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单选题
Intercoolers installed on starting air compressors, reduce the possibility of（）
A
dust entering the high pressure stage
B
lube oil carbonization
C
discharge pulsations
D
inter-stage vapor lock
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更多 “单选题Intercoolers installed on starting air compressors, reduce the possibility of（）A dust entering the high pressure stageB lube oil carbonizationC discharge pulsationsD inter-stage vapor lock” 相关考题
考题
第二组Under normal operation, some lubrication oil mist may be discharged from the air compressor to the air start system. This oil may be from excess compressor cylinder lubrication, from faulty oil scraper rings, or may even be suspended oil vapor contaminating the engine room atmosphere and drawn in at the compressor suction. Oil discharge is kept to a minimum by draining the after cooler, air receiver and starting system. If small quantities of lubrication oil do get passed into the starting air system, they will deposit as thin moist film over internal pipe surfaces but are not readily combustible. If a cylinder non-return valve leak while the engine is in operation, some hot gas, possibly with unburned fuel and cylinder lubrication oil, may be blown through the valve to the adjacent air manifold. With further heating from the leaky valve, this, together with the already deposited oil film, will carbonize and form. incandescent carbon. If starting air is applied to the system while still hot, the high pressure air coming into contact with the burning carbon may cause an explosion. Such an explosion will cause a flame to pass back through the air start pipe system, evaporating the deposited oil film and igniting it in the presence of air. Very high velocities and shockwaves are generated which may rupture pipes and fittings.Alternatively, if excessive oil has entered the air start system, a mixture of air and oil droplets may be discharged through the open cylinder non-return valve during starting. This spray may ignite due to high temperatures in the cylinder, causing a flame through the still open valve to the air manifold.To prevent an explosion, air start valves must be correctly maintained and lubricated to ensure correct timing and free movement with positive closing. Oil in the system must be kept to a minimum, pipe lines must be drained and cleaned internally when necessary and oil discharge from air compressors must be kept to a minimum by good maintenance.The passage is mainly aboutA.crankcase explosionB.scavenge box fireC.starting air pipeD.the danger of explosion in the starting air system
考题
Vessels having main engines arranged for air starting are to be provided with at least__.A.one automatic drain serving both containersB.two air starting containers of approximately equal sizeC.one control air container and one starting air containerD.one additional means of starting the main engine
考题
In an operating diesel engine, which of the following conditions is an indication of a leaking air starting valve?A.Noise coming from that air starting valveB.Continuous operation of the starting air compressorC.Zero air pressure in the air starting systemD.Overheated starting air pipe to the cylinder head
考题
Compressed air is supplied by air compressors to______.A.the air receiversB.the starting valvesC.the cylinder coversD.the distributors
考题
单选题Vessels having main engines arranged for air starting are to be provided with at least （）A
one automatic drain serving both containersB
two air starting containers of approximately equal sizeC
one control air container and one starting air containerD
one additional means of starting the main engine
考题
单选题Hot gas defrosting uses the hot gas from （） to defrost the evaporator.A
starting air bottlesB
diesel enginesC
boilersD
refrigeration compressors
考题
单选题The opening or closing of the cylinder starting valve is controlled by （）.A
the starting air distributorB
the cut-off valve on the air mainC
the main starting valveD
the air bottle control valve
考题
单选题By far the greatest use is for diesel engine starting using air pressure of 25 bar or more provided by （）.A
rotary compressorsB
reciprocating compressorsC
centrifugal compressorsD
screw compressors
考题
单选题Which of the following may cause that an engine doesnt turn on starting air?（）A
too low starting air pressureB
main starting valve closedC
neither A nor BD
A and B
考题
单选题During the inspection, the starting air valves should be closed （） the engine from turning.A
to increaseB
to speed upC
to preventD
to reduce
考题
单选题Diesel engine starting difficulties due to cold intake air temperatures, can be overcome by using a/an（）A
increase in starting air pressureB
increase in lube oil viscosityC
compression expansion deviceD
jacket water heater
考题
单选题Which of the following may lead to the engine NOT to start on air?（）A
starting air pressure too highB
correct timing of starting air valvesC
three of the six starting valves stuckD
the turning gear disengaged
考题
单选题Which of the following methods is used to prevent throttling of compressed air through the diesel engine air starting valves?（）A
Holding the valve open for a long periodB
Increasing the starting air pressure usedC
Opening the stating air valve quicklyD
Reducing the starting air valve size
考题
单选题A diesel engine is turned at normal cranking speed and no ignition occursThis could be the result of （）A
low lube oil temperatureB
low starting air temperatureC
air bubbles in the fuel oil systemD
water in the starting air system
考题
单选题Which of the following statements is true concerning the overall efficiency of air compressors?（）A
High pressure compressors are more efficient than low pressure compressorsB
Mechanical efficiency divided by compressor efficiency will equal the overall efficiency of the compressor unitC
Two stage compressors are generally more efficient than single stage compressorsD
The volumetric efficiency is decreased in multistage compressors
考题
单选题Which of the following may cause that an engine doesnt run on starting air?（）A
too low starting air pressureB
main start valve closedC
neither A nor BD
A and B
考题
单选题The pressure of pilot air is usually （） than that of starting air.A
higherB
lowerC
lowD
high
考题
单选题Air receivers installed in starting air systems are to be （）.A
cylindrical in shape with service connections located at the top and bottomB
opened and made available for inspection during biannual inspections providedC
with automatic drain traps for the removal of moistureD
so installed as to make the drain connections effective under extreme conditions of trim
考题
单选题Air compressors are equipped with unloading systems for the purpose of（）.A
removing all but the frictional load during startingB
relieving intercoolers of high temperature buildupsC
providing high starting torque in the drive motorD
seating valve plates during compressor shutdown
考题
单选题An un-loader is installed on an air compressor to （）.A
bypass the high pressure stage to the low pressure stage on 100% of the air compressors in serviceB
prevent excessive inter-stage pressure buildupC
control compressor discharge pressureD
remove all but the frictional load during starting
考题
单选题Pump up the starting air reservoirs to their maximum pressure and （）the air reservoirs and air system.A
openB
closeC
drainD
vent
考题
单选题When starting air is admitted, a diesel engine turns over very slowly without firingThe cause may be （）A
an obstruction in an cylinderB
water accumulation in some engine cylindersC
low starting air pressureD
low scavenge air pressure
考题
单选题In an operating diesel engine, which of the following condition is an indication of a leaking air starting valve?（）A
noise coming from that air starting valveB
continuous operation of the starting air compressorC
zero air pressure in the air starting systemD
overheated starting air pipe to the cylinder head
考题
单选题By far the greatest item of maintenance of the reciprocating air compressors concerns （）.A
the lubricationB
the coolingC
the moisture separationD
the valves
考题
单选题Explosions do occur （） caused by the ignition of oil or vapour gaining access from compressors or defective engine starting valves.A
in boiler drumsB
in refrigerating plantsC
in starting air pipesD
in air coolers
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