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NEW CHANGES MADE ON 11-AUG-2023
ANSWER OF FOLLOWING QUESTIONS IS LISTED BELOW
1)During standstill liquid may condense in the crankcase or oil separator. Why is it important to heat up the oil before start?
a)The compressor will run better.
b)It should never be done.
c)To avoid the compressor-oil disappearing from the crankcase during starting.
d)Compressor oil regulating system will operate better.
2) Personnel working with refrigeration systems, and subject to the exposure of refrigerants should wear
a)face shield
b)a respirator
c)rubber gloves
d)an all purpose gas mask
3) People familiar with ammonia refrigeration systems become accustomed to its odor and may forget that the vapors
a)in a low concentration can cause death
b)will dissolve in pespiration and cause caustic burns
c)will burn or explode
d)all of the above
4) When the relief valve opens it discharges high pressure refrigerant vapor to the
a)liquid strainer
b)refrigerant inlet of the condenser
c)inlet side of the evaporator
d)suction side of the compressor
5) In a direct expansion type multi-box refrigeration system, the compressor is set up to cycle on and off by the
a)pressurestat
b)high pressure cut out
c)solenoid valve
d)low pressure cut out switch
6) Which of the listed operations will cause an automatically controlled refrigeration compressor to restart?
a)closing of the solenoid valve
b)closing of the expansion valve
c)an increase in the suction pressure
d)decreasing the suction pressure
7) In a direct expansion type cargo refrigeration system, a box is normally changed from chill to freeze by adjusting the
a)hand expansion valve
b)compressor suction valve
c)solenoid bypass
d)back pressure regulating valve
8)Which of the problems listed could be indicated if a sight glass in the refrigerant liquid line is full of bubbles?
a) excess refrigerant charge
b)faulty expansion valve
c)insufficient refrigerant
d)solenoid valve stuck open
9) A liquid indicator sight glass is useful in determining whether or not a refrigeration system is sufficiently charged. It is generally located in the
a)high pressure liquid line
b)low pressure liquid line
c)high pressure vapor line
d)low pressure vapor line
10) If the refrigeration compressor crankcase is sweating, the cause may be due to
a)a shortage of refrigerant
b)the compressor running continuously
c)liquid refrigerant returning to the compressor
d)the compressor short cycling on the high pressure cutout
11) If a refrigerating compressor crankcase is sweating, the trouble could be caused by
a)excessive superheat
b)a minor amount of air in the system
c)normal oil circulation with the refrigerant
d)the expansion valve being stuck in the open position
12) Frosting or sweating of the suction line of a reciprocating refrigeration compressor indicates a condition which could result in severe damage due to
a)minor amout of oil in the refrigerant
b)liquid slugging
c)insufficient refrigerant
d)a failed heat interchanger
13) Refrigeration system compressor crankcase sweating is an indication of
a)insufficient lube oil circulating throgh the system
b)excessive circulation of lube oil through the system
c)insufficient refrigerant in the system
d)an overworked compressor
14) Sweating of the refrigeration system compressor crankcase is caused by
a)too much super heat
b)insufficient super heat
c)suction pressure too low
d)excessive refrigerant returning to the compressor
15) Oil separators installed in refrigeration systems serve to
a)remove excess oil from the system
b)remove oil entrained in high pressure liquid line
c)return oil entrained in refrigerant vapor back to the compressor crankcase
d)all of the above
16) The oil separator (trap) used in a shipboard refrigeration system is located between the
a)compressor discharge valve and the condenser
b)condenser and the receiver
c)receiver and the king valve
d)receiver and the expansion valve
17) The purpose of the refrigeration system low pressure cutout switch is to
a)protect the compressor from liquid flood back
b)protect the compressor from low discharge pressure
c)start and stop the compressor upon system demand
d)-start the compressor after a drop in the evaporator pressure
18) The sensing line for the low pressure cutout switch to a refrigeration system is located
a)in the chill box
b)before the receiver
c)on the suction side of the compressor
d)on the discharge side of the compressor
19) The refrigeration system low pressure cutout switch is actuated by
a)an electric system manager
b)a sensing bulb at the tail coil of the evaporator
c)pressure changes in the suction line
d)failure of the king solenoid valve
20)When you adjust thermostatic expansion valve
a)refrigerant must be bled off the sensing line before adjustments are made
b)all refrigerant must be pumped into the receiver before adjustments are made
c)time must be allowed for conditions to stabilize in the evaporator before further adjustments are made
d)all refrigerant must be routed through the dehydrator while changing the superheat setting
21) Low compressor head pressure in a refrigeration system can be caused by
a)insufficient condenser cooling water
b)excessive condenser cooling water
c)air in the refrigeration system
d)excessive refrigerant in the system
22) Which of the problems listed would cause the discharge temperature of an Freon refrigeration compressor to increase?
a)thermal expansion valve frozen open
b)suction gas heat exchanger bypassed
c)condenser clogged or fouled
d)high pressure cutout switch inoperative
23) One cause of high head pressure occurring in a refrigeration system can be
a)insufficient cooling water flow to the condenser
b)a low refrigerant charge in the system
c)the liquid valve is open too much
d)high evaporator superheat
24) If the head pressure of a reciprocating refrigeration compressor is excessive,
a)the relief valve should open before the high pressure cutout
b)the relief valve should open and allow the excess refrigerant to flow to the receiver
c)the high pressure cutout switch should operate before the relief valve opens
d)you should close in on a suction valve
25) If the refrigeration compressor was developing higher than normal discharge pressure, this could be a result of
a)air or noncondesable gases in the system
b)leaking discharge valves
c)leaking suction valves
d)liquid refrigerant flooding back from the cooling coil
26) If the water failure switch should fail to shut down the refrigeration compressor, the refrigerant pressure will build up in the high pressure side of the system to the point where the
a)compressor discharge valves would be damaged
b)condenser tubes would rupture
c)system relief valve would open
d)high pressure cutout switch would function
27) High suction pressure to a refrigeration system compressor is caused by
a)the expansion valve is insufficiently opened
b)the expansion valve being open too wide
c)the king valve is insufficiently open
d)a dirty dehydrator
28) If a refrigeration compressor had developed a high suction pressure, the problem could be a result of
a)a minor accumulation of air or uncondensable gases in the system
b)a leaking king valve
c)a clogged subcooler
d)liquid refrigerant flooding back from the cooling coil
29) Which of the conditions listed could cause excessively low refrigerant pressure at the compressor suction?
a)insufficient flow of condenser cooling water
b)the system is low on refrigerant
c)the solenoid valve to the chill box is "frozen" in the open position
d)the high pressure cutout switch is inoperative
30) Which of the conditions listed may be an indication of an excessive amount of refrigerant circulating through the system?
a)sweating of the compressor crankcase
b)colder than normal solenoid valve
c)frosting of the evaporator
d)weeping at the purge valve
31) Leaking suction valves in a refrigeration compressor are indicated by
a)higher than normal suction pressure
b)lower than normal suction pressure
c)lower than normal evaporator temperature
d)noticeable increase in compressor noise
32) If the discharge valves on the refrigeration compressor are leaking badly, the compressor should
a)run continuously
b)not start
c)have high discharge pressure
d)short cycle on the high pressure switch
33) If a refrigeration system were short of refrigerant, the condition would result in
a)continuous running of the compressor
b)high suction pressure
c)high discharge pressure
d)short cycling of the compressor on the water failure switch
34) A warmer than normal compressor suction line might be caused by
a)insufficient lubrication
b)insufficient refrigerant
c)excess refrigerant
d)excessive opening of the expansion valve
35) what causes the refrigeration system to short cycle on a HP cutout-
a)dischg valve leaking
b)pressure cutout set incorrectly
c)system overcharged with refrigerant
d)insufficient cooling water.
36) When purging a refrigeration system, the compressor is—
a)running
b)running but the condenser is secured.
c)shut down
d)running with the bypass open
37) The refrigerant temperature is at the maximum before it enters the—
a)expansion valve
b)compressor
c)condenser
d)evaporator
38) The solenoid valve controls the
a)pressure in the evaporator coils
b)amount of refrigerant entering the evaporator
c)flow of refrigerant to the expansion valve
d)amount of circ water to the condenser
39) Closing the solenoid valve will stop the compressor through the
a)low water pressure cut out switch
b)bypass relief valve
c)LP cutout switch
d)HP cutout switch.
40) The temperature bulb of the thermo expansion valve is attached to the
a)icebox coil
b)evaporator coil outlet
c)evaporator coil inlet
d)wall of the ice box
41) The temperature bulb of a solenoid valve is attached to the-
a)icebox coil
b)wall of the icebox
c)evaporator coil inlet
d)evaporator coil coutlet
42) The suction pressure regulating valve
a)cuts in the compressor
b)maintains the back pressure in the evaporator coils
c)cuts out the compressor
d)controls the expansion valve
43) The cooling water regulator is automatically actuated by
a)discharge pressure of the refrigerant
b)temperature of the refrigerant
c)an electric relay
d)a thermo relay
44) The LP control switch
a)is a safety device
b)actuates the coling water
c)cuts out the compressor to maintain proper flow.
d)regulates the king valve
45) A hot crankcase and cylinder head accompanied by low suction pressure would be caused by—
a)excess refrigerant
b)insufficient refrigerant
c)air in the system
d)stuck discharge valve
46) When securing a system the first step would be to—
a)open bypass valve
b)close receiver king valve
c)open solenoid valve
d)cut out compressor on HP
47) External frost on inlet of expansion valve indicates-
a)expansion valve plugged or dirty
b)head pressure too high
c)refrigerating comnpartment too cold
d)air in system
48) When the crankcase is cooler than the suction line it is because-
a)too much refrigerant
b)insufficient refrigerant
c)expansion valve open too wide
d)suction valve leaking
49) Closing the solenoid valve stops the compressor through the
a)HP cutout switch
b)low water pressure cutout switch
c)low pressure cutout switch
d)high water pressure cutout switch.
50) Tubing joints are –
a)brazed
b)welded
c)screwed
d)silver soldered
51) Which of the following would cause a compressor to run continiously-
a)LP switch jammed
b)HP switch jammed
c)clogged strainer
d)defective thermal bulb
52) The solenoid valve is a-
a)pressure controlled stop valve
b)temperature controlled stop valve
c)Freon controlled check valve
d)none of the above
53) The scale trap is located between the –
a)compressor and oil separator
b)expansion valve and evaporator coils
c)king valve and expansion valve
d)evaporator coils and compressor
54) Too low suction pressure could be caused by-
a)too much oil in the system
b)dirty scale traps
c)shortage of refrigerant gas
d)any of above
55) Sweating of a crank case is caused by-
a)too much oil in the system
b)too much superheat
c)insufficient superheat
d)expansion valve hung up
56) Slugging is usually caused by-
a)too much refrigerant in the system
b)too much oil in the system
c)expansion valve not operating properly
d)too much cooling water to condenser.
57) A device for holding open the suction valve and drawing gas from the suction manifold and returning it to the suction line without compressing is called-
a)relief valve
b)cylinder unloader
c)suction line bypass
d)dischg line bypass.
58) A hot suction line is caused by-
a)insufficient lubrication
b)insufficient refrigeration
c)too much refrigerant
d)expansion valve closed too much
59) If a solenoid valve is closed accidentally , the compressor would be stopped by-
a)automatic trip
b)low water cutout switch
c)low pressure cutout switch
d)HP cutout switch.
60)If the compressor short cycles on HP cutout, check for—
a)too much refrigerant in the system
b)condenser tubes need cleaning
c)system is starved of cooling water
d)all of above
61) If the compressor short cycles on LP cutout- the trouble could be
a)too much frost on evaporator coils
b)dirty traps and strainers
c)lack of refrigerant
d)any of above
62) If the compressor were to run continiously without lowering the temperature-the trouble could be—
a)leaky dischg valves
b)leak in the system
c)insufficient refrigerant
d)any of above
63) Which of the following would cause a high suction pressure-
a)expansion valve open too wide
b)dirty dehydrator
c)king valve not open wide enough
d)expansion valve not open wide enough
64) If a compressor runs continiously , the cause might be-
a)clogged scale trap
b)stuck HP switch
c)defective thermal bulb
d)stuck LP switch.
65) Low suction pressure is caused by—
a)expansion valve causing flooding back
b)solenoid valve not functioning properly
c)leaky compressor suction valves
d)air in system
66) If the compressor dischg temp is higher than the receiver temperature-
a)add more refrigerant to the system
b)decrease the amount of cooling water to the condenser
c)increase the amount of cooling water to the condenser
d)remove some of the refrigerant from the system
67) Air can be prevented from entering into the system by-
a)running the refrigerant through an aereator
b)keeping the dehydrator clean at all times
c)keeping all glands and stuffing boxes on the HP side tight.
d)keeping all glands and stuffing boxes on the LP side tight
68) If there is too much Freon in the system—
a)the safety valve will discharge
b)the compressor will short cycle
c)the compressor will run continiously
d)it will mix with the oil in the crankcase
69) Frost on the outside of the thermal expansion valve is may be caused by-
a)too much superheat
b)air in the system
c)moisture in the system
d)any of the above
70) When starting a refrigeration system, always—
a)vent the evaporator
b)bypass the condenser
c)vent the condenser
d)none of the above
71) Solenoid valve controls the –
a)amount of refrigerant entering the evaporator coils
b)amount of refrigerant going to the expansion valve
c)amount of refrigerant going to the compressor
d)pressure of refrigerant going to the evaporator coils.
72) The solenoid valve is controlled by—
a)amount of liquid in the system
b)amount of gas in the system
c)temperature of the condenser
d)temperature of the icebox
73) A leaky dischg valve can be detected by
a)a drop in the icebox temperature
b)a dischg pressure lower than normal
c)a fluctuating high pressure guage
d)any of above
74) What will you do if the liquid start rising in the Surge Drum? (Direct cooling system)
a)Immediately reduce on the suction valve, and watch the Open more on the suction valve gauge.
b)Stop the compressor
c)It will never happen.
d)Open more on the suction valve.
75)Why is it so important to suck back as much freon liquid as possible from the evaporators, before stopping the compressor?
a)To prevent low condensing pressure during start up.
b)To prevent low suction pressure during start up.
c)To prevent freezing of line.
d)To avoid liquid coming back to the compressor during start up.
76)To get the best possible efficiency from evaporators, the superheat should be regulated to:
a)-5 to -10 deg C
b)+5 to 10 deg C
c)40 to 50 deg C
d)0 to 1 deg C
77)The thermoexpansion-valve does the following job--
a)Regulating freon liquid flow to the evaporator.
b)Regulating the freon flow to condenser.
c)Regulating cooling water temperature.
d)Regulating the suction pressure.
78)If the reefer plant has air in the system , from where will you vent the air out?
a)From the evaporator.
b)From the compressor.
c)From the receivers bottom.
d)From the condenser.
Answers:
1c
2a
3d
4d
5d
6c
7d
8c
9a
10c
11d
12b
13b
14d
15c
16a
17c
18c
19c
20c
21b
22c
23a
24c
25a
26d
27b
28d
29b
30a
31a
32a
33a
34b
35a
36c
37c
38c
39c
40b
41b
42b
43a
44c
45b
46b
47a
48a
49c
50d
51a
52b
53c
54d
55a
56c
57b
58b
59c
60d
61d
62d
63a
64d
65b
66b
67d
68b
69c
70c
71b
72d
73d
74a
75d
76b
77a
78d
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