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______continuously extract the crankcase atmosphere, via a pipe system, and move it past a sensitive and accurate opacity(不透明性) measuring track.
A.The oil mist detectors
B.The smoke detectors
C.An oily water monitor
D.Oil discharge monitoring and controlling system
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更多 “ ______continuously extract the crankcase atmosphere, via a pipe system, and move it past a sensitive and accurate opacity(不透明性) measuring track.A.The oil mist detectorsB.The smoke detectorsC.An oily water monitorD.Oil discharge monitoring and controlling system ” 相关考题
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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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Excessive oil foaming in the crankcase of a refrigeration compressor is most likely to occur when the compressorA.has run continuously for a long periodB.suction pressure is below normalC.oil level is below normalD.starts after a long idle period
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If the flame from combustion in the cylinder of a four-stroke engine past the piston into the space below, the accumulation of flammable mixture would be ignited, thus resulting in _____.A.the crankcase explosionB.lifting of the cylinder safety valveC.a scavenge fireD.opening of the manhole
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单选题A refrigeration system compressor crankcase is sweating or unusually coldThis is an indication of().A
a shortage of refrigerant in the systemB
air in the systemC
an accumulation of liquid refrigerant in the crankcaseD
a shortage of oil in the crankcase
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单选题If a refrigeration system compressor crankcase is sweating, you should ().A
add refrigerant to the systemB
adjust the thermal expansion valve to the proper settingC
adjust the float valve to the proper holding pressureD
open the hand expansion valve
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单选题A technician is attempting to use a command line prompt to continuously ping a remote server to check availability and reliability of the connection. Which of the following provides the ping command needed to continuously ping the system?()A
ping -aB
ping -fC
ping -rD
ping -t
考题
单选题In general, the oil mist detectors include a built-in heating unit and a compact plug for electrical connectionThe function of heating unit is to ()A
avoid false alarms as a result of condensing water vaporB
avoid danger of frost under very cold weatherC
reduce the viscosity of the crankcase atmosphere in order to improve the fluidityD
keep the temperature of the oil mist detectors in an appropriate range
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单选题What function is provided by the crankcase ventilation system on some diesel engines?()A
Increases the sludge forming tendency of lube oilB
Prevents the accumulation of combustible gasesC
Improves lube oil coolingD
Improves cold weather starting
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单选题Clouds form().A
as a mass of warm,humid air rises into the atmosphere and cools,condensing moisture into small dropletsB
as winds blow across bodies of water,the sun causes the moisture to be absorbed and move upward forming cloudsC
dry air compresses moisture from the atmosphere into cloudsD
when the relative humidity of the atmosphere is low
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单选题In a diesel engine, blow-by is a result of combustion gases leaking into the crankcase past the ()A
wrist pin bushingsB
compression ringsC
cylinder liner sealsD
cylinder liner sealing ring
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单选题In the () refrigeration compressor one end of the crank shaft extends through the crankcase house for connection, via a coupling or pulley, to an external drive motor.A
open-typeB
hermeticC
semi-hermeticD
all the above
考题
单选题If the flame from combustion in the cylinder of a four-stroke engine past the piston into the space below, the accumulation of flammable mixture would be ignited, thus resulting in ().A
the crankcase explosionB
lifting of the cylinder safety valveC
a scavenge fireD
opening of the manhole
考题
单选题The accumulation of air and other non-condensable gases in a refrigeration system will ().A
cause a loss of the liquid sealB
create a vapor lock in the liquid receiverC
collect in the condenserD
cause foaming of the oil in the crankcase
考题
单选题In engines with system, the lubricating oil can be added to the engine through the filling hole in the crankcase cover, by using a hand oil can, or through the separator pipe()A
lubricating oilB
dry sumpC
circulated tankD
wet sump
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单选题A diesel engine crankcase ventilation system ()A
prevents spark generationB
removes combustible gasesC
determines the level of combustible gasesD
provides inert gas generation in crankcase
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单选题The blower type crankcase ventilation system ()A
removes combustible gases in the crankcaseB
prevents the formation of combustible gases in the crankcaseC
cools lubricating oilD
improves cold weather starting
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单选题To prevent the unnecessary loading of an air conditioning system while maintaining the designed dry bulb temperature and relative humidity in an air conditioning system, you should ()A
admit only enough fresh outside air to provide proper ventilationB
reduce the air reheating system loadC
lower the compressor head pressureD
operate the purge recovery unit continuously
考题
单选题The oil mist detectors continuously() the crankcase atmosphere, via a pipe system, and move it past a sensitive and accurate opacity measuring track.A
detractB
extractC
pump upD
pump down
考题
单选题Sweating of the refrigeration system compressor crankcase is caused by ().A
too much superheatB
insufficient superheatC
suction pressure too lowD
excessive refrigerant returning to the compressor
考题
单选题The pipe friction and the resistance will () as a result of an increase in the amount of fluid flowing through the system.A
reduceB
riseC
raiseD
fall
考题
单选题()continuously extract the crankcase atmosphere, via a pipe system, and move it past a sensitive and accurate opacity measuring track.A
The oil mist detectorsB
The smoke detectorsC
An oily water monitorD
Oil discharge monitoring and controlling system
考题
单选题Excessive oil foaming in the crankcase of a refrigeration compressor is most likely to occur() when the compressor.A
has continuously for a long periodB
suction pressure is below normalC
oil level is below normalD
starts after a long idle period
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