Pass Benchmark: 70% (21/30) • Standard: USCG NMC / 46 CFR
USCG Refrigeration & Air Conditioning (Set 14)
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Question 1 of 30
Which of the listed statements describes the reason why oil foaming occurs when starting a refrigeration compressor?
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30 MCQs #1 Which of the listed statements describes the reason why oil foaming occurs when starting a refrigeration compressor? #2 A reciprocating refrigeration compressor may be tested for leaking discharge valves by stopping the compressor, turning the discharge service valve all the way in, and then turning the compressor over by hand. If the discharge valves are leaking, the compound gage will show pressures which react in which way? #3 Unusual noise coming from a refrigeration compressor can be caused by which of the following conditions? #4 When starting a reciprocating refrigeration compressor that has been shut down for a period of time, you should manually throttle which valve? #5 What is the drive arrangement of refrigeration compressor shown in figure "B" of the illustration? Illustration GS-RA-41 #6 When opening or closing compressor service and line isolation valves on a typical refrigeration system that is fitted with packed valves, what must you do? #7 For most multi-box refrigeration systems, the refrigerant sight glass would be located where in the system? #8 A liquid indicator sight glass is useful in determining whether or not a refrigeration system is sufficiently charged. Where is it generally located in the system? #9 The primary purpose of the liquid line strainer used in a refrigeration system is to prevent dirt and scale from entering what system component(s)? #10 Zinc plates commonly found in refrigeration systems and used as sacrificial anodes are located where? #11 The coil temperature measured at the expansion valve sensing bulb of an operating system is 10°F. The low side pressure with the compressor running as shown on the gauge illustrated indicates 15 psig. What adjustments or changes, if any, should be made to the system? Illustration GS-RA-16 #12 Which of the following statements describes the accepted method for testing a thermostatic expansion valve? #13 Moisture in a refrigeration system can cause which of the following conditions? #14 In a low-pressure refrigeration system, excessive running of the purge recovery unit generally indicates which probable condition? #15 Excessive moisture being collected in the purge unit of a low-pressure refrigeration system could indicate which probable condition? #16 An evaporator coil of a single evaporator, air-cooled refrigerator is accumulating excessive frost due to a failure of the defrost mechanism. If the refrigerator features a thermostatically controlled box solenoid and a low-pressure cutout controlled compressor, as well as a high-pressure cutout, in terms of the compressor, what would be the most likely operating symptom? #17 In a refrigeration system, the bulb for the thermal expansion valve is always located where? #18 In a vapor compression type refrigeration cycle, the refrigerant temperature decreases the most when passing through which system component? #19 When the sensing bulb of a thermostatic expansion valve is charged with a fluid different from the charge used in the system, what name of the charge is associated with the power element? #20 The thermostatic expansion valve in a refrigeration system further opens when the diaphragm flexes downward. With all other conditions being the same, what single condition causes this? #21 A typical shipboard domestic multi-box refrigeration system operates with one compressor and condenser. What is the purpose of the sensing line connected to the thermal bulb at the evaporator coil outlet? #22 Concerning the proper installation of the sensing bulb of a thermal expansion valve that is attached to the evaporator tail coil on a horizontal run, what statement is true? #23 In refrigeration systems with multiple evaporators, the metering of refrigerant to each refrigerated space evaporator is accomplished by what device? #24 The low-pressure cutout switch settings vary with the refrigerant used and the temperature application. If the low-pressure cutout switch for a particular application is set with a cut-in pressure of 5 psig, what would be the cut-out pressure if the differential is 7.5 psig? #25 The sensing line for the low-pressure cutout switch for a refrigeration system is typically connected at what location? #26 Which of the listed operations will cause an automatically controlled refrigeration compressor to restart if the system features a pump down cycle? #27 What would be an indication that the vegetable box back pressure regulator is set too low? #28 Corrosion has wasted away large sections of the fins attached to an air conditioning cooling coil. In assessing the effects on the system you would assume which of the following to be accurate? #29 Sludge may form in the crankcase of an air conditioning compressor as a result of what condition? #30 While securing the air conditioning compressor you close the suction valve and the compressor stops after a short period of time. Subsequent attempts to start it produce no result. What control component would you suspect is preventing the compressor from starting?
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