RETA CARO case studies
RETA CARO · Put your knowledge to work in context.
The Certified Assistant Refrigeration Operator (CARO) is RETA's entry-level certification for people who work in industrial refrigeration under supervision. It is one of three RETA credentials accredited by ANAB (ANSI National Accreditation Board) to the ANSI 17024 standard, and it is designed to show that an operator has the basic knowledge to function safely in an engine room. The RETA CARO case studies are 5 cases and about 2,148 words.
1Low-Side Float Level Alarm After Load Change
You operate a single-stage ammonia plant with a flooded evaporator fed by a low-side float valve. At 06:00 the plant runs at 40% load with 4 of 10 evaporator fans running and the suction pressure steady at 2.1 barg.
458 words, about 2 min2Hot-Gas Defrost Overpressure on a Cold Morning
A two-stage ammonia plant serves four freezer rooms at -30 C evaporating and a high-side receiver that normally sits at 35 C condensing on an evaporative condenser. On a cold morning the condenser fans are cycling and the receiver pressure falls to 8.5 barg.
445 words, about 2 min3Ammonia Leak Alarm in the Machine Room at Shift Change
At 05:55, during shift change, the fixed ammonia detection system in the machine room alarms at 25 ppm on the low-level sensor near the compressor skid. Two operators are in the room.
440 words, about 2 min4Pump-Down Before Opening a Strainer
Maintenance must clean the strainer on the liquid line feeding a freezer evaporator. The line normally runs at 2.0 barg suction-side pressure with the plant at 60% load.
375 words, about 2 min5Relief Valve Discharge and Receiver Overfill
During a hot afternoon the high-side receiver level climbs to 85% and the condenser subcooling falls. The receiver relief valve has been piped by a contractor to discharge just above the machine room roof, about 1.5 m above the roof surface and close to an air intake for the control room.
430 words, about 2 min