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单选题
Before starting an air compressor, It should be （）.
A
turned
B
oil level checked
C
filled with water
D
A and B
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If the head pressure of a reciprocating refrigeration compressor is excessiveA.the relief valve should open before the high pressure cutoutB.the relief valve should open and allow the excess refrigerant to flow to the receiverC.the high pressure cutout switch should operate before the relief valve opensD.you should close the discharging valve
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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
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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
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Before starting the engine, the air bottle should be ____.A.pumped upB.loadedC.dischargedD.closed
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______device is provided to prevent starting air from being admitted to the cylinder before the reversing is completed.A.An automaticB.A transmissionC.A self-regulatingD.An interlocking
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Your vessel has a gasoline engine and a mechanical exhaust ventilation system．BEFORE starting the engine，the exhaust blower should be run long enough to ______．A.warm up the exhaust blower motorB.provide a proper supply of fresh air for the engine（s）C.see the system is in good operating conditionD.insure at least one complete change of air in the compartments concerned
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单选题When the order （） is received from the bridge, the main air stop valve in the starting air line should be shut.A
stand-by engineB
full aheadC
finished with engineD
full away
考题
单选题During working of an air compressor, （） should be drained.A
oil sumpB
oil separatorC
outlet pipeD
inlet pipe
考题
单选题The unloading system on an air compressor will （）.A
increase compressor discharge pressure on demandB
increase compressor operating speed as necessaryC
allow the motor to turn the compressor opposed only by frictionD
reduce the compressor frictional load when starting
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单选题Before starting the engine the air bottle should be （）.A
pumped upB
loadedC
dischargedD
opened
考题
单选题Open the （）before starting an air compressor.A
unload valveB
cooling waterC
oil cupD
sump
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单选题Which of the following conditions may be attributed to a fouled turbocharger compressor inlet screen or filter?（）A
Decreasing scavenge air pressureB
Increasing exhaust temperatures before the turbineC
Reduction in engine speedD
All of the above
考题
单选题Open the （）of inter cooler before starting an air compressor.A
cylinder coverB
cooling waterC
oil cupD
drain valve
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单选题Which of the listed items should be secured before performing any maintenance on a solenoid operated air start valve?（）A
Electric power and starting airB
Lube oil standby pump and control airC
Hydraulic switch and engage jacking gearD
Motor drain and pneumatic control system power
考题
单选题If the head pressure of a reciprocating refrigeration compressor is excessive, （）.A
the relief valve should open before the high pressure cutoutB
the relief valve should open and allow the excess refrigerant to flow to the receiverC
the high pressure cutout switch should operate before the relief valve opensD
you should close in on the suction valve
考题
单选题Before starting an air compressor, It should be （）.A
unloadedB
primedC
filled with waterD
greased
考题
单选题During working of an air compressor, （） should be drained.A
inter coolerB
cylinderC
outlet pipeD
inlet pipe
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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Starting air for auxiliary engines may be taken directly from the main reservoirs or through （）.A
an auxiliary reservoirB
a controlling air bottleC
an emergency air compressorD
a main air compressor
考题
单选题Air compressor cylinder un-loaders enable the compressor to （）.A
vary their speed according to temperature and loadB
start and come up to speed before air compression beginsC
change speed according to overload demandsD
reduce compressed air charge density
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单选题If the main engine starting consecutively failed （） times, it should be found the cause before another starting.A
2B
3C
4D
5
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单选题Air compressor receivers should be “blown down” at least （）.A
yearlyB
quarterlyC
monthlyD
daily
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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
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单选题Routine maintenance on a Central Control Room hermetically sealed air conditioning unit should include （）A
changing the air filterB
recharging the systemC
changing compressor lubricantD
renewing container vacuum
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单选题The starting air bottle should be pumped up to maximum pressure by the （） before start of the engine.A
air compressorB
refrigeration compressorC
vacuum pumpD
purifier
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