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单选题
In a refrigeration system, foaming of the crankcase oil may cause the （）.
A
expansion valve to overfeed
B
compressor to knock
C
water regulating valve to fail
D
crankcase drains to plug
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更多 “单选题In a refrigeration system, foaming of the crankcase oil may cause the （）.A expansion valve to overfeedB compressor to knockC water regulating valve to failD crankcase drains to plug” 相关考题
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Crankcase explosions in propulsion diesel engines result from ____.A.the splashing of lubrication oil by the crankshaftB.the dilution of crankcase oil with particles of combustionC.broken fuel lines spraying oil on the crankcaseD.the ignition of unburned fuel and air in the crankcase
考题
If the refrigeration compressor crankcase is sweating, the cause may be due toA.a shortage of refrigerantB.the compressor running continuouslyC.liquid refrigerant returning to the compressorD.the compressor short cycling on the high pressure cutout
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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
考题
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
考题
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
______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
考题
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(氧化) of the lube oil from overheatingD.reducing the floc or cloud point of the oil
考题
单选题Before starting a diesel engine, you should always（）A
check the pyrometer readingsB
check the crankcase oil levelC
check the fuel oil strainersD
clean the fuel system
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
考题
单选题Refrigeration system compressor crankcase sweating is an indication of （）.A
insufficient lube oil circulating through the systemB
excessive circulation of lube oil through the systemC
insufficient refrigerant in the systemD
an overworked compressor
考题
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
考题
单选题Large crosshead type engine generally has two lubrication systems, a function performed only by crankcase oil system is（）A
lubricatingB
coolingC
cleaningD
neutralizing
考题
单选题Excessive oil foaming in the crankcase of a refrigeration compressor can result in （）.A
overheated compressor bearingsB
excess lube oil viscosityC
carbon deposits on the compressor piston ringsD
wax crystals forming in the lubricant
考题
单选题If the refrigeration compressor crankcase is sweating, the cause may be due to （）.A
a shortage of refrigerantB
the compressor running continuouslyC
liquid refrigerant returning to the compressorD
the compressor short cycling on the high pressure cutout
考题
单选题Foaming of the oil in a refrigeration compressor crankcase is caused by （）.A
refrigerant boiling out of solution from the lube oilB
liquid refrigerant flooding the compressor and systemC
lube oil viscosity being reduced by refrigerant dilutionD
compressor suction pressure suddenly increasing
考题
单选题An excessive charge of refrigerant in an air-cooled refrigeration system can cause （）.A
oil foaming in the compressorB
higher than normal suction and discharge pressures with a higher box temperatureC
higher than normal discharge pressure with a normal box temperatureD
the compressor to run continuously
考题
单选题Crankcase explosions in propulsion diesel result from（）A
the splashing of lubrication oil by the crankshaftB
the dilution of crankcase oil with particles of combustionC
broken fuel lines spraying oil on the crankcaseD
the ignition of unburned fuel and air in the crankcase
考题
单选题Excessive oil foaming in the crankcase of a refrigeration compressor at start up can cause（）.A
compressor damage from improper lubricationB
refrigerant absorption by the lubricantC
increased viscosity in the lubricantD
carbon deposit on the compressor suction valves
考题
单选题Crankcase sweating in a refrigeration system is caused by （）.A
a stuck solenoid valveB
a shortage of refrigerantC
too much oil in circulationD
too much superheat
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
考题
单选题Sludge may form in the lubricating oil crankcase of a reciprocating air conditioning compressor as a result of （）.A
wax precipitation in the lube oilB
contamination by dust, scale, or moistureC
refrigerant bubbles in the lube oilD
refrigerant reducing the lube oil viscosity
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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