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单选题
A knocking sound emitted from an unloaded air compressor is probably caused by （）.
A
damaged intake valves
B
excessively tight mounting bolts
C
insufficient cylinder lubrication
D
a loose piston
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更多 “单选题A knocking sound emitted from an unloaded air compressor is probably caused by （）.A damaged intake valvesB excessively tight mounting boltsC insufficient cylinder lubricationD a loose piston” 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
When removing the cap from a sounding tube on a ship，the sound of air escaping indicates the tank ______．A.Is fullB.May be partially floodedC.Level has droppedD.Is completely flooded
考题
A person may operate an air compressor in which of the following areas on board a tank barge ________．A.PumproomB.Generator roomC.A space adjacent to a cargo tankD.A space two meters from a cargo valve
考题
单选题The text suggests which of the following about air pollution?A
Further attempts to reduce emissions from gasoline-fueled vehicles will not help lower urban air-pollution levels.B
Attempts to reduce the pollutants that an individual gasoline-fueled vehicle emits have been largely unsuccessful.C
Few serious attempts have been made to reduce the amount of pollutants emitted by gasoline-fueled vehicles.D
Pollutants emitted by gasoline-fueled vehicles are not the most critical source of urban air pollution.
考题
单选题The sudden reduction of pressure occurring within the crankcase of a refrigeration compressor during starting causes the （）.A
sudden evaporation of wax crystals in the lubricantB
sudden evaporation of entrapped air in the lubricantC
release of refrigerant from the oil/refrigerant mixtureD
release of dissolved lubricant from the refrigerant
考题
单选题Air blowing from the intake air filter of an operating air compressor indicates （）.A
broken inlet valvesB
broken discharge valvesC
pulsations in the air distribution systemD
overloading of the air distribution system
考题
单选题Condensate must be drained periodically from the air compressor receivers to prevent （）.A
second stage cylinder lockupB
oil sump contaminationC
faulty operation of pneumatic valvesD
corrosion of air receiver baffles
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
考题
单选题（）are supplied by main switchboard directly.A
Suez Canal searchlight, air compressor and air conditioning compressorB
Air compressor, boiler blower and refrigeration plantC
Boiler blower, Suez Canal searchlight and refrigeration plantD
Suez canal searchlight, air compressor and boiler blower
考题
单选题Broken valve strips in an operating low pressure, air compressor will cause （）.A
an immediate crankcase explosionB
oil contamination in the compressed airC
a decrease in compressor capacityD
no immediate loss of the compressed air capacity
考题
单选题The air compressor pumps air to the （）.A
expansion tankB
combustion chamberC
air receiverD
evaporator
考题
单选题A knocking sound from one cylinder of an operating air compressor indicates （）.A
a defective or broken high pressure un-loaderB
a loose valve plateC
excessive overloadD
no compression
考题
单选题The purpose of an air compressor unloading device is to （）A
drain water from the air receiverB
drain water from the cylindersC
delay the compression process until the motor is up to speedD
check pump alignment
考题
单选题The air compressor pumps air to the （）.A
air cylinderB
combustion chamberC
steam drumD
expansion tank
考题
单选题The air compressor pumps air to the（）.A
engine cylinderB
air bottleC
evaporatorD
condenser
考题
单选题The air filter is fixed in the （） of an air compressor.A
inlet pipeB
outlet pipeC
inter coolerD
after cooler
考题
单选题If an air compressor is used to supply compressed air to outlets throughout the engine room and on deck of a vessel, the system is known as the （）.A
combustion control air systemB
supply air systemC
ships service air systemD
low pressure deck air system
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
考题
单选题A centrifugal compressor’s purge recovery unit（）A
reclaims waterB
purges air without losing refrigerantC
purges air with some loss of refrigerantD
purges lube oil from the refrigerant
考题
单选题An air compressor can be unloaded at start-up by （）.A
holding the discharge valve openB
relieving the intercooler pressure to the atmosphereC
using an enlarged, permanently opened clearance expansion spaceD
a pre-charged accumulator
考题
单选题Sludge may be formed in the oil in the crankcase of a reciprocating air conditioning compressor as a result of （）A
refrigerant bubbles in the lube oilB
refrigerant reducing the lube oil viscosityC
oxidation of the lube oil from overheatingD
reducing the floc or cloud point of the oil
考题
单选题The loss of （） from an air compressor could lead to an overheated air discharge and possibly an explosion in the pipelines leading to the air reservoir.A
lubricating oilB
compressed airC
cooling waterD
sealing ring
考题
单选题If an air compressor is used to supply air primarily to the combustion control system and other pneumatic controllers, the entire system is known as the （）.A
control air systemB
forced draft air systemC
supply air systemD
ships service air system
考题
单选题“This increase in charge air density is accomplished on most modern diesel engine types by use of exhaust gas turbo-charging, in which a turbine wheel driven by exhaust from the engine is rigidly coupled to a centrifugal type air compressor” According to this sentence, we can know that increases density（）, drives the compressor directly（）A
a modern diesel engine；a turbine wheelB
a modem diesel engine；exhaust gasesC
a compressor；an exhaust gas turbochargerD
a compressor；a turbine wheel
考题
单选题A person may operate an air compressor in which of the following areas on board a tank barge?（）A
PumproomB
Generator roomC
A space adjacent to a cargo tankD
A space two meters from a cargo valve
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