Guidelines for the Construction and Operation of Marine Steam Plant S

For small boilers without circulating pumps, the Guidelines for the gradual raising of temperature and pressure is construction and operation important. (30 minutes per foot of boiler of marine steam plants. diameter) First fill the boiler to the manufacturer's recommended level.

The following information was compiled by Paul Secondly, prove the accuracy of the water gauge Malpas for participants at Clayton Capers IV in glass by opening the gauge glass lower cock and 2002. While including it for members’ watching the water level return. information, the SBAA does not endorse the To heat the lower parts of the boiler (particularly content, and steam plant operators should Scotch type) blow-down to the working water ascertain the suitability of the information for level at about 8-10 psi. their application. Many thanks to Paul for his dedication. With 20 psi / 140 kPa on the steam gauge, prove the gauge glasses clear and then ease the safety INTRODUCTION valve to ensure air is removed and the valve is The following information is offered to ensure mechanically free to function. that you enjoy trouble free steaming and to Do not force the fire with blast pipe while present your pride and joy in public or for formal raising steam. inspection, with confidence. Constant attention to the water gauge and Your boiler is a pressure vessel, which imposes a handing???, to blow through the cocks to statutory obligation on the OWNER or confirm water levels, will avoid misleading MANAGER, the responsibility of registration indication. with the Dept. of Administration & Information Services. (formerly Industrial Affairs, Labor & Marking the working water level and also the Industry South. Aust.)compliance with all furnace crown level on the boiler casing near the statutary regulations currently in force in your glass is a good idea. State. Be aware of the boat trim, for bad indication. There is a duty of care to comply with Low Water Alert Occupational Health and Welfare Regulations when operating in the public domain. When the water level fails to give any reading on the gauge glass, you have not kept tabs on To design, build, operate or repair a boiler proceedings. Shut off steam to engine, blower outside these parameters will not only alienate and auxiliaries. Open the firebox door. Remove you from a dedicated world of enthusiasts and the fire. jeopardize their hard won status, but, may have your friends buying you flowers. Allow the boiler to cool. Compliance, on the other hand, is a ticket to a Present the boiler for inspection. unique community of priceless advice and In an extreme case where the furnace crown is enjoyment. exposed, cool the fire rapidly. The annual inspection fee,fee is good value for Open the fire door for cooling air and close the your peace of mind and cheaper than a dental damper. check. Do not release the safety valve or run the engine (don't tell him that!) as this can impose added stress to a possibly red hot crown. Allow the boiler to cool naturally, before inspection. GETTING UP STEAM DO NOT ADD FEEDWATER TO A HOT DRY Protecting your boiler from thermal stress by BOILER uneven or sudden heating or cooling will guarantee its long and trouble free service. Feed water can be 200 F difference. Preheating minimizes thermal shock and hand pumping cold water into a boiler will induce stresses and kill protected with a cast iron sleeve, it should be performance in particular. withdrawn to check if it has burned away. Be aware that ball valves will not lift if feed Vertical multi-tube boilers can suffer the same water gets beyond 601 C. problem although the smaller tubes are less prone to overheating. Varying the water level Maintaining Furnace will minimize localized damage. To get the best performance from your boiler and Do not over-fire with less than 3/4 gauge glass. fuel, do not have too deep a bed of coal that airflow is choked, or too thin, that cool air For those boilers raised on a brick ring under the bypasses the fuel through grate bars. foundation flange, corrosion of the firebox and the shell, by damp ash, will be rapid. Keep the fire door closed. A few holes through the door, behind a heat shield will provide Direct Tube-Scotch Boiler secondary air to aid complete combustion. In marine boilers, like the Scotch type, the Air, preheated prior to introduction below grate bottom of the shell dips under the stokehold floor will also enhance thermal efficiency. or exposed to the bilge water causing rapid corrosion. The shell should be kept well painted. EXERNAL CORROSION Cause and Cure Attention to Shell and Ash-pan The greatest enemy of steam boilers is pitting or corrosion, pitting being a localized form of the The combination of condensation, leaks, rain or latter. Boilers set in brickwork, insulated with just damp air, combining with ash rich in sulphur lagging and with refractory cement are especially and other chemicals is a bad recipe. liable to external corrosion due to dampness Periodically remove the bars, clean all the scale penetrating these materials in places where it is off the plates below the fire-bar bearers and give difficult to find. a coat of fireproof or graphite paint to the whole Vertical Boilers interior of the firebox and around the bottom of the shell on the outside of the boiler. The vertical boiler is prone to abuse, due to its installation in all kinds of cramped situations It is pointless to paint over any corrosion present. -where reasonable access is difficult. It must be chipped off with a scaling hammer. Carefully check for any reduction of the plate Ash must not be allowed to accumulate round thickness and if uncertain, seek advice from a the inside of the ash pan and under the firebox. boiler inspector. Keep tops of cross-tubes, or top of the tube plate, free from soot and moisture, especially when DO NOT attempt welding or repairs. (AS 3788- boiler is idle. 01 applies) Leakage Where white furry deposit is seen around mud- hole doors or fittings, leakage and therefore corrosion can take place. The plate surrounding these points should be kept well painted, holding corrosion at bay until proper remedial action can occur. All boilers, particularly verticals, should have a Cowl (Chinaman's Hat) to cover the funnel to prevent rain getting into the boiler or smoke-box. Expansion Mounting and Plumbing Check holding down bolts and brackets for corrosion, they usually reside in the hot and Protecting Uptake Tube moist environment of the bilge and may look in good condition, but remember, the damage is With cross tube boilers, the length of the uptake generally within joints, where you can't see it. tube above the water level can overheat. If Also inspect blow-off pipes and keel condensers. Secondly, and far more serious, is the danger due Some installations are rigidly set cement or to poor conduction, of overheating of plates and through hull fittings where corrosion is invisible tubes with their consequent collapse. or even worse the inability to expand has The lower tubes in water tube boilers are fractured the fittings. particularly prone. Boiler fittings, steam pipes and inspection Scale can coat fusible plugs to a point where, if openings in the shell, should be checked for the tin melts out, the scale can still bridge and leaks or ash accumulation where rusting can block the passage of water. initiate. Air in feed water Channel Corrosion Dissolved oxygen and other gases in the feed Condensate laying in steam pipes, absorbs gases water are a cause of internal corrosion and can from the atmosphere, to form acidic solutions. be minimized by preheating the feed or An example is the keel condenser. By mounting neutralizing the acids they form. the outlet below the hot-well surface, the Oil in feed water concentrated solution will not occur. Allowing oil into a boiler, even in minute To Sum Up quantities, is not recommended and must be (1) External corrosion is the chief enemy to the avoided. life of boilers, more are scrapped due to this Oil combines with other suspended matter, effect than any other. coating heating surfaces, and at best, causes (2) Repairs by welding must be performed by a priming, and at worst, its long term effects of qualified pressure vessel welder and only if corrosion and insulation of heated surfaces can approved by a certified engineering boiler lead to boiler failure. inspector. (AS 3788-01 applies) (is this It can be prevented with absorption filters in the the correct AS?) hotwell but is to be avoided at all cost. The Naval limit was 1 part per million. INTERNAL CORROSION Cleaning Incrustation Using soft water, a boiler in regular service should be opened for cleaning every 500 hours. The incrustation or ‘furring up' by hard water impurities, is one of the most common problems. The water should be blown down an inch or so, In large plants, it is usually processed in water of the glass, daily to remove sludge. treatment plants before entering the boiler. Using hard water, a boiler should be opened for Boilers of traction or ploughing engines and cleaning every 100 hours. steam boats, which have to pick up water where The water should be blown down daily when the available, suffer from internal corrosion and pressure is low to remove sludge. therefore need close attention to feed water chemical treatment. Blowing down is usually an intermittent process, but can be continuous, usually through a scum The loss is in evaporating efficiency, due to scale pan just below the operating level of the boiler build up, (equally soot deposit on heating and the flow regulated via a metering valve. The surfaces) and therefore, use of fuel, is shown on heat is recovered to the boiler by a coil through the following table:- the feed tank. Scale thickness Loss of Fuel 1/16” (1.5mm) 9% BOILER WATER TREATMENT 1/8” (3mm) *18% Small boilers at low pressures 1/4” (6mm) 38% The object of internal treatment is to convert ½” (12mm) 60% scale forming impurities into a dispersed sludge, which can be removed by blowing down. *TIME FOR SCALE REMOVAL The chief compound is calcium sulphate, Dissolved solids should be below 1500 ppm, because of its inverted solubility, it can be ideally by chemical water treatment and converted to calcium carbonates or phosphates, blowdown. by adding sodium carbonate or sodium Suspended Solids phosphate. By allowing a water sample to stand overnight (below 150-250 psi --- 1.05-1.75Mpa.) the precipitation of solids can be gauged. Tannins are a safe option, in that they are Alkalinity can be alkaline, they inhibit foaming by precipitating controlled with: suspended solids and inaccurate application will do no harm. Caustic Soda should be avoided for acidic Mono-sodium Acid neutralising countermeasure as it can be phosphate ...... corrosive to condensers, gaskets, 'O' rings and Di-sodium Neutral fittings and may lead to embrittlement of steel. phosphate ...... The principal danger of internal treatment with Tri-sodium Alkaline chemicals is over or under dosing. phosphate ...... Unless you have an accurate water analysis, they can become harmful. Testing The rule is to BLOWDOWN REGULARLY, but be aware that you lose some of your compounds. Analysis is the first step to identify which treatment is applicable. This is an exacting process and impractical for small boilers, WATER TREATMENT PROCESSES however, there are some simple tests, which can give a reasonable guide to minimize ill effects. A. Fresh water from natural earth catchment: All tests must be performed in a clean container, 1 .Filter to crystal clear condition (to remove as contamination with salt or oil will give undissolved solids) incorrect results. 2. Pass through water softener. Hardness (to remove temporary hardness) Keep a soap solution of Castile soap in distilled 3. Heat water to 950 C. water for test purposes. (to remove dissolved gasses) A few drops of HARD WATER in a small 4. Add chemical treatment. and quantity of test solution will go cloudy, and not precipitate permanent hardness, removed by hold a lather for 5 minutes. blowdown. Alternatively, a few drops of the soap dissolved B Rainwater: in alcohol, will cloud HARD WATER. 1. Use crystal clear water only Acidity 2. Add Tannin to give ‘weak tea’ colour. Litmus papers, should be carried and used to test 3. For small boilers 2-4 seconds blowdown every a (clean) sample of boiler water drawn from the hour. gauge glass or hot-well. Maintain PH 10.5 -– 11 (look at Tandex data) C. Salt water: A slightly alkaline water will neutralise acidic 1. Distil the water in an evaporator. corrosion from dissolved oxygen and carbon or 2. Add alkali to neutralize all acidity. sulphur dioxide. 3. Treat as received. Dissolved Solids N.B. High pressure feed above 450 psi (3.1 Mpa) must not have, even moderately accepted levels of total dissolved solids, as the high speed of water leads to erosion of the The firebars should be taken out, the, tubes tubes, in watertube boilers. swept and all ash removed. Leave flue and fire doors open to prevent condensation. LAYING-UP A BOILER Drain the pressure gauge siphon or it may be It is often necessary to lay up a boiler for an damaged if there is a risk of freezing. extended period and unless proper precautions are taken, damage may be done both internally and externally. THE CARE OF STEAM FITTINGS Drain Boiler The efficient and safe working of a steam boiler Draw the fire and blow the boiler right down depends on the state of the controlling fittings once the pressure has dropped to a few pounds. Safety Valves The heat -will dry it out. Man hole and mud hole doors are removed to allow circulation of air. Larger boilers normally have two safety valves. Leakage of the valve seat may be caused by wear If all moisture- has not evaporated, a small fire or foreign matter on the seating face. may be lit with a few sticks but beware of overheating -the fusible plug. Should a valve fail to seat after blow-off, a quick release or tap on the lever will often clear it. Leaving, Boiler Filled Should this fail, the seat should be inspected for The other method is to leave the boiler quite scale and cleaned when the boiler is cold. A filled with all openings closed, but water should. damaged seat must be reground and bedded. be non-acidic and gases driven off by steaming (AS 3788-01 applies) before closure. Springs should be checked for corrosion or A boiler preserved in this way is not softening. recommended for long term storage, say for Remember, the release pressure is only as more than a month. accurate as your pressure gauge. It must be free from frost, as freezing will expand the water and destroy the boiler. All exposed parts and smoke-box should be well painted to prevent rusting. STEAM FITTINGS Water Gauges Water Gauges should be given special care and protection from cold air or water. The consequences of a broken glass can be serious. Check alignment of fittings and renew packing, which can harden and weld to the glass. The Klinger type with flat plate glass and ribbed for better visualization is a safer option. Type A for low pressure work Type B for medium pressures, employs glands at the handle ends.

SPRING LOADED -POP' OR QUICK LIFT SAFETY VALVE If the boiler will not sustain pressure when closed, then this item would be a good candidate for attention. Pressure Gauges Only cold water must enter the gauge. If steam is allowed to get into the curved tube the heat can damage it with consequent reading inaccuracy. Generally they require little attention other than care to avoid water entry into the casing and a periodic test against a gauge of known accuracy.

The passages may become choked with scale, which can be cleared by carefully passing a rod or drill through the cock body and passage into the boiler. The lower cock which is opened each time the level is tested, gets far more use than others and the effects of sediments will lead to leakage which may go unnoticed down the waste pipe. If the plug is grooved, grinding in may not be successful and replacement the best remedy. All cocks should be checked periodically, as they can "set" and cases have been known where GAUGE handles have sheared without the cocks being Cleaning the Siphon closed. As there is no flow through the siphon, it can Stop Valves become choked with sediment and scale after Valves should be checked for effective seals and long working, and should be cleaned annually. packing on spindles renewed periodically as It must be refilled with water before replacing compaction over a long period can harden and the gauge, although the first steaming will score the shaft. produce sufficient condensate. Stopping leakage by undue force on the handle is dangerous, causing further damage or even fracturing the valve body. Worn seats can be resurfaced but replacement is a good policy. A perfectly tight valve tested under hydraulic pressure may leak under steam. Check Valves These are the hardest workers, against boiler pressure in unison with the feed pump, they are subject to shock and considerable wear. The maximum lift must not exceed 1/4 of its diameter. Terry Lance’s suggestions vented in a way that its operation does not direct steam at passengers.  The boiler and funnel and engine GENERAL MACHINERY should be adequately secured to (not to intrude into companionways) prevent movement in rough PIPING conditions  A start-up, general operation, (lagged to prevent burns) emergency and shutdown checklist BLOWDOWN (piping to drain away from crew) should be developed for each boat with the input of other members

MAIN ENGINES, AUXILLIARIES (Rotating parts, hot oil etc) PROPELLER SHAFTING (covered or guarded)

FIRST AID KIT (Burn treatment incl)

EMERGENCIES Broken Gauge glass Fire on Board MOB Emergency Procedures to be provided to crew (verbal on boarding) The Master is LAW at sea.

Peter Cowie’s suggestions  Boilers must have a gauge glass to indicate the level of water in the boiler… elaborate on position, construction etc  Fittings exposed to full boiler pressure must not be made with soft solder or constructed from brass… elaborate on reasons why  Gauge glasses should have devices fitted that protect individuals from injury should the gauge glass fail.  Boiler pressure gauges must be protected by a pigtail.  At least two methods of boiler feed must be provided  At least one safety valve must be fitted with direct, unimpeded access to the steam space and properly