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1. What is emergency air compressor ?<\/strong> 2. Air compressor safety devices ? <\/strong><\/p>\n \udbc0\udc31 Bursting discs are fitted on the cooler shells (At water side). 3. Purpose of unloder valve (moisture drain valve) ?<\/strong> 4. What would be affect of suction valves of an air compressor having too much lift ?<\/strong> 5. Affects of reduced volumetric efficiency of air compressor ?<\/strong> 6. Different between relief valve and bursting disc ?<\/strong> Fusible plug<\/strong> 7. Why multistage compressors are mostly used than single stage compressor ?<\/strong> 8. Advantages of inter cooling of air compressor ?<\/strong> Why intercooler will fitted in Main air compressor?<\/strong> Advantages of after cooler purpose<\/strong> 9. How to start the air compressor manually ?<\/strong> 10. How do you check compressor efficiency while running ?<\/strong> 11. Safety devices on main air bottle ?<\/strong> 12. Where is the fusible plug fitted ? Purpose ?<\/strong> 13. Can you fit the relief valve at the space of bursting disc and why ?<\/strong> FACTORS AFFECTING VOLUMETRIC EFFICIENCY<\/strong> 15. Difference between intercooler and after cooler ?<\/strong><\/p>\n INTERCOOLER<\/strong> AFTERCOOLER<\/strong> 16. Why need bumping clearance ?<\/strong> 17. How to adjust the bumping clearance ?<\/strong> 18. Main air compressor bumping clearance taking procedure ?<\/strong> 19. At what condition fusible plug is fitted main air bottle ?<\/strong> 20. Purpose of bursting disc? Where is fitted ?<\/strong> 21. Why bursting disc need to be annealed ?<\/strong><\/p>\n Due to heating and time expanded bursting disc is harden so to get back the normal relief pressure . It must be annealed.<\/p>\n 22. First start arrangement ?<\/strong> 23. Why provide air compressor on board ?<\/strong> 24. Why need minimum lubrication ?<\/strong> 25. VALVES LEAKING<\/strong> First stage delivery<\/strong> 26. FALLS OF COMPRESSOR PERFORMANCE<\/strong> How to maintenance air compressor efficiency ?<\/strong> Air bottle pressure test<\/strong> Purpose of drain valve (Compressor and Air bottle)<\/strong> 1. What is emergency air compressor ? It is a small compressor independently driven by diesel engine or hand operated. It must be fitted to press up the emergency air bottle and to start auxiliary engine of a dead ship. It has no connection between the main air bottle. 2. Air compressor safety devices ? […]<\/p>\n","protected":false},"author":1,"featured_media":5839,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[79],"tags":[],"class_list":["post-5836","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-marine-engineering-competency-exams-study-blogs"],"_links":{"self":[{"href":"https:\/\/seadonna.com\/blog\/wp-json\/wp\/v2\/posts\/5836","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/seadonna.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/seadonna.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/seadonna.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/seadonna.com\/blog\/wp-json\/wp\/v2\/comments?post=5836"}],"version-history":[{"count":5,"href":"https:\/\/seadonna.com\/blog\/wp-json\/wp\/v2\/posts\/5836\/revisions"}],"predecessor-version":[{"id":5843,"href":"https:\/\/seadonna.com\/blog\/wp-json\/wp\/v2\/posts\/5836\/revisions\/5843"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/seadonna.com\/blog\/wp-json\/wp\/v2\/media\/5839"}],"wp:attachment":[{"href":"https:\/\/seadonna.com\/blog\/wp-json\/wp\/v2\/media?parent=5836"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/seadonna.com\/blog\/wp-json\/wp\/v2\/categories?post=5836"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/seadonna.com\/blog\/wp-json\/wp\/v2\/tags?post=5836"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
\nIt is a small compressor independently driven by diesel engine or hand operated.
\nIt must be fitted to press up the emergency air bottle and to start auxiliary engine of a dead ship. It has no connection between the main air bottle.<\/p>\n
\n\udbc0\udc31 Relief valves are fitted to discharge side for every stages.
\n\udbc0\udc31 Moisture drain valve (unloader) are fitted at each cooler side
\n\udbc0\udc31 Cooling water failure alarm.
\n\udbc0\udc31 Low L. O pressure alarm.
\n\udbc0\udc31 Delivery air high temperature alarm on after cooler outlet (Max 93\u00b0C)
\nLP discharge pressure 4 bars : HP discharge pressure 30 bars.
\nIntercooler inlet air 130\u00b0C : Intercooler outlet air 35 \u00b0C
\nAfter cooler inlet air 130\u00b0C : After cooler outlet air 35\u00b0C
\nIntercooler is single pass type : After cooler, double pass U-tube type<\/p>\n
\nAt starting this valve must be opened, this reduced the starting torque for the machine and clear out any accumulated moisture and oil in the system.<\/p>\n
\nThe valve will be late in closing and this would reduce the volumetric efficiency of the machine .The valve too much lift reach at the end of their travel will grater force and therefore are more liable to break.<\/p>\n
\n\udbc0\udc29 Greater bumping clearance.
\n\udbc0\udc29 Sluggish opening and closing of suction and delivery valves.
\n\udbc0\udc29 Insufficient cooling water that effect of high air temperature.
\n\udbc0\udc29 Dirty or partially chocked suction air fitter.<\/p>\n
\n\udbc0\udc40 Excess pressure is released by opening the valve.
\n\udbc0\udc40 It opens at 10% over working pressure.
\n\udbc0\udc40 Valve lift is proportional to excess pressure build up.
\n\udbc0\udc40 Valve setting pressure can be altered by spring tension. Bursting disc
\n\udbc0\udc29 Pressure is released by bursting the disc.
\n\udbc0\udc29 It permanently damaged.
\n\udbc0\udc29 It burst at setting pressure.
\n\udbc0\udc29 Setting pressure cannot be altered in place.<\/p>\n
\n\udbc0\udc29 When the temperature high (above 105 \u00b0C) Pressure is released by melting (fusing) the metal.
\n\udbc0\udc29 It cannot be used next time. ( permanently damage)
\n\udbc0\udc29 Release all content or pressure to empty.<\/p>\n
\n\udbc0\udc40 More stages are needed to increase the required final pressure.
\n\udbc0\udc40 Easier to control the air temperature.
\n\udbc0\udc40 Reducing in air compressor size.
\n\udbc0\udc40 Lubrication problem does not exit.
\n\udbc0\udc40 Reduced the thermal stress.
\n\udbc0\udc40 Lower work done to compressing air.
\n\udbc0\udc40 Improve compressor efficiency<\/p>\n
\nTo avoid excessive temperature rise associated with higher compression ratios, and to approach isothermal compression.
\n\udbc0\udc09 Saving in power.
\n\udbc0\udc09 Volumetric efficiency is increased.
\n\udbc0\udc09 Reduced the volume of air delivered and also reduced the compressor size.
\n\udbc0\udc09 It can reduce the air temperature.
\n\udbc0\udc09 Due to less temperature suction & delivery valves remain cleaner without being fouled with carbonized oil.
\n\udbc0\udc09 It can avoid a danger of an explosion takes place in compressor cylinder.
\n\udbc0\udc09 It allows good lubrication of the compressor piston.
\n\udbc0\udc09 Moisture separation is easier through inter cooler drains.
\n\udbc0\udc09 It also enables to deal with a greater wt of air for the same energy expended.<\/p>\n
\n1. Reduced air temperature, volume and increased air density for next stage
\n2. So increased Volumetric efficiency and compressor efficiency.
\n3. Due to reduced temperature give better lubrication for cylinder and piston rings
\n4. Drain are fitted from which water and excessive oil can be drained out, to prevent air bottle corrosion and starting air explosion and fouling of inter coolers and pipe.
\n5. Save the work done.<\/p>\n
\n\udbc0\udc09 To reduce final discharge air temperature thus air bottle seize can be reduce.
\n\udbc0\udc09 To reduce air volume after it has been compressed to the final pressure.
\n\udbc0\udc09 So greater amount of air could be stored in air bottle.
\n\udbc0\udc09 Increase volumetric efficiency<\/p>\n
\n\udbc0\udc40 Change the switch to manual position on the switch board.
\n\udbc0\udc40 Check the L.O sump level and condition.
\n\udbc0\udc40 Open the moisture drain valve.
\n\udbc0\udc40 Open the compressor discharge valve & charging valve of air bottle.
\n\udbc0\udc40 Open cooling water system valves.
\n\udbc0\udc40 Turn the compressor flywheel by hand (one turn).
\n\udbc0\udc40 Start the motor, after draining the moisture shut the drain valve.
\n\udbc0\udc40 Check the motor ampere consumed.
\n\udbc0\udc40 Check the pressure gauge readings.
\n\udbc0\udc40 Frequently drain the moisture.
\n\udbc0\udc40 When charging full, open drain valve and stop the compressor.<\/p>\n
\n\u2329\u232a\u00a0Checked by filling time with the previous record and also check the first stage discharge pressure. If compressor efficiency is lower, compressor will run longer and compressor temperature will rise.
\n\u2329\u232a\u00a0First stage and second stage pressure gauge must be correct and stabled
\n\u2329\u232a\u00a0No escape air from suction filter
\n\u2329\u232a\u00a0Intercooler and after cooler outlet air temperature should not be high
\n\u2329\u232a\u00a0If open drain valve nothing can found
\n\u2329\u232a\u00a0Low L.O consumption
\n\u2329\u232a\u00a0Oily air mixture must not blow out from breather pipe.<\/p>\n
\n\udbc0\udc40 Pressure relief valve.
\n\udbc0\udc40 Fusible plug.(if safety valve is not directly fitted on the bottle)
\n\udbc0\udc40 Pressure gauge.
\n\udbc0\udc40 Low air pressure alarm.
\n\udbc0\udc40 Moisture drains valve.<\/p>\n
\nFusible plug is fitted under side of the pipe between relief valve and air bottle.
\nIt is fitted to release the compressed air in the event of abnormally high compressed air temperature. Fusible plug melt at 105 \u00b0C and release all content of air. It is made by 50% Bismut, 30% tin, 20% lead.
\nA fusible plug is fitted after the second stage cooler to limit the delivered air temperature and thus protect the compressed air reservoirs and pipe work.<\/p>\n
\nAt the compressor, relief valve can not be fitted at the bursting disc, because of their difference operation.
\nBursting disc is fitted for totally release and stop operation circuit.
\nRelease valve opens excess pressure at compressor running and reseat at when pressure reduce or when the compressor is stopped. Thus cooling water can enter to compressed air space; it can cause water hammer when the next start of compressor.<\/p>\n
\n1) The bumping clearance (the larger the bumping clearance the less air is discharged per stroke)
\n2) Sluggish opening and closing of suction and delivery valves
\n3) Leakage past compressor piston rings.
\n4) L.P inlet air temperature too high
\n5) L.P inlet filter dirty and choked
\n6) Inlet cooling water temperature too high
\n7) Insufficient cooling water owing to fouling of coolers<\/p>\n
\n\udbc0\udc40 Fitted intermediate stages.
\n\udbc0\udc40 Saving in power.
\n\udbc0\udc40 Increase volumetric efficiency.
\n\udbc0\udc40 Reduce temperature for next stage and it can avoid a danger of explosion in compressor cylinder.
\n\udbc0\udc40 Can provide good lubrication of the compressor piston.
\n\udbc0\udc40 No carbonized material form of discharge valve.
\n\udbc0\udc40 Moisture separation is easier through intercooler drain.<\/p>\n
\n\udbc0\udc40 Fitted at the final stage discharge side.
\n\udbc0\udc40 Reduce final discharge air temperature to room temperature.
\n\udbc0\udc40 Increase volumetric efficiency.
\n\udbc0\udc40 Air bottle size is smaller.
\n\udbc0\udc40 Moisture separation is easier through after cooler drain.<\/p>\n
\nThis is a clearance must be provided between the piston top and the cylinder head when the piston is top dead centre. it must be kept as small as possible for achieving the best compressor efficiency.
\n\udbc0\udc40 To prevent mechanical damage to the compressor.
\n\udbc0\udc40 To provide for thermal expansion and
\n\udbc0\udc40 To provide necessary space for valve operation.<\/p>\n
\nIt can be adjusted by two ways.
\n\udbc0\udc40 By altering the head gaskets (cover joint ) thickness,
\n\udbc0\udc40 By adding and subtracting shims between the connecting rod food and bottom and bearing.<\/p>\n
\n\udbc0\udc31 Stop the compressor and (lock off) take out fuse.
\n\udbc0\udc31 Drain the cooling water.
\n\udbc0\udc31 Remove the cylinder cover.
\n\udbc0\udc31 Clean the cylinder head face and piston crown.
\n\udbc0\udc31 Place the lead wire ball on the top face of the piston. That is larger size than expected by clearance.
\n\udbc0\udc31 Cylinder cover is placed on the cylinder with correct joint thickness and tightens the head bolts.
\n\udbc0\udc31 Turn the compressor slowly by hand over top centre so that lead wire ball is pressed.
\n\udbc0\udc31 Then remove cylinder cover again.
\n\udbc0\udc31 Remove the compressed lead wire ball.
\n\udbc0\udc31 Take the measurement of lead wire thickness by using micrometer.<\/p>\n
\nFusible plug is fitted at main air bottle, when relief valve is fitted indirectly to the air bottle. It can cause any obstruction by human error.<\/p>\n
\nIt is fitted on each cooler shell of air compressor, to give ample relief of pressure when cooler tubes burst.<\/p>\n
\n\udbc0\udc29 Firstly start the emergency air compressor to fill up the air to the emergency air bottle up to desired pressure obtained.
\n\udbc0\udc29 Drain out oil and water.
\n\udbc0\udc29 Open emergency air bottle outlet valve and pressed up desired pressure.
\n\udbc0\udc29 Then start the generator with correct procedure.
\n\udbc0\udc29 Close the breaker and switch on the lighting.
\n\udbc0\udc29 Start the required machinery ( especially G\/E FO booster pump, S, W cooling pump, E\/ R blower).
\n\udbc0\udc29 Start the main air compressor and press up to main air bottle.
\n\udbc0\udc29 After that, made M\/E warming by using generator jacket water and start the L.O pump.<\/p>\n
\n(1) Starting Diesel engines,
\n(2) Instrumentation and control systems,
\n(3) Various pneumatic tools and cleaning equipments,
\n(4) Boiler soot blowing and
\n(5) Ship’s whistle.<\/p>\n
\n\udbc0\udc40 To prevent carbonizing of the valves
\n\udbc0\udc40 To avoid loss of compressor efficiency due to sluggish action of valve
\n\udbc0\udc40 To avoid loss of cooler efficiency due to deposition of oil on the cooling surface
\n\udbc0\udc40 To prevent air line explosion, to prevent air bottle corrosion<\/p>\n
\nValves can leak and finally fail. Valves may fail owing to wear and fatigue, insufficient of over-lubrication, presence of foreign particles, oil decomposition and excess valve lift.
\nEFFECTS OF VALVES LEAKING<\/strong>
\nFirst stage suction<\/strong>
\n1) Reduce air delivery
\n2) Reduce second stage suction pressure
\n3) Increase running time
\n4) Unload the compressor<\/p>\n
\n1) Reduce delivery
\n2) Increase discharge temperature
\n3) Less air drawn in due to high pressure air leaking back into the cylinder
\nSecond stage suction<\/strong>
\n1) High pressure in suction line of 2 nd stage
\n2) High temperature in suction line of 2 nd stage
\n3) Reduce delivery
\n4) Increase running time
\nSecond stage delivery<\/strong>
\n1) Increase suction pressure in2nd stage
\n2) Reduce delivery in 2nd stage
\n3) Increase delivery pressure from 1st stage<\/p>\n
\n(Causes of poor performance)<\/strong>
\n(01) Choked air suction strainer
\n(02) Leaky or sticky valves
\n(03) Too much L.P bumping clearance
\n(04) Leaky piston rings
\n(05) Leaky cover and gaskets
\n(06) Leaky drains
\n(07) Leaky relief valves
\n(08) Leaky coolers
\n(09) Worn crankpin or bearings
\n(10) Faulty capacity controller<\/p>\n
\n1. Cleaning of suction air filter
\n2. Adjusting bumping clearance
\n3. Regular overhaul the suction and delivery valve and checking bearing
\n4. Check the piston rings and liner
\n5. Clear the cooler drain free from deposits
\n6. Clean the cooler<\/p>\n
\n01) Gag the relief valve
\n02) Close all openings
\n03) Fit test pressure gauge
\n04) Remove filling valve and fill F.W completely
\n05) Air purge and connect hydraulic pump at filling line.
\n06) Apply pressure 1.5 times of working pressure and maintain at least 30 min
\n07) Check leaking points.<\/p>\n
\nIt is process to remove the accumulation of oil water and sludge from the air bottle, scavenge space, compressor intercooler and settle and service tank.
\n01) To drain the water and surplus oil in the air bottle.
\n02) To avoid air bottle corrosion
\n03) To prevent staring air line explosion and sluggish & corrosions system valve.<\/p>\n","protected":false},"excerpt":{"rendered":"