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单选题
The purpose of the purge valve at the top of the condenser in a refrigerating system is to（）
A
remove any air that may accumulate in the system
B
take out unpleasant fumes from the refrigerant
C
vent off excess refrigerant in an emergency
D
permit opening the refrigerating system for cleaning and inspecting
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考题
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考题
Which of the conditions listed will cause a refrigeration compressor to run constantly without simultaneously decreasing the temperature in the refrigerated space?( )A.Shortage of refrigerant oilB.Slight shortage of refrigerantC.Excessive condenser cooling water flowD.Faulty expansion valve
考题
If a refrigeration compressor is short cycling on high head pressure, you shouldA.purge the condenser if the waterside is dirtyB.check for proper water flow through the condenserC.increase the high pressure cutout settingD.reduce the cooling water flow
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考题
which of the following is not true about the classification of the cantainers？（）A、containers are classified as general purpose (dry cargo) container and specific purpose containerB、general purpose container (GP) is suitable for the widest varieties of cargoC、specific purpose container is suitable for the specific cargoD、bulk container， reefer container， open-top container are all general purpose containers
考题
单选题Cross scavenging requires the fitting of （） to prevent air or exhaust gas escape when the piston is at the top of the stroke.A
a exhaust valveB
a piston skirtC
a piston crownD
an air suction valve
考题
单选题Which of the conditions listed will cause a refrigeration compressor to run constantly without simultaneously decreasing the temperature in the refrigerated space?（）A
Shortage of refrigerant oilB
Slight shortage of refrigerantC
Excessive condenser cooling water flowD
Faulty expansion valve
考题
单选题What is the purpose of sub cooling R-12 in the condenser?（）A
to increase the system efficiency by sensible heat transferB
to stop the liquid from flashingC
to reduce the load on the compressorD
to remove latent heat of vaporization and the suction piping transfer
考题
单选题In a compression refrigeration plant the refrigerant is under low pressure in the （） and under high pressure in the （）.A
compressor；condenserB
condenser；evaporatorC
throttle valve；evaporatorD
evaporator；condenser
考题
单选题On the all-purpose nozzle，the position of the valve when the handle is all the way forward is（）.A
shutB
fogC
solid streamD
spray
考题
单选题Fire protection regulations for towing vessels require any fuel line subject to internal head pressure from fuel in the tank to（）.A
be fitted with a positive fuel shut-off valve located at the tankB
have a shut-off valve at the top of the tankC
have a gate valve easily accessible in the space where the tank is locatedD
have a drain cock at the lowest point in the fuel line
考题
单选题The purpose of the programmed purge cycle on an automatically fired auxiliary boiler is to（）A
cool the furnace to prevent pre-ignitionB
remove explosive vapors from the furnaceC
evaporate accumulated unburned fuel oilD
provide sufficient air in the furnace to allow ignition of the fuel
考题
单选题What is the purpose of a striker plate? （）A
Provides surface for applying force on machineryB
Provides landing surface for the sounding bobC
Absorbs machinery vibrationD
Prevents valve stem over-travel
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In order to properly remove air from the casing of a centrifugal pump when starting, the pump should have a （）.A
positive headB
negative suction headC
mechanical sealD
vent valve attached to the casing at the top of the volute
考题
单选题Valve lash, or clearance refers to the （）A
clearance between the top of the valve stem and the rocker armB
compression of the valve springsC
clearance between the valve seat inserts and the headD
out of roundness of the fuel injection cams
考题
单选题Starting air valves are held firmly on their seats by（）A
cam rollers on the camshaftB
spring forceC
air pressure on top of the valve differential pistonD
air pressure on the bottom of the valve differential piston
考题
单选题To add refrigerant to the high side of an air conditioning system, you should introduce the refrigerant through the （）.A
discharge service valve as a vaporB
suction service valve as a liquidC
charging valve as a liquidD
condenser purge valve as a vapor
考题
单选题While troubleshooting a refrigeration system for low head pressure, liquid refrigerant flooding back from the evaporator is determined to be the causeIt may be necessary to （）.A
change the expansion valve adjustmentB
readjust the water regulating valve to increase the flow of waterC
purge air from the condenserD
clean the waterside of the condenser
考题
单选题The principal purpose of sub-cooling liquid refrigerant prior to its entering the expansion valve is to （）.A
increase the refrigerating effect, by decreasing the amount of flash gasB
allow the refrigerant to enter the throttling device in a saturated conditionC
increase the refrigerating effect by increasing the amount of flash gasD
minimize the temperature drop of the liquid as it passes through the solenoid valve to the outlet side
考题
单选题In a refrigeration system, if the cooling water to the condenser fails, the（）.A
box temperature solenoid valve will closeB
expansion valve will closeC
compressor will shutdownD
king valve will open
考题
单选题The emergency bilge suction valve is typically used （）.A
to inject cleaning additives when the bilges are extremely dirtyB
when the main condenser becomes fouled, in order to provide additional cooling water circulationC
to connect the rose box to the independent bilge suctionD
if the bilges become flooded and they can not be emptied by any other means
考题
单选题What is the purpose of a relief valve?（）A
to fill 2 tanks at the same timeB
to use pump at a higher pressureC
to return liquid to suction side if discharge valve is closedD
All of the above are true
考题
单选题Which of the listed components is considered to separate the high pressure side of a refrigeration cycle from the low pressure side of the cycle?（）A
The condenser and the expansion valveB
The king valve and the solenoid valveC
The compressor and the expansion valveD
The condenser and the solenoid valve
考题
单选题If the engine is naturally aspirated, or is a small high-speed type with a centrifugal turbocharger, the period of valve overlap（）,ie when both valves are（）, will be and the exhaust valve will close some 10°top dead canter（）.A
open；short；afterB
closed；short；afterC
open；long；beforeD
closed；long；before
考题
单选题In a turbocharged four-stroke/cycle diesel engine, the exhaust valve remains open until after top dead center and the intake valve opens before top dead center to（）.A
produce a scavenging effect in the combustion spaceB
equalize cylinder and exhaust manifold pressuresC
alleviate the difference in valve size between the intake and exhaustD
flush out condensate that collects after each compression stroke
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