Book 2 Chapter 25: Compressor Refrigeration System Pre-Startup Procedures Flashcards
Why should oxygen not be used to pressurize a system for leak checking purposes?
A) It could result in explosion
B) The oxygen can cause pitting of the parts of the system
C) An external source of moisture free oxygen is required
D) The oxygen combines with any non-condensable gases present to increase the system head pressure
A) It could result in an explosion
After a refrigeration system is installed, a positive pressure testis performed using:
A) Propane
B) Methane
C) Nitrogen
D) Oxygen
C) Nitrogen
What personal protective equipment (PPE) is required when charging a system with refrigerant?
A) Goggles
B) Face shield
C) Rubber gloves
D) Encapsulated suit
A) Goggles
What are some of the non-condensable gases that can be found in a refrigeration system?
A) Air
B) Impurities in the refrigerant
C) Gases caused by lubrication breakdown
D) All of the above
D) All of the above
When it’s required to add oil to an operating refrigeration compressor and an oil pump is unavailable, what alternate method can be used to add oil?
A) Throttle the suction and feed oil to the crankcase
B) Throttle the discharge and feed oil into the suction line
C) Throttle the suction and feed oil into the suction line
D) Throttle the discharge and feed oil into the crankcase
A) Throttle the suction and feed oil to the crankcase
The presence of non-condensate gases in the refrigeration system:
A) Produces higher than normal high side pressure
B) Reduces compressor capacity
C) Reduces system efficiency
D) Produces added stress on the compressor
E) All of the above
E) All of the above
Non-condensable gases tend to accumulate at the:
A) Valves in the compressor discharge line
B) Elbows in the compressor discharge line
C) Low points in a refrigeration system
D) Highest point of the condenser
E) Lowest point of the evaporator
D) Highest point of the condenser
A sulphur candle is a test for:
A) Ammonia leaks
B) Air leaks
C) Vacuum seal
D) CFC leaks
E) Freon leaks
A) Ammonia leaks
When pressure testing a new refrigeration system, which of the following gases are used?
A) Oxygen
B) Helium
C) Nitrogen
D) Carbon monoxide
E) Hydrogen
C) Nitrogen
Leak testing on a refrigeration system:
A) Is done with a vacuum in the system
B) Is done with litmus paper for Freon refrigerant
C) Is done with a sulphur stick for Freon refrigerant
D) Must be done with the compressor running
E) Is done with an electronic leak detector for HFC’s
E) Is done with an electronic leak detector for HFC’s
It is very important to slowly open oil drain valves and plugs in the crankcase for which of the following reasons?
A) The oil is very cold
B) Residual pressure in the crankcase may blow refrigerant vapour and oil out
C) Oil can never be drained below the critical minimum level
D) Old oil is contaminated with refrigerant and may be very acidic
E) The oil is very hot
B) Residual pressure in the crankcase may blow refrigerant vapour and oil out
When draining or replacing oil from a refrigeration compressor, it is important to:
A) Lock out the compressor motor or driver
B) Exercise caution when removing drain plugs
C) Reduce crankcase pressure to almost atmospheric
D) Shut down and isolate the compressor
E) All of the above
E) All of the above
Combustion of HFC’s (halocarbon refrigerants) produces:
A) Chlorine gas
B) Carbon dioxide
C) Water vapour
D) Helium
E) Phosgene gas
E) Phosgene gas
To generate a vacuum in the crankcase of a refrigeration compressor the:
A) Discharge is throttled
B) Recirculation valve is throttled
C) Bypass is cracked
D) Crankcase vent is opened
E) Suction is throttled
E) Suction is throttled
Leaks in the refrigeration systems that operate below atmospheric pressure:
A) Result in frequent purge unit operation
B) Result in a frequent need to add refrigerant
C) Do not have to be identified before adding refrigerant
D) Do not impair performance
E) Cause higher oil consumption
A) Result in frequent purge unit operation
Where on the system is the initial refrigerant charge given?
A) The expansion valve
B) The low side of the system
C) The high side of the system
D) The heat exchanger
E) The evaporator
C) The high side of the system
Which of the following is not a recommended step during the procedure for which dry nitrogen is used for a system leak test?
A) Set the pressure reducing valve for the minimum design pressure of the high side
B) Connect the nitrogen cylinder to the system charging valve
C) Remove controls and relief valves that may be damaged by the test pressure
D) Open the liquid line shut-off valve
E) Open the cylinder shut-off valve and disconnect the nitrogen cylinder
E) Open the cylinder shut-off valve and disconnect the nitrogen cylinder
Which of the following statements about adding oil to a system is true?
A) Oil is added by charging it into the crankcase
B) Oil cannot be added while the compressor is in operation
C) Since the crankcase is pressurized it is not possible for air to get in the system when adding oil
D) The system must be recharged, purged and re-pressurized after the oil has been added
E) None of the above
A) Oil is added by charging it into the crankcase
Often adding oil to refrigeration compressors:
A) Is done when the compressor discharge valve is closed
B) Is done with the charging line open
C) Is done with a vacuum in the crankcase
D) Requires preheated oil
E) Is done with the equalizing valve closed
C) Is done with a vacuum in the crankcase
Non-condensable gases are removed by the:
A) Collection tank
B) Oil filters
C) Evaporators
D) Purge system
E) Condenser sump
D) Purge system
In a process called “copper plating” the acids remove copper from heat exchanger surfaces and redeposit it at points of:
A) High flow
B) Low temperature
C) High pressure
D) High temperature
E) Low pressure
D) High temperature
The pressurizing gas is admitted to the refrigeration system through the _______ valve.
A) Queen
B) Drain
C) Charging
D) King
E) Isolation
C) Charging
Evacuation of the refrigeration system should not be attempted unless the temperature of the surrounding air is ________ or higher.
A) 15ºC (59ºF)
B) 10ºC (50ºF)
C) 5ºC (41ºF)
D) 0ºC (32ºF)
E) 20ºC (68ºF)
E) 20ºC (68ºF)
Overcharging a system causes _____________ creating high compressor power consumption.
A) High condenser pressure
B) High compressor suction and discharge pressures
C) Low suction evaporator pressure
D) High receiver temperature
E) Low evaporator temperature
B) High compressor suction and discharge pressures
During the charging process the refrigerant that passes through the system is stored in liquid form in the:
A) Chiller
B) Compressor
C) Receiver
D) Evaporator
E) Expansion valve
C) Receiver
Positive pressure testing of a refrigeration system is done using dry ___________ gas as the pressure agent.
A) Oxygen
B) Nitrogen
C) Hydrogen sulphide
D) Helium
E) Carbon monoxide
B) Nitrogen
Non-condensable gases in a refrigeration system consist mainly of _______ that may have leaked into the system by improper operating or maintenance procedures.
A) Impurities in the refrigerant
B) Sulphur dioxide
C) Air
D) Nitrogen oxide
E) Gases caused by lubrication breakdown
C) Air
It is the ________ part of the refrigerant molecular composition that during combustion causes the green flame of the halide detector.
A) Chlorine
B) Fluorine
C) Carbon
D) Hydrogen
E) Iodine
A) Chlorine
Oil is added to the refrigeration system by _________ while the compressor is in operation.
A) Pouring it into the condenser
B) Pouring it into the crankcase
C) Charging it into the evaporator with a suitable pump
D) Charging it into the condenser with a suitable pump
E) Charging it into the crankcase with a suitable pump
E) Charging it into the crankcase with a suitable pump
Regulations of the authority having jurisdiction may require that a ________ be reported.
A) Loss of refrigerant
B) Change of the compressor
C) Flush of the condenser
D) Evacuation of the evaporator
E) Loss of cooling water
A) Loss of refrigerant
