Glasgow Main Drainage: the Mechanical

Proceedings.] MOHTON ON GLASGOW MAIN DRAINAGE. 213

(Paper No. 3 9 8 I .)

“ GlasgowMain Drainage : the Mechanical Equipment of the Western Works and of the Kinning Park Pumping- Station.”

By DAVIDHOME MORTON, M. Inst. C.E.

THE main-drainage works of Glasgow and of the adjoining burghs, including certaindistricts inland, havebeen described generally in the Paper presented by Messrs. A. B. McDonald and G. Midgley Tay1or.l Themap given therewith shows the positions of the severalworks described in thisPaper. Although the Author’s duties included the design of the various stations, and in some cases of the building works, the space at disposal renders it necessary for his remarks to be confined to the mechanical details ; and even these cannot be dealt with by any means as fully as he could wish.

PARTICKPUMPING-STATION (Fig. 1, Plate 7). The sewage discharged from the Glasgow and Partick intercepting sewers, the former having a diameter of 6 feet and the latter of 5 feet, is dealtwith at this station. The head to beovercome is 35 to 36 feet, including a sufficient allowance for loss of head while passing through screens, etc., and for giving assurance that the intercepting sewers will, except during very heavy rain, always have a clear fall into the station. The sewage flows across the station and, after being raised by the pumps, is delivered directly over forebays into the main outfall-sewer,where it joins the high-level sewage passing through the aqueduct over the Kelvin, and flows with it to Dalmuir.There are practically no horizontalpipes: the flow of sewage and the behaviour of the pumps are under easy observation

’ Ante, p. 167.

In Table I of the Appendix are given the quantitiesof sewage to be dealt with at this station. These, as well as the quantities for the various other stations referred to in this Paper, calculatedare on the basis of 70 per cent. of the flow during 24 hours being dealt with in 12 hours, which as a generalstatement is fairly correct, though the maximum flow during the hours from 10 a.m. to 4 or 5 p.m. often considerably exceeds this. Another matter largelyaffecting the capacity of the pumping- plant is the allowance for rainfall, which is here stated simply as 3 inch of rain in 24 hours, and is added to the rate (70 per cent. in 12 hours multiplied by 2) for sewage alone. The equivalent quantity of rain falling uniformly during 24 hours is relatively unimportant in arriving at suitable proportions for the pumps ; rain does not fall in this manner, and in a cityalmost wholly paved the result of even a moderate shower is quickly felt in thepumping-station. This t inch of rain in 24 hours, or inoh in 1 hour, is frequently quoted in relation to sewerage, but in most cases it seems doubtful whether it is used in the sense intended by the originators of the allowance. In the discussion on Messrs. Worth and Crimp's Paper on the Main Drainage of London, in 1897,' Sir Alexander Binniestated that Sir Joseph Bazalgette " had provided for an average flow of sewage in 24 hours of 5 cubic feet, or 31; gallons, together with & inch of rainfall in 24 hours. But the sewers wereconstructed (and that was what so many people forgot) to carry one-half of that total quantity in 6 hours of the day." Attention is also drawn to a quotationby Sir AlexanderBinnie from Sir Joseph Bazalgette immediately following this, to the effect that " it is probable that if the sewers are made capable of carrying off a volume equal to a rainfall of 4 inch per day during the 6 hours of maximum flow, there would not bemore than 12 days in a yearon which the sewers wouldbe overcharged, andthen onlyfor a short period during such days." These statements indicate not merely provision for a flow of sewage equal to 70 percent. in 12 hours, but for 50 per cent. of the total in 6 hours of maximum flow, including, during these 6 hours of maximum flow, an allowance for rainfall at a rate equivalenteither to 6 inch or 1 inch of uniformfall in 24 hours. This last proportion of rainfall is rather seriously different from an allowance of inch during 24 hours, and represents more nearly thequantities which must be carried and pumpedwhen rain coincides with the hours of maximum sewage-flow, if very frequent

1 Minutes of Proceedings Inst. C.E., vol. cxxix, p. 135.

surcharge of sewers or use of storm-overflow weirs is to be avoided. It is also of obvious importance to be able to pump vigorously in the early hours of a rainfall, particularly after drought, so that the sewers may bewell flushed. Then if raincontinues, discharge over the storm-weirs is less objectionable. On the other hand, the flow of sewage during the night is very small and may readily fall toone-third of the avera.ge dry-weather flow; the pumps must therefore be able to continue working at very low speeds without risk of stopping. After a thorough study of all the circumstances it was decided to install at Partick three similar units, makingprovision for a fourth to be added if found necessary (Pig. la, Plate 7). The pumps selected were of the three-throw single-acting plungertype, each with a capacity of 1,800 cubic feet per minute (16,200,000 gallons per 24 hours). It was decided todrive each unitdirectly by a verticalthree-crank triple-expansion engine. Obviously, centri- fugalpumps similar to those employed on otherdepartments of the Glasgow main-drainage works might have been adopted, but having regard to thecontinuous nature of the work, the reciprocat- ingtype was preferred, because of its superior efficiency. When properly designed, this type of pump gives a velocity of flow second only in uniformity to that of the centrifugal pump, and markedly superior to that of any other type or combination of displacement pumps with rotatory motion. Had the actualdry-weather flow of sewage remained as scheduled, probably one engine would have sufficed for the whole day’s work. In practice, however, two are generally required during the 6 or 7 hours of greatest flow, running at about two-thirds of full speed. During the rest of the day one engine suffices, and in the small hours of the night the speed is reduced to 8 or 9 revolutions per minute, the normal full speed being 20 revolutions. Two engines running up to full speed deal with all but the heaviest rainfall, leaving the third as a stand-by for pump-cleaning and repairs. The sewage entersthe station from the City and the Partick intercepting-sewersthrough penstocks, the frames of which are secured by long anchor-bolts built into the walls, so that the doors can withstand a pressure equal to that due to the highest recorded tide.The penstock-chamber is 33 feet wide by 10 feet 6 inches long (in the direction of the flow), to the face of the rough screens which guard the entrance to threescreening-channels. These rough screens are composed of strong wrought-iron frames l1 feet high, the barsbeing vertical and4 inches apart in theclear. Similar horizontal grilles are fitted between the heads of the vertical

screens and a tidal wall 25 feet high(forming the north side of the chamber) to prevent thepassage of large solids to thefine screens intime of surcharge. In front of each screening-channel, on the face of the tidal wall, is placed a penstock 5 feet wide by 7 feet high; the channels are made 7 feet wide and are fitted with fine screens of wrought steel 6 feet 6 inches wide, set at an inclination of nearly 45". These are of plates + inchthick, perforated with l-inch holes so closely drilled thatthe effective passage-area is 50 percent. of the total. The holes are countersunkon the discharge side. Power-driven scrapers and rakes travel slowly on the face of the inclined screens, raising the screenings into hoppers, from which they are lifted periodically by light bucket elevators. Two screening-channels usually suffice for the work of the station, and with ordinary attention on the part of the workmen the loss of head can be kept down to a few inches. Behind the screens, distributing-channelscarry the sewage to the pump-wells, of which there are four. In addition there is a deeper well into which the others may be draineddry. All wells are guarded by penstocks fixed inside the walls, so that the pressure tends to force the doors fromtheir frames. All penstocks are provided with small side guide-rollers of gun-metal, whereby the doors are made to run clear of the frames immediately they begin to rise. All are balanced and can be raised or lowered by one man. The main pump-wells are each 12 feet wide by 33 feet long, and the levels in them do not vary more than 2 inches when the pumps are running at full speed. Sludge-pipes 12 inches in diameter are provided to drain off the sludgewhen the main wells are being cleaned, and it is subsequently lifted by an auxiliary steam-pump or by a pulsometer. Owing to the solidity of the foundation material, transversewalls in the pump-house were unnecessary, and the lower pump-chamber has been left open from end to end, thus rendering themain pumps unusually accessible in every direction. The pumping-engines have theirshafts athwart the house ; the pumps rest on brickwork foundations with granite bed-stones ; the upper works and engines are carriedon box girdersspanning the house. The engine-floor beams are carried on pillars rising from the box girders and braced by diagonal struts. The pumps have plungers 36 inches in diameter and the bores of the steam-cylinders are 15 inches, 24 inches and 40 inches, the stroke being 4 feet 6 inches. It isadmitted that a shorterstroke, say 3 feet.,would have given a much lighterand cheaper engine. Butthe maintenance of EL pumping-enginebeing largely determined by the number of

revolutions in a given time, the engine with a long stroke is in all respectsdesirable from the proprietors’point of view. Judging from examples, the good qualities of the three-throw pump are not alwaysunderstood. In the present case thewater flows into an enlarged suction-chamber directly open to the suction-valves of all three plunger-chambers ; similarly all delivery-valves open directly into a common discharge chamber, and the volume of water to be sbarted and stopped is thus reduced to a minimum. The plunger- chambers are also made large compared with the plunger-displace- ments, so that the reactions at the turn of the stroke arereduced in intensity. For each pump there are one hundred and twenty valves, twenty for each suction group, and twenty for each delivery. The greatest area of openingthrough each group of twenty valves is nearly l$ times that of the plunger. The frames and seatings are of hard gun-metal, and thevalves themselves are of cast iron faced with hide leather. The plungers are of hard gun-metal 3 to 4 inch thick, the stuffing-boxnecks and the glands being lined with white metal. The neck bushes are 24 inches deep,but thespace for packing is only 4 inches. There is thusno temptation to allow the packing to become old, hard,and useless. !Che plungerscan be runwithout packing ; this is used, however, to prevent air- and water-leakage. The stuffing-glands have very large water-cups (similar to those on the Kinning Parkpumps, Fig. 2, Plate 7), which provide a service of clear water to wash the snrfaces of the plungers as they rise and fall. The suction-pipe is 3 feet 6 inches in diameter, expanding near the bottom of the well to a large bell-shaped intake; and a large air- vessel is fitted to the head of this suction-pipe. The large-capacity plunger-chambers, besides favouring smooth running, are of great service in reducing the quantity of grit which passes through the delivery-valves ; yet notwithstanding this, considerable quantities are sometimes found about the head of the rising main. The sewage itself is used as cooling-water in the condensers,:and a separatecirculating-pump is thus avoided.The whole of the sewage from each pump passes through the tubes of the condenser. These tubes are 136 in number, 32 inches in diameter and 3 feet long over all. The condensers require very little attention beyond the cleaning out of gritand solids at theusual times of pump- cleaning. They absorb about 1 per cent. of the total head, and the vacuumranges from 26 to 27 inches. The air-pump for the condenser is driven from the low-pressure cross-head by wrought-steel evers and links. The several discharge-bays are connected together by 7-inch pipes

fittedwith valves, so that any pump about to be started can be charged from any other pump in motion. In stormy weather each pump can be charged from its own forebay. The behaviour of a pump an be observed at any moment ; normally the stream discharged is practically steady like that from a. centrifugal pump, and the net lift from the level in the wells to that in discharge-bays can be measured within 2 inches. The engines may be described as of normal type, with the connecting-rods rising from the plunger-rods to thecrank-shaft, instead of depending fromthe piston-rod croshead. The guide-bars are bolted to theair-vessels and to the rising mainover the pumps. The lower crossheads are of cast steel, and each has two dia,gonal arms to take the pump side-rods. A somewhat similar connection is made to the piston crosshead, the diagonal position of the pump- rods enabling the cranks and connecting-rods to have their paths between the two. The fly-wheels are 15 feet in diameter, and each weighs 73 tons. Two of these wheels are fitted to emh pump, and they enable the engines, which are, of course, in perfectstatic balance, torun at the low speeds required during the night. There are three bed-plates toeach engine, adjusted and fixed to the floor-beams, and the engine-frame is built of steel columns with a simpleform of arched entablatureto carry the steam-cylinders. These are all jacketed and are fitted with Corliss valves in the top and bottom covers, so that the clearance at the ends of the stroke is reduced to 2 per cent. Receivers are provided between the first and second and between the second and third cylinders, and are fittedwith tubular interheaters. All cylinder-covers andinter- heatersare verythickly insulated with carbonate of magnesia lagged withteak staves and finished over allwith polished sheet steel. Except inthe cases of guide-barsand cylinder-interiors the lubricating-cups are supplied with semi-solid unguent. The engine- floor andthat of the gallery below it arelaid throughout with strong iron plates of open pattern, to admit good light down into the pump-chamber. The width of the pump-house just allows room to raise the largestof the castings composing the mainpumps between the wall andthe engine-beams. The bottom of the pump-wells is 53 feet, and the engine-room floor is 10 feet, below the street, which is also 15 feet higher than the south yard. A 12-ton power crane commands the area of the pump-house. The boilers are not quite SO close to the pumping-engines as they might be, the space immediately behind the pumps being occupied by the screen-house, penstock-chamber, and distributing-channels to the pumpwells-

Downloaded by [ York University] on [20/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] MORTONGLASGOWON MAIN DRAINAGE. 219 which were details deemedto be of greater importancethan a few feet of extra steam-pipe. The triangular plan of the siteis also concerned in this matter.The boiler-housefloor is 33 feet above datum, beingat the same level as the intermediate floor of the pump-house. Over the boilers, at street-level, is a coal-store from which fuelis delivered directly to the furnaces by hoppers and vertical shoots. There are four Lancashire boilers of Galloway type, each 7 feet in diameter by 26 feet long. The two furnace-tubes are 2 feet 9 inches in diameter and are fitted with mechanical stok:ers of the sprinkler type. The main flues have four verticalswivel dampers, and fourla.rge cleaning- doors, so that they can be cleaned in sections without stopping work. A feed-water heater of 240 cast-iron tubes is placed in the flue and raises the temperature of the feed-water from 100' to 270" F. or more.The draught is natural only, the chimneybeing 6 feet in effective diameter and 160 feet high over the grate-bars. The upper parts of the boiler-shells are covered with 4 inches of non-conducting material, and in addition a still-air casingis formed by B floor of Arbroath paving resting on light steeljoists and dwarf walls. Thesteam-pipes are of lap-welded steel, special junctions and valve-chests being of cast steel. The feed-pipes are of copper, withvalve-chests and special junction-pieces of gun-metal.The steam-pipes are arranged in an auxiliary-ring system, the auxiliary part, though materiallysmaller than the main, being large enoughto serve when jointing is being renewed on the latter. The feed-pipe systemis generally in duplicate, and copper is used in order to avoid the destructivepitting which is foundto follow the use of Glasgow water w-hen wrought-iron or steel pipes are employed. Feed-pumpsare provided in duplicate, and haveautomatic feed- regulators. The boilers maybe fed either from thehot wells or from the Corporation's mains, or from the Kelvin River. Two smalltriple-expansion engines, one of which is always in service, drive the auxiliary plant in the station through a line of shafting. This plant consists of the screening-gear, the mechanical stokers, and economizer gear, the barring-gear for the main engines, the travelling crane, the workshops, andthe lighting-dynamo. Three boilers would have sufficed for the station in its present condition but four were laid down. Notwithstanding the fact that all four were built together, from plates rolled by one of the best mills in Scotland, and that they satisfied the usual physical tests equally, bothfurnace-tubes in boiler No. 4 showed seriouscracks during work, and eventually had to be replaced. Test-pieces, cut both hot and cold, from the plates which had crackedor broken, confirmed the original test resultethat the plates were of good ductile material;

whereas actually they were dangerously brittle. This disagreeable incident illustrates a fact which is now being recognized, namely, that steelmay possess proper strengthand ductility and yet be subject to thegrave defect of obscure brittleness, for the elucidation of which further systematic tests are necessary, in order to prevent the use of such material in structures andmachinery. The averagesteam-consumption of the engines on testing was 12 lbs. per indicated horse-power-hour, and themechanical efficiency, measured bythe ratio of water horse-power to indicated horse- power, was 85 percent. The efficiency of the boiler department was, on the contrary, rather poor, being less than 70 per cent. The fuel was that usually supplied tothe station, Lanarkshire slack having a thermal value of about 12,000 B.Th.U. with 11 per cent. of ash and more than 7 per cent. of free water. The pumpshave worked very satisfactorily for 7 years; valves break rarely, and after the first few months, when the cleaning out of the pumps began to be done after a stated term of continuous work, usually about 30 days of 24 hours, the number of renewals of leather faces of valves has been very moderate, in spite of the factthat the sewage is heavily charged not only with ordinary detritusbut also withgranite grit. With few exceptions, all streetsare paved withwhin or granite, and practically none is immune from heavy industrial traffic. The quantity of heavy solid material taken from each pump, chiefly from the plunger-chambers, has varied from about 1 ton up to as much as 4 tons, after 30 days’ continuous work. Other materials have been tried for refacing the valves, such as canvas or gutta-percha,but leather remains the standard. Valves with metal-to-metal faces could not be kept tight. The plungers are always in good condition, and are now free from scoring and very little worn. The staff of the pumping-station is eighteen men, including the Superintendent, an assistant, who is also a working mechanic, and a, clerk. The work is divided into three shifts of 8 hours each, but in ordinary circumstances only three men are on duty in the station from 6 p.m. to 6 a.m. Partick pumping-station occupies a good site, in a good district, being opposite the gates of the Western Infirmary, and quitenear to theUniversity and Art Gallery buildings. There is no nuisance, and prevention consists principally in keeping the sewage moving, giving abundant ventilation, andusing the washing-hose freely. The pump-floorsover wells are practically air-tight, but the man-ways are usually open. The discharge-bays to the outfall-sewer, in front of the station, are enclosed, and an air-duct iscarried from there to

Downloaded by [ York University] on [20/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] MORTONON GLASGOW MAINDRAINAGE. 221 the chimney. The principal ventilation is allowed on the south side of the station, and over the penstock-chamber in the lower yard. Theapproximate total cost of the mechanical equipment was &48,000, exclusive of buildings, foundations, tools, electric light and other minor accessories. This fi,gure, however, includes the whole of the iron framework, and the floors and stairs in the pump-house onLy. DALMUIRSEWAGE-PURIFICATION WORKS. These works are situate on the right bank of the Clyde, a short dishnce west of DalmuirStation, And thus have access to both rail and river.The greater part of the mechanical equipment is housed in the machinery buildings which stand to the north-east of the precipitation-tanks(Fig. 3, Plate 8). Thetreatment of the sewage includes the following procedure :- Rough screening and removal of large solids. Fine screening and removal of screenings. Pumping of low-level sewage to join high-level. Passage of all sewage very slowly through a long catch-pit of large area to allow the deposition of heavier solids. Periodical removal of deposited material by dredging. Administration of chemical precipitants. Passage of treated sewage to large precipitation-tanks. Continuousprecipitation and very slowpassage of sewage through tanks. Continuous discharge of clarified effluent to river. Emptyingprecipitation-tanks at regularintervals by under- surface drainers. Periodical removal of sludge from tank-bottoms by gravitation. Periodical pumping of sludge into largeoverhead storage-tanks on the river-bank. Periodical loading of sludge by gravitation into tanksof steamer, and sending to sea. The sewage brought down by the Clydebank sewer has to be raised by pumping through a height of 19 to 20 feet (Figs. 3a and b, Plate 8). The figures in Table I1 of the Appendix show the measured and estim:eted quantities of sewage to bepassed through the Dalmuir works, during both dry andwet weather. The remarks alreadymade under the head of the Partick Station, in regard to variation in the rate of flow during the 24 hours and to the quantity of rainfall, are equally applicable in the present case. Thebuildings do notrequire special comment. Theyare of

plain substantialcharacter, chiefly of brickwork, and are divided intothe following departments: (a) boiler-house andcoal-store; (a) power-house ; (c) Clydebankpump-house ; (d) screen-house ; (e) catch-pit house ; (f)lime-house, and (g) " acid " house. On the north boundary are the repair-shops, stores, offices and laboratory. South of the main buildings are limewater settling-tanks, and on the south-west saturation-tanks foriron-liquor. Thesludge-tanks, sludge-pump house, and sludge-loading gear are on the river-bank. Boiler-House.-This contains four Lancashire boilers, each 7 feet 6 inches in diameterand 30 feet long, working at a pressure of 160 lbs. per square inch. The coal store is in front of the boilers ; a small motor-driven elevator andscrew conveyor raises and discharges the fuelinto the grate hoppers of the mechanical stokers. The economizer has 384 tubes and is capable of raising the feed-water to 220" F. and upwards. The feed-pipes are of steel, as suitable water can beobtained from Duntocher Burn. The chimney, which is placed with its foundations well clear of the Clydebank sewer, is about 152 feet high and 6 feet 6 inches in internal diameter. It is of pressedbrickwork set in lias lime, the copingcourse being bound witha heavycopper ring,sunk flush andforming the collector for the spikes of the lightning-conductor. Power-House and Pump-House.-These houses are combined, and asthey bound the boiler-houseon two adjacent sides theyare bothconveniently served by short steam-pipes. The floor of the power-house is 31 feet above datum, or 1 foot higher than the yard, while the floor of the pump-house is 11 feet lower. Electric transmission is used in all cases, except for the Clydebank pumps, the condensing installation, and the boiler feed-pumps. The enginedriving the larger pump is similar to thosedriving the dynamos, and small compoundengines are usedfor the air- and circulating-pumps tothe condensers. Thirty-two motors, having an aggregate capacity of 500 B.HP., are distributed throughout the works ; several of the more important, however, are in duplicate. The lighting equipment includes sixty arc-lamps and two hundred glow-lamps. The power-housecontains threegenerating-sets, two of 300 electrical HP. and one of half this capacity. Thegenerators are of the multipolartype, and are driven by three-crank triple-expansionengines. Direct current is employed, at B tension of 220 volts. One of the large sets can usually meet the requirements of the works, owingto the intermittent manner in which the several processes are carried on, and the small set can take the night duty.

The pump-housecontains three direct-coupledcentrifugal sets, one with a21-inch case and impellers 42 inches in diameter, and the two others with 15-inch cases and impellers 30 inches in diameter. The large pump delivers about 8,000 gallons per minute, and the twosmaller 3,800 gallons each. The steam-consumption of these pumping-enginesper pump-horse-power is approximatelydouble that of the reciprocating pumps at Partick ; but for the lower lift and the diminished quantities there wouldbe no justification for the adoption of the moreexpensive type of engine,even if the efficiency remained the same under the alteredcircumstances. The large pump has a triple-expansion engine similar to those driving the electric sets, but the small pumps, because small, have only two-cylinder compound engines. The pumps are made with steel impellers of the open-vane type, and the inside cheeks of the casings are lined with renewable steel plates. Hand-holesare provided for inspection and cleaning. The suction- and delivery-pipes are of conical form, the former having largebell-shaped intakes. Reflux-valves are provided inthe discharge-pipes, the orifices being always under water. The well is divided into two chambers to facilitate cleansing. On the pump floor and partly beneath the gallery at the south end of the power-house are placed twoindependent surface condensers, the circulatingwater being clarified sewage obtained from the main precipitation-tanks, which are tapped 300 feet from the head. Thiscirculating water then passes to the lime-mixers. For both of these uses it is found quite satisfactory, although the condenser-tubes are only of the usual 3-inch outside diameter. Screen-House.-The orifice of the Clydebank sewer in the screen- house isguarded by a 6-footpenstock, similar in all respects to that on the city sewer at Partick. The double orifices of the main outfallhave no penstocks, but can beclosed bystop-planks. In designing the screens ample area and efficient mechanical scrapers have been provided, with the result that one man can take charge of six or eight screens. All screening-channelshave theirentrances guarded byrough screens, each of which is suspended from two wire ropes shackled to the frame.They are balanced with cast-iron weights, and are capable of beingraised by a hand-chain and sprocket-wheel.The lifting grip is obtained simply by the bight of the balance-rope in acute V grooves, formed in the rims of the overheadsheaves. Rough screens with wide clearances between the bars are generally fixed, as are those at Partick, but it has been found very advanta- geous to beable to raise them,not only to clear away the grit

and sand which gather on their sills, but also tocut away the fibrous materials which collect on and wind themselves firmly around the bars. The fine screens for the Clydebank sewage are also of the lifting type, being convenient for the site. Those,however, for the main outfall sewage are precisely the same as at Partick. Two small reversingmotors are provided, one at each end of the overhead platform ; these drive through spur wheels and clutches the hoist- ing-shafts, pulleys, and ropes for raising the scraper-gear from the water.The lower part of thisgear, including the bottom shaft, sprocket-wheels, and axle-boxes, is partly counterbalanced to facilitate lifting,enough weight being left to keep the scrapers well down on the screen-plates, but not enough to prevent the shaft with its wheels and scrapers from rising over any heavy obstruction which might find its way through the rough screens. CchtclL-pit and House.-The streams of sewage from the main outfall flow directly through the screening-channels into the catch- pit, where theyare joined by the sewage pumped up from the Clydebank wells. Thiscatch-pit, which is ratheran outstanding feature of the works, measures 156 feet by 24 feet, and is 26 feet deep below the house-floor,which is here at yard-level, 30 feet above datum. The upper sides are plumb, the lower sides and ends are inclined at 45", and the invert is 3 feet in radius with ends semicircular in plan. The pit is thus devoid of inaccessible corners andcontains nostanchions or obstructionsbehind whichobjec- tionablematter might collect. The floor overhead iscarried on cantilevers, which also carry a line of rails (standard gauge) on the middle longitudinal line of the pit. The space between the rails is left open fromend to end, giving access to the long ladder of a travelling dredger, which thus commands the whole length of the pit and is able to dredge to the invert. The application of dredgers of this type to this particularservice has been general since the design of this first example. The dredger is carried on a strong box-framed wagon of wrought- steel plates, 18 feet long by 8 feet wide, with a 9-foot wheel-base. The ladder is 47 feet 6 inches long from the centreof the top to the centre of the bottom sprocket-wheel. It is swung on trunnions so that it can work to the bottom of the pit at a suitable angle, and the upper part above the trunnions isof a length toenable thespoil tobe delivered into a railway-wagon while dredging at any likely angle. The shoot on the ladder-head has an angularadjustment, and a continuation trunk descending into the wagon reduces splashing. The wagonis coupled tothe dredger andtravels with it. The

buckets are 15 inches wide, and the bottom of the ladder is fur- nished with curved skids to keep them clear of the brickwork. The shaft of the lowersprocket-wheel is extendedon both sides and fitted with wrought-iron stirrers, like small two-bladed propellers ; these are of material advantage, assisting not only in keeping the buckets free to work but also in feeding them with spoil. Power is transmitted by a 15-B.HP. enclosed reversing motor. The speed of the bucket-ladder is up to 70 feet per minute, and the rate of travel when dredging is about 25 feet per minute. When designing machines of this class the first idea is to make them self-acting, but practice discoversthe most economical methods. The deposit is not made uniformly along the length of the pit, and its incidence varies with the weather,being much reduced in the dry seasons. The spell of dredging is usually takenin the morning, and after a storm four or six wagons may be loaded during a short spell of work. In fine weather dredging may be discontinued for a few days without inconvenience. The yield of the catch-pit is in round figures 3,000 to 4,000 tons per annum, the average weight of solids taken from the screens being about 200 tons per annum. Theinterception of thesequantities of more or less solid and objectionable refuse greatly reduces the work of cleaning the precipitation-tanks. The dredger can be hauled on its own carriage to the workshop forrepairs, but so farthis has beenunnecessary. Two dredgers wereincluded in the original specification, one as a reserve, but this stand-by machine was omitted. There is ample time to effect all ordinary repairs and adjustments during idle hours. The chemical precipitants are administered to the sewage during its passage through the catch-pit. Persulphate of iron is admitted from a wooden trough over the east discharge-bay of the Clydebank pumps.Lime-water flows in near the westend of thepit. (It is deemed essential that the iron-liquor should be administered before the admission of the lime-water.) No particular means of mixing seem to be necessary, but in passing out of the catch-pit into the channels leading to the precipitation-tanks the sewage is deflected under two adjustable balanced weirs, which may serve as mixing- diaphragms. The position of the storm-overflow has been criticized in relation to the fact that chemicals may be wasted by passing over the weir just after they have been added to the sewage ; but overflowing is only an occasional incident, and the management does notwaste its storeswhile rainfall is doing the work of purification. The Author’s reason for placing the overflow behind the screens and at [THE INST. C.E. VOL. CLXXXIS.] Q

the west end of the catch-pit was,chiefly, that all sewagewould receive the first part of the treatment before being allowed to overflow into theriver, and so that the appearance of disagreeable solids near the outfallof the clarified effluent mightbe avoided. Another point concerning which there may be room for difference of opinion is the question of the relative positions of the catch-pit and the screens-whether the screensshould guardthe entrance to the pit, or should be at its discharge end. The latter course has been adopted at the southern works, but this has involved the use of two separate screening departments, one being required for the pumps.The absence of screens infront of the catch-pitin- evitably increases the difficulties in working the dredger, which in this case is liable to be obstructed by all kinds of foreign matter, rags and the like. Lime-house.-The revolving lime-mixers, of which there are four, with provision for extension, are placed on the south side of the lime-house,being supported on foundation-beams spanning the overflow-chamber. These mixers have strong cast-iron pans, 11 feet in diameter and 3 feet 6 inches deep, with overhead gear frames and vertical shafts, on which stoutcast-iron cruciform armsare keyed. The mixing- plates are perforated and are roughly serrated on the advance side. The batteryof mixers is driven byan overhead shaft so arranged that the pans may be run in pairs. Each end of the shaft is fitted with a large pulley fly-wheel and connected by belt with a 40-B.HP. motor. The mixers run at about 12 revolutions per minute ; the speed was originally a good deal higher, but the centrifugal action was excessive, and the present speed enables a charge of 5 cwt. to be slaked and thoroughly mixed into milk of lime in 10 minutes. The clarified effluent used for mixing is sent forwardfrom the circulating- pumps, any deficit beingmade up bymotor-driven centrifugal pumps. There are three lime-water tanks for storage and settlement, so that whenone is beingcharged another may be settling,and a third discharging. Eachtank is 90 feet long, 32 feetwide, and 6 feet deep, withwalls 32 inches thick and a smoothbottom of cementconcrete. The discharge-valve isa little above thetank- bottom.A saturated solution of lime-water is used in preference to the direct administration of milk of lime, as economy in the precipitant and more accurate control are thereby secured. With the direct use of milk of limea very material tonnage, spentand unspent, found its way into the precipitation-tanks, thus wasting the limeand increasing the cost of sludge-removal. Withthe

Downloaded by [ York University] on [20/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] MORTON ON GLASGOW XAIN DRAINAGE. 227 more recent methods the excess lime in suspension is retained in the settling-tanks. Acid House.-The iron-liquortanks for the preparation of the protosulphate of ironare placed in parallel with the lime-water tanks just described, but to the west of the covered feed-channels to the precipitation-tanks.The plant for the conversion of the protosulphate into the persulphate is housed in the acid house or north chemicalhouse. These agentsbeing of avery destructive character, all tanks and pipes carrying them have to be constructed with great care, and the roof-trusses>are,allof timber withconcealed metal fastenings. The three saturation-tanks measure each 31 feet by 27 feet and have a depth of 4 feet 6 inches. The side and intermediate walls are of brickwork in cement, the former backed with puddle clay, and all are lined inside with 45- by 9-inch creosoted timber. This is fastened to the walls by con- cealedanchor-bolts, all holesbeing carefully plugged with wood. The bottoms are of fine concrete covered with a layer of pitch. A space of 1 inch is left between the brick walls and the back of the wood lining, that space and all seams between timbers being filled solid with pitch. The bottom is afterwards paved with blue brick keyed against and secured to the lower ends of the vertical timbers, the whole floor being finally grouted up with pitch. At first the iron-liquor was prepared by the direct solution of light swap in sulphuric acid, but it was subsequently found convenient and economical to purchase ferrous-sulphatecrystals. These are dissolved in water at a temperature of about 100" in the same tanks, a small percentage of sulphuric acid being added in'order to prevent re-crystallization. Stoneware cocks were used at first forthe discharge-pipes, but they were fount1 to be too fragile and have been replaced by valves of regulus metal. The liquor is raised from the receiving-well below the floor by a pneumatic lifter. The conversion of the protosulphate is an intermitt,entprocess, and charges of liquor are drawn from an overhead tank into the oxidizing-drums. There are now three of these, each 12 feet long by 10 feet in diameter, and they are fitted withrevolving paddles. The mixing-paddles were first made too small relatively to the diameter of the drum, leaving too muchroom for idle air in the upper zone, butthis has sincebeen remedied. The shaftsare of hard wood, 12 inches square and with the paddle-arms driven into through mortices.Roller bearings are now used, woodenbaffles and shutters preventing thecreeping of the liquor. A small quantity of nitrite of soda is added to the charge, and 30 to 45 minutes afterthe paddleshave been set in motion Q2

Downloaded by [ York University] on [20/09/16]. Copyright © ICE Publishing, all rights reserved. 228 MORTON ON GLASGOW MAINDRAINAGE. [Minutes of the oxidation is complete. The charge, now persulphate of iron, is withdrawn into vatsbelow the drum, andcarried thence in wooden troughing to the delivery point. The proportions of the precipitants varywith the strength and nature of the sewage, but average 8.51grains of persulphate of iron md 4.88 grains of limeper gallon. This involves thehandling of 9 * 68 tons of burntlime and 5 -62 tons of ferrous crystals in 24 hours. The conversionof protosulphate of iron into persulphateis a comparatively inexpensive process, and, compared with the administration of the protosulphate direct, effects important economies ; the efficiency of theiron is doubled and the proportion of lime required is reduced to one-half. In the event of a scarcity of ferrous crystnls the plant is capable of usingsulphate of alumina-the precipitant used at theEastern works before the introduction of the persulphate of iron. The cost of machinery-buildings, workshops and offices, including deep foundations and sewer connections, but exclusive of buildings for sludge-tanks, was nearly 256,000. The cost of the machinery and electricaleqnipment was about 240,000.

DISPOSALOF SLUDGE. A very complete installation for dealing with the sludge has been installed on the river-bank at Dalmuir (Figs. 4 and 4a, Plate 8). After precipitation the sludge is discharged from the main tanks, periodically andin sequence, into sludge-culverts below. These deliver into a pump-well 60 feet 6 inches long by 15 feet wide, from which the sludge is pumped up into tanks. The foundation of these is water-bearing sand and gravel, and in order to secure a reliable foundation the Author thought it desirable to cover the whole site with a layer of concrete. On this israised a comparatively light substructure of walls lightened by piers and arches. There are two tanks, weighing about 550 tons empty, and each having a capacity of 1,500 tons; so that the loaded tanks weigh 3,550 tons. Adding the weight of thesubstructure, the load on theground becomes about 1 ton per square foot. This is a light load, but 1,500 tons of the total is being changed periodically from one side of the foundation to theother. The Author looked into the question of using wrought-steel tanks with semi-circular bottoms, similar to those in use at the Barking Outfall Works on the Thames ; but finding no advantage in price compared with cast iron, he decided to adopt the latter as being probably more durable. The tanks each measure about 150 feet in length by 35 feet wide, and are 10 feet 3 inches deep inside. They

are made externally as one, the middle division line being common to both, and are stayedby rods of round and I section. The bottom plates are 1 inch thick, the lower tier of side and division plates H inch, and the upper tier 3 inch thick. The bottom is supported by joists, 5 feet apart, running longitudinally. The sides and ends of large cast-iron tanks must not only be stayed by tension-rods but must also be stiffened, if they are to be erected and maintained instraight lines. For this purpo,se, horizontalchannel stringers, well bolted to the plates, are fitted continuously on sides and ends, and to these are bolted the stay-ends. The elevation of the tank-bottoms is 133 feet above the wharf- a good deal lower than that of the loading-tanks at Barking, but quite sufficient to give the discharging-head, and to load the steamer in 30 minutes.The use of the cakch-pit, good screening,and the generally uniform character of the sludge, probably account for the smaller head needed. In the pump-house arethree 10-inchmotor-driven centrifugal pumps, each capable of raising 1,500 gallons, or 7.16 tons of sludge per minute.The lift, averages 40 feetto a maximum of 44 feet, intothe storage-tank. Each motor is of 50 B.HP., entirely enclosed andwatertight, to guardagainst possibleflooding. The pumpshave steel impellers, andadjustable steel-lined cheeks,as described for the Clydebankdrainage-pumps. The suction-pipes have large bell-shaped inlet castings, but no strainers. Under the north gallery aretwo motor-driven vacuum pumps, with a vacuum-chamber, so that anypump-chamber canbe exhausted and charged with sludge. During settlement of the sludge in the tanks the thinnerliquor is drawn off by means of a special drainer, of a type designed by Mr. Melvin, General Manager of the department,and first used onthe precipitation-tanks at theEastern Works, Dalmarnock.The drainer consists virtually of two side cheeks made tight to the sides and bottom of the tank, the front part, through which the draining is effected, being made up of a series of iron slats 3 feet long by 6 inches deep. These have planed edges which lie butt to buttwhen closed, and practically tight with eaoh other. The slats are mounted on double-pitch chains, nearly balanced, and provided with hand-gear. When the slats are closed ,each pair of links in the chain behind is slack, and falls back into a loose knee or toggle ; but when the gear begins to lift the slats, the links behind each straighten in turn, leaving a gap of 3 inches or other desired opening between the slats. It will thus be seen that each drainer can be simply adjusted to provide a surface discharge weir practically at any level through the depth of the tank, and

that the thin liquor can be withdrawn accordingly. By this means the moisture in the sludge is reduced from 93 per cent. to 86 per cent. The decanted liquor Bows back to the Clydebank pump-well ; it is, of course, a highly concentrated sewage, and thus diluted with the incoming sewage it receives again the full treatment. The sludge is then discharged through an orifice in thechannelled bottom,by means of an 18-inch pipe, which iscontinued to the wharf. There it branches intoeither of twodischarging arms, which :me swivelled and finish with a short flexible leather trunk, .ts shown in the Figure. These are reduced to 16 inches and raised or lowered by a small motor, being made specially light for ease of manipulation. Thearms can thus discharge intothe steamer at any state of the tide. The cost of deep foundations, culvert connections, substructure for sludge-tanks,pump-house, and other builders’ workin connection withthe sludge-pumping,storage, and loading plant was about X11,140. The cost of the sludge-tanks,sludge-pumping plant, penstocks, pipe connections, valves, and all accessories was about 29,250.

KIKKIKCPARK PUNPIXG-STATIOX. Atthis station the sewage israised 39 feet 6 inches intothe high-levelsewer, 1,900 feetaway. This involves the use of two 36-inch risiug mains in parallel, whioh cause an additional friction- head of 5 to 7 feet. Thequantities scheduled to bepumped at the Kinning Park station are given in Table I11 of the Appendix, in the same manner as in the cases of Partick and Dalmuir, and the remarksin regard to rainfall apply herealso. Thti pumping-engines installed :we as originally proposed by tlle Author, namely, triple-expansion steam-engines, as shown in Figs. 2 and 2a, Plate 7. They are very similar to those at Partick. It had been suggested that pumping by electricity would be more economical, and the matter was referred to a committee consisting of the City Engineer, the Engineer of the Electricity Department, and the Author. The unanimous finding,however, was that with electricity at ;d. per unit,the cost of pumping by steamdirect would not be half the sum required for electrical working. Again, compound engineswere suggested as beingsmaller and cheaper. This caused theAuthor to make rough outline designs and to invite preliminary tenders from contractors for compound and triple-expansion engines with two and three plungers respec- tively. The differences in cost and in space occupied were trifling,

Downloaded by [ York University] on [20/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] MORTON ON GLASGOW MAIN DRAINAGE. 232 andthere couldbe no justification fortaking sucha retrograde step. There are, it seems, still people who cannot see the merits of a three-throw pump, even as a pump, and apart from the simple manner in which it can be driven by one of the most economical types of engine. These andother suggestionsdelayed thepreparation of the station and designs, but it was eventually agreed that the station and machinery as originally proposedby theAuthor shouldbe proceeded with. The catch-pit was reduced in size, and, owing to the introduction of flying buttresses tostrengthen the south wall, a travelling dredger like that at Dalmuir, on a small scale, was replaced by Q travelling grab, which has given stttisfactory results. The catch-pit, screening-channels, andtheir plant occupy the position which is usually given to the boilers, but here the latter are deemed of less importance, and the advantage of having the deep foundation work compact and symmetrical is evident. There are now three water-tube boilers, one serving each engine. These are of the long, inclined, straight-tube type, with front and back headers, connected with a long horizontal steam-and water-drum. The heating-surface of each is 1,265 square feet, and the working- pressure is 180 Ibs. per square inch. The superheaters give about 120" F. of added heat, Mechanicalstokers of the underfeed type are fitted, and a fandelivers air under a slight pressure beneath the grates.The economizer has 240 tubes and is placed in the main flue as at Partick. Similar arrangements for cleaning the flues in sections are also provided. The engines runat 5 maximum speed of 23 revolutionsper minute, with a stroke of 4 feet 6 inches. The pump-plungers are 36 inches in diameter, so that compared with the Partick pumps a slight increase in the volume pumped is provided for. The capacity of eachpump is practically 2,000 cubic feet perminute, or 179 milliongallons per day of 24 hours.The power required is just under 180 LHP. per engine. The engines have the same scantlings asthose at Partick, except that the cylinders are madeslightly larger,namely 154 inches, 25 inches and 42 inches in diameter. A steam-pressure 10 or 12 percent. higher, combined with the largerdiameters, is sufficient to overcome the additionalhead of about 25 per cent. The pumps (Figs. 2, Plate 7) are generally similar to those at Partick,but they are set directly over the wells, instead of on foundation-walls, the object being to obtain vertical continuity of the main transverse walls, in the interest of strength. The valve

frame-plates are of cast steel,as are also the leather-faced flaps. Theplungers are of close-grainedcast iron,and the longwhite- metal neck-bushes, and stuffing-boxes, are asdescribed forthe Partick station. As the pumps in starting may have to overcome the inertia of the column of water in the rising main, the delivery- chamber in each is fittedwith two9-inch by-passes withreturn pipes to thewell, so that the column may be set in motion gradually. Each pump can be isolated from the mains by a 36-inch sluice- valve, and each of these valves is connected with a special casting which forms the base of an air-vessel, B feet in diameter by 13 feet high above the base casting. The manner of making the connection with the two rising mains is shown in the Figure. The whole of the sewage from each set passes through a condenser. The engine-floor is fixed conveniently at 39 feet 9 inches, a fen inches above street-level, and as the space below was rather limited for the adoption of the arrangement of the guides under the floor, and the connecting-rods rising to the crank-shaft, the more usual arrangement shown in Figs. 2, Plate 7, was preferable. The bearing beams for both the engines andpumps have their ends planed on the underside, and are bedded perfectly on granite bedstones without reliance on grouting. They are fastened down by long bolts built in. Pairs of steel stanchions connect the undersides of each pair of engine-beams with the pump-chambers below ; the heads of the two air-vessels on each of the pump-chambers are also steadied to the undersides of the engine-beams, so that there can be no vertical movement of the engine sole-plates. Eachengine has three sole- plates, andthe crank-shaft with its two fly-wheels is carriedin four bearings, as at Partick. Thestandards are marine type, A-shaped box castingswith legs well spread, andseparate flat-planedguides of hardmetal secured to the upper parts. At the bottoms of the guides are pairs of horizontal bolts with cast-iron distance-pieces binding together each pair of standards. A lightentablature binds the standard heads and carries thecylinders, the arrangement, details, andvalve- gear of which are practically the same as at the other station. Theair-pump, with its cylinder, 114 inches indiameter by 39inches stroke, isdriven by linksand leversfrom the middle crosshead, and is fixed to one of the air-vessels below the floor. Eachengine is fittedwith barring-gear having an automatic throw-out pinion, which engages with a spur rack cast on the rim of one of the fly-wheels. This pinion is driven by a 15-HP. motor with reduction-gear, all placed just below floor-level. A 12-tonthree-motor travelling crane, whose track is 38 feet

above the engine-room floor, commands the whole, and was erectedbefore the bulk of the machinery was fixed. The Author had adopted a similar policy in carrying out other work, and had foundthe result equallysatisfactory to the engineer and to the contractor.Many modern pumping- and power-stations arestill provided with slow and tiresome hand-cranes, but in every case it would be wellto consider whetherthe extracost of a first-class power- crane would not be justified. The difference in price is not so great as formerly, and contractors arebecoming fully aliveto theeconomies which attend the use of electric power in carrying on their work. The depth from the engine-room floor to the bottom of the suction pipes is about 39 feet, and the height from this floor to the top of the cylinders is about 27 feet. There is no vibration on the cylinder- platforms, because of the stiffness of the enginestandards. The feed-pumps are in duplicate, and a.re of the low-speed steam-driven type used at Partickand Dalmuir. The feed-tank is fittedwith filter-frames, and receivesall unpolluted water delivered from steam-separators,steam-pipes and steam-jackets. Oil-filters are fitted to the feed-pipes on the pressure side, and the boilers may be fed either from the hot-wells, with a make-up of Corporation water, or they may be fed entirely with Corporation water using only the condensed water which is freefrom oil. Inthe latter case the water bill is not a serious matter, because of .the low rate, 4d. per 1,000 gallons. The pumping-engines were started for preliminary runs inMarch 1910, and it was soon discovered that after an engine had been at work for a time the head or resistance gradually increased until it reached about 7 feet above the normal. The head was measured by a mercury gauge connected with the pipesin the area by the southwall of the pump-house. This pointed t80 some peculiarityin theworking of the rising mains, which are described in Mr. Easton’s Paper.1 There are siphon summits on the mains where they pass under West Scotland Street at about 220 yards from the station, and on thesehad been placed air-valves of the class commonlyused for clear-water mains. It was evident, that while the large air ball was capable of discharging the air when the main was beingcharged with water, the small valve was quite incapable of discharging the air and gas in the sewage, supplemented no doubt by the air taken in by the snifting valves on the pumps, which were then opened too freely. The air graduallyaccumulated inthe siphonhead, throttling the waterway until a pressure was reached suEcient to

Ante, p. 19i.

send the remainder down the siphon towards the delivery-orifice. Immediately the large ball was forced down,the pressure would fall to normal. Various experiments were made to overcome the difficulty, and it wasproposed to erect an air-stand pipe in an adjacent enclosure, but eventually common enclosed safety-valves with light adjustable loads were fitted. The delivery-pipes from these were led into the street sewer, thus allowing a trifling discharge of sewage along with the air. These valves serve their purpose, but require regular super- vision on account of the intrusion of small pieces of wood and other light matter carried on the crown of the stream. Owing to the decision to reduce the size originally intended for the catch-pit, the Author had some misgivings as to whether solids might not be deposited in the rising main. In consequence, he fitted 8-inch scour-pipes and valves at the point where the mains pass out of the station-yard, and 12-inch pipes with valves were provided at the lowest point of the mains ; it is gratifying, however, to be able to say that so far neither the scour-pipes nor the pressure-gauges havegiven any indication of deposit likely to causetrouble. In spite of the catch-pit,however, considerable quantities of solid material are found in the pumps and even in the lower part of the condensers when the time for cleaning comes, once in 50 days. Althoughnumerous efficiency-tests showed that the working of the machinery was satisfactory,perhaps the figures derivedfrom normalwork are of more value. Comparing results with Partick, notwithstanding that the total lift is about25 per cent. greater, the total working-expenses are Ss. 6d. per million gallons as against 10s. Thebetter result is accounted for primarily by higher efficiency in the combustion of fuel ; in a less degree it is due to the use of a moderatesuperheat, and to higher efiiciency inthe pumping- engines,owing to thegreater lift and prebably tothe better alignment of the movingparts. The working-expenses of the auxiliary machinery are included in these figures, but if they are eliminatedthe differenceremains very much the same,namely, 89. 2d. for Partick as against6s. 7d. for Kinning Park. Both results may be regarded as satisfactory, andthe contemplated introduction, at Partick, of new mechanical stokers of a type better adapted to the fuel than those now in use, will bring them more nearly to equality. The steam-consumption found at the official trials was 11 -62 lbs. perindicated horse-power-hour, and14 percent. of this total was condensed inouter jackets. Thepressures andrelative temperatures whichcontractors elected to use in these jackets, however, were, in the Author’s experience, too high to secure the

best results. The preliminary investigations at Kinning Park and the earlier trials at Partick showed conclusively that the temperatures in the second and third jackets should not be much higher than the initial temperatures of the steam entering the respective cylinders. With suitable adjustment of jacket-pressures the steam- consumption wouldbe maintainedcontinuously at 11 lbs. per indicated horse-power-hour. The mean rate of evaporation under working conditionswas 9-09 lbs. of water per pound of coal, the calorific value of the coal being 12,672 B.Th.U. per pound. The rate of consumption of small coal worth 79. 6d. per ton was 1.28 lb. per indicated horse-power-hour. The mechanical effioiencyof a pumping-engine is involved with the displacementeEciency of the pump, and with regard to the latter,in the absence of directmeans of measuring the volume discharged, there is room for some uncertainty. It is well known that properly-designedpumps, withoutair-pockets in any of the chambers between suction- and delivery-valves, have a displacement efficiency of practically 100 per cent., when run at speeds suitable to their valve- and passage-areas. Contracts for waterworks engines are frequently based on this undertaking, no reduction being made for slip. It is reasonable, however, to allow a small percentage for loss by slip, particularly when pumping sewage, and B per cent. is stipulatedin the present case, tbough for ordinaryrough work 10 per cent. is sometimes allowed. Indicator-cards taken from the pump-chambers are also sometimesaccepted as a measure of the water horse-power. The pump-d-iagram aims at the measurement of net or effective horse-power, while the power required to maintain the movement in the pump is hidden in the indicated horse-power of the steam cylinders. The pump diagram is a record of the forces exertedwithin the pump-chamber during a cycle, and it is not necessarily an accurate measure of water horse-power. In practice, however, when accurate means of measuring the water are available in conjunction with carefully obtained pump-diagrams, the results are usually in close agreement. No systematic series of cards was taken from the pump-chambers at KinningPark, but throughout the trials at Partickthis was done. Snifting valves are usually fitted to large pumps to admit automatically a small allowance of air, which softens the shock at the turn of the stroke. Care must be taken in their adjustment, however, if the displacement of the pumps is notto be rather seriouslyimpaired. Thus, experiments at Partick revealed that with these valves closed the loss measured by card-area was only 0 75 per cent. at 20 5 revolutions per minute, while with the valves

on the pump-chambersopened by one full turn of the adjusting screws the loss was 7.5 per cent. With the snifting valves on the suction-pipe slightly open and those on the pump-chambers closed, the loss was 3 * 5 per cent. During official trials at Partick the pump diagrams showed an average efficiency of rather more than 95 per cent., the mean speed being 22 revolutions per minute. In January, 1905, underthe direction of Mr. W. C. Easton, hourlyobservations were takennight and day during five con- secutive days, to determine the quantities of sewage flowing in the outfall-sewer,above and below the station, in order to secure an accurate comparison with the quantities registered in the station books. By actual measurement in thesewer, the aggregatedischarge from thestation for 5 days was76,695,750 gallons. By displacement of pump-plungers and revolutions, less 5 per cent., the aggregate was 76,555,800 gallons, so that the slip of the pumps found by measurement in the sewer was 4-82 per cent. With regard to the mechanical efficiency of the pumping-engines at KinningPark, some time elapsedbefore theAuthor had an opportunity of examining the tabulated figures, among which the mechanical efficiencywas put down at 95per cent. This was obviously an impossible efficiency under the conditions, with X correspondingly absurd duty in foot-pounds. No doubt the reason was thatthe snifting valveswere used too freely, the slip in ,consequence being nearer 10 per cent. than 5 per cent. With the valves adjustedto give 5 percent. slip the mechanical efiiciency would be about 90 per cent., and the duty from 112 lbs. of small coal would be 147,600,000 foot-lbs. Thequantity of sewage actually flowing intoKinning Park stationappears to agree closely withthe quantity scheduled. Usually two engines running a littleover half-speed,or, occasionally, one at full speed, are required during the hours of maximum flow. During rainfall two engines are required, and in heavy rains these must run at their maximum speed. The total cost of the machinery equipment at Kinning Park was about E38,OOO. TheAuthor desires to recordhis indebtedness to his son and partner, Mr. A. Home Morton, M. Inst. C.E., and to his partner, Mr. Geo. H. Gibson, M. Inst. C.E., for their assistance in carrying out the works.

The Paper is accompanied by five prints, from which Plates 7 and 8 have been prepared ; also by the following Appendix. [APPENDIX.

C m X C h. 7 l. +* 3+

m h 3 W 0 10 c?

00 Orn ha

tD ."+

* Y m d k

TABLEII.-SEWAGE TO BE DEALT WITH AT DALDIUIRPURIPICATIO~-WORKS.

Sewage Alone. I Sewage andRainfall Comhinerl. l . ~~~~~~ ___ Rainfall, Rate, Rate, 1 +Inch in70per Icent. in 1 &~~~~),1 70 percent. ill 1 Actual drained. 24 Hours. 1% Hoars X 2. j 12 Hours X 2. . - -.-______.~~_I I -4ores. lGal1onsperday.l Gallons per day.lGallonsperday.~Gallons per day.~Gallonsperday.

Prraent Dischrcrp. 6,863138,926,077 I 37,633,675126,580,483 1 76,555,752 1 65,806,559

I'ltinmte Disc7~avge. 9,05151,336,139 j 68,318,71548,799,082 1 119,654,854'100,135,221 l l

Theae figures iuclude the sewage raisedfrom the Clydebank intercepting sewer, and the proportion to be pumped wa~scheduled as follows :-

To he Punqmi?fmw C~ydcfmnkf+lcrv.

R ainfall, Rate Rainfall, ' +Inch in 70per cerk in I &:z&,.7Oper cent. in drained. 1 24 Hours. 1 12 Eorirs X 2. i Hours X 2. l2 - 1 Acres. lGal1onsperday.l Gallons per day. Gallon- per day.' Gallons per day.'Gallons per day.

Prescvt Discharge. 816 I 4,628,250 1 3,750,750 1 2,700,536 j 5,409,000 1 7,328,756 l'ltimatc Bischarp.

816 j 4,628,250 I 5,761,750 l~ 4,115,536 lO,Y90,000 1 S,743,756

l j '., PLAN OF PARTLCK PUMPI#G-STATlOM.

PARTICK, SECTIOH THROUGH PUMP-UO~SE. KINMINC PARK, SECTION THROUGH PUMP- MOUSE. CROSS sEcT1ou THROUGVI PUMP- HOUSE an0 BOILER-HOUSE

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