but most modern installations are either on mains hydrants and also gives dimensions for the open­ The principal types of hydrant at present in use in usual gland and stuffing box. rullling underneath the pavement or, where the ings of the surface boxes for use with such this country are as follows: main is in the roadway, on branch pipes which hydrants. This hydrant is hydraulically very efficient, and, bring them under the pavement. This has the 4.7.1 Sluice Valve Hydrant when the valve is open, gives a full waterway with advantage of causing the minimum obstruction of The spindles of all British Standard hydrants are a negligible loss of pressure. the roadway when hydrants are in use, and obviates screwed so as to close when turned in a clockwise This type of hydrant (Figure 4.3) is not placed the hydrant pit and cover being subjected to the direction, and the direction of opening is perma­ above the main, but alongside it on a short branch, 4.7.2 ScreW-down Hydrant strain from the passage of heavy vehicles which nently marked on the hydrant spindle gland. The the water flowing horizontally past the valve, and may make the covers difficult or impossible to cast iron parts of hydrants are treated with an not vertically as in the screw-down type. It consists This is probably the commonest type, being found open. However, to lay or re-lay mains in existing approved rust-proofing process. ofthree main castings, the inlet piece which is con­ in one or other of its forms in most parts of the highways means that mains and hydrants may be nected to the pipe, the sluice valve itself, and the country. It is attached directly to the main, which is located in roadways due to the lack of space on Hydrostatic tests which fire hydrants should with­ duckfoot bend leading to the outlet. The opening provided at the chosen point with a vertical branch pavements. Putting hydrants on branches to locate stand are also specified in the Standard, the manu­ and closing of the waterway is effected by means having a flange to which that of the hydrant is bolt­ them in the pavement may result in a "water qual­ facturer being responsible for carrying out such of a gate or wedge which may have gunmetal faces ed. A mushroom type valve (obturator) (Figure 4.4) ity hazard" by creating dead legs and also increas­ tests; the Standard also requires that hydrants shall or be coated in a vulcanised rubber compound to closes on a seating in the base of the hydrant body be of a pattern which, when fitted with a standard es costs. effect a seal. Rotation of the spindle raises the just above the inlet flange. The valve has a facing of BS round thread outlet shall be capable of deliver­ 4.6.3 Standardisation of Hydrants ing not less than 2000 IImin at a constant pressure of 1. 7 bar at the hydrant inlet. Note: this clause is Under the Fire Services Act 1947, the Secretary of concerned purely with the hydraulic efficiency State was empowered to make regulations for the of the hydrant and does not place an obligation standardisation of fire hydrants. At the time of on the water undertaker to ensure this pressure publication all hydrants are being installed to and flow are available from the main. British Standard 750: 1984 but a new European Standard, which will include pillar hydrants, is cur­ The British Standard recommends minimum open­ rently being written. The British Standard does ing dimensions for hydrant boxes and specifies concern itself with certain details of design but is that hydrant covers should be clearly marked by being amended to be more performance-based in having the words Fire Hydrant or the initials FH some areas. Manufacturers are free to develop cast into the cover.

Figure 4.3 Sec/ion through typical sluice valve hydrant.

1 Bolt - zinc plated 10 Bonnet 19 Screw - stainless steel 2 Washer - zinc plated 11 Bodylbonnet '0' ring 20 Spindle - frost valve Wedge _ 3 Operating cap 12 Body - integral seat 21 Sealing washer 4 Stem fixed valve sls 13 Washer - zinc plated 22 Spring - stainless steel 5 Washer - zinc plated 14 Bolt &nut - zinc plated 23 Washer - nylon 6 Wire clip 15 Stem nut 24 Outlet '0' ring 7 '0' ring - EPDM 16 Gate 25 Screwed outlet - grooved 8 '0' ring - EPDM 17 Gate seal 26 Cap - black polypropylene 9 Seal bush 18 Retaining dish 27 Label 'Fixed Valve - Test'

Figure 4.4 A typical modern screw-down type hydrant. (BS. 750) (Diagram courtes\' of Saint Gobain Pipelines plc)

36 Fire Service Manual Hydraulics. Pumps and Water Supplies 37 rubber or other suitable resilient material, while the made to open clockwise. In any cases of doubt, However, all recent double hydrants (Figure 4.6) 4.8.6 Hydrant Pit and Cover seating may be of gunmetal or other suitable mate­ both directions should be tried. All new British have a separate valve for each outlet, so the flow to Standard hydrants and the underside of their pit rial. The valve is attached to the lower end of a each can be controlled independently. The pit in which the hydrant is contained has above screwed stem, and is lifted from its seating by the covers are permanently marked with the direction it a metal frame and cover (Figure 4.7) which is of opening (Figure 4.5). rotation of a spindle into which the stem screws On old large capacity mains an outlet is sometimes flush with the roadway or pavement. British until it is clear of the waterway. Guides are provid­ found of the same diameter as the suction hose Standard 750 gives dimensions for all new hydrant ed to ensure accurate seating of the valve. The out­ 4.8.4 Outlets (Figure 4.7), enabling this to be connected pit covers and for surface box frames. British let is normally bolted to the upper end of a bend directly to the hydrant. This outlet can be found in Standard 5306 Part 1: 1983 gives details of typical leading from the valve seating. The hydraulic effi­ The link between ground hydrants and the hose is conjunction with a 65mm round-thread outlet as a forms ofhydrant pit construction for either precast provided by the standpipe, the base of which must ciency of this type varies greatly with the design of double hydrant. Adaptors are also available which concrete sections or cemented brick-work, and rec­ valve and outlet bends. connect to the outlet ofthe hydrant while the upper enable suction hose to be connected to a standard ommends that the depth of the pit should be such end provides the connection for the hose. All hydrant outlet. A suction outlet gives a significant that the top of the hydrant outlet is not more than hydrants are now fitted with the standard round­ 4.8 Hydrant Gear and increase in water output, especially when the nor­ 300mm below the surface of the road or Characteristics thread outlet (Figure 4.3) as detailed in British mal running pressure is low, but if, as a conse­ pavement. Standard 750. However, older hydrants may have quence oflarge demand, the pressure in the main is 4.8.1 Frost Valves to be fitted with a round-thread adaptor. reduced to below atmospheric, there is a strong 4.9 Hydrant Marking possibility that, in the vicinity of leaks, escaped Many hydrants on the larger sizes of main are When the valve of a hydrant is closed after use, a water may be drawn back into the main. Section 14(3)(a) of the Fire Services Act 1947 certain amount of water is trapped in the body of made with a double outlet, to obtain a greater makes water undertakers responsible, at the the hydrant between the valve and the outlet. This flow. On some older installations both outlets are There are instances on record where polluted expense of the fire authority, for causing the is a source of danger in a cold climate, as it may controlled by a single valve so that one outlet and toxic water has entered a main because of situation of every fire hydrant provided by the freeze and so prevent the valve being opened, or cannot be shut down independently of the other. the negative pressure created by a large fire­ undertakers to be plainly indicated by a notice or may crack the hydrant body. Where frost is likely With this type it is also impossible to get to work fighting demand. Re-lined mains also present a distinguishing mark, which should be fixed to a to be experienced, therefore, the hydrant should be with a single outlet without first blanking off the problem because, under negative pressure, the conspicuously sited post erected for the purpose. fitted with means for draining off the water. The other, and a second line of hose cannot be added lining may collapse. (In cases where it is not possible to site an indica­ simplest and most common way ofdoing this is by without shutting down the first line. These diffi­ tor post the indicator plate should be fixed to a a hole drilled in a small gunmetal plug screwed culties can be overcome by using a standpipe nearby wall.) Lamppost mounting, where permis­ into the body at its lowest point (as in Figure 4.5). fitted with a rack valve. If, at the start of opera­ 4.8.5 Small Gear sion has been granted, is being increasingly used. The disadvantage of this method is that water is tions, such a standpipe is connected to the outlet constantly discharging through the hole while the not immediately needed, a second line can easily Apart from standpipes, certain small gear for oper­ All recent hydrant plates conform to British hydrant is in use, though the loss is comparatively be brought into use when required by opening the ating hydrants is carried by all firefighting appli­ Standard 3251: 1976 and are made of vitreous small. Older hydrants are frequently fitted with rack valve. ances. This gear includes devices for lifting the enamelled mild steel, cast iron, aluminium alloy or either a manually operated drain cock or an auto­ hydrant cover and for operating the valve. The plastics. The plates are yellow, with all characters matic drain valve which opens as soon as the method of employment of such equipment is usu­ and digits in black (Figure 4.8). Where required the hydrant is shut down. ally obvious. yellow background may be of reflective material. 4.8.2 False Spindles

The spindle of a hydrant is usually made of stainless steel, bronze or gunmetal, and, in order to protect the squared top from wear caused by the loose-fitting hydrant key, a cap known as a false spindle (or operating cap), made ofa harder metal, such as cast iron or steel, is fitted over it and secured with a pin or screwed stud (see Figure 4.4).

4.8.3 Direction of Opening

Although British Standard 750 requires that all new hydrants should be made to open by turning Figure 4.5 The underside ofa typical hydrant pit cover Figure 4.6 Double hydrant with each outlet controlled by Figure 4.7 Hydrant filled with suction outlet. Note the the spindle anti-clockwise, in the past some were showing direction ofopening the hydrant. a separate valve. special draincock operated by a separate handle.

Fire Service Manual 38 Hydraulics. Pumps and Water Supplies 39 The Standard makes provision for four types of Class C plates are the same size as Class B plates • To ensure the hydrant is in fully operative indicator plate, as follows: and again the legend is at the discretion of the o condition. purchaser to suit the particular location concerned. The hydrant is marked conspicuously to Class A plates: Hydrant indicator plates for Class C plates are intended for use in any appro­ • aid quick location. general use except on roads of motorway priate situations, including motorways. • To increase the topographical knowledge standard. of operational personnel. Where water is fed into industrial premises for o Class B plates: Hydrant indicator plates for The counter arguments are multifarious and business purposes through a meter it is a common SINGLE CLASS 'N use on roads of motorway standard. practice for a by-pass to be fitted. In the event of include the following: the water supply on the factory side of the meter Class C plates: Indicator plates for emer­ SINGLE CLASS 'B' being required for firefighting, the meter can be The maintenance of hydrants is not a legal respon­ gency water supplies ('EWS'). by-passed, thus eliminating the frictional resis­ sibility of fire authorities, indeed Section 57 of the Class D plates: Indicator plates for meter tance through the meter. In addition, the water used Water Industry Act 1991 (duty to provide a supply by-pass valves. for firefighting does not register on the meter. The of water for firefighting) states under paragraph 3: position ofthe valve controlling the by-pass is gen­ 'It shall be the duty of every water undertaker to Both Class A and Class B plates can refer either to erally marked by a standard Class D indicator plate keep every fire hydrant fixed in any of its water single hydrants (indicated by the letter H) or to (Figure 4.8) so that a firefighter can open the valve mains or other pipes in good working order and, for that purpose, to replace any such hydrant when double hydrants (indicated by HO), and in each without loss of time. The figure on the plate indi­ DOUBLE CLASS 'N case the upper figure should denote the diameter cates the distance in metres between the plate and necessary". It is likely that, should fire brigades of the main in millimetres while the lower figure the valve. cease the inspection ofhydrants, water undertakers DOUBLE CLASS 'B' gives the distance in metres between the indicator would be obliged to take this task on and would plate and the hydrant. Due to cost factors, increasing use is being made pass on the costs of this work to fire authorities. of class A size plates to indicate open water o METER 0 It is possible that on some older plates the two fig­ supplies and by-pass valves with information dis­ BY-PASS A hydrant flow test using one of the specially TO designed flowmeters described in Chapter 2, can ures refer to inches and feet respectively but, as a played in the "main size" area of the plate. HYDRANT general rule, it can be assumed that if the figure in only provide a 'snapshot' of the hydrant's capacity the upper portion of the 'H' consists of two digits 4.10 In pection and Testing of at the time of inspection - it provides no guarantee 1 0 ~ 0 or more, the size of the main is in millimetres and Hydrants that a similar flowrate will be available the next the distance ofthe plate from the hydrant will be in CLASS'C' CLASS'D' time that it is used. The constantly changing pattern metres. If, however, the figure in the upper portion 4.10.1 Background ofdemands for water by customers (see Figure 4.2) results in varying pressures in the system, negating has a single digit, the main diameter is in inches Figure 4.8 British Standard hydrant plates o/Class A and the distance will be in feet. In the past, hydrant inspection and testing was car­ and Class B standard/or marking Single and double the value of data taken at a specific point in time. ried out based on the procedure described in hydrants. Class C plates indicate the position 0/ Water undertakers, seeking to comply with ever The appropriate National Grid Reference may be Technical Bulletin 1/1994. emergency water supplies. Class D plates denote the more stringent water quality standards, are becom­ position ofa meter by-pass valve. marked at the top of a plate (above the figure indi­ ing increasingly concerned over the discoloration cating the main diameter). Tests were carried out on a regular basis though the of mains water by the fire service testing hydrants. frequency was left to individual Fire Authorities to To a lesser degree, they are also concerned about The numerals may be removable, in which case determine. fully open and close the hydrant valve. The argu­ the 'wastage' of water such tests involve. they fit from the rear of the plate into slots, so that ments for and against such testing together with the figures are displayed through apertures in both When it had been thought necessary to conduct a recommendations for a future testing methodology The range of testing conducted by fire brigades the upper and lower portions of the letter H. flow test on a hydrant, because of uncertainty are summarised by the National Liaison Group in varies enormously and may have little regard for Alternatively, hydrant plates may have raised or about the capability of a main to deliver sufficient its publication "Guidance on Inspection, Testing guidance issued by manufacturers, but the often flush fixed letters and numerals. water in an emergency situation, one of the specif­ and Abandonment of Fire Hydrants". The contents used method of 'cracking the valve' (to see that the ically designed flowmeters described in Chapter 2 of this document are reproduced, largely in the main has water in it) is viewed by water engineers Class B plates are larger than Class A plates, hav­ had been employed. original form, in paragraphs 4.10.2 to 4.10.7. as having no engineering value. Indeed it is felt ing additional space below the H or HD for the that this partial opening may cause more prema­ inclusion of suitable legend to indicate the location However, the Government's initiative on Best 4.10.2 Reasoning behind the Fire ture wear to the spindle and seat than if it was left of the hydrant, the legend being at the discretion of Value has recently prompted the CACFOA Brigade Testing of Hydrants in the closed position. In practice, fire brigades the purchaser. This is necessary because fire Benchmarking and Best Practice Project Team to report more defects during testing than at other hydrants are not normally located within the con­ challenge the need to conduct frequent testing of The three popularly stated principal reasons for the times and it is possible that the test process itself fines of motorways. fire hydrants and, in particular, the stated need to fire service testing hydrants are: has caused many of the defects. The five known

40 Fire Service Manual Hydraulics, Pumps and Water Supplies 41

> U.K. hydrant manufacturers/suppliers have been weighs them against its legal obligations and the In line with the National Guidance Document on valve to allow a small amount of water to flow consulted and none requires an annual wet test. benefit to society of being able to fight fires. the Provision of Water for Firefighting, fire (equivalent to a domestic tap). A blank cap is to be brigades and water undertakers are encouraged to fitted in the standpipe head, or the valve in the The requirement to provide adequate training for Both industries have an obligation to the public and move away from the flow testing of hydrants and head closed and the hydrant fully opened. Whilst service hydrant test/maintenance personnel under their customers to ensure that they discharge their use other methodologies. This is not seen as a test under pressure, all joints are to be visually the Highways Works Regulations removes valu­ obligations effectively and efficiently. In seeking to for maintaining a hydrant and, for the reasons inspected for signs of leakage and only those leak­ able time and effort from fire service core business achieve these objectives, water undertakers and fire highlighted in paragraph 4.10.2, there is little ages that would impair the hydrant for firefighting activities. The testing of hydrants may result in a brigades should review the content of their policies purpose to this test. As a result, the flow test is purposes, or cause a hazard, should be reported to higher incidence of accidents to fire service per­ in these areas. They should test jointly the validity not included as one of the examinations of the water company. The hydrant is to be turned off sonnel and vehicles due to increased road mileage of continuing historic practice against their current hydrants. without excessive force and the standpipe and the activity on the roadside. Increased fuel obligations and common objectives. removed. usage is both expensive and environmentally Above Ground Examination unfriendly as is the increased wear and tear on 4.10.4 Risk Assessment Approach This test should only be carried out where there vehicles. Time spent by fire service personnel This will involve a visual inspection of the hydrant is reason to doubt the hydrant's integrity or that on hydrant inspection and testing is lost to other Risk assessment is a term that both the fire service frame, cover, surface surrounding the hydrant and it is at an interval recommended by the hydrant causes such as for example community fire safety and water undertakers are becoming ever more the hydrant indicator plate. The period between manufacturer. education, training, etc. familiar with. The culture of the past which inspections should be risk assessed and take into required the monotonous inspection and testing of account such likely factors of area location and 4.10.6 Recommended Procedure 4.10.3 Objectives and Issues for equipment is now being superseded by the modern risk, hydrant position, age, material, previous his­ following use by Fire Brigades Consideration in Formulating day risk assessment approach and this is very tory, etc. of Hydrants at Operational Policy much encouraged through the National Guidance Incidents Document on the Provision of Water for E.g. For a hydrant situated in the pavement of a The prime concern of water undertakers appears to Firefighting. The advantages of this approach residential urban area free from vandalism, the fire Following use at an operational incident, the be the impact of hydrant inspection, testing and being applied to the inspection and testing of brigade may determine to inspect on a 1-2 year opportunity should be taken to record the hydrant flow testing activities by fire brigades on the qual­ hydrants will ensure that hydrants are monitored basis, whereas a hydrant set in a country lane that number/location and to note any defects which ity of water in their distribution systems. The and maintained to meet the requirements of has regular farm traffic driving over it may need would otherwise have been found during a prime concern of fire brigades appears to be the Section 57 of the Water Industry Act 1991 and at inspecting every 3-6 months to ensure it is clear of hydrant examination highlighted above. This will validity of hydrant testing and inspection and the the same time provide the following benefits to mud, etc. reduce the time fire brigades have to spend cost of repairs. Local discussion on the relative both fire authorities and/or water companies. inspecting hydrants and will provide a record of benefits of these activities may help undertakers Below Ground Examination when the hydrant was last used. This may be par­ and fire brigades to review their polices. • Significant reduction in hydrant repairs and ticularly important should a third party have used maintenance budgets. This will involve the visual inspection of the or damaged the hydrant and the fire brigade The various objectives of fire brigades and water • Reduced administrative costs. hydrant pit and the hydrant itself. Defects which receive an invoice for the hydrant repair. Water undertakers in relation to fire hydrants are: • Reduced risk of causing discoloration of would affect the ability to deliver water for fire­ undertakers would also welcome being notified drinking water. fighting purposes or create a hazard should be where a hydrant has been used at an operational • To ensure that there is access to water • Resources redirected to more proactive reported immediately. The period between inspec­ incident as it will aid their monitoring of usage for firefighting purposes. tasks (eg community fire safety). tion should be risk assessed and take into account and leakages. • To maintain hydrants efficiently at • Improved liaison arrangements between the area location and risk, hydrant position, age, mate­ minimum cost. organisations. rial, previous history, etc. 4.10.7 Maintenance Costs • To minimise, if not eliminate, the risk of disruption and discoloration of water 4.10.5 Recommended Future Hydrant E.g. For a hydrant situated in the pavement of a Cost is driven by a number of factors, but supplies. Inspection and Testing residential urban area free of vandalism, the fire includes: the number of hydrants in a fire brigade Methodology brigade may determine that an inspection should area, inspection and testing policy, direct mainte­ There is a balance of risk, cost and benefit to soci­ be carried out every 2-4 years, whereas a hydrant nance practices and administrative procedures. ety in the continuing provision and maintenance of It is recommended that future inspection and test­ that regularly silts up may require inspecting every There will be a wide range of local circumstances a hydrant on a distribution system. The fire ing of hydrants should consist of one of the three 6 months. that contribute to current practice across the brigades trade off the benefit of being able to have examinations: country. The following points may help water access to water in the event of a fire against the Wet and Pressure Test undertakers and fire brigades to question and, ongoing costs of providing and maintaining the • above ground therefore, improve current practice through liai­ hydrant. The water undertaker carries the risk of • below ground The hydrant test is conducted by fitting a stand­ son and agreement. interruption or discoloration of supplies, but • wet and pressure test pipe to the outlet and then partially opening the

42 Fire Service Manual Hydraulics. Pumps and Water Supplies 43 Hydraulics, Pumps and p r Water Supplies Number of Connected Hydrants "Safety at Street Works and Road Works -A Code of Practice", available from TSO. • Review through a risk assessed approach the number of hydrants required for a given area. • Review policy for the provision of new Chapter 5 - Pumps and Primers hydrants. • Consider a phased programme of abandon­ ment spread over a number of years. • Consider a policy to abandon hydrants as an alternative to repair. Introduction centrifugal pumps, both vehicle mounted and • Consider opportunistic abandonment of portable, and their cooling and priming systems. hydrants during water undertaker mains Essentially, a pump is a machine, driven by an Chapter 6 deals with practical pump operation. renewal or rehabilitation schemes. external power, for imparting energy to fluids. Power may be provided by the operator, as in hand 5.1 Operating Prioci e of Maintenance Practices pumps and hand operated primers, or by coupling on-Centrifugal IUp the pump to a suitable engine or motor. This • Consider standard repair packages. Chapter is principally concerned with the latter, Non-centrifugal pumps used by the Fire Service • Allocation of repair tasks between water although it deals with the general principles of all are based on one of two operating principles. undertakers and fire brigades. types. These are: • Economies of scale of operations with other water undertakers or brigades. The Fire Service has come to rely mainly on cen­ 5.1.1 Positive Displacement Pumps • Economies of scale through standardisation trifugal pumps and these, together with the primers or joint purchasing. necessary to get them to work from open water, are These usually have a reciprocating piston which • Reduce inspection and testing frequency described in detail. The first part of the Chapter makes an air- and liquid-tight seal with the cylin­ based on a risk analysis. looks at the principles of operation of all the types der in which it moves. The principle of operation • Timing of inspection and repair throughout of pump which may be used by brigades and then of the pump is shown in Figure 5.1. the year to match available resources. progresses to a more detailed examination of

Administrative Procedures

• Preparation of accounts, e.g. monthly, quarterly, etc. • Formulation of fixed prices for standard repaIrS.

4.11 ew Roads and treet Works Act 1991

Sections 65 and 124 of this Act require anyone carrying out work under the Act to do so in a safe manner as regards the signing, lighting and guard­ Valve ing of the works. This has implications for the fire A service when hydrant testing and inspections and other minor works by arrangement with water authorities are undertaken. The regulations empha­ sise the importance of making sure that all work­ ers engaged in street and road works are safe and that drivers and pedestrians are made aware of any Upward Stroke Downward Stroke obstructions well in advance. Details of how to comply with the regulations are explained fully in Figure 5.1 The principle o/the reciprocating pump.

44 Fire Service Manual Hydraulics. Pumps and Water Supplies 45 On the upward stroke of the piston a reduced pres­ Water under pressure from another pump (the pro­ The quantity of water lifted by an ejector pump sure is created in the cylinder causing the inlet pellant) emerges in jet form from a small internal will vary according to: valve (A) to open and the outlet valve (B) to close, nozzle and enters the delivery tube via an opening so that air or water is drawn into the cylinder known as the throat. The narrowest part of the (i) the height of the ejector above the water through the inlet valve. On the downward stroke throat is slightly larger than the orifice of the noz­ level; the inlet valve closes and the contents of the cylin­ zle and is separated from it by a gap which is open der are forced, under positive pressure, through the to the surrounding fluid. As the jet passes the gap (ii) the height of the discharge point above or outlet valve. and rapidly expands, the consequent fall in pres­ below the ejector. sure at the throat causes surrounding water at Application of the reciprocating pump principle, atmospheric pressure to join the stream. If the discharge point is above the ejector, the out­ though with a more efficient valve arrangement, put will be reduced appreciably, and it is therefore may be found in the stirrup pump (described fully in Figure 5.3 shows, in diagramatic form, a typical important to keep the discharge outlet as low as the current Book 3 of the Manual of Firemanship: example of an ejector pump which may be sus­ possible. The actual amount of water pumped out Hand pumps, extinguishers and foam equipment) pended above the water line and propelled by water is normally the difference between the input and and in certain fire pump primers which will be supplied via a standard instantaneous coupling. the total discharge. It is possible for the water described later in this Chapter. being pumped out by the ejector pump to be recir­ Ejector pumps are light and easy to handle, and culated via the primary pump, thereby providing 5.1.2 Ejector pumps can be used in situations where it is undesirable to the necessary propellant for the ejector pump. The use conventional pumps, e.g. due to hazardous surplus water may then be discharged by other There are several varieties of ejector pump in use fumes. Furthermore, their operation is unaffected primary pump deliveries. in the Fire Service. This Section refers to those by an oxygen-deficient atmosphere which would used for pumping water. The exhaust gas ejector cause an internal combustion driven pump to stall. Another type of ejector pump is the submersible primer, which works on a similar principle, is dealt Once set up they require little or no attention type, examples of which are shown in Figures 5.4 with separately in Section 5.4.2. except the removal of debris that may have col­ and 5.5, which may be used for pumping out water lected in the suction strainer. The primary pump from depths greater than the maximum suction lift. Figure 5.4 A typical small hosereel propelled submersible The principle of operation of an ejector pump, supplying the water to the ejector pump can be The pump may rest on its base, which is the ejector pump. (Courtes" oj West Midlonds hre Sel1,jce) which is referred to in Chapter I, may be more placed in a convenient and safe position e.g. away suction inlet and is fitted with a low-level type of fully appreciated by reference to Figure 5.2. from smoke and other hazards. strainer. The body of the pump has an inlet for water from the primary pump, and a discharge out­ let. The example shown in diagrammatic fOlm in Outlet Figure 5.2 Figure 5.5 has a two-stage ejector nozzle incorpo­ Connection The operating principle ofthe rated and its performance characteristics are =~~ ejector pump. shown in Figure 5.6. Fluid & Propellant u.&.I.a.:':.I.::~ Propellant ~======::::::::=~~~~~ Example 1

What will be the total amount of water discharged from the submersible type ejector pump when Two Stage Figure 5.3 Diagram of operating at a lift of 8 metres if the input is 864 Ejector Water Inlet a typical suspended litres per minute at 7 bar? Nozzle Connection type ejector pump. Inspection of the appropriate graph indicates that the total output will be approximately 1875 litres per minute so that the amount of water pumped out Base will be about 1000 litres per minute.

The maximum possible lift for the two-stage type of pump is about 18m.

Figure 5.5 A submersible type nvo-slage ejector pump in diagrammatic(orm.

46 Fire Service Manual Hydraulics, Pumps and Water Supplies 47 A centrifugal pump consists essentially of a spin­ Figure 5.8 Simplified 17 diagrams showing the "ntq ning circular metal casting with radial vanes, 16 ...... -'7e~1 called the impeller (Figure 5.7), enclosed in a cas­ operation ofa single 15 """'-.. ~ "1If~ stage centrifugal pump. 14 I""...... ing. Water at the centre of the impeller is thrown ~ 9~$ ,~ Left: without guide 13 ""'-it outwards by centrifugal force as the impeller L ,.(-1/.. ~ >q~ vanes. Right: with 12 rotates and discharged at the periphery thereby '~ ~~~~ guide vanes. ~"""-. causing a partial vacuum to be created at the cen­ Guide 86"1 I ""'" '''4>,,/ '" Vanes 1~ ...... Ir.--~1It. '" ~ '" tre. This causes more water to be forced into the I "'t~ ...... 8.q \ impeller from the supply source so that flow from :S 8 " 7 -...... : "- \ the centre of the impeller to its periphery is con­ I'. , 6 I tinuous...... 5 ..." 4 The action of the impeller in thrusting water out­ 3 r I Impel/er 1400 1600 1800 2000 2200 2400 2600 Water wards naturally creates considerable turbulence Inlet Water 1500 1700 1900 2100 2300 2500 2700 and friction and, as these factors cause some ofthe Inlet Total discharge (litres per minute) power used to drive the pump to be wasted and so reduce pump efficiency, it is important to min­ Figure 5.6 Performance characteristics. imise their effect. This is achieved by careful design of the casing, and possibly by the introduc­ Figure 5.9 tion of a system ofguide vanes called a diffuser, to A typical set ofpump 16 FOR TEST CONOmONS 5.2 Operating Principles of ensure that flow is, as near as possible, stream­ characteristics for SEE 05474 Centrifugal pumps lined. Figure 5.8 shows simplified diagrams of a different lifi conditions 14 centrifugal pump with and without guide vanes. As as presented in the ~~ Centrifugal pumps are the most widely used for water moves away from the centre of the impeller, manufacturer et 12 brochure. <{ firefighting. They are unable to pump gases (and and travels on its way to the outlet, the area of e. therefore have to be primed), have no valves, pis­ cross-section of the path along which it passes C 10 <{ tons or plungers and do not work by displacement. increases, thereby causing the velocity and kinetic w Instead they make use of centrifugalforce (i.e. the energy of the water to decrease but with a conse­ ::I: 8 ....J force which a rotating body experiences tending to quent increase in pressure. With many pumps a ~ make it flyaway from the axis ofrotation) in much further increase in cross-sectional area ofthe chan­ 0 ~ 6 the same way as a spin dryer uses centrifugal force nel occurs in a snail shaped part of the casing to remove water from wet clothes. called the volute. 4 LIFT 7.5m 3.0m FLOODED 2 400 800 1200 1600 2000 Figure 5.7 FLOWRATE (L/MIN) Vanes Water Discharged The construction of at Periphery a typical impeller. The changes in energy which the water undergoes means ofwhat is known as the pump characteristic as it passes through the pump and the subject of (Figure 5.9) for any given pump/engine combina­ pump efficiency are both discussed in Chapter 1. tion and is usually available, in this form, from the pump manufacturer. 5.2.1 Pump Characteristics Although it is possible to produce a characteristic For effective use of a fire pump in an emergency for any given engine speed, the most useful, for situation and particularly in pre-planning, it is practical purposes, is the one obtained at the max­ important for firefighters to know the maximum imum throttle setting (but probably with an upper output in litres per minute (l/min) of which the limit imposed on engine r.p.m.) which therefore pump is capable at any given operating pressure. indicates the limits of performance for that partic­ Water Inlet This information is best presented graphically by ular pump.

48 Fire Service Manual Hydraulics, Pumps and Water Supplies 49 > Inspection ofthe characteristics shown in Figure 5.9 of lObar. The pump whose characteristics are relatively low pressure after passing through the called a regenerative type, IS employed for that indicates that the pump develops maximum pres­ shown in Figure 5.9 is marketed as a 10/10 first stage only, or at high pressure (up to about 55 stage. sure when the discharge from it is zero, that the because (at 3m lift) it is easily able to deliver bar) after passing through subsequent stages. It is pressure decreases as the discharge increases and 1000 (10 x 100) IImin at lObar. It might equally also possible to deliver water at both high and low At least one major pump manufacturer has, for that the maximum discharge is obtained when oper­ well have been described as a 1400 IImin pump pressure simultaneously. safety reasons, a design policy for firefighting ating against minimum pressure. In Chapter 3 it was because it is easily able to deliver this amount pumps such that, at any given engine speed, the explained that suction lift affects pump perfor­ at 7 bar. Vehicle mounted pumps are normally two-stage and first stage pressure cannot exceed one quarter of mance, so it is important, when data on performance designed to be driven through the power take-off of the second stage pressure. is presented, to specify the relevant lift conditions. Care should be exercised, when comparing the engine of a stationary appliance. The speed at Figure 5.9 shows three characteristics - for lifts of pumps on the basis of their outputs, to ensure which the pump can run is, therefore, conditioned The use of the regenerative impeller not only 7.5m, 3.0m and zero (for example with the com­ that these outputs are quoted at the same oper­ by the capability of the engine from which it is results in a saving on the wear and tear of the pound gauge reading zero as might be the case in a ating pressure. taking its power. Pumps designed for high speeds, moving parts but makes a speed increasing gear water relay). If only a single characteristic is pre­ however, may have a speed-increasing gear built unnecessary. A regenerative impeller is shown in sented, or ifthe data is given in a different way, such 5.2.2 Multi-stage pumps into them or at the power take-off. Figure 5.1 0 and its operating principle may be as by quoting the maximum output at a particular understood by reference to Figure 5.11. pressure, it will usually be for a lift of 3m. Pumps with a single impeller, as described above, Portable pumps are invariably single stage. are capable of developing pressures ofanything up The regenerative impeller has, at its periphery, a It is because the pressure available from a pump to about 20 bar, depending on the particular design 5.2.3 Regenerative (peripheral) pumps ring of guide vanes and is enclosed in a casing (for any given f1owrate) decreases with increasing and the f10wrate required. If higher pressures are which fits closely around the central part of the lift, that, in a water relay supplied from open water, required, for the operation of high pressure A two-stage pump consisting of two identical impeller but leaves a channel around the part con­ it is recommended that the distance from the base hosereels for example, there are two methods by impellers would develop a second stage working taining the vanes (see Figure 5.11). Water enters pump to the first intermediate pump should be which they might be achieved with a single pressure of approximately twice that of the first this channel via an inlet, drops to the base of the slightly less than the spacing between the remain­ impeller of this type: stage, and, for that second stage pressure to be guide vanes, and is then thrown outwards between der of the pumps. high enough for hosereel operation, very high the vanes by centrifugal force. It then moves to the (i) by increasing the speed of the impeller; engine speeds would be required. This, in turn, base of the vanes again and the process is repeat­ When interpreting pump characteristics it should (ii) by increasing its diameter. would mean that the first stage pressure could be ed. This happens several times whilst the water is be appreciated that: dangerously high for use with normal low pressure dragged round in a circle by the rotating impeller, Increasing the speed of the impeller can only be firefighting hose and branches. Therefore in order until it finally reaches the outlet. The water there­ (i) 0 combination of pressure and flow achieved by increasing the speed of the engine and to achieve a high second stage pressure at a mod­ fore follows a spiral path around the channel. The represented by a point beyolld the it may be neither practicable nor desirable to do erate pump speed a different sort of impeller, cumulative effect is to develop a sufficiently high characteristic line is achievable. this. Increasing the diameter is comparatively inef­ ficient and would make the pump more bulky. (ii) Combinations of pressure and flow Hence, to achieve a high outlet pressure, it is bet­ represented by points on the ter to use a multi-stage pump, i.e. a pump with two characteristic line are achievable or more impellers in series. The impellers are dri­ only at maximum throttJe/r.p.m. ven by the same rotating shaft with water fed from the periphery of the first impeller to the entry to (Hi) Combinations of pressure and flow the second etc., so that, neglecting friction losses, ~+-~Outlet represented by points within the the pressure increasing ability of the centrifugal characteristic line are achievable at pump is applied a number oftimes. Ifthe impellers reduced th rottle settings. are of the type already described, then several stages are required to achieve the high pressures It is common practice for manufacturers to quote needed for hosereel operation and, although pumps pump performance in terms of the maximum out­ of this type are in use, most fire service pumps put available at a specific pressure - typically consist of only two stages and use a different type 7 bar - so, for example, a 2250 IImin pump is of impeller for the second stage. This type of described as such because it is able to achieve impeller, called the regenerative (or peripheral) Figure 5. j 0 a (above) A regenerative impeller. (Courtesy a/Fire Se/vice College) that flowrate when operating at this pressure. type, is described in the next section. However, it is becoming more common, because of proposed European standards, for manufactur­ Practical multi-stage pumps have the important Figure 5. jOb (right) Components ofa two-stage pump. ers to quote pump output at an operating pressure advantage that water may be discharged at (Courlesl' r,( Ha(e Products t;urope)

50 Fire Service Manual Hydraulics, Pumps and Water Supplies 51 of227 l/min at 24.1 bar at an engine speed less than Figure 5.14 (i) represents the LP (i.e. change over PERIPHERAL IMPELLER the maximum recommended by the manufacturer valve open) mode but with no discharge. Once a INLET OUTLET for continuous duty running. temperature in excess of about 42 degrees Celsius is attained the thermal relief valve (TRY) opens to Yehicle mounted pumps, because of the need to allow a certain volume of water to escape and a provide a choice of pumping pressure, are almost corresponding amount of cold water to enter. invariably of the multi-stage type. Figure 5.13 shows a sectioned diagram of the recently intro­ Figure 5.14 (ii) shows the change over valve closed duced GODIYA World Series two-stage type of and no discharge from either delivery. If the pump pump. It has a normal centrifugal impeller as the speed is high enough to cause pressure in excess of first stage and a regenerative type for the second. 55 bar in the HP stage the pressure relief valve Figures 5.14 (i) to 5.14 (viii) illustrate the various (PRY) opens and allows circulation from the HP to modes of operation of the pump. the LP stage. Again the TRY will open, if neces­ sary, to prevent excessive temperatures. Whenever HP operation is required the Change Over Yalve must be closed, otherwise water from Figure 5.14 (iii) shows HP only operation. The the HP stage will simply escape back to the LP TRY remains closed but the PRY will open if stage. excessive pressure is attained in the HP stage.

Under conditions of no discharge It IS Important Figure 5.14 (iv) shows simultaneous HP and LP that a limited escape ofwater takes place otherwise operation. The PRY and TRY remain closed. overheating will occur. Figure 5. JJ (leji and above) Diagram showing the operating principle o/the regenerative pump. pressure' for hosereel operation and water-fog production but at a pump speed of the order of 55 3000 rpm. The characteristics, at given engine ~ speeds, for a typical two-stage pump are shown in 50 Figure 5.12. \~, 45 3m sUC1ion lift _High-pressure stage 5.3 Vehicle Mounted Fire Pumps _Low-pressure stage 40 \\ 5.3.1 Examples of vehicle mounted pumps \\' At the present time, the specification for vehicle mounted pumps is that of JCDD/3/1 as amended :1\ \ in October 1985. However, a draft European 5 \\\ Standard, prEN 1028, is in the course of prepara­ tion and eventually a new JCDD specification will 0 \ be based upon it. , 3400 .... JCDD/3/l requires that the low pressure stage of a 5 , , 3000'l'!' multi-stage pump should be capable of delivering a -~~ 0 minimum of2270 l/min at a pressure of6.9 bar and, "'~ 2500 - simultaneously, the high pressure stage a minimum hS, 5 - \ 0 o ~ ~ ~ ~ ~ - ~ - Figure 5. J2 (right) Performance characteristics for a DISCHARGE (l/MINI Figure 5. J3 The Godiva World Series ty.!o-stage pump. (Courlesy of/-Iale Products Europe) typical two-stage vehicle mounted pump.

Hydraulics. Pumps and Water Supplies 53 52 Fire Service Manual Figure 5.14 Modes Figure 5.14 (v) shows LP operation but with the involved in the high pressure stage require the water 5.14 (i) 5.14 (ii) Hose Reels Hose Reels ofoperation ofthe change over valve closed. The PRY opens to pre­ to be filtered before it enters that stage. The location ClOsed Ciosed Godiva World Series vent excessive pressure in the HP stage. of this inter-stage filter is shown in Figure 5.14. Pump. (Coul'lesy q(/-Iale Products Europe) Figure 5.14 (vi) shows both HP and LP deliveries Figure 5.15 shows a view of a typical pump bay and the change over valve open so giving LP oper­ with the change over valve indicated. ation in both lines. Figure 5.16 shows a diagrammatic representation Figure 5.14 (vii) shows the HP delivery closed and of a multi-stage vehicle mounted pump of a type the LP delivery open. With the change over valve which is being used by a number of brigades. HP open, circulation from the HP stage is allowed so is achieved by the water passing successively

LP MODE. NO DISCHARGE NO DISCHARGE. PRV OPEN HIGH SPEED there will be no possibility of excessive tempera­ through three additional conventional impellers. tures. Although, traditionally, the controls, instrumenta­ 5.14 (iii) 5.14 (iv) Host! Reels Figure 5.14 (viii) shows the LP delivery closed but tion and deliveries for a vehicle mounted pump H p, Dlscha~g ng the HP delivery and the change over valve open. have been situated on, or close to, the pump itself. Under these circumstances only LP is available at recent Health and Safety legislation has resulted the hosereels - a mode of operation suitable for in increasing concern about the noise level to damping down. which the pump operator is exposed. Because the solution of this problem, by the wearing of ear One disadvantage of the modern regenerative defenders, makes communication with other per­ impeller is that the extremely close clearances sonnel difficult, some appliance manufacturers are

HP and LP SIMULTANEOUS MODE HP OPERATION Engine Change Low Compound High speed over pressure gauge pressure 5.14 (v) 5.14 (vi) Indicator valve gauge gauge Hose Reel Closed

L.H. R.H. hose­ ~!J.-:~H hose­ reel reel

LPOPERA N HPUNES

5.14 (vii) 5.14 (viiQ l1o$e.Reels Hose ~ b Closed LP Di"".l'Ql

'Ch:lr:gd Over Valve 0 Pre-SSlore r Inter· Stage Fitter ReI ~fValvQ ~ Thermal Rel r Valve i---- r

l.P MODE. LP DISCHARGE ONLY ~P MODE LP OISCkAROE FROM HOSE REaS ONLY Figure 5.15 A typical pump bay. (Courles)' of/-Iale Producls El/rope}

54 Fire Service Manual Hydraulics, Pumps and Water Supplies 55 Figure 5./6 Each primer will discharge approximately 1 litre of (b) Water ring primers Diagrammatic water during a complete priming operation and representation ofa a characteristic "popping" noise will be heard. A water ring primer is a form of positive displace­ Needle Roller Bearing L.P. Impel/er H.P. Casing H.P. Impel/ers multi-stage pump. Once pump pressure is generated it is communi­ ment pump. It is widely used in the Fire Service, (Diagram courte,yof cated to the back of the piston which lifts off the and is engaged and disengaged either manually or Rosenbouer) cam so that the primer effectively disengages automatically. (Figure 5.17 (iv)). The principle of operation is again very simple Like a number of continental pumps, the Godiva (see Figure 5.18). A vaned impeller with a hollow Pump Shaft World Series pump utilises twin horizontally centre rotates in an elliptical housing around a sta­ opposed reciprocating primers. tionary hollow boss which is a projection from the housing end cover. This boss has four ports in its The engine speed may be controlled automatically periphery, which communicates with the primer but, where it is not, the operator should take care suction and delivery connections. not to exceed the speed recommended by the manufacturer - typically 2500 rpm.

(I) Pump at rest pi) Induction stroke Alr dnJWn m pump casting and lIIJdlon Pump Gland Pump Gland Pump Gland L.P. Casing Priming ,---..... valve

Inlet vDIII... locating the pump in a soundproof booth with con­ The pnming devices most commonly found on Exha trol levers etc. passing through mbber gaiters to vehicle mounted pumps are: ~-======::;~~--tt-lYe minimise the amount of sound transmitted. Vehicle Plalon returns due to apring lOAd exhausts should obviously discharge at a point well • reciprocating; away from the pump operator. At least one brigade • water ring. has specified that its 4500 IImin pumps should be mounted centrally but with the operator's control (a) Reciprocating primers panel, pump inlet and outlets at the rear of the appliance. The series of diagrams in Figure 5.17 show the (lli) Exhaust stroke (iV) Pump Primed Pressurised System principle of operation of a simple reciprocating Air dlKharge 10 Dtmoeph nt All_la clOMd

5.3.2 Primers for vehicle mounted pumps piston primer. It consists of a small piston which is Atmospheric driven by an eccentric cam on the main pump drive Preeaunt Before a centrifugal pump can be got to work from shaft. (See also Figure 5.13.) On the induction Piston lifted by means of open water, the air in the suction hose and pump stroke (Figure 5.17 (ii», a vacuum is created in the eccentric on shaft casing must be expelled so that atmospheric pres­ priming valve body. Atmospheric pressure causes sure will force the water up into the pump. This the automatic priming valve to open and air is process is called priming, and a device has to be drawn, by the piston, through the inlet flap valves provided for this purpose. It may be operated either from the suction tube. On the exhaust stroke manually or automatically, according to the type of (Figure 5.17 (iii», air in the primer is forced out centrifugal pump used. through the exhaust flap valves to atmosphere. PllIlon lifta off dU41 to pump PR......

Figure 5./7 A reciprocating primer.

56 Fire Service Manual Hydraulics, Pumps and Water Supplies 57 Figure 5.18 Figure 5.19 General A water ring primer. layout ofa closed Discharge Ports circuit appliance I--- cooling system. Engine coolant Water Ring Stationary Boss (Engine coolant: Power I- Radiator orange. Hydraulic oil: Engine take off Automatic Fire green. Fresh lvater: gearbox .... pump I- blue) H.X. ISup. , I H.X. r1---

Filter 11 I I Gearbox 01l9ystem I • I

Rotating Impeller Suction Port 5.4 Portable pumps and stipulates a single-stage centrifugal pump, cou­ pled direct to the engine, to keep weight down. 5.4.1 Examples of portable pumps Although there are a number of pumps which (a) General come within this specification, manufacturers have tended to design and build to brigade require­ When pnmmg commences and the impeller 5.3.3 Cooling systems for vehicle mounted All brigades have, as part of their pumping capac­ ments. This has led to anomalies, e.g. units called rotates, the liquid in the housing is compelled by pumps ity, pumps which can be manhandled into position. LWPs which are heavier than the specification and centrifugal force to move outwards and follow the These are usually carried on appliances and are some that are lighter with, ofcourse, performances contour of the housing, thus forming a hollow Because an appliance has to use its engine whilst especially useful in areas where vehicles cannot to match. Figure 5.22 shows a variety of portable elliptical vortex. This liquid "ring" rotates in the stationary, its normal closed circuit cooling sys­ get to water supplies. All have carrying frames and, pumps with performances ranging from 250 J/min housing with the impeller and as it rotates from the tem, which also indirectly cools the automatic depending on their weight, can be transported by at 3.8 bar to booster pumps capable of delivering minor diameter of the ellipse towards the major gearbox, is specially augmented by making use of two or four personnel. Most are driven by internal 2300 I1min at 7 bar. diameter it moves radially outwards between the water from the fire pump. combustion engines but a few are electrically impeller vanes. After it passes the major diameter powered. (b) ElectricaJ)y powered pumps and rotates towards the minor diameter it moves Figure 5.19 shows, in schematic form, the general radially inwards. As the liquid moves radially out­ layout of an appliance cooling system. A supple­ The current specification for portable pumps is Electrically powered pumps used in the fire ser­ ward between the vanes air is drawn into the mentary heat exchanger, adjacent to the gearbox that of JCDO/30 as amended in 1976. However a vice will generally be of low capacity and are usu­ impeller through ports in the centre which com­ coolant heat exchanger, is fitted to ensure the cor­ draft European Standard is in the course ofprepa­ ally employed for pumping out where other types municate with the suction ports in the central sta­ rect working temperature when the vehicle is ration and eventually a new JCOO specification are not suitable: e.g. in basements where it is diffi­ tionary boss and so with the pump suction line. As stationary and the fire pump is in use. Water is will be based upon it. JCOO/30 defines a light­ cult to disperse exhaust fumes. the liquid moves inward this air is forced through taken from the delivery side of the pump, passed weight portable pump (LWP) as a self-contained the impeller ports into the "discharge" in the cen­ through the supplementary heat exchanger and petrol-driven unit having a nominal output of at A typical example of a submersible pump used by tral boss. returned to the suction side ofthe pump. This sup­ least: a large county fire and rescue service is shown in ply from the pump can also be used to cool the oi I Figures 5.20 and 5.2 I. Since the impeller is located centrally in the ellip­ in the power take-off. The water is routed firstly to Type I- 360 I1min at 5.5 bar, or tical housing there are two pumping actions in the power take-off and then to the supplementary Type 2 - 1130 I1min at 7 bar. This pump weighs only 17kg and operates from a each revolution. heat exchanger before returning to the pump. I 10volt generator supply. It can pump from a sub­ It should be capable ofbeing carried by two persons merged depth of 20m and provides a maximum The appropriate engine speed for the operation of and not weigh more than I 25kg. The specification output of 550 J/min. It can pump water down to a water ring primers is about 2500 rpm. also lays down an exhaust ejector priming system level of 2mm.

58 Fire Service Manual Hydraulics, Pumps and Water Supplies 59 The pump can also be used to provide a firefight­ 5.4.2 Primers for portable pumps ment primer is shown in Figure 5.22 ii. H wever, ing jet in excess of 10m at maximum output for the majority of portable pumps employ a primer such purposes as firefighting at sea. Water ring and positive displacement primers. based on the ejector pump principle, described ear­ 1iEl1----H which have already been described in the section lier in this Chapter, and use the exhaust gas from As with all electrically driven appliances involving on vehicle mounted pumps, may also be found on the engine as the propellant. Figure 5.23 illustrates water, electrical integrity is vital and firefighters portable pumps and an example ofa small portable the principle of operation. should be careful to ensure that safety instructions pump with a manually operated positive displace- for use and testing are carried out correctly. (Guidance is contained in DCOL 11/1988 ­ Fireground Electrical Equipment: Safety Requirements.) A .,.~/ o

o

G ---au;

Key to diagram above

A Air valve B Outer casing of corrugated steel C Built-in motor protector o Patented shaft seal E Stator with class F insulation

Figure 5.20 (above) Afirefighter carrying an electricallv F Impeller of chromium-alloyed driven submersible pump. (PholOgraph ("our/cs\' o(Grindex) white cast iron G Adjustable diffuser H Clamped cable entry • Figure 5.21 (righr) A Grindex Minex submersible pump. Figure 5.22 A range a/portable pumps (Clockwise starting top left: i Angus LW 2300. ii Godiva GP 250: iif Godivil ({)iagram courtesy of Grinde.\) GP 2300. iv Godiva GP 8/5. and v Godiva GP 10/10)

60 Fire Service Manual H)'draulics. Pumps and Water Supplies 61 The ejector becomes operational when the primer The action of pulling the rod closes the butterfly With the enoine running and the pump primed, the b . rod (l) is pulled to the limit of its travel (Figure valve (2) in the ejector housing (3) which then Cylinder head engine exhaust gases pass from the exhaust mam- causes the exhaust to be deflected through the 5.23 bottom). fold, through the ejector housing and mto the ejector nozzle (4) thereby creating a vacuum in the silencer in the normal way (Figure 5.23 top). priming pipe (5) and, on the outlet side of the non­ return valve (6). This causes the non-return valve to lift off its seating against the pressure of its Exhaust spring (7). It also draws the diaphragm (8) down, Gas Flow which moves the sealing washer (9) against the pressure of the spring (10) into the open position. The depression then allows water to flow into the volute under atmospheric pressure. Pump As the pump is primed, evacuated air and then water pass through the system and into the silencer Figure 5,24 A closed circuit cooling system on (11 ). a portable pump.

When pump priming is complete (indicated by the 10 first positive needle movement of the pump pres­ sure gauge) the priming rod (I) is released and circulates round the engine block by means of a returns to its static position under the influence of circulatory pump similar to that in an appliance, a return spring, causing the butterfly valve (2) to and can have anti-freeze mixture added to it. open. The exhaust gases then resume their normal path (Figure 5.23 top), the depression in the prim­ It is important that, as soon as a portable pump ing pipe (5) and outlet housing side of the non­ of this type is started, there should be a supply of l!:::=:=====~ return valve (6) is destroyed and the valve closes water to the pump to prevent overheating. _._----~------, under the influence of its spring (7). The Exhaust 11 Key Gas Flow diaphragm (8) returns to its static position under 5.5 Safety the influence of the spring (10) and the sealing 1 Primer Rod 7 Non-return Valve Spring 2 Butterfly Valve 8 Diaphragm washer (9) contacts its seating. (a) As with all operational equipment, the pur­ 3 Ejector Housing 9 Sealing Washer chase of all pumps, whether hand-operated, 4 Ejector Nozzle 10 Diaphragm Spring Some modern pumps have an automatic priming portable or vehicle-mounted, must be con­ 5 Priming Pipe 11 Silencer valve so that only the exhaust butterfly needs to be ducted so as to satisfy the requirements of 6 Non-Return Valve closed to prime the pump. the Provision and Use of Work Equipment Regulations 1992. These regulations require With this type ofprimer, efficiency depends on the that all work equipment is assessed for speed at which the gases leave the ejector nozzle. suitability prior to purchase and is used, Priming is, therefore, carried out at high engine maintained, tested, inspected and disposed revolutions i.e. full throttle. of safely.

5.4.3 Cooling systems for portable pumps (b) The major hazards associated with portable and vehicle-mounted pumps are: Air from Volute and Suction Tube Although many of the smaller portable pumps have an air-cooled engine, the majority employ an • nOise; indirect closed water circuit system. In order to reduce weight and bulk, instead of a fan-cooled • high pressure. radiator a header tank is fitted within which are .. h b jt and priming valve closed. Bo{/om: exhaust water cooling coils supplied from the delivery side In addition, portable pumps present significant Figure 5,23 An exhaust gas ejector pmnel: Top,' ex aust utter yopen .' of the pump (Figure 5.24). This water, after pass­ risk to personnel from manual handling. (See also hu{/erfly closed and priming valve open. The exhaust gases are shown in brown and the water 111 green, ing through the coils, is returned to the suction side Fire Service Manual - Training.) of the pump. The tank itself contains water which

Hydraulics, Pumps and Water Supplies 63 62 Fire Service Manual

bE Hydraulics, Pumps and hap Water Supplies

All these risks can only be effectively controlled by brigades having systems in place which ensure that: • personnel at risk are aware of the hazards; Chapter 6 - Pump Operation and the equipment is purchased to minimise the • risks; Distribution of Water on the Fireground

safe systems of work such as limiting • exposure to noise are implemented; Introduction is pressure-fed the pump does not require priming and the primer should never be used. equipment is effectively maintained in a This Chapter deals with the subject of practical As soon as the pump has been connected, a deliv­ • safe condition. pump operation and covers such points as getting to work from hydrants and open supplies, estima­ ery valve should be opened and the hydrant turned tion of required pump pressures, fault finding, on again, to allow air to be expelled from the hose maintenance and testing and recent developments and pump and avoid the build-up of excessive in automatic pump and tank fill controls. internal pressure. When water begins to flow from the valve it can be shut down and the delivery hose 6.1 Getting to Work from a Hydrant connected.

Where only one pumping appliance is available, it When all connections have been made and the is regarded as good practice to situate it as close as delivery val ve is opened again, the compound possible to the fire in order to facilitate good com­ gauge and pressure gauge will indicate the pres­ munications between the pump operator and other sure of the supply to and from the pump. If pump firefighters and to reduce friction loss in the deliv­ revolutions are increased to rai e the delivery pres­ ery hose. However, in situations where the run­ sure, the reading on the pressure gauge will rise ning pressure in a main is low, some advantage and that on the compound gauge will fall (because may well be gained by positioning the pump of increased pressure losses in the main and soft close to the hydrant. This is because the pressure suction). in the main has to overcome friction, not only in the main itself, but also in the hydrant, standpipe Depending on the main's capacity, a point may and soft suction, and if the friction loss in the soft eventually be reached when the pump is deliv­ suction can be reduced, a greater quantity of water ering all the water the hydrant can supply. The will be delivered before the supply is over-run. If compound gauge will then read zero and any the distance between the fireground and the further attempt to increase the output from the hydrant is more than a few hose lengths it may be pump, e.g. to supply more je,ts, by increasing its necessary to set up a relay (see Chapter 7) in order speed will over-run the supply, tend to create a to obtain the maximum flowrate from the main. vacuum in the soft suction and so cause it to col­ lapse under atmospheric pressure. As explained After the standpipe (preferably double-headed) has in Chapter 4, taking water from a second, near­ been attached, the hydrant should be 'flushed' i.e. by hydrant on the same main may prove to be of turned on briefly to expel any foreign matter from only marginal benefit. the outlet. The pump collecting head should then be connected to the standpipe by soft suction, usually A competent pump operator will be able to tell, by standard 70mm hose. It is desirable to lay twin lines feeling the soft suction, whether there is sufficient of hose at the outset, to ensure that the maximum water for additional jets, in which case the hose output of the main is available to the pump. The will be quite hard, or, if it feels soft, that the limit strainer should be left in the suction inlet in order to of the main's supply capability is being reached. protect the pump from stones etc. which occasion­ ally find their way into water mains. As the supply

Hydraulics, Pumps and Haler Supplies 65 64 Fire Service Manual .... There are several rules on the use of hydrants that When the demand for water is greater than the Figure 6.1 The right firefighters should bear in mind: ability of the hydrant to supply it, the operator will, and wrong methods of Packing of course, find it impossible to maintain the water leading suction hose • The hydrant valve should be opened level in the tank. over a wa/! or other slowly to allow the hose to take up the obstruction. pressure and expel the air. 6.2 Getting to work from open water • The valve should be closed slowly to prevent water hammer. Personnel who are at risk of

• The valve should not be opened if the pit accidentally entering water should is flooded unless a standpipe or hose is be adequately protected. first connected. Otherwise, if the main is Protection can range from a lifc­ empty, water from the pit could enter and pollute the supply. jacket to, in particularly hazardous circumstances, lines and harnesses. • If a hydrant has no water available Air Pocket in r ',--- Suction Hose e.g. it has burst or the supply has been shut down, firefighters should ensure that 6.2.1 Setting up the valve is shut before unshipping the standpipe or hose. The vacuum needed to lift from open water means that only hard suction, specially designed to with­ • If possible firefighters should avoid stand external pressure, can be used. This type of collecting water from a street water-main hose is much less flexible than delivery hose and and a dirty-water supply simultaneously. must be laid out carefully to avoid acute bends. Although collecting heads have non­ return valves any defects could cause the The pump should be positioned as close to the street main to become polluted. open water supply as possible with the suction laid out in a straight line and coupled up using suction • The hydrant valve should be properly wrenches to obtain airtight joints. A metal strainer closed to avoid leaks and any frost valve should be placed on the end of the suction hose checked to see that it operates correctly. and, if it is considered necessary, a basket strainer The pit should be left clear of water and over it. Figure 6.2 Sketch debris and, if available, the outlet cap showing vortex formed replaced. Before the suction is lowered into the water it through a/!owing the suction strainer too should be secured by a line to the appliance or near the surface of Ifthe appliance has automatic tank fill control (see other suitable point, to take the greater part of the the supply. Section 6.8), it is normal practice to connect the weight off the inlet coupling and also to make it soft suction to the tank fill inlets so that water is easier to draw up the hose to clean the strainer. If supplied to the pump via the tank. This has the the suction is passing over a rough edge e.g. wall, Vortex advantages of: quayside, dam, the underside should be protected from chafing. Care must be taken to avoid any / (I) enabling pumping to continue without the sharp vertical bends above the suction inlet, as interruption which might be caused by these could lead to air pockets causing a poor switching over from the tank supply to the supply (Figure 6.1). pressure fed supply; To get the most satisfactory results at the pump, (2) allowing the pump operator greater control the top of the strainer should be submerged to a over delivery pressures which are no longer depth ofat least three times the suction hose diam­ affected by pressure fluctuations in the main eter. At any less distance the strainer will tend to supply. rise, causing vortices to form (Figure 6.2) and air

Fire Service Manual 66 Hydraulics. Pumps and Water Supplies 67 The suction should then be lowered into the water, maintained to hold the water at a pressure of not to enter the suction, resulting in a poor supply with The priming lever should then be operated and the with a light line such as a belt line bent onto the less than 1.5 bar. This will ensure circulation of crackling and inefficient jets and, probably, a com­ gauges watched. The compound gauge will regis­ blank cap to prevent its being lost. The pump sufficient water through the cooling system. The plete loss of water necessitating re-priming. If ter an increasing vacuum reading as the lift is should be run at a fairly brisk speed and the blank pump operator must, however, remember that the working from a fairly shallow supply, it may be achieved and, when a constant vacuum reading is cap removed under water, either by hand or with a length of time for which the pump may be run necessary to use a special low-level strainer or to obtained, the pressure gauge should show a posi­ tool. If all joints are airtight and no air pockets are under these conditions will be limited unless a anchor the strainer to the bottom using a weight. A tive reading. When this happens the priming lever left, the pump will now lift water without difficul­ thermal relief valve is fitted. This is because the strong current in a river may also tend to make suc­ should be released and the throttle eased back. On ty. The suction strainer(s) should then be attached, impeller imparts energy to the water which is con­ tion hose rise and it should, if possible, face some pumps the primer is automatically engaged provided that this can be done whilst keeping the verted to heat, and, with the added heating effect of upstream, and will probably also need anchoring. when the pump is started and automatically disen­ gaged when priming is complete. With an exhaust end of the suction adequately submerged. the engine, the temperature in the pump casing will rise, causing possible overheating problems. The When getting to work from an open supply: gas ejector primer it may be necessary to crack a delivery valve to allow the escape of air from the An alternative method of dealing with the prob­ functioning of a thermal relief valve, which is fit­ lem, provided a second pump is temporarily avail­ ted as standard to many modern pumps, is • Situate the pump as close as reasonably pump casing before releasing the primer and throt­ able, is to fit a collecting head to the outlet of the described in 5.3.1 When the order 'Water on' is possible to the supply in order to reduce tling back. faulty pump and then to connect it, via hard suc­ received, the delivery valve should be opened care­ the vertical lift and the number of lengths tion, to the inlet of the second pump, which may fully and pump revolutions gradually increased to of suction hose required (and hence the The compound gauge will indicate whether or not then be used to do the priming. This method has give the required pressure at the branch without a friction loss). However, in deciding how the priming has been successfully effected. If, the advantage that it is unnecessary to disturb the sudden branch reaction. many lengths of suction to use, bear in after about 45 seconds, lift has not been achieved suction, strainer etc. already connected to the mind that the water level may drop if the then: faulty pump. 6.3 Cooling systems supply is limited. (a) the lift is too great, or 6.2.3 Holding water As stated in Chapter 5, all modern vehicle mount­ • Make sure that the strainer is free from (b) there is an air leak on the suction side of ed pump engines and the larger portable pumps obstruction but not too near the water the pump or in the pump itself (glands, When priming has been effected, the water should have closed circuit cooling systems, augmented surface (otherwise vortices may form gauge connections etc.), or be held until the branch operators are ready to by secondary coolant supplied from the pump and so allow air to enter the stream). (c) one of the defects mentioned in Section 6.6 below applies. receive it. Sufficient impeller speed should be itself, and a gauge to tell the pump operator the • When a substantial vertical lift is unavoidable pump operators should be Before attempting to prime again, all joints and aware that the pump's performance will connections should be checked for air leaks. If priming still cannot be achieved, it may be neces­ 1 Water pump be significantly reduced and that 5 5 2 Water tank I~ sary to try to re-position the pump in order to 3 Suction increasing the throttle setting beyond a 11-----" , 4 Deliveries certain point will actually reduce the out­ reduce the lift. 5 Hose reel put because of cavitation in the impeller. 6 p.T.a. Ifthe priming system in a pump is defective and no 7 Tank to pump valve 2 Deliveries 8 Hose reel valve 6.2.2 Using a primer replacement pump is available, priming can be 9 Gauge cock effected manually with the help of a blank cap. The 10 Sight tube /' 11 Drain cock Before a centrifugal pump can be got to work from pump should be connected to the suction hose in ....--- 12 12 Pressure gauge ~ open water it must be primed. To do this a priming the normal way, but with a delivery valve left 15 17 1 1 9' I /' 13 13 Press-vac gauge 1 'I ~ }< 14 Tank overflow device, either manually operated or automatic, is slightly open. The last length of suction hose, with I ~ 15 Hydrant to tank I------.....,---....L..., J8l I~ 9 16 Hosereel cross-over valve brought into action. The various types of primers no strainer on the end, should then be held above ~ rn 17 Primer the level of the pump, and water poured in until it 11 3 18 Primer header tank are described in Chapter 5. I ; 16 ~-\'\-\ '-- ...J fills the pump casing; this will be indicated by r ~ The throttle should be set at the recommended water flowing from the open delivery, and the High pressure stage 1-181 .!.. valve should then be closed. More water should be .-- ....J - priming speed; with reciprocating primers this is 1 poured into the suction hose until it is completely normally about 2500 rpm, and may be controlled PTO, Cooling line automatically. Water ring primers also require full, the end being held vertical for this purpose. about 2500rpm. Pumps fitted with exhaust ejector While it is being filled, the hose should be moved I 6 I primers, however, need to be run at full throttle to about in order to release any air pockets. The blank prime. On some portable pumps the throttle set­ cap should then be lightly screwed onto the end of ting is automatically adjusted until priming is the suction. Figure 6.3 Schematic layout ofa typical appliance pipework system, completed.

Hydraulics. Pumps alld Water Supplies 69 68 Fire Service Manual temperature of the engine coolant (see 6.4.6 one metre but a pump lifting approx 3 metres may the pressure drops back appreciably the engine (ii) It is no longer necessary for every below). Where a water-cooled portable pump does show a reading of -0.4 bar. The extra -0.1 bar rep­ should be stopped immediately, but the operator delivery to work at the same pressure. not have a temperature gauge, the operator must resents the losses due to the other factors. must remember the firefighters operating branch­ Different size nozzles can be controlled by keep watch on the filler cap of the header tank to es and try to make alternative arrangements for the pump operator and, when operating see that the water does not boil. If it does, the 6.4.2 Tachometers their supply. an aerial appliance, the correct flowrate pump should be shut down immediately, allowed for the monitor can be maintained, when to cool, and the tank then topped up with fresh It is helpful to a pump operator to know the speed 6.4.5 Fuel tank contents its height is changed, simply by adjusting water if necessary. Some models incorporate an at which the engine is running. The number of rpm the pump rpm. automatic device to shut down the engine or can be critical when priming with a reciprocating This gauge is also found usually in the cab. reduce its speed if overheating occurs. primer and also it is a very good indication of the Provided that the driver/pump operator has com­ (iii) By assisting the pump operator to identify efficiency of a pump under test. When new, a pleted the necessary checks on taking over the the causes of changes in the readings of Operators should ensure that they keep an ade­ pump is capable of delivering a certain quantity of appliance there will be an adequate supply of fuel the pump pressure gauges. quate flow of water through the pump as per water at a given pressure, suction lift and pump at the commencement of pumping, but allowance the manufacturer's recommendations. speed. If, later, a higher pump speed is required to should be made for the distance run to the incident. (iv) Where hosereel induction systems are obtain the same output it is an indication that the The operator should have a reasonable idea of the fitted, which induce additives into the 6.4 Instrumentation efficiency has dropped. consumption when pumping, but should still check pump, the use of hosereel flowmeters the gauge at frequent intervals and remember to enables the pump operator to supply the The number of gauges on modern appliances has 6.4.3 Water contents gauge inform the officer-in-charge, in good time, of the correct quantity of water to one or two proliferated but, for the pump operator, there are need to obtain further supplies. branchmen or, if no branches are in use, usually seven that are essential: On many appliances the depth ofwater in the water to turn off the supply. tank is shown by a vertical calibrated transparent 6.4.6 Engine coolant temperature • Pressure gauge(s) pipe. When filling the tank, from whatever source, (v) Experience indicates that, with flow • Water tank contents the pump operator should watch the gauge to This gauge is found either on the instrument panel meters, operators generally run pumps • Compound gauge ensure that the tank is not overfilled. If an in the cab or by the pump controls. If it indicates at reduced rpm settings, whilst still • Oil pressure appliance is standing on soft ground, any overspill an excessive rise in temperature, the engine should providing effective jets or spray for fire­ • Tachometer (rpm) could possibly cause the appliance to become be shut down immediately. fighting, and so reduce wear and tear on • Fuel tank contents bogged down, and in a water 'shuttle' situation the appliance. • Engine coolant temperature (see Chapter 7) this could have serious implica­ 6.4.7 Flowmeters tions. (vi) The control and monitoring of available Most of these can be seen in Figure 5.15. Whilst the delivery pressures at pumps need to be water supplies and of the total amount of 6.4.4 Oil pressure gauge constantly monitored for safety reasons, there are a water used at incidents (e.g. ship fires) is In recent years, some brigades have also requested number of practical advantages to the measure­ greatly improved. the fitting of flowmeters on each pump delivery, All modern pumping appliances and portable ment of flowrates from pumps and in individual but appliances so equipped are still in a minority. pumps are fitted with oil pressure gauges. On hoselines. (vii) Flowmeters have proved useful in appliances these are usually in the cab and any low the evaluation of foam monitors and 6.4.1 Pressure and compound gauges pressure may in addition be indicated by a warning Following trials conducted by the Fire for special service calls where there is a light in the cab. Pump operators must remember to Experimental Unit (FEU) in three brigades during requirement for the delivery of a specified A pump operator should watch the pressure and check the pressure regularly, especially under pro­ 1989 it was concluded that flowmeters, fitted to amount of water (e.g. chemical incidents compound gauges carefully whilst operating as tracted pumping conditions. Neither the gauge nor the main deliveries and hosereel supplies of fire where it may be necessary to dilute they give a reliable indication of how the pump is the warning light indicates the level of the oil in service pumps, would be of benefit in the follow­ spillages by a known amount). performing and how the water supply is being the sump and this must be ascertained by taking a Ing ways: maintained. The working of these gauges is dealt dipstick reading. In spite of these positive conclusions, flowmeters with in Chapter 2. (i) Flowmeters can ensure that flow rates at are being included in specifications for new appli­ The experienced operator will come to know the the branch can be handled safely, and ances by only a limited number of brigades at the The compound gauge, on its vacuum side, registers different pressures which should be indicated on reduce the need to calculate the pressure present time. Figure 2.14 shows a pump fitted with any variation of lift when pumping from open the gauge for different conditions. A cold engine loss between the delivery and the branch. analogue flowmeters on each of its main deliveries. water, but pump operators should remember that should give a relatively high reading but, as the Also the pump operator can quickJy iden­ the vacuum shown on the gauge includes not only engine warms up, this should drop back to the tify burst lengths, because of the unex­ At the time the FEU report was written, most the height of the lift but also the other factors working pressure. This pressure will depend on the pectedly high flow, and vandalised dry ris­ flowmeters were of the paddle-wheel type, but referred to in Chapter 3, Section 3.2. For practical type of engine, and a worn engine will probably ers if there is flow after the riser has been lately the electromagnetic type seems to be pre­ purposes, -0.1 bar would indicate a lift of about give a lower reading than one in good condition. If charged. ferred. Both are described in Chapter 2.

70 Fire Service Manual Hydraulics, Pumps Clnd Wafer Supplies 71 To achieve sufficient accuracy for fireground use same amount deducted for every metre it is below factor, if the pump pressure is reduced by 50%, the (ii) Debris fallen onto the delivery hose or a (say + or -10%) careful design ofthe installation in the pump. The friction loss in the hose, which is flowrate will decrease by approximately 30%. vehicle's wheels parked on it. the deliveries and calibration are required. now of greater significance because of the trend to (iii) A bad kink in the delivery hose the use ofsmaller diameter hose on the fireground, Whilst it is unrealistic to expect precise calcula­ (iv) A remote possibility, when using small 6.5 Estimation of required should also be added. Normally this estimation of tions of friction loss on the fireground, operators diameter nozzles, that a stone may have pump pressures pump pressure should be the task of the branch should be aware of the magnitude of the losses passed through the internal strainer, pump operator who is better positioned to assess these which might be incurred, particularly with the and hose and blocked a nozzle. Pump performance, which is discussed in factors than the pump operator. smaller hose diameters. When policy decisions are Chapter 5, is usually rated in litres per minute at a being made concerning the types of nozzles and (c) Decreased delivery pressure whilst pressure of 7 bar with a stated suction lift of 3m Friction loss calculations (Chapter 1), for the hose hose diameters to be carried on appliances, care at work and an experienced pump operator will know the diameters most likely to be used on the fireground, should be taken to ensure that the two are compat­ approximate quantities his pump will deliver at give the values in Table 6.1 for the flowrates indi­ ible and do not result in a need for unreasonable (i) A burst length of hose on the delivery side different pressures and from different suction lifts. cated. pumping pressures. of the pump. The operator should also know the approximate (ii) A hand-controlled branch being opened up. '- rates of discharge from the types of nozzles used Example I It is flowrate which extinguishes fires ­ by the brigade and, where it is significant, the not pressure 6.6.2 Working from open water approximate friction loss in the type of hose used. What pump pressure is required to supply a branch which delivers 400 litre/min at 5 bar when it is For 19mm hosereels, with all the hose laid on the (a) The pump fails to prime For safety reasons, when the pump operator first working on the fifth floor of a building, 15 metres ground, a typical flowrate of 100 IImin results in supplies water it should be to give moderate nozzle up, using six lengths of 64mm hose? a pressure loss of approximately lObar over 55 If the pump fails to prime, the compound gauge pressure. If a request is received for more, or less, metres. This increases to approximately 16 bar will show either no vacuum reading or a very high pressure, it should normally be altered by I bar at Pressure required at the nozzle 5.0 bar with most of the hose wound on the drum. vacuum reading: a time. If a number of branches are at work at dif­ Pressure equivalent of 15 metres head 1.5 bar ferent levels, the operating pressure may have to be Pressure loss in 6 lengths at 0.2 bar/length 1.2 bar 6.6 Identification of faults No vacuum reading a compromise as each line, ideally, would be sup­ Pump pressure required 7.7 bar (i) Suction strainer not adequately submerged plied at a different pressure. In extreme cases the The ability to interpret, intelligently, what the (see Figure 6.2). correct pump operating pressure for one line might Had 45mm hose been used, the friction loss alone gauges are indicating is the hallmark of a good (ii) Faulty joints on suction hose and inlets or air be such as to endanger a firefighter operating from would have been 6 (6 x 1.0) bar and the required pump operator. It should be possible not only to leaks in suction hose. a different line and, in such cases, it may be neces­ pump pressure no less than 12.5 bar to achieve the recognise a developing situation but also to tell, (iii) An open drain cock, or loose drain plug, in sary to shut down one or more branches and re­ same discharge! In practice a much lower operat­ within fairly close limits, the cause. The following the pump casing or air leak in a gauge con­ connect them to another pump. ing pressure would probably be requested with the checklist covers the most common faults. The nection. result that the discharge from the jet would be less methods of rectifying them are shown only where (iv) Delivery valve not seating properly. The To estimate the required pump pressure, 0.1 bar for than desired. However, the penalty, in terms of they are not self-evident. non-return valves should seat and hold a every metre the branch is above the pump should flowrate, for a reduced pumping pressure is not as vacuum. be added to the branch operating pressure and the severe as might be expected. Ignoring the height 6.6.1 Working from a pressure-fed supply (v) Defective pump seal - should become apparent through regular testing before it (a) Failure or reduction of water supply prevents priming. Table 6.1 Friction loss per 25m length ofhosefor various flowrates and hose diameters (vi) Incorrect seating of the exhaust valve in an This may be caused by: exhaust gas ejector primer. diameter (mm) friction loss (bar) tor the tlowrates (Iitre/min) indicated (vii) Defective drive to mechanically driven 200 400 600 800 1000 1200 1400 1600 1800 2000 (i) Failure of the supply e.g. fractured main or pnmer. burst length of hose between supply and (viii) Defective priming lever linkage. 38 0.7 . 2.9 6.8 Impractical li pump. (ix) Lack of water in water-ring primer. 45 0.3 1.0 2.1 4.0 6.0 (ii) Choked internal strainer of the pump. (x) Compound gauge cock closed. o (iii) Over-running the supply. 64 0.2 0.4 0.7 l.0 1.2 2.0 2.7 3.3 4.2 Consider Many of the above faults should become apparent 70 0.1 0.3 0.4 0.7 1.0 .7 1.3 1.7 2.2 Cl (b) Increased delivery pressure whilst during regular testing (see Section 6.7). 90 0.1 0.2 0.3 0.4 .5 0.7 0.9 1.1 egligible at work A very high vacuum reading Note: lllines are Minlled, the loss ill each line will be reduced to a quarter otthe value in the lable. (i) The closing down of a hand-controlled (i) Blocked metal or basket strainer. branch. (ii) Collapsed internal lining of suction hose.

72 Fire Service Manual Hydraulics, Pumps and Water Supplies 73 (b) Changes in the compound gauge reading 6.7 1aintenance and Testing 0.8 bar vacuum which shall be achieved pressure surge, which may result from within 45 seconds. the shutting down of a large jet, and Some changes in the compound gauge reading, Although firefighters are not normally responsible which might endanger other branch whilst the pump is at work, are to be expected. for the routine maintenance of pumps, in the inter­ Having achieved this, the compound gauge operators, is substantially reduced. They will result from such factors as: est of a long trouble-free pump life, attention shall then not fall to 0.3 bar within 1 minute. should be paid to the following: (ii) delivery pressure regulation is automatic (i) changes in the level ofthe open water supply; Failure to achieve the above performance indi­ when the supply pressure from a hydrant (ii) changes in the demand from the pump. A (i) Strainers must be used where appropriate cates an excessive air leak within the system changes, when changing over from a greater demand will mean increased losses and checked and cleaned afterwards. which may be due to leakage at pressure gauge tank supply to a hydrant supply and on the suction side of the pump with a con­ connections, delivery valves, couplings etc." when the water level of an open source sequent reduction in the gauge reading. (ii) Following pumping from salt or polluted changes. water the pump, primer, hose reels, water tank Any other testing, including pump output tests, (c) Cavitation and pipework should be thoroughly flushed may be carried out in accordance with the manu­ (Hi) a warning can be given if predetermined with clean water to prevent corrosion. facturer's instructions. pump pressure cannot be achieved. When pumping from an open supply, the pressure on the inlet side of the pump can be so low that the (iii) In cold weather, the pump should be drained 6.8 A si ted Pump and Automatic (iv) the need for priming is detected and water can vaporise at the ambient temperature. of all water after use to prevent possible Tank F'II Controls the appropriate pump speed set Vapour bubbles then form (this is known as cavita­ freezing. If drain plugs need to be removed, automatically. tion) and the pump gives off a distinctive rattling they must be replaced securely. Drain cocks 6.8.1 Assisted Control Systems (ACS) sound. When this sound is heard the pump opera­ should be closed after use. for Pumps (v) the pump operator, whilst still required, tor should appreciate that the maximum flowrate is able to perform additional tasks. for the prevailing conditions has been achieved and (iv) On portable pumps if, for any reason, the Although more sophisticated systems are in use should throttle back until the sound disappears. mixture ofwater and anti-freeze fluid for the abroad, a typical ACS system, as currently used by With ACS systems it should always be possible to The compound gauge will not normally give an cooling system is spilt onto the pump, or its a number ofbrigades in the u.K., is simply a means revert rapidly to manual control if the need arises. early indication that cavitation conditions have frame, it should be carefully washed off and of maintaining a pre-determined pump pressure, been reached. The danger of cavitation is obvious­ dried. under varying demands for water, in order to pro­ 6.8.2 Automatic Tank Fill Controls ly greater if the water is hot (see Chapter 3). vide a safe and steady supply to branch operators. The only requirement for the testing of pumps, at An automatic tank fill control allows water from a (d) Crackling jets the present time, is that laid down in Technical The Home Office Fire Research and Development positive pressure supply, such as a hydrant, to be Bulletin 1/1994. It is a quarterly test for both vehi­ Group, after evaluation of a number of commer­ fed direct to the tank via a valve (see Figure 6.4) A crackling jet is caused when air is taken into the cle mounted and portable pumps and is described cially available overseas systems and discussions which automatically responds to a signal received pump with the water. The water and air are pres­ as follows: with experienced firefighters, produced a draft from level sensors (Figure 6.5). Thus, provided the surised and the air expands explosively as it leaves specification for a system to meet the needs of the water demand from the pump (which is normally the nozzle. Again, the explanation may be that the Quarterly Dry Vacuum Test u.K. Fire Service. Trials of such a system were working from the tank) is not greater than the strainer is too near the surface, allowing air to be conducted in four brigades and the conclusions, capacity of the supply, the level within the tank is drawn down, or there could be a slight leak on the "It is anticipated that this test will normally which were broadly favourable provided the sys­ maintained between specified limits. suction side of the pump. be conducted by station personnel. tem could be made reliable, were published, together with a revised specification, in Research An important design feature of such systems, (e) Mechanical defects An initial visual inspection of all the lengths Report No.42 (1991). which are more common in European brigades of suction hose to undergo testing shall be than in Britain, is that the pipework between the Regular servicing and testing should reduce conducted. A number of systems are now commercially avail­ tank and the pump should be "full flow" i.e. of mechanical defects to a minimum and major prob­ able, and, although there are some differences large enough diameter to deliver the full rated out­ lems should not, therefore, occur on the fireground. All the lengths of suction hose that have between them, generally speaking they give the put of the pump. However firefighters should be aware that pumps been visually inspected shall then be cou­ following advantages: are usually designed with a number of drillings, pled to the suction inlet of the pump with a The advantages of automatic tank fill controls are: drains or "holes to atmosphere", blockages of blank cap in place on the end of the final (i) changes in throttle setting, which are which may seriously affect the performance. Drips length and with the blank caps removed normally required to maintain a (i) variations in supply pressure do not from practically any of them are indicative of leak­ from all deliveries. constant operating pressure when there affect branch operators. ing diaphragms, faulty drain valves etc. and, are variations in water demand, no because they may develop into serious failures, The pump shall then be operated at the longer require the intervention of the (ii) the problem of air, contained in long should be reported at an early stage. specified priming speed in order to obtain pump operator. Thus, the problem of lengths of dry hose, entering the pump

74 Fire Service Manual Hydraulics, Pumps and Water Supplies 75

b Hydrau ics Ch ter

(v) when it is necessary to reduce branch pressure in an emergency, this can be done simply by use of the throttle. If the pump is fed direct from a hydrant it may be necessary to shut down the delivery as weJl. Chapter 7 - Pre-Planning The disadvantages are:

(i) it is not possible to take advantage of high hydrant pressure which would Introduction (i) The extent to which the fire is likely to have normally reduce the throttle setting Figure 6.4 An automatic tankflll control valve. spread before firefighting commences. (Photograph courtesy (~{ West lv/id/and.'; Fire Service) for a given demand. The pre-planning ofwater supplies forms an impor­ tant part of strategic risk assessment. In many areas (ii) The size of the building/area at risk. (ii) there is no obvious indication, except mains water supplies are inadequate for firefight­ and causing significant interruption in for the tank level gauge, if the demand ing, difficult to access or, in some cases, non-exis­ (iii) The fire loading. supply to branch operators, is eliminated. exceeds the capacity of the incoming tent. Even where the supply is normally adequate, it supply. may be insufficient to cope with a major incident, (iv) Environmental factors - the possibility that (Hi) problems of high inlet pressures which e.g. a large industrial fire. The task ofproviding suf­ nearby water courses may become contami­ (iii) if the appliance is not on level ground, affect some additive induction systems ficient water as quickly as possible in such cases nated. are avoided. the level sensor may be deceived needs pre-planning and, sometimes, special equip­ regarding the actual amount of water ment. Obviously the first step is to estimate what the (v) The construction ofthe building - materials, (iv) there is always a reserve supply of water in the tank. water supply needs are likely to be for a particular compartmentation etc. in the tank. risk and then, if these requirements exceed the amount immediately available on appliances and (vi) The need for the protection of adjacent from local hydrants, to decide how to make up the risks. deficit. Pre-planning for major fires should involve fire officers at every level of incident command so (vii) The value of the building and its contents. that an overall strategy can be achieved. (viii) Whether there is a life risk. Supplying water to combat an incident can present widely differing problems to different brigades. Because there are so many factors to consider, for What constitutes a difficult task to a predominant­ a large fire risk, it will be difficult to estimate VVaterlevelsensors ly rural brigade may not appear to be of such mag­ accurately the quantity of water likely to be nitude to a brigade operating in a heavily urbanised required for a worst case scenario, but an attempt area and able to mobilise adequate reinforcing to do so should be made. There are a number of appliances quickly. Nevertheless, the principles of approaches. pre-planning still apply. The Central Fire Brigades TANK Advisory Council classifies a 'major' fire as one in 7.1.1 Estimations based on compartment which 20 or more jets are required and a survey of size PUMP such fires has indicated that they generally require Outlet at least 17 000 litres/min of water to contain and A formula used in the United States, the Iowa extinguish them. Rate of Flow Formula, predicts the rate of flow required to control a fire in the largest single com­ 7.1 E timatioD ofWater partment of a building when the area is fully VVater inlet Requirements involved. When translated into metric units the formula becomes: Control valve The flowrate required to deal with a particular risk and the period oftime for which that flowrate must litres per minute = 1. x ~olum~ of compartment be sustained depend on many factors. Some of 3 III cubiC metres Figure 6.5 Diagrammatic representarion ofan automatic tankjill.\~ystem. these are listed below.

76 Fire Service Manual Hydraulics, Pumps and Water Supplies 77 The assumption is made that the water is evenly dis­ 45mm diameter hose - 300 IImin (iv) Shopping, Offices, Recreation and 4 jets at 500 litres per tributed over the surface of the burning contents. 70mm diameter hose - 600 IImin Tourism - from 20 l/sec (1200 IImin) to minute require 4 x 500 = 2000 litres per minute. 90mm diameter hose - 1200 IImin 75 l/sec (4500 I/min) depending on the the ground monitor Example 1 extent and nature of the development. requirement = 1200 litres per minute 7.1.3 Guidelines on Flow Requirements total requirement = 3200 litres per minute What is the rate of flow required to control a fully for Firefighting (v) Education, Health and Community developed fire in a compartment 20m long, 12m Facilities water available wide and 3m high? The LGNWater UK National Guidance Document from main = 1000 litres per minute on the "Provision of Water for Firefighting" gives Village Halls - mlDlmum of 15 I/sec required flowrate from . 4 x 20 x 12 x 3 the following flowrates as the minima necessary (900 l/min) through any single hydrant on storage tank = 2200 litres per minute Flowrate reqUIred = 3 for firefighting in the particular risk categories the development or within a vehicular dis­ where new developments are under consideration tance of 100 metres from the complex. If D is the diameter and h the depth of the tank, = 960 litres per minute. and suggests their achievement be a condition of both measured in metres, the capacity in litres is planning consent. If additional capacity main is Primary Schools and Single Storey Health given by: It is not suggested that the use of this formula required for firefighting purposes, for which the Centres - minimum of 20 IIsec (l 200 IImin) should be the sole basis for detennining required developer refuses to pay, then the fire authority through any single hydrant on the develop­ capacity = 800 D2h (Appendix 3) flowrates, but it may be interesting to compare the will have to meet the cost ofthe water company. In ment or within a vehicular distance of = 800 x 8 x 8 x 1.5 result with that obtained using a more subjective all cases the figures should be regarded only as a 70 metres from the complex. = 76 800 litres method. guide and the final decision on requirements will be with the fire authority. Secondary Schools, Colleges, Large Health Time for which firefighting 7.1.2 Estimation based on the number of and Community facilities - minimum of may continue _ 76800 jets likely to be used (i) Housing - from 8 IIsec (480 l/min) for 35 I/sec (2100 lImin) through any single - 2200 detached or semi detached of not more than hydrant on the development or within a Such an estimate is likely to be based on an expe­ two floors up to 35 l/sec (2100 IImin) for vehicular distance of 70 metres from the = 35 minutes approximately rienced firefighter's judgement of how many and units of more than two floors, from any sin­ complex what types of branches will be required to deal gle hydrant on the development. Because this is a relatively short period of time, with the risk in question. If standard, A-type, 7.2 As essment of. dditional Water depending on the nature of the risk it may be con­ branches are employed, the flowrate for each may (ii) Transportation - 25 IIsec (1500 l/min) for upplie sidered wise to plan for additional supplies from be simply determined using the nozzle discharge lorry/coach parks, multi-storey car parks other, possibly more distant, sources. formula (derived in Appendix 4): and service stations from any hydrant on the Once the likely water requirements have been development or within a vehicular distance established for a particular risk scenario, the ques­ Example 3 of 90 metres from the complex. tion arises as to whether these may be met from the local mains supply or whether other sources such It is proposed to take water for firefighting from a However, today, diffuser type hand-controlled (iii) Industry (industrial estates) - it is recom­ as storage tanks, swimming pools, lakes, reser­ swimming pool which is 12m long, 4m wide and branches are much more likely to be used and the mended that the water supply infrastructure voirs, rivers and more distant mains will be need­ has a depth which varies uniformly from 0.8m to water requirements of these will depend on the should provide as follows with the mains ed to make up a deficit. The examples which 2.0m. Ifthe demand is expected to be 800 litres per precise models in use with the brigade, their oper­ network on site being normally at least follow make use of some of the formulae for minute, how long will the supply last? ating pressure and on how they are adjusted (it is 150mm nominal diameter: capacity which are derived in Appendix 3. possible to set some branches to deliver a particu­ Capacity of pool in litres lar flowrate). Up to one hectare 20 IIsec (1200Ilmin) Example 2 = length x breadth x average depth x 1000 Some firefighters make an estimate of the water One to two hectares 35 I/sec (2100 IImin) It is anticipated that 4 jets each of which delivers requirements at an incident which is based on the 500 IImin and a ground monitor which delivers = J2 x 4 x 0.8 + 2.0 x 1000 number of lines of hose of the diameter likely to be Two to three hectares 50 l/sec (3000 l/min) 1200 IImin will be required for a particular risk. 2 employed. Practical tests have indicated that, pro­ The local main is capable of delivering only 1000 = l2 x 4 x 1.4 x 1000 vided hose diameters have been suitably matched Over three hectares 75 IIsec (4500 l/min) litres per minute and it is proposed to make up the to the branches which they supply, and that no deficiency from water stored in a cylindrical tank = 67 200 litres more than 4 or 5 lengths are used in each line, the High risk units may require greater flowrates. ofdiameter 8m and depth 1.5m. For how long may following are reasonable estimates of the likely firefighting continue before the stored water runs flowrates: out?

78 Fire Service Manual Hydraulics, Pumps and Water Supplies 79

------Time for which supply lasts _ 67 200 minutes 3. The equipment and methods available for 3. The total time taken to mobilise the appli­ (b) How many water carriers would be required - ----soo- carrying or relaying water. ances can usually be reduced. and how many trips per hour would they be 4. The time factors involved in assembling the 4. The number of water-carrying journeys is involved in? = 84 minutes necessary equipment. reduced. 5. Firefighting appliances are not committed (a) A water tender will be able to maintain the Example 4 Once the full picture has evolved, a study of the merely for carrying water. required supply for: various options open to the brigade officer can be 6. The operating costs are reduced. A remote country house has a limited mains sup­ made. These are discussed in the following para­ 1800250 = 7'mmutes (.I)approximate y ply but this may be supplemented, for firefighting graphs. Against these advantages has to be set the capital purposes, by water from a nearby lake. The esti­ cost of purchasing and maintaining these special mated surface area of the lake is 1200 square 7.4 Water Carrying appliances, though leasing arrangements with Time to refill and discharge a water tender with metres and its average depth is 0.7 metres. What is other owners may be negotiated. 1800 litres the available supply in litres? In rural areas where distances between water = 6 minutes ( 4 min. for fill + 2 min. for sources and the fireground can be considerable, Comparison between the two methods described discharge) Capacity in and where the requirement is for a relatively limit­ can be made for an incident on a motorway. A cubic metres = ~ x surface area x average depth ed, but continuous, supply of water over a lengthy major problem facing an officer in charge of this Round trip travelling time = 15 minutes period, then a system of water carrying may be type of incident is likely to be the 'round trip' dis­ preferred to a long water relay. tance which appliances need to travel to refill their Complete trip time = 2 I minutes =~XI200XO.7 tanks and return. Because of the distance to access Water carrying can be tackled in one of two ways. points, a travelling time of 30 minutes is not Thus, each water tender will be able to make Firstly, a number of water tenders can be used to uncommon in these instances, and so the advan­ approximately 3 trips per hour and, since each = 560m3 collect water from the source and deliver it either tages of water carriers become more apparent. tankful lasts 7 minutes, in order to maintain a con­ into the tank of a fireground appliance or into a tinuous supply: Capacity temporary dam. The second method, employed by It is important to appreciate that for water carrying in litres = 560 000 several brigades, is to use one or more bulk water to be practicable, storage arrangements for the the number of tenders required = 2 1 = 3 7 carriers. A recently conducted survey has shown delivered water must be available at the fire­ that these appliances may carry from 3800 litres (a ground. One or more additional water tenders, an which, between them, will have to make a total of 7.3 Supplying Water to the demountable pod) to as much as 13500 litres, inflatable or an improvised dam might be suffi­ approximately 9 trips per hour. Fireground together with a portable or integral pump and a cient. portable dam. The process of delivering water to When water has to be conveyed from distant (b) A water carrier will be able to maintain the the fireground and refilling from a source is con­ Once estimates have been made for travel, fill and sources to the fireground the two main methods required supply for: tinued as often as is necessary. discharge times it is possible to calculate the min­ are: imum resources required for a water carrying oper­ 9000 . It should be borne in mind that the nearest source ation. In practice, one or more additional 250 = 36 mmutes (i) to utilise a number of water tenders or of water may not necessarily be the one which appliances should be ordered, where possible, to water carriers to maintain a 'shuttle' should be used, since abundance and ease ofaccess cover any unforeseen delays or other problems. from the supply; Time to refill and discharge a water carrier with are impoliant factors. This is particularJy impor­ 9000 litres tant when considering the use of water carriers, as Example 5 (ii) to relay the water over the distance using = 20 minutes (J 5 min. for fill + 5 min. a slightly longer transit time may be more than pumps and hose. for discharge) compensated for by a reduction of the time A pre-planning assessment ofan incident indicates required to complete each filling operation. that a continuous supply of 250 IImin will be When determining an overall policy for water car­ Round trip traveJJing time = 15 minutes required for an indefinite period. The nearest rying or relaying, the factors which should be The advantages of using water carriers as against a viable hydrant yields 600 IImin and involves a taken into account are: Complete trip time = 35 minutes larger number of conventional water tenders are as round trip travelling time estimated at 15 minutes. follows: A water tender holds 1800 litres and a water carri­ I. The additional quantity of water needed and Thus, to maintain the required supply: er 9000 litres of water. In order to meet fireground the time for which it will b required. I. The total number of appliances required is requirements: ~~ 2. The location and size of sources, taking into the number of carriers required = = 1 less. account the time of year and the distance 2. The human resources required are much (a) How many conventional water tenders involved for water carrying or relaying. less. would be required and how many trips per which will have to make approximately 2 trips per hour would they have to make? hour.

80 Fire Service Manual Hydraulics, Pumps and Water Supplies 81 This example clearly illustrates the advantages of For a given flowrate, the maximum spacing The information contained in these tables has been using water carriers with regard to effective use of between appliances will be determined by the dis­ obtained from a variety of sources and should be personnel and equipment. tance over which the pressure in the hose falls to regarded only as a reasonable guide to perfor­ slightly above atmospheric so that it becomes nec­ mance. The flowrate required in the example (250 I/min) is essary to boost the pressure with another pump. extremely limited and it is clear that the resources Rather than perform lengthy friction loss calcula­ which would be required for more substantial risks tions to determine this distance, use may be made will prohibit water carrying, by either water ten­ of the information in Table 7.1 a and Table 7.1 b. ders or bulk carriers, as an acceptable option.

7.5 Water Relaying Table 7.1a Maximum distances for requiredflowrates between pumps operating at 7 barfor 70mm and 90mm hose with standard instantaneous couplings. A water relay comprises a number of pumps spaced at intervals along a route between a water REQUIRED MAXIMUM DISTANCE BETWEEN PUMPS (metres) OPERATING AT 7 bar source and the point where the water is required. FLOWRATE 70mm single 70mm twinned 90mm single 90mrn twinned At one time two types of relay were commonly in Iitres/min all with standard instantaneous couplings use, namely closed circuit (in which the water is pumped through hose direct from one pump to the 400 1500 6000 3900 15700 next) and open circuit (in which it is pumped Figure 7. J Diagram illustrating the closed circuit relay 500 1000 4000 2500 10000 through hose via portable dams placed between the method. 600 690 2700 1700 6900 pumps). The aim when organising a water relay is to deliv­ 700 500 2000 1250 5000 The principal advantage of the open system, i.e. er the required quantity ofwater with the minimum 800 390 1550 980 3900 the ability to maintain flow at the fire even if the of equipment. Without careful pre-planning it is base pump becomes inoperative, is offset by the likely that a greater number of appliances will be 900 310 1200 770 3000 greater amount of equipment and effort required. used than is strictly necessary, or that the quantity 1000 250 1000 620 2500 Because of this, the open circuit method is now of water delivered will not be sufficient to meet 1100 210 820 500 2000 seldom used and the closed circuit system, which firefighting needs. will now be described, is usually adopted. 1200 175 690 430 1700 However, the use of a portable dam at the fire­ The flowrate available from a water relay depends 1300 150 590 350 1400 ground is recommended because it can act as an on two factors: emergency supply in the event of relay pump 1400 125 500 320 1250 breakdown and also enables better control over (i) the performance of the pumps used. 1500 110 440 270 1100 jet pressures. 1600 100 390 245 980 (ii) the ability of the hose to convey the water. In a closed circuit relay (Figure 7.1), the first, or 1800 75 300 190 775 base, pump takes its water from the source and A pump's performance can be determined from an 2000 60 250 155 620 pumps through hose lines either directly, or via a inspection of its characteristic or from a knowl­ 2200 50 205 130 520 series of booster pumps, to the fireground pump. edge of the maximum flowrate available at a quot­ The function of these booster pumps, when they ed pressure e.g. 7 bar or lObar. These issues are 2250 50 195 120 490 are used, is to compensate for the pressure lost due discussed fully in Chapter 6. The ability of hose to 2500 40 160 100 400 to friction in the hose. The distance between the convey water is limited by friction loss and is 70 280 pumps is regulated by the amount of friction loss therefore highly dependent on its diameter. 3000 110 and the contours of the route. 3500 80 50 200 The planning of an effective water relay 4000 60 40 155 depends on matching the pumps' ability to deliver water with the ability of the hose to con­ 4500 30 125 veyit. There is no point in having large capacity pumps attempting to deliver water through long lengths of small diameter hose.

82 Fire Service Manual Hydraulics. Pumps and Water Supplies 83 Table 7.1 b Maximum distances for requiredflowrates between pumps operating at 7 barfor 90mm, Fire service pumps are capable of a variable output water supply is of limited capacity, some thought 125mm and 150mm hose with Storz couplings. according to the discharge pressure at which they should be given as to just how much of the scarce are operated. For many pumps currently in use the resource is required simply to fill the hose. REQUIRED MAXIMUM DISTANC BETWEEN PUMPS (metres) OPERATING AT 7 bar nominal output is quoted at a pressure of 7 bar and FLOWRATE 90mm single 90mm twinned 125mm single 150mm single this has been regarded as the normal operating Example 8 pressure for a water relay. However, it is now litr. min all with Storz couplings becoming common practice for manufacturers to What is the volume of water contained in 1000m 500 3000 12000 17500 50000 standardise on a pressure of lObar when quoting of 125mm hose? 1000 750 3000 4700 14000 pump performance, and recent improvements in hose construction enable it to cope with this high­ The capacity of Im of hose IS given by the 1500 350 1400 2100 6500 er pressure, but ifa higher standard operating pres­ formula: 2000 190 780 1200 4000 sure than 7 bar is adopted for a water relay, this will have the effect of increasing the distance pos­ . 8 d2 2250 150 600 950 3100 capacity = 10 000 (appendix 3) sible between pumps at the expense of decreasing 2500 125 500 750 2500 the amount of water available. What is regarded as 3000 80 350 550 1800 the optimum arrangement for a relay occurs when so the required capacity is: the distance between pumps is the maximum 3500 60 250 400 1350 which will allow them to deliver their full rated 8 x 125 x 125 x 1000 4000 50 200 300 1000 output through the hose selected and this may eas­ 10000 4500 35 150 2 0 8 0 ily be determined from Table 7.1 as has been shown in the example above. However, the water = 12500 litres 5000 30 125 200 700 demands at an incident may not be such as to require the full rated output ofthe pumps, in which Ideally the pumps used in a relay should all have Distances may be increased by approximately Example 6 case it becomes possible to operate with longer the same capacity and, with the possible exception 40% if pumps operate at 10 bar. stages. of the first two, should be equally spaced. Pumps capable ofdelivering 2500 litres per minute If If, for a given flowrate, a line of hose is twinned at 7 bar pressure are to be used in a water relay. Example 7 pumps of different capacities are used, the flowrate in each line will be halved and con­ How many intermediate pumps will be required the maximum output of the relay will be dictat­ sequently the friction loss, which depends on the for this amount of water to be delivered over a Ifa water relay is required to deliver 1000 litres per ed by the output of the pump with the lowest capacity. square of the flowrate, will be reduced to a distance of 600m using (i) twinned 70mm hose minute at an incident, assuming a pumping pres­ quarter of its former value. Thus, with twinned (ii) single 90mm hose with standard couplings sure of 7 bar, what is the maximum distance If lines of hose, the distance between pumps may (iii) twinned 90mm hose with standard couplings between stages using (i) twinned 70mm hose (ii) the pumps are not equally spaced, the maxi­ be four times as great as it is with a single line. and (iv) single 125mm hose? twinned 90mm hose with Storz couplings and (iii) mum output of the relay wiJI be dictated by the single 125mm hose? Oowrate in the longest stage.

Table 7.1 indicates that the distances are as Table 7.1 indicates that the maximum distances between pumps and the follows: 7.6 Practical Considerations consequent numbers of intermediate pumps required are as follows: (i) for 70mm twinned hose - 1000m (i) for 70mm twinned hose 160m needing 3 pumps 7.6.1 Relaying over undulating ground (ii) for 90mm twinned hose - 3000m (i i) for 90mm single hose lOOm needing 5 pumps It frequently happens that the ground over which a (iii) for 125mm single hose - 4700m (iii) for 90111111 twinned hose 400m needing I pump relay is laid is not level, and jf the gradients con­ cerned are sufficiently great some adjustment of (iv) for 125mm single hose 750m none required The only requirement regarding the pumps is the distances between pumps becomes necessary. that they should be able to maintain a flowrate of at least 1000 IImin when operating at 7 bar Where the ground between pumps is uphill, some pressure. ofthe pump pressure will be used up in raising the water to the higher level with the result that less Examples 6 and 7 illustrate clearly the advantages, pressure wi II be available to overcome frictional from the resource point of view, of twinning lines resistance in the hose. It may be possible to and increasing hose diameter. However, if the increase the pump pressure in order to compensate

84 Fire Service Manual Hydraulics, Pumps and m/fer Supplies 85 for this, provided that the pump is not already Ifthe relay has to be laid downhi 11 on a similar gra­ be positioned a short distance away from the working at full throttle, but otherwise the intended dient, the distance between pumps could be pumps because of the noise of the engines. flowrate can only be maintained by reducing the increased by: distance between the pumps. Conversely, where 7.6.5 Charging with water the ground between pumps lies downhill, the stat­ 1. x 200 = 57m ic head offsets the frictional resistance in the hose, 7 Provided good communications have been estab­ so the pumps can be spaced farther apart. lished, it may be advantageous, especially if large i.e. to 257m diameter hose is being used, to partially charge the An appropriate method for determining the spac­ hose as the relay is being assembled. One delivery ing is to estimate the difference in height between 7.6.2 Position of the base pump on each booster pump should be left open, in addi­ adjacent pumps in metres and divide this by 10 to tion to the deliveries connected to the hose lines, to give the static head requirement in bar. This figure The output from the base pump, which has to sup­ facilitate the removal of air from the system. As should then be divided by the operating pressure of ply the water, will control the flow through the soon as water reaches the pump, this extra delivery the relay and the distance between pumps reduced relay. If this pump is not working efficiently, the should be closed. or increased by the resulting fraction. whole of the relay will be impaired. The base pump should run at about halfspeed until Stage 1 Example 9 When working from open water, suction condi­ the whole system has been charged. When the offi­ tions will govern the input of the base pump; the cer in charge is satisfied that the relay is working A section of a relay, for which the appropriate full rated output can be expected ifthe vertical suc­ satisfactorily, the speed of the base pump should spacing for pumps operating at 7 bar on level tion lift is not more than 3 metres and no more than be gradually increased until the full pressure is ground is 200m, has to be laid up a hill with a gra­ three lengths of suction hose are used. The base reached. During this period and subsequently, the dient such that the difference in level over this dis­ pump should therefore be situated as near as prac­ booster pump operators should keep the relay in tance is estimated to be 20m. What should be the ticable to the water source, with the minimum suc­ balance by gradually adjusting their throttles to a spacing on the hill? tion lift. position where the compound gauge is reading just above zero. Booster pumps, having no suction The pressure equivalent to 20m head of water is 2 7.6.3 Spacing between first two pumps conditions to contend with, should be running at a bar, so the effective pressure for overcoming fric­ slightly slower speed than the base pump. tion is reduced to: Because a base pump working from open water has to use a part of its energy in lifting the water 7.6.6 The Porter Relay 7 - 2 = 5 bar from the source to the pump inlet, there will be something of a reduction in the pressure available This incorporates a procedure to quickly establish In order to maintain the flowrate, the spacing to pump the water through the hose on the delivery a relay when the number of appliances initially Stage 2 should therefore be reduced by: side to the first booster pump. In such circum­ available is limited and, as more appliances arrive, stances it may be appropriate to reduce the dis­ to gradually increase its capacity, but without at tance between the base pump and the first booster any time needing to interrupt the water supply. 1. x 200 = 57m 7 pump to compensate for this loss of pressure. The arrangement was originally conceived for 2250 l/min pumps each of which carried 14 i.e. to 143m 7.6.4 Communications lengths of 70mm hose. However there is no reason why the principle could not be adapted to work It should be noted, however, that where the differ­ For the efficient operation of a water relay, it is with other equipment. Figure 7.2 shows the three ence in level between successive pumps is less than important to maintain good communications along stages in the building up of the relay to its full 10 metres, the percentage variation in flowrate will the route, so that changes in conditions, orders to capacity, starting with just 3 pumps and a single be in single figures, so differences in level of less shut down, etc. can be acted upon quickly. The line of hose but ending up with 5 pumps and than 10 metres may normally be disregarded. type of communications adopted will, of course, twinned hose. be dependent on conditions, availability of

resources, and so on, and it is the responsibility of Figure 7.2 The stages ofthe Porter Relay the relay officer to devise an appropriate system. If Stage 1: /4 lengths ofsingle 70mm hose between using radio sets, particularly at large incidents, one appliances. channel should be dedicated solely for use by Stage 2: Intermediate appliances positioned when they an'ive and Stage 3 water relay officers and operators. Whatever sys­ second line deployed without disturbingjirstline. tem is used, the communications operators should Stage 3: 7 lengths oftwinned 70mm hose between all appliances.

86 Fire Service Manual Hydraulics, Pumps and Water Supplies 87 7.6.7 Mechanical Breakdowns 7.7 Special Equipment Figure 7.3 Storage ofhose jor rapid deployment. (Courtesy ofWes( J\4idlamls Should a booster pump suffer a mechanical defect, 7.7.1 Use of Hose Layers Fire Service) provided the lines have been twinned there is usu­ ally no need to shut down the relay completely When hose is being laid direct from a hose-laying because when a replacement pump arrives the lines lorry, the vehicle should be driven at a steady IS to may be connected to it one at a time. The relay will 25km/h. This speed may be increased to a maxi­ continue to function, although of course there will mum of about 40km/h in ideal conditions, but be a drop in the output and the throttles ofthe other extreme care must be taken as, at this speed, the booster pumps will have to be adjusted in the light hose is likely to over-run when the vehicle slows of the changed conditions. The incident comman­ down, particularly at corners. This is likely to der should, if possible, have a spare pump of the cause unnecessarily large bights of hose which same capacity available, with crew, ready to set in would result in excessive snaking and kinks when to the relay. Careful consideration should be given the hose is charged. to the substitution of portable pumps for a major pump. For example, if a 2250 IImin pump operat­ If possible, after the hose has been laid and before ing in a twin line relay has to be replaced with it is charged, a check should be made to see that it portable pumps then, if the performance of the is lying at the side of the road and is causing no relay is not to be compromised, one will need to be obstruction to traffic. The oppol1lmity should be substituted in each line. taken to remove any kinks before charging. Careful consideration should be given at, the pre­ A hose deployment and retrieval unit currently 7.6.8 Safety Precautions When it is necessary to take hose across a road, planning stage, to the route over which large diam­ used in brigades and capable, with manual assis­ ramps or bridging units should be used. eter hose is to be laid, particularly where it crosses tance, of retrieving up to 1000m of l25mm or Among the factors which should be considered in roads and in the area around the fireground, 150mm flaked hose directly back onto the hose the interests of safe systems of work are: Some Brigades have water tenders fitted with hose because once charged, it presents an obstruction to laying vehicle ready for re-use is shown in 'coffins' which store flaked hose within a side the movement of fire appliances and other vehi­ Figure 7.4. (i) Positioning warning signs and coning off locker at the rear of the fire appliance. Hose is cles. Suitable large hose ramps are available but an for the protection of firefighters from deployed in the same way as with a specialist hose alternative solution to the problem of obstruction Figure 7.5 shows a hose laying and retrieval sys­ passing traffic. layer, enabling the first line of a water relay to be ofroads etc. is to use, in the problem areas, a num­ tem, recently introduced by West Sussex Fire quickly established. The hose 'coffin' is mounted ber of lines of 90mm hose with appropriate divid­ Brigade, which is based on systems extensively (ii) The wearing of hi-viz clothing. on rollers and can be easily pulled free from the ing and collecting breechings. However, this used in the United States. It consists of two large locker, as shown in Figure 7.3, thus enabling the procedure will to some extent reduce the hydraulic hydraulically driven hose drums capable of carry­ (iii) Carefully pre-planning the route of the hose to be restowed after use. efficiency of the relay. ing a total of 1200 metres of I50mm diameter hose relay and positioning the hose lines and appliances so as to cause the minimum 7.7.2 Deployment and Retrieval of Large obstruction to passing traffic. Diameter (Hi-Vo)) Hose Figure 7.4 A flaked hose (iv) Protection of personnel from long-term Hose layers for the rapid deployment of standard deployment and retrieval exposure to the noise of pumps. lengths of 70mm and 90mm hose have been in use unit. for some time and, because each length is relative­ (Diagram COllrtes,' a/Angus Fire) (v) Clearly defined and well practised means ly flexible and lightweight, retrieval of the hose of communication between relay opera­ after an incident presents no great problems. The tors. distinct advantage of larger diameter hose for water relaying has been made clear earlier in this chapter but, because its weight increases in pro­ portion to its diameter and, because, for speed of deployment and hydraulic efficiency, it is made in much longer lengths, the problem of retrieval is much greater. It is for this reason that systems have recently been developed for the rapid deployment and retrieval of this larger diameter hose.

Hydraulics, Pumps and Water Supplies 89 88 Fire Service Manual s Figure 7.5 The West Sussex Fire Brigade hose laying unit. D 1­ (Photo: West Sussex Fire Brigade; ulc

l

Figure 7.6 The Hoffand Fire System pumpingfrom an open source.

and has the advantage that all deployment and If personnel are required to access (ii) a 60m long transmission system consisting (v) a truck for the transportation of all of the of hydraulic hose capable of operating at above equipment. retrieval operations may be carried out with per­ the tlatbed of a hose laying unit sonnel at ground level. Closed circuit television pressures up to 320 bar. enables the driver of the unit to monitor both the during deployment and retrieval Figure 7.6 shows, diagrammatically, how the (iii) a 133kW diesel powered hydraulic drive equipment is deployed. operation of the drums during deployment and opc.-ations then, in order to retrieval and also, in the interest of safety, the unit. movement ofpersonnel around the rear ofthe vehi­ minimise the risk of accidents, an Figure 7.7 shows the submersible pump, drive unit, cle. A forklift truck, carried at the rear of the unit, appropriate safe system of work (iv) a hosebox containing Ikm of 150mm hose and the truck mounted hosebox and hose retrieval (units capable ofstoring up to 3km are avail­ system. is provided to assist with the movement of the must be devised. drums and for the handling of pallets of additional able). flaked hose and hose fittings. 7.7.3 The Holland Fire System for Figure 7. 7 The Before commencing retrieval of large diameter Pumping from Open Water Components ofthe hose, water should be allowed to free flow out of Hoffand Fire System. the hose and, where water sits in hollows on undu­ (Photo: Kuiken H\'Irans) It has already been explained in Chapter 3 that the lating ground, the couplings should be broken, the performance of a typical pump is significantly hose drained and the couplings re-attached. reduced when operating at a lift ofmore than a few Because Hi-vol hose is manufactured in long metres. One way of overcoming this problem is to lengths, the pressure due to the head of water at a employ a hydraulically driven pump which is coupling near the bottom of a hill may be such as immersed in, or floats on, the water supply. The to make it difficult to break. The insertion of a Holland system uses 150mm diameter hose and dividing/collecting breeching (Figure 7.10) at such depending on the lift required (which may be up to points will facilitate drainage from the hose and so 60m) and the distance to the fireground, is able to allow the coupling to be broken and the device pump up to 4250 litres per minute. It is a con­ removed before retrieval. tainerised system consisting of:

The driver of the retrieval unit should move for­ (i) a hydraulically driven portable submersible ward at a speed similar to the rate at which the hose pump. is being collected in order to avoid excess tension on, or over-running of, the hose line.

90 Fire Service Manual Hydraulics, Pumps and Water Supplies 91 7.7.4 Large Diameter Hose Couplings instantaneous coupling outlets and screw thread 7.7.5 Use of Helicopters sufficiently large open source, including an appro­ and Ancillary Equipment inlets for hard suction, adapters are needed in priately designed portable dam with a minimum both cases to facilitate connection to the Storz Though used only by a limited number of brigades, depth of 1.2 metres, and, by opening a remotely If advantage is to be taken of large diameter hose, hose couplings. It is therefore necessary for a in particular those with a responsibility for large controlled electrical valve situated at the base of then appropriate couplings, adapters, collecting component box of such equipment to be stored on areas of forest or moorland, helicopters have in the the bucket, water may be discharged either direct­ heads etc. must be used. Since, at the present time, appliances. Figures 7.8 to 7.11 show some ofthese past few years proved to be extremely effective in ly onto the fire or into a portable dam (Figure 7.13) pumping appliances are fitted with standard components. situations where access to the fire is difficult for or all-terrain vehicle. The use of helicopters for the both firefighters and firefighting equipment. In laying of hose from an underslung drum, although addition to their use for aerial observation and the an attractive proposition, has been ruled out by the transportation of personnel and equipment, they civil aviation authority because of the danger of may also be used to transpOIi water to a point close the hose snagging and the risk of crossing high Figure 7.8 An inter­ to the seat of the fire or to discharge water direct­ voltage power lines. mediate pump component ly onto the fire. box with. on the le/i, Storz A helicopter is an extremely expensive item of to screw thread adapters for connection to the pump For the transportation of water to an incident, a equipment to purchase outright and even leasing inlet. large bucket suspended beneath the helicopter and costs may amount to several hundred pounds per (Photo: Northamptonshire Fire capable of containing several hundred litres of hour. However, its ability to provide rapid inter­ and Rescue Service) water is used. This can rapidly be filled from any vention at incidents such as forest fires, where

Figure 7.9 A Storz to instantaneous Figure 7.10 A dividing/collecting Figure 7.11 A 'Phantom Pumper' male collecting breeching to breeching for use when multiple which enables hose with standard facilitate connection to the pump lines are required. (Photo. Angus Fire) couplings to be connected directly outlets via a number ofshort to the large diameter line. lengths of70 or 90mm hose. (Photo: Angns Fire) (Photo: Angus Fire)

Figure 7.12 A helicopter collecting from open water Figure 7.13 Another discharging into a portable dam. using an underslung bucket. (Courtesy Derbyshire Fire and Rescue Service)

92 Fire Service Manual Hydraulics. Pumps and Water Supplies 93 Hydraulics, Pumps and Water Supplies access for wheeled vehicles would be difficult and time consuming, may well result in the early con­ clusion of firefighting procedures which might otherwise prove to be very prolonged with propor­ tionally high costs in manpower and equipment. Glossary of Hydraulics Terms At the time of writing, further operational trials to establish the full potential of helicopters for fire service applications are being conducted. Base pump The first pump in a water relay, taking its water direct from the source.

Booster pump 1. A pump used to increase the pressure in a water main.

2. In a water relay, any pump set in between the base pump and fireground pump.

Casing The chamber surrounding the impeller in a centrifugal pump.

Cavitation The formation of bubbles of water vapour in a pump, caused by the water boiling at low pressure.

Centrifugal pump A pump in which water is moved by the spinning action of an impeller.

Closed circuit 1. Cooling system: one in which all the cooling water from the fire pump is returned to the pump, none of it being discharged to waste.

2. Water relay: one in which the water is pumped direct from one pump to another.

Collecting breeching A connection designed to join two lines of hose into one.

Compound gauge A gauge designed to measure both positive and negative pressures.

Delivery On a pump, the valved outlet through which water is discharged.

Diffuser A system of guide vanes in the casing of a pump to reduce turbulence.

Ejector pump A pump which lifts water by means of a partial vacuum created by a jet of water under pressure from another pump.

Friction factor A figure expressing the degree of internal roughness of a particular type of hose or pipe. It must be taken into account when calculating friction loss.

Hydraulics, Pumps and Water Supplies 95 94 Fire Service Manual ,., Friction loss Loss of water pressure caused by the frictional effect of the walls Monitor A piece of equipment for delivering very large quantities of of the hose or pipe through which the water passes. water. It may be freestanding (ground monitor) or appliance mounted (eg TL monitor). Full-flow coupling A type of coupling which allows water to pass from one length of hose to another without obstruction or reduction of diameter. MUlti-pressure pump A centrifugal pump which combines a conventional low pressure stage with a high-pressure stage. Gland A device fitted around a shaft, eg in a pump or hydrant, which exerts pressure in order to prevent leakage. Multi-stage pump A centrifugal pump with two or more impellers.

Governor A device which automatically controls the speed of a pump Negative pressure Pressure lower than that of the atmosphere (atmospheric pressure engine in order to maintain a preset pump pressure. being regarded as 'zero' in this context).

Guide ring A ring of guide vanes in the casing of a centrifugal pump Non-percolating hose Any non-porous hose. designed to reduce turbulence. Open circuit 1. Cooling system: one in which the cooling water from the Hard suction Large-diameter hose internally braced to prevent collapse under fire pump discharges to waste. (This system is no longer atmospheric pressure. used on fire appliances in the United Kingdom.)

Head 1. The vertical distance from a given point in a fluid to the Open circuit 2. Water relay: one in which the water is pumped via portable open surface of that fluid. dams placed between pumps. (Seldom used nowadays.)

2. The depth of open water equivalent to a given pressure. Percolating hose Any unlined, porous hose.

Heat exchanger A cooling device in which heat is conducted from the hot Peripheral pump A special type of centrifugal pump in which the water follows substance to a cool circulating fluid. a spiral path around the edge of the impeller.

HiVol The name given to hose with a diameter in excess of 90mm. Positive pressure Pressure higher than that of the atmosphere (atmospheric pressure being regarded as 'zero'). Hydrostatic To do with forces arising from a stationary fluid. Power take-off (PTO) A device to divert engine power from running an appliance to Impeller The spinning part of a centrifugal pump which imparts a high running equipment on it, such as a built-in pump. velocity to the water. Pressure 1. Force exerted per unit of area. Instantaneous A type of interlocking coupling designed to be connected by pressing onto a seal (as opposed to being screwed in). 2. In practical firefighting: same as positive pressure.

JCAEU Joint Committee on Appliances, Equipment and Uniform Pressure gauge A gauge designed to measure positive pressure only. (a committee of the Central Fire Brigades Advisory Council). Formerly JCDD. Primer A device for filling a centrifugal pump with water to enable it to operate from a non-pressure-fed supply. JCDD Joint Committee on Design and Development of Appliances and Equipment. PTO Power take-off.

Kinetic To do with motion. Rack valve standpipe A type of standpipe with a valve at the head enabling the flow to be shut off. LWP Lightweight portable pump. Reciprocating pump A pump in which water is moved by the action of a piston or Mechanical seal A seal which uses a spring to maintain contact, instead of plunger in a cylinder. packing material.

96 Fire Service Manual Hydraulics. Pumps and Water Supplies 97 I Hydraulics, Pumps and p e di Water S pplies Seal Another name for a gland.

Shuttle A system in which a number of water tenders or water carrier are used in rotation to convey water to the fireground.

Single-stage pump A centrifugal pump with one impeller. Appendices

Sluice valve 1. A valve in a water main, used to shut down the main if necessary, or to divert water.

2. A valve found in one type of hydrant. Ai . ymbol and nits

Soft suction Non-reinforced hose designed for use in positive pressure ..\2 Transposition of Formulae situations. AJ Calculation ofAreas and Volumes Static pressure The pressure at a hydrant or pump when the water in it is stationary. AA Derivation of Hydrauli s Formulae

Static suction lift The vertical distance from the surface of an open water source AS Summary of Formulae and Oth r Data to the eye of the pump. . 6 . e tions 57 and "8 of the Water Industry ..\ t 1991 Statutory water Any regional water authority or statutory water company. undertaker ..\7 Metrication

Stuffing box A chamber, eg in a hydrant, on which pressure is exerted by a gland in order to prevent leakage around a spindle, shaft etc.

Tachometer An instrument for measuring the speed of an engine.

Tuberculation The roughening of the internal surface of a pipe due to the build up of deposits.

Twinning The laying of two lines of hose along the same path.

Vacuum 1. An empty space, ie one containing no matter.

2. In practical firefighting: same as negative pressure.

Vacuum gauge A gauge designed to measure negative pressure only.

Volute A type of casing in a centrifugal pump, shaped like the shell of a snail, where kinetic energy is converted to pressure energy.

Vortex A swirling depression in the water surface caused by the drawing down of air when a suction strainer is insufficiently submerged.

Water carrier A vehicle used for conveying large quantities of water to an incident where it is difficult to obtain an adequate supply otherwise.

98 Fire Service Manual Hydraulics, Pumps and Water Supplies 99 APPE DIX 1 APPE DIX 2

Symbols and Units Transposition of Formulae

Throughout this Publication various symbols are used to denote pressures, dimensions, etc. A.2.1 The need for Transposition The symbols are shown below and should not be confused with standard abbreviations for SI units which are given in the Guide to SI units. In order to illustrate the need for transposition let us take a typical hydraulics formula such as:

A cross-sectional area (square metres) WP = 100LP 60 a cross-sectional area (square millimetres) b breadth (metres) which enables us to calculate the water power (WP) of a pump when we know the discharge BP brake power (watts) (L) from it and the pressure (P) at which it is operating. C circumference (metres) D diameter (metres) The term on its own on the left of the equals sign, in this case WP, is called the subject of the d diameter (millimetres) formula. E efficiency (per cent) F force (newtons) It is just as likely, however, that we might wish to determine L given the numerical values for f friction factor P and WP. What we then need, ideally, is a re-arranged version of the formula in which L is g acceleration due to gravity (= 9.81 m/s2) the subject (i.e. appears on its own on the left of the equals sign) and with all the other terms H metres head on the right. The process of re-arrangement, which results in a new subject of the formula, is h depth (metres) called transposition. L flow (litres per minute) I length (metres) In the example chosen, because there are three variables (WP, P and L) there will be three pos­ m mass (kilograms) sible ways of arranging the formula, and the choice we have is between memorising all three pressure (newton/square metre) versions or being able to perform simple transposition on the one normally remembered in pressure (bar) order to derive the other two. Bearing in mind the proliferation of hydraulics and other for­ pressure lost in friction (bar) mulae where the problem might occur, the acquisition of the ability to apply the limited num­ flow (cubic metres per second) ber of rules required to transpose the great majority of formulae would appear to be the better reaction (newtons) alternative. r radius sum of the sides of a triangle s A.2.2 The basic rule for Transpo ition time (seconds) v velocity (metres per second) Let us return to the example in the above paragraph where the problem posed was to re­ WP water power (watts) arrange the Water Power formula so as to make L the subject. Our objective may be consid­ density (kilograms/cubic metre) (Greek symbol ro) P ered as twofold: (i) to get L on the left of the equals sign and (ii) to get all the other symbols 1t 3.1416, or 22/7 (Greek symbol pi) on the right. is equal to is approximately equal to [Can also appear as n or =;] The equals sign in any formula is making the statement that, when appropriate numbers are .. therefore substituted for the symbols and any subsequent arithmetic performed, the two sides will reduce to the same numerical value. It must, therefore, be equally true to make the same state­ ment in reverse

Thus:

100LP 60 WP stage J

100 Fire Sen1ice Manual Hydraulics. Pumps and Water Supplies 101 + APPENDI ' 2 continued

Though not a particularly spectacular move, we have achieved the first part of our objective ­ The following two rules summarise the processes described above: L is now on the left of the equals sign. 1. We may reverse the formula. Again, if two numbers are equal, the results of multiplying (or dividing) them both by the same quantity will also be equal. We may therefore multiply both sides of the above formula 2. We may transfer symbols and numbers from one side of the formula to the other by 60 if we wish. provided we move them diagonally across the equals sign.

Let us see the result of doing this. A.2.3 Applying the rules

60 x6~00LP = 60 x WP We will consider a number of different cases.

Example 1 Clearly the '60's will now cancel out on the left-hand side leaving us with: Transpose the formula for the percentage efficiency of a pump: lOOLP = 60WP stage 2

E = WP x 100 (note that there is no need to retain the line under the left-hand side since there are no BP symbols remaining in the denominator) to make WP the subject. Now let us divide both sides of the formula by 100: In this example the proposed new subject is above the line and uncomplicated by the 100LP 60WP presence of roots or indices. JO() 150 Applying rule I(reversing the formula) gives: Again the' lOO's cancel out on the left leaving:

WP x 100 = E stage 3 BP LP = 6~'t/ Applying rule 2 (moving the unwanted symbols on the left diagonally) gives: FinaLly let us divide both sides of the above formula by P:

WP = E x BP LP 60WP 100 P lOOP

Cancelling the 'P's on the left gives: Example 2

L- 60WP stage 4 Transpose the formula for the velocity of a falling body: - lOOP

v = gt and we have finally achieved our twofold objective with L on its own and on the left of the equals sign. to make t the subject.

Ifwe now compare our newly transposed formula (stage 4) with the reversed form ofthe orig­ In this case there is no line on the right hand side, because there are no symbols in the inal formula (stage I) we can see that the net result of the intermediate stages is that numbers denominator, but the rules are applied in exactly the same way. and symbols which we wished to remove from the left-hand side (' 100' and 'P' and '60') have moved diagonally across the equals sign; those which were above the line on the left at stage Applying rule I gives: I (' lOO' and 'P') appear below it when transferred to the right at stage 4 and the '60', which was below the line at stage l, appears above it when transferred to the right at stage 4. gt = v

102 Fire Service Manual Hydraulics. Pumps and Water Supplies 103 APPENDIX 2 continued

Applying rule 2 gives: However. it is above the line, so the first step is the usual one of reversing the formula:

2d 2 P t = -'Lg ---L3 -

Now we apply rule 2 to leave only -Jp on the left. Make no attempt, at this stage, to remove Example 3 the root sign:

Transpose the formula for force: 3L P =2d2 F=mv t Finally, to remove the root sign, we multiply each side by itself: to make t the subject. / _I 3L x 3L \PxvP=2d2 2d2 In this example the proposed new subject is below the line and we do not apply rule 1 3L)2 Applying rule 2 to t (moving it diagonally) gives: P = ( 2d 2

tF = mv It is extremely important to include the brackets around the terms on the right. Without them the power 2 would apply only to 1. (note that the order of the symbols does not matter but if numbers are involved we put them first) Example 5

Applying rule 2 to F gives: Transpose the formula for friction loss:

mv 900~f1U t=- P = F r d)

Both of these steps may be carried out at the same time of course. to make L the subject.

A2A Transposition where roots or indices are involved The proposed new subject, L, is raised to the power 2.

Example 4 However it is above the line. so the first step is the usual one of reversing the formula:

Transpose the formula for nozzle discharge: 9000flU = P dS f

Now apply rule 2 to leave only U on the left. Make no attempt, at this stage, to remove the power 2: to make P the subject. P dS L" -----'-f__ The formula is best re-written as: • = 9000fl

2 L = 2d ,JP 3 Finally, to remove the power 2, we take the square root of each side: to make clear what is above and what is below the line. .1 P dS L =V 90~Ofl The proposed new subject, P, appears in the formula under a square root sign.

104 Fire Service Manual Hydraulics. Pumps and Water Supplies 105 APPENDIX 2 continued APPE DIX 3

A.2.5 Summary

Application of the rules described above enables us to transpose the great majority (but not all) of formulae likely to be encountered in the field of hydraulics and other areas.

They may be summarised as follows: Calcula ion of Areas and Volumes The calculation of areas and volumes, especially of rectangular and circular shapes, is a fun­ 1. The first step is usually to reverse the formula in order to get the new subject on damental part of the mathematics required by firefighters when making calculations involv­ the left of the equals sign. An exception to this is when the new subject is below the ing water resources and requirements. It is proposed, therefore, in this appendix to deal with line, in which case go straight to step 2. the general principles of measurement. 2. Move numbers and symbols diagonally across the equals sign to leave only the new subject on the Jeft. Do not attempt to deal with any root signs or indices at this A.3.t Area of regular figures stage. The area of a rectangle or triangle is easily calculated, as shown in Figure 1. 3. Squaring both sides will eliminate root signs.

4. Taking the square roots of both sides will eliminate powers of 2.

h

b

Figure I Areas ofregular figures

Area of rectangle or square = base (b) x vertical height (h)

= base (b) x vertical height (h) Area of a triangle 2

The area of a triangle can also be calculated when the length of each side is known but when it is impossible to measure the vertical height, as for example, in the case of a large triangu­ lar-shaped pond or lake. The required formula is:

Area of a triangle = -is (s-a)(s-b)(s-c)

where s = one half of the sum of the sides, a, band c.

Hydraulics, Pumps and Water Supplies 107 106 Fire Service Manual APPE DIX 3 continued

A.3.2 Area of irregular figures

To find the area of irregular figures it is generally nec ssary to divide them into regular shapes such as rectangles or triangles and find the area of each.

p

Figure 3 Method o.('calculating the area 0('al7 irregular shape. (1) by calculation ofapproximate areas. (2) by the lIse ofsquared paper.

The area of the rectangle should be calculated and the sum of the areas of the e. temal trian­ gles and rectangles subtracted.

More accurate results can be obtained by drawing the shape of the pond or lake to . n appro­ priate scale upon squared paper (Figure 3(2» and then subtracting the areas ofthe squares left outside from the total squared area. When adding up the squares, any which are less than one half of a square should be disregarded.

A.3.3 Area of circ es

Calculation of the area of a circle involves the lIse of the constant pi which is represenled by the Greek symbol IT. It is the ratio of the circumfer nce (C) of a circle la it' diameter (D). Careful measurement of both on any circular cylinder, as shown in Figure 4, will show that:

n = g= 3.1416 or approximalely 3 1/,

Figure 2 Areas o{"irregular/igures

The area of the quadrilateral ABCD (Figure 2 i) can be found by dividing it into two triangles ABC and ACD, and adding together the area of each.

The ficrure ABCDE (Figure 2 ii) can b divided into three triangles, ABC, ACE and CDE, b . whilst the figure ABCDEF (Figure 2 iii) can be divided into a rectangle ACDF, and two tn- angles ABC and DEF. Figure 4 Measurement ofcircumference and diameter ofa cvlinder. If it is required to ascertain the surface area of an lffegularly-shaped pond or lake, this can be calculated by sketching its shape (Figure 3(1 n, drawing a rectangle ABCD around it and then It can be shown that the area (A) of a circle is found by squaling the radius (r) and multiply­ inserting such rectangles and triangles as will roughly fill the area outside the water surface, ing by n, but inside the rectangle. I.e. A =: Jtr?

Hydraulics. Pumps and Water Supplies 109 108 Fire Service Manual APPENDIX 3 continued

In hydraulic calculations, it is often more convenient to use the diameter of a circle rather than If the dimensions of the tank in Figure 5(1) are length 7.5 metres, breadth 2 metres, depth its radius so that ubstituting 0/2 for r we have: 1 metre, the volume (in cubic metres) will be:

7.5 x 2 x I = 15 cubic metres (m 3) or 15 x 1000 = 15000 litres

Capacity of a rectangular tank in litres = I x b x It x 1000 dividing 3.1416 by 4 0.7854 0 2 (b) Rectangular tanks with a sloping base

Thus, we may choose whichever is the most convenient formula for the area of a circle from: The capacity of rectangular tanks with uniformly sloping bases such as swimming pools, can be obtained by proceeding as in (1) above but multiplying by the average depth, which is 1t02 > asc rtained by adding together the values for the deep and shallow ends and dividing by 2. [n A = m2 or 4 or 0.7854 0- Figure 5(2) the capacity (all dimensi ns being in metres) would be:

The result of the calculation will be in square metres or square millimetres depending on .I x b X h, + h, . whether the radius and diameter are expressed in metres or millimetres. capaCIty = 2 - (cubIc metres)

A.3.4 Volumes Where the container is more complex in shape it is usually possible to estimate its total capac­ ity with a reasonable degree ofaccuracy by dividing it up into a number ofsimpler shapes for When working out the area of a figure, two lengths ar multiplied. In calculating volumes, each of which it is easy to calculate the capacity. For example Figure 5(3) shows a tank with three lengths must be multiplied. For containers of constant cross section this means multi­ a sloping end. The capacity of such a tank is easily calculated by dividing it into a rectangu­ plying the surface area by the depth. For large containers the three lengths are most conve­ lar part ABeD with uniform depth DE, and a triangular part DEF. niently measured in metres and the volume calculated will then be in cubic metres. Since there are 1000 litres in a cubic metre, the result of the calculation can be expressed in litres simply The volume of a tank of triangular section is obtained by multiplying the area of the triangle by multiplying by 1000. OEF by the length (b).

(a) Rectangular tanks Therefore, the capacity ofthe tank shown in Figure 5(3) is found by adding together the capac­ ities of the rectangular and triangular portions. The volume of a rectangular tank (Figure 5( 1» is calculated by multiplying the length (l) by the breadth (b) by the depth (h). (c) Circular tanks

The volume ofa circular tank (Figure 6) is determined by calculating the surface area and mul­ tiplying by the depth (h), all measurements being in the same units. This can be expressed as

Radius (R)

Depth (h)

Figure 5 Volumes 0/ (I) a rectangular tank; (2) a rectangular tank with Figure 6 VolllmE' of{[ cirClllar tank. a uniformlv sloping hase and (3) a rectangular tank with a sloping end

Hydraulics. Pumps and Water Supplies III 110 Fire Service Manual • APPE DIX 3 continued

The capacity of a circular tank 10 metres in diameter and 4 metres deep would be: As 12.5664 is approximately = 100 8 another quick formula for calculating the capacity of a circular tank in cubic metres is: 0.7854 x la x 10 x 4 = 314.16 cubic metres

Quick formula 2: capacity of circular tank Multiplying by 1000 gives the capacity in litres = 314 160 litres.

cubic metres (1) Quick method 1

The capacity of a circular tank has been shown to be 0.7854 x D2h cubic metres, but or, multiplying by 1000 to convert cubic metres to litres:

0.7854 ~ 0.8 = 80 Oh litres therefore a good approximation is: The error introduced when either of these two formulae is used is only about 0.5% and is therefore likely to be within the limits of accuracy of the measurements themselves when Quick formula 1: Capacity of circular tank = 0.8 D2h cubic metres (m 3) these have been obtained in a practical situation. where D = diameter and h = depth, both in metres. (d) Capacity of hose or pipeline In the above example, this would give Once a length of hose is filled with water under pressure it becomes a horizontal circular 0.8 x la x 10 x 4 = 320 cubic metres cylinder so one of the approximate formulae derived above, such as: (which is about 2 per cent too high)

capacity = 800 D2h litres Alternatively, the capacity in litres can be obtained by multiplying by 1000 may be applied. In this formula D is the diameter in metres and h is now the hose length. Capacity of circular tank = 800 D 2h litres I.e. However, hose diameter is usually measured in millimetres so we must make the substitution:

(2) Quick method 2 _ d D- 1000 The capacity of a circular tank when only the circumference, (C), and depth, (d), are known is found by making the substitution: gIVIng: capacity xIO~O 800 x 10dOO x h litres D=C re 2 = 8 d h litres in the formula: la 000

re D2h capacity = 4 Taking just I metre of hose (i.e. h = I) gives: giving: capacity = 8 d2 litres per metre 10000

(e) Cones, pyramids and spheres Oh 4re Firefighters are not often required to calculate the volume of cones, pyramids or spheres when dealing with hydraulic problems, yet it is advantageous to know the formulae for such calculations. C2h 12.5664 (1) Cones and pyramids

The volume of a cone or pyramid (Figure 7) is obtained by multiplying the area of the base by one-third of the vertical height.

Volume of a cone or pyramid = area of base x h 3

112 Fire Service Manual Hydraulics, Pumps and Water Supplies 113 APPE DIX 3 continued APPENDIX 4

Derivation of Hydraulics Formulae

The derivations which follow assume an understanding of the concepts of force, work, ener­ gy, power etc. many ofwhich are discussed in the Manual of Firemanship Volume 1 'Physics and Chemistry for Firefighters'.

AA.1 Relationship between Pressure and Head

Figure I shows a vessel having an area of cross section I square metre and height H metres filled with a liquid of density p kilograms per cubic metre. Figure 7 Volume ola cone or pyramid.

(2) Spheres .L /-1m --'----Y--.-__ 1m To calculate the volume of a sphere, the cube of the diameter is multiplied by rr/(" or the cube T of the radius is multiplied by 4rr/3

rr d 3 4 rr r 3 Volume of a sphere = 6 or -3- H metres

(I) Irregular-shaped tanks

The volume or capacity of irregular-shaped tanks or ponds is calculated by finding the surface area by one of the methods already explained and multiplying by the depth. In the majority of cases the depth of ponds and lakes is not uniform, and the capacity is conservatively calculat­ ed as being two-thirds of the value obtained by multiplying the surface area by the average depth. Figure I Capacity of a pond or lake (cubic metre) -1 (surface area x average depth) -3 The volume of liquid in the container is:

1 x H cubic metres

A very approximate estimate of the capacity of such a pond or lake ID litres would be and its mass (volume x density) is: 700 x surface area in square metres x average depth in metres.

Hp kilograms

Remembering that each kilogram of mass experiences a force due to gravity ofg newtons, the weight of this column of liquid (and hence the force exerted on the base of the container) is:

Hpg newtons

Because pressure, p, is defined as the force acting on unit area then

p = Hpg newtons per square metre

114 Fire Service Manual Hydraulics, Pumps and Water Supplies 115 APPENDIX 4 continued

A.4.3 Water Power (\VP) A.4.2 Velocity and Flowrate in Hose and Pipes Figure 3 shows a pump which is discharging L litres of water per minute at a pressure of P . .. movin with a velocity of v metres per second in a pipe of dial~eter :l~~~i~:t~~;sI::I~~~~nd ~olume bars along a pipe with an area ofcross section ofA square metres. Suppose the distance moved the of liquid discharged will be that of a circular cylmder by the column of water in 1 minute is I metres. v metres long and d millimetres in diameter. Asq m

l~~"~.~""'_."'-IIi'-.~_"-"''l'~~ ------~~-__v_--=--=--=--=-=-=-~y } d ----~--v-----_../ V metres in 1 second I metres

Figure 2

The volume of a circular cylinder is given by the formula:

cubic metres Figure 3

where D is the diameter in metres and h is the height or length in metres. The force (pressure x area) exerted on the column of water is:

Making the substitutions: 100 000 x P x A newtons (N)

o = _d_ and h == v (the factor of 100000 appears because I bar = 100 000 N/m 2) 1000 The work (force x distance) done by the pump in I minute is: d d cubic metres Volume discharged in 1 second 0.7854 x 1000 x 1000 x v 100000 x P x A x I joules (J) d x _d_ x v x 1000 litres 0.7854 X 1000 1000 But A x I is the volume of water discharged in I minute measured in cubic metres and this, in turn, is equal to the number of litres, L, discharged in I minute divided by 1000. 0.7854vd2 litres 1000 So, the work done by the pump in I minute is:

L The number of litres discharged in I minute is therefore: 100000 x P x 1000 joules

60 X 0.7854vd2 litres L= 1000 = 100LP joules

vd2 The water power (power is defined as energy expended or work done per second) delivered I.e. L= litres per minute 21.2 by the pump is therefore given by the formula:

The transposed version of this formula: WP = 100LP watts (W) 60

v=--21.2L metres per second d 2 Strictly speaking P is the increase in pressure created by the pump so, if there is a positive pressure at the inlet, this value should be subtracted from the outlet pressure. Likewise, if the is useful for finding the velocity of flow in a hose or pipe when the flowrate is known. inlet pressure is negative because the pump is lifting from an open source, the appropriate value should be added to the outlet pressure to take into account the work the pump is doing in lifting water.

Hvdraulics. Pumps and Wafer Supplies 11 7 116 Fire Service Manual APPENDIX 4 continued

AAA Bernoulli's formula Applying the principle of the conservation of energy:

This is a relationship involving the pressure, velocity and height of a liquid flowing along a Total energy of the liquid at position I + work done by the pressure PI pipe ofvariable diameter at two different points in the pipe. Its derivation makes use ofone of Total energy of liquid at position 2 + work done by the pressure Pz the fundamental principles of science; the Principle of the Conservation of Energy. This states that energy may neither be created nor destroyed but only transformed from one form into The energy at both positions is made up of potential energy (mgh) and kinetic energy (mvZ) another. T The work done by the pressure at position 1 is: The formula is included here because many important concepts of hydraulics follow directly from it. force x distance = pressure x area x distance Figure 4 shows a liquid flowing along a pipe between two points indicated in the figure as = PIAJI position I and position 2. At position I the area of cross section is AI square metres, the pressure PI newtons per square metre, the velocity VI metres per second and the height above and likewise at position 2 some arbitrary horizontal reference line (e.g. the ground) hi metres. At position 2 these Thus values change to, respectively, A z' Pz' vz' and hz·

12 Dividing throughout by m gives: ~

VIZ PIAI!1 V Z PA! + h + z +gh +~ V2 T g, -----r:rl = 2 z m P2

Substituting All,p and A)zp for m on the Jeft- and right-hand side respectively: A2 V z p,A/, _z_v z PzAiz 2 -'- + gh +-- + gh2 +-- 1 2 l A/IP 2 Aiz p h 2 glvlllg: v z vz2 pz • + gh. +R! + gh + T p "2 2 p P1

In this form of Bernoulli's equation, the three terms on each side of the equals sign represent, h'{_A_1 ------respectively, the kinetic energy, potential energy and pressure energy per kilogram of liquid. The large number of variables in the formula make it appear complex but, in many applications, it will simplify because certain factors take the same value on both the left- and Figure 4 right-hand sides of the equals sign. For example, ifwe apply the formula to a nozzle, both the inlet and the outlet are, for all practical purposes, at the same horizontal level so that the two Suppose the liquid at position I travels a short distance " along the pipe and that, in the same gh terms are the same and the formula reduces to: period of time, liquid at position 2 travels a distance!2" If we assume that the liquid is incom­ pressible then the two volumes displaced, and consequently the two masses, will be the same. Z V z + P2 The two volumes displaced are: 2 P

Before attempting to use the Bernoulli formula it should be noted that pressure must be measured in newtons per square metre (pascals) and that, for water, the density, p, may and the two masses (volume x density): be taken as lOOOkg per cubic metre.

An alternative version of the formula expresses the pressures at the two points in the pipe in terms of the head in metres at those points. It is obtained by making the substitutions:

118 Fire Service Manual Hydraulics, Pumps and Water Supplies 119 APP DIX 4 continued

Thus: V 2 v 2 2 ---L HIP g 2 H,p g I.e. v 200P + gh l +-- + gh +--- 2 P '2 2 p or v 14.14'VP I.e. v 2 v 2 1 + gh + Hlg --..l.. gh + H g '2 l 2 2 2 AA.6 The Nozzle Di charge Formula

Dividing throughout by g gives: This formula is obtained by substituting the expression for v given by the velocity ofjets for­ mula into the relationship for tlowrate (L), in terms ofpipe diameter (d) and velocity offlow (v): V 2 V 2 _I + hI + HI = 2 + h + "2 2g 2g 2

Again, if the pipe is horizontal so that hi and h2 are the same, this simplifies to give: I.e. 14.14-VPd2 V 2 V 2 L ...... !...-+ H = _2_+ H 21.2 2g I 2g 2 Le. A.4.5 Velocity of Jet

Figure 5 shows a conventional straight stream nozzle operating at a pressure of P bars and dis­ AA.7 The Jet Reaction Formula charging water at a velocity of v metres per second. Figure 6 shows water discharging with a velocity v metres per second from a conventional straight stream nozzle of diameter d millimetres and operating at a pressure of P bars.

v

Figure 5

Since water enters and leaves the nozzle at the same horizontal level, then we may apply the Figure 6 simplified version of Bernoulli's formula: To obtain the formula for jet reaction we make use ofthe relationship, discussed in the Manual 2 of Firemanship Volume 1 Physics and Chemistry for Firefighters, between force, mass and v2+-l.P 2 P acceleration.

If the hose diameter is large compared with the nozzle diameter, then the velocity, VI' of the I.e. force = mass x acceleration water when it is in the hose may, without undue error, be taken as zero. Also, the (gauge) pres­ sure, P2' of the water as it leaves the nozzle is zero. Making these two substitutions gives: Where the force, F, is measured in newtons, the mass, m, being accelerated is measured in kilograms and the resulting acceleration, a, is measured in metres per second per second. V 2 2 2 Acceleration is defined as change in velocity in I second. For a body starting from rest it becomes acquired velocity, v, divided by time taken, t. Because 1 bar = 100 000 newtons per square metre (i.e. PI = 100 OOOP) and p, the density of water, is 1OOOkg per cubic metre, then: So F = m~ t tOO OOOP We can apply the above formula to the water discharged from a straight stream DOlZl in 1000 I minute. In this case m is the mass in kilograms discharged in I minute which is numerical­ ly equal to the number of litres, L, so:

120 Fire Service Manual Hvdraulics, Pumps and Wafer Supplies 121

• PPE TDIX 4 continued APPE DIX 5

- Lv F - t

But: 2d2~P, V = 14.l4~P L-- "3 and t 60

2d2~P x 14.l4~P Summary of Formulae and Other so F 3 x 60 Data 0.157 P d2 A.5.l Approximate fireground calculation This formula gives the force which must be applied to the water in the hose in order to create the j et but, according to Newton's third law ofmotion (action and reaction are equal and oppo­ Loss of pressure due to height = 0.1 bar for each metre rise site), it is the same as the reaction experienced by whoever or whatever is supporting the branch. Thus: 3 2 Capacity ofpond or lake (m ) = t (surface area (m ) x average depth (m)

R = 0.157 P d2 Capacity of circular tank (m 3) The reaction, R, is measured in newtons, the nozzle pressure, P, in bars and the nozzle diam­ eter, d, in millimetres. _ 8C 2h - 100 The reaction may also be expressed in terms of the area of cross section, a, ofa nozzle: In litres:

Since a = 3.14 d2 sq. mm 4 then d2=~ A.5.2 Hydraulic formulae 3.14 (approx) Capacity of hose (litres/m) so R = 0.157P x 4a 3.14 Pressure and head P = H x 0.0981 I.e. R = 0.2Pa H = P x 10.19 where a is the area of cross section of the nozzle in square millimetres. (approx) P H 10

H = P x 10 (approx)

Water power (watts) wp = 100 x L x P 60

WP x 100 Percentage efficiency E BP

Brake power (watts) BP WP x 100 E

Velocity and discharge v

vd 2 L 21.2

122 Fire Service Manual Hydraulics, Pumps and Water Supplies 123 APPENDIX 5 continued

Friction loss Pr = 9000flU .5.6 Volumes d5 Sloping tank = length x breadth x average depth Nozzle discharge L = 2 d2';P 3 Circular tank (cyl inder) = rrr2 x depth or lId2 x depth 4 Jet reaction R = 0.2Pa Cone or pyramid Area of base x vel1. height 2 = 0.157Pd 3

Sphere A.5.3 Hydrau ic data

1 litre of water has a mass of I kilogram A.5.7 Capacity mea ured in litres

1 litre of water exerts a downward force of approx 10 newtons (N) Capacity of a container in litres = Volume (Cll. metres) x 1000

I cubic metre ofwater exerts a downward force of approx 10 kN

1 metre head of water equals approx 0.1 bar

1 bar pressure of water equals approx 10 metres head

.5.4 Constant g (acceleration due to gravity) = 9.81 m1s 2

Normal atmospheric pressure at 20°C = 1.013 bar

Normal atmospheric pressure at 20°C = 10.3 metre head of water n (pi) = 3.1416 (3 117)

II = 0.7854 4

Circumference of a circle = nd (or) 2rrr

A.~ .5 rea

Circle

Triangle (s = Ih sum of sides) =';s x (s-a)(s-b)(s-e)

= base x perp height 2

124 Fire Service Manual Hydraulics. Pumps and Water Supplies 125 APPENDIX 6 APPE DIX 6

57.9 In any proceedings against any water undertaker for an offence under subsection 8 above it shall be a defence for that undertaker to show that it took all reasonable steps and exercised all due diligence to avoid the commission of the offence."

Sections 57 and 58 of the Water Section 58 of the Act relates to specially requested fire hydrants at factories or places Industry Act 1991 of business and reads as follows: "58.1 A water undertaker shall, at the request of the owner or occupier of any factory or place ofbusiness, fix a fire hydrant, to be used for extinguishing fires "57.1 It shall be the duty of a water undertaker to allow any person to take and not other purposes, at such place on any suitable water main or other pipe water for extinguishing fires from any of its water mains or other pipes on which of the undertaker as near as conveniently possible to that factory or place of a fire hydrant is fixed. business. *57.2 Every water undertaker shall, at the request of the fire authority con­ 58.2 For the purpose of subsection 1 above a water main or other pipe is suit­ cerned, fix fire hydrants on its water mains (other than its trunk mains) at such able, in relation to a factory or place of business, if- places as may be convenient for affording a supply of water for extinguishing any fire which may break out within the area of the undertaker. (a) it is situated in a street which is in or near to that factory or place of busi­ ness; and 57.3 It shall be the duty of every water undertaker to keep every fire hydrant fixed on any ofits water mains or other pipes in good working order and, for that (b) it is of sufficient dimensions to carry a hydrant and is not a trunk main. purpose, to replace any such hydrant when necessary. 58.3 Subsection 5 of section 57 above should not apply in relation to expens­ 57.4 It shall be the duty of a water undertaker to ensure that a fire authority es incurred in compliance, in relation to a specially requested fire hydrant, with has been supplied by the undertaker with all such keys as the authority may its obligations under subsections 3 and 4 of that section. require for the fire hydrants fixed on the water mains or other pipes ofthe under­ taker. 58.4 Any expenses incurred by a water undertaker- 57.5 Subject to section 58.3 below, the expenses incurred by a water under­ (a) in complying with its obligations under subsection 1 above; or taker in complying with its obligations under subsections 2 to 4 above shall be borne by the fire authority concerned. (b) in complying, in relation to a specially requested fire hydrant, with its obligations under section 57(3) and 57(4) above, 57.6 Nothing in this section shall require a water undertaker to do anything which it is unable to do by reason of the carrying out of any necessary works. shall be borne by the owner or occupier of the factory or place of business in question, according to whether the person who made the original request for the 57.7 The responsibilities of a water undertaker under this section shall be hydrant did so in their capacity as owner or occupier." enforceable under section 18 above by the Secretary of State.

57.8 In addition, where a water undertaker is in breach of its obligations under this section, the undertaker shall be guilty of an offence ...

* In spite ofthis clause, some water authorities are prepared to allow hydrants to befixed on trunk mains.

126 Fire Service Manual Hydraulics, Pumps and Water Supplies 127

• d APPENDIX 7 APPENDIX 7

Metrica ion

List of SI units for use in the fire service.

Quantity and basic Approved unit of Conversion factor Quantity and basic Approved unit of Conversion factor or derived SI unit measurement or derived SI unit measurement and symbol and symbol

Length Energy, work metre (m) kilometre (km) I mile = 1.609 km Joule (J) joule (J) I British thermal unit metre (m) I yard = 0.914m (= I m) kilojoule (kJ) = 1.055 kJ millimetre (mm) I foot = 0.305m kilowatt-hour (kWh) I foot Ib force = 1.356 J J inch = 25.4 mm Power Area watt (W) kilowatt (kW) 1 horsepower =0.746 kW square metre (m 2) square kilometre (km 2) I mile2 = 2.590 km 2 (= I .l/s = I Nm/s) watt (W) I foot lb force/second square metre (m 2) I yard 2 = 0.836 m2 = 1.356W square millimetre (mm 2) I fooP = 0.093m2 I inch2 = 645.2 mm 2 Pressure 5 newtonlmetre2 ( /m2) bar = 10 N/m 2 1 atmosphere = Volume millibar (m bar) 101.325 kN/m 2 = cubic metre (m3) cubic metre (m3) 1cubic foot = 0.028 m3 (= 102 N/m 2) 1.013 bar litre (I) (= 10-3m3) 1gallon = 4.546 litres metrehead 1 Ib forcclin 2 = 6894 76 N/m 2 = 0.069 bar Volume, flow I inch Hg = 33.86 m bar cubic metre per second cubic metre per second 1foot 3/s = 0.028 m3/s J metrehead = 0.0981 bar (m3/s) (m3/s) 1gall/min = 4.546 I/min I foothead = 0.305 metrehead litres per minute (I/min = 10 3m 3/min) Heat, quantity of heat Joule (J) joule (J) I British thermal unit Mass kilojoule (kJ) = 1.055 kJ kilogram (kg) kilogram (kg) I Jb = 454 kg tonne (t) Iton=1.016t Heat flow rate (I tonne = 103kg) watt (W) watt (W) I British thermal unit/ hour kilowatt (kW) = 0.293 W Velocity I British thermal unit/ second metre per second (m/s) metre/second (m/s) I foot/second = 0.305 m/s = 1.055 kW International knot (kn) lint. knot = 1.852 km/h I UK knot = 1.853 km/h Specific energy, calorific kilometre/hour (km/h) I mile/hour = 1.61 km/h value, specific latent heat joule/kilogram (J/kg) kilojoule/kilogram (kJ/kg) I British thermal unit/ Ib Acceleration kilojoule/m3 (kJ/m3) = 2.326 kJ/kg J J) metre per second2 (m/s2) metre/second2 1 foot/second 2 = 0.305 m/s 2 joule/m (J/m I British thermal unit/ft3 3 3 J 'g' = 9.81 m/s2 megajoule/m (MJ/m ) = 37.26 kJ/m

Force Temperature Newton (N) kiloNewton (kN) I ton force = 9.964 k degree Celsius (QC) degree Celsius (QC) I degree centigrade = . cwton (N) I Ib force = 4.448 I degree Celsius

128 Fire Service Manual Hydraulics. Pumps and Water Supplies 129 Hydraulics, Pumps and Water Supplies

Acknowledgements

HM Fire Service Inspectorate is indebted to all who helped with the provision of information, expertise and validation to assist production of this manual, in particular:

Keith Davies The Fire Service College Martin Fraser Tony Bames Fire Experimental Unit: Or Martin Thomas and staff CACFOA: CFO Martin Chapman CFO Peter Coombs Graham Dash Angus Fire Hale Products (Godiva) Wessex Water Water UK

Fire Brigades:

Cheshire Dorset Durham and DarIington Fife Greater Manchester Hampshire Hertfordshire London Lothian and Borders Merseyside Norfolk Shropshire West Midlands

130 Fire Service Manual