CARO Piping Systems and Valves 1 — Questions and Answers
Question 1: What is the primary purpose of a hand expansion valve (HEV) in an ammonia refrigeration system?
- To automatically regulate refrigerant flow based on superheat
- To manually control refrigerant flow into a vessel or evaporator (Correct answer)
- To relieve excess system pressure during emergencies
- To separate liquid refrigerant from vapor in the suction line
Correct answer: To manually control refrigerant flow into a vessel or evaporator
A hand expansion valve is a manually operated valve used to throttle or control refrigerant flow into a vessel or evaporator, not an automatic device.
Question 2: Which type of valve is most commonly used as a stop valve (shutoff valve) in ammonia refrigeration piping?
- Ball valve
- Gate valve (Correct answer)
- Globe valve
- Butterfly valve
Correct answer: Gate valve
Gate valves are the most common stop/shutoff valves in ammonia refrigeration systems because they provide full-bore flow with minimal pressure drop when fully open.
Question 3: What does a check valve do in a refrigeration piping system?
- Regulates pressure by venting refrigerant to atmosphere
- Prevents refrigerant from flowing backward in the piping (Correct answer)
- Controls superheat at the evaporator outlet
- Balances pressure between high and low sides
Correct answer: Prevents refrigerant from flowing backward in the piping
A check valve allows refrigerant to flow in only one direction, preventing reverse flow that could damage compressors or disrupt system operation.
Question 4: A pressure relief valve on a refrigeration vessel is required to discharge to:
- The compressor suction line
- The condenser inlet
- A safe outdoor location or treatment system per code (Correct answer)
- The evaporator pan
Correct answer: A safe outdoor location or treatment system per code
Pressure relief valves must discharge to a safe outdoor location or an approved treatment/containment system to protect personnel and comply with codes such as IIAR and ASHRAE 15.
Question 5: What is the function of a solenoid valve in a refrigeration system?
- To manually throttle refrigerant flow
- To electrically open or close refrigerant flow on demand (Correct answer)
- To continuously modulate refrigerant pressure
- To separate oil from refrigerant vapor
Correct answer: To electrically open or close refrigerant flow on demand
A solenoid valve uses an electromagnetic coil to open or close the valve electrically, allowing automated control of refrigerant flow in response to a control signal.
Question 6: What material is most commonly used for ammonia refrigeration piping in industrial systems?
- Copper tubing
- PVC pipe
- Carbon steel pipe (Correct answer)
- Aluminum tubing
Correct answer: Carbon steel pipe
Carbon steel pipe is the standard material for ammonia refrigeration because ammonia is incompatible with copper, brass, and zinc, which corrode rapidly in its presence.
Question 7: What is the purpose of a fusible plug installed on a refrigeration vessel?
- To prevent refrigerant from freezing in cold ambient conditions
- To melt and release refrigerant if vessel temperature reaches a dangerous level (Correct answer)
- To regulate liquid level inside the vessel
- To isolate the vessel for maintenance
Correct answer: To melt and release refrigerant if vessel temperature reaches a dangerous level
A fusible plug contains a low-melting-point alloy that melts at a set temperature, releasing refrigerant to prevent vessel rupture due to fire or extreme heat.
CARO Piping Systems and Valves 1
What is the primary purpose of a hand expansion valve (HEV) in an ammonia refrigeration system?