MARINE AUXILIARY BOILERS1.Smoke tube Tank type • Combustion gas pass through inside of tubes, water is outside of tubes. 2. Water tube Drum type • Water is in tubes, smoke pass outside of tubes. Smoke tube single pass composite Boiler 24 February 2013 2 WATER TUBE BOILER (1) • • • • Steam drum – One largest cylinder at top. Collect & separate steam & water, come up from generating tubes. Steam leave from top. Distribute water to down comer tubes. Receives feed water. (2) Water drum – Cylindrical shape, half size of steam drum at bottom. • Distribute water to screen& generating tubes. • Provides a space for accumulating suspended solids precipitated from boiler water. • Blow down v/v is fitted. 1 manhole is at front end. (3) Headers – Cylindrical or rectangular shape, half size of water drum, • At bottom opposite side of water drum. • Perform as water drum. • Only hand hole at front end for cleaning. large heat exchange surfaces.(4) Generating tubes – • Large quantity small diameter (32mm) tubes • placed in main flow of hot gases between steam drum& water drum. to prevent over heating (6) Down comer tubes –Water from steam drum down to header(50mm) . • Large diameter (50mm) to keep ratio of steam to water. (5) Screen tubes – Place in front of generating tubes • to protect from direct heat of flame. • Steam generated at mid portion of generating tubes and raise up together with hot water to steam drum. Water tube boiler steam drum Down comer tube 1300 C steam water Furnace front header under floor tubes water drum . • (2) STEAM STOP VALVE – • SLSD v/v on top of steam space.AUXILIARY BOILER MOUNTINGS • Mounting mean v/vs & fittings direct attached to pressure sides. • . . • Drain pipe without v/v fitted at chest. • (1) SAFETY VALVE • Protect overpressure. • 2 valves on same chest with single pipe at top of steam space. draining condensate. . • Extended spindles fitted to operate from convenient position--• Always ensure v/v can be operated easily & quickly • have open/ close position indicator • feed p/ps are positive pumps. • 1 feed check v/v (NR) and 1 feed stop v/v between shell and feed check v/v.• (3) MAIN & AUXILIARY FEED V/VS • Fitted to steam space. • 2 inlet lines are fitted on same feed line. at water level. • To prevent loss of water in boiler • Due to burst tube or fail to feed.• (4) WATER LEVEL INDICATOR (GAUGE GLASS) • At least 2 for each boiler. . • (5) LOW AND HIGH WATER LEVEL ALARM • Float and Electrically operated. • Place on each side of boiler at direct visible positions. • Pipe from this v/v connected between 2 bottom blow down v/vs. Consist 2 v/vs in series. . connected by a pipe to ship side discharge v/v.• • • • • • (6) BOTTOM BLOW DOWN V/VS Fitted to lower water space to blow out water and sediments. internal pipe reach to bottom. • (7)SCUM BLOW DOWN V/V – • Fitted in upper water space • to discharge oil or floating particles on surface of water • in way of a pan just below normal water level. • (10)SALINOMETER V/V • Fitted at mid of water space to get water sample.• • • • • (8)DRAIN VALVE At lowest water space. Direct and remote reading. • • • • (11)PRESSURE GAUGE At top of steam space. Connect to pressure switch for a auto combustion. . (9)AIR VENT At top of steam drum. To drain water completely. To release air at filling water or raising steam. Cycle of steam and water . Very low water level cut out burner.Safety valve & easing gear prevent over pressure.SAFETY DEVICES ON BOILER 1.Very high steam pressure cut out burner. 3.Low and high water level alarm.Low and high pressure alarm. 5. 4. 2. . . DOUBLE SIDED GLASS PLATE TYPE (HP above 30bar). 2.Boiler gauge glass or water level indicator • 1. SINGLE SIDED GLASS PLATE TYPE (Used in LP 17 bar and MP17~ 30 bar) Forged steel body in which is reflex glass plate. METHODS OF FITTING ON BOILER • 1. On bore pipe 3. Direct on shell 2. • Drain is vertical downward at close & horizontal at open. to prevent change of position due to vibration. . On hollow column 4. On solid column • GAUGE GLASS CROSS BLOWDOWN • COCK POSITIONS • Steam & water cocks are vertical downward at open& horizontal at close. form gas in fuel line.BOILER F.O about 60C come from F. rotated by motor or hand • Then oil pass an control v/v. • Pass coarse filter& pump. which regulate oil pressure to burner relative steam pressure in boiler. • Then pass through auto-clean fine filter.O tank. • Then heated in heater about 100C controlled by viscorator. • If low. poor combustion and back fire. high cracking occur.O BURNING SYSTEM• F. • . then enter burner. • If temp. shut by hand rapidly in emergency. • D. at desired value. • .O line also fitted for flash up boiler from cold.• Air controller maintain correct ratio of fuel & air to furnace. to shut off fuel when boiler water loss. • 2 emergency v/vs are fitted. one quick shut off v/v or safety cock. and another one shut of v/v with a steam actuator. • To maintain oil temp. a v/v is fitted to circulate oil back to p/p suction and closed when burner is in operation. • Quick closing v/v on fuel tank outlet pipe & Emergency stop of fuel p/p operated from out side of E/R is fitted.• Burner is ignited by 2 electrodes. bypassing automatic control v/v and oil supply pressure by hand wheel on spring loaded relief v/v. . • Whole system should be above floor plate. well lighted to see leakage • Can easily change to manual. • Pressure gauges & thermometers are fitted. alarm & cut out burner.(relay) High flue gas temperature alarm & cut out (temp. .• • • • • • • • SAFETY DEVICES ON FUEL BURNING SYSTEM (UMS) Flame failure alarm & cut out burner (by photo cell) Low & high fuel temp. sensor) Smoke density alarm & cut out burner (by photo cell) Air fuel ratio alarm & cut out controlled by air damper. sensor) Low fuel pressure alarm & cut out burner (by pressure switch) Force draught fan failure alarm & cut out burner (by electric relay) Power failure alarm.(by temp. close vent v/v. When boiler get warm more firing times till air come out from vent. When steam come out from vent./ 45 min.. open air vent . 6. raise steam to working pressure.4 times flash up 5min. Other v/vs kept shut. Fill up water about ¼ of sight glass. First 3. pressure gauge. Run force draught fan to purge out furnace. then 5min. . 2. 5. 4./ 30 min. 3.BOILER RAISING STEAM FROM COLD 1. gauge glass v/vs steam & water. blow down. • When water level come into glass. . inform to C/E to stop engine. If higher. Close non essential steam consumers.• ACTION TO BE TAKEN WHEN WATER LEVEL DISAPPEAR IN GAUGE GLASS • • • • • Stop fire. and inform to duty officer if involve with inert gas generator on tanker. Restart burning and put in service. If lower-reduce boiler load and fill water. Close main steam stop v/v Make sure lower or higher than glass. • If water level still disappearing. Boiler operation . Boiler pressure always in limit 4 to 7 bar. Drain oil from feed tank water surface. FO temp.& press. Safety v/v easing gear to be made ease. 7. in limit. 6. 4. Cross blow gauge glass. No leakage in steam and fuel v/vs or pipes. wipe out with paper.CHECK POINTS ON BOILER AT BIGINING AND KEEPING WATCH 1. Flame color must be clean. fill water. clear and bright yellow. . 2. ( feed tank sketch) 8. not white or black smoke. 5. 3. Gauge glass water level about ½ glass. nozzle defect. collect on floor. air/fuel ratio and burner in good condition. Keep good combustion. Fire blow back to boiler front through inspection door and air passage. well ventilate furnace before ignite fuel. clean burner tip. Then get firing temp. oil leak fr.• • • • BOILER BACK FIRE Unburnt fuel due to improper combustion (by low fuel temp.. improper air/fuel ratio. maintain correct fuel temperature. suddenly explode during firing (or) Flammable gases in furnace from previous time explode when supply air and ignition for next start. . burner. • To prevent. by radiation of burning flame. • (3) Combustion system – Maintain correct fuel pressure. Check and clean air regulator system. Clean and overhaul burner. temperature. • (2)Clean gas side and water side regularly.BOILER MAINTENANCE • (1) Boiler water test and treat daily. . . to prevent high pressure in pipe between boiler & ship side. • noising at high press discharging. noise level fall. crack and gradually open intermediate v/v to control discharge rate.BOILER BLOW DOWN • Open ship side discharge cock and v/v first. • Ship side v/vs are usually non-return or one more n-r v/v fitted before ship side cock. • While blowing down. • Handle on cock can be removed when only close position. • Fully open blow down v/v (scum or bottom). • Never control discharge rate by boiler v/v. to prevent seating of v/v from damage and leakage when closed. low. when press. close blow down v/v first. • When fall to ¼. then close ship side cock. watch gauge glass water level and pressure gauge all the time. SCALES Dissolved alkaline ( temporary hardness) decompose by heat and become (permanent hardness).PRIMING 5. . Iron is more ready to dissolve in acid. FOAMING 6.CORROSION 3. Iron can corrode even in pure water(condensate) High chloride show s. SCALES 2. SLUDGE 4. CARRY OVER.BOILER PROBLEMS 1.w leak to boiler and get corrosion. Then stick on heating surfaces and become scale. Tubes over heat& damage. 1. CORROSION • • • • • Oxidation / Reduction Reaction If a metal meet acid or alkaline. 2. • SCALE reduce heat transfer & boiler efficiency. become oxidized. due to oil. To prevent –Make sludge down to bottom by (Liquid Coagulant) and blow down. baked on heat surfaces and become insulation. PRIMING –Surface suddenly rise by expansion large amount of water. 6. contaminate and scaling in steam lines. FOAMING – Thick bubbles form on water surface. 4. Effecting water hammer. SLUDGE --Combination of suspended materials in water (loose corrosion products. by rapid opening steam stop v/v or high water level in boiler. 5.3. loss of water. organic substances and high amount of total dissolved solids (TDS) in water. . CARRY OVER –Water carry with steam. insoluble mineral precipitates & oil). 2.Phenolphthalein alkalinity test 3.Excess phosphate test or hardness test .Chloride test 5.Hydrazine test .Total alkalinity test or pH test 4.BOILER WATER TESTS 1. pH is tested with litmus.Know condition in boiler. • SAMPLING # Taken while boiler is in operation • # Before taking blow off salinometer valve to clear scales .(4) Remove suspended solids & dissolved oxygen. Hardness is tested with soap solution. no need pH test. no need hardness test.WHY BOILER WATER TEST AND TREAT • By Test--. . dose. blow down. maintain pH11. • By treat---(1) Remove scale forming particles (2) Maintain alkaline condition to prevent corrosion (3) Improve boiler efficiency. One shot water treatment (DREW AKG 100) is enough for LP boiler. • • • • • If test Alkalinity. If test excess phosphate. • • • • FEED WATER TREATMENT To reduce TDS. 60~70C to promote de aeration of hot well) . use evaporated water To arrest suspended solids (use feed line filter) to prevent feed system corrosion (maintain correct pH of feed water by GC) • To reduce dissolved O2 (dose Amerzine and maintain hot well temp. Take care not to scratch surfaces of swirl& orifice plate during cleaning.MAINTAIN BOILER OIL FUEL BURNER • Regularly or when flame condition become bad. check by gauge. • Renew if orifice wear beyond limit. dismantled and clean the tip. • Assemble all parts correctly. burner to be removed. • Immediately rectified any oil leakage. • Clean burner tip. they can lead to fire in air register and back fire. .