RETA CIRO case studies

RETA CIRO · Put your knowledge to work in context.

The Certified Industrial Refrigeration Operator (CIRO) is a RETA credential for experienced industrial refrigeration operators who are ready to demonstrate supervisory-level knowledge. CIRO requires documentation of at least two years of experience as an industrial refrigeration operator. The RETA CIRO case studies are 5 cases and about 4,408 words.

Booster Trips on Low Oil Pressure After Every Restart

A 300-hp ammonia booster compressor serving a -40°F blast freezer trips on low oil pressure about 20 minutes after every restart. The freezer is being pulled down after a defrost.

920 words, about 5 min 2

Two-Stage Plant: High Discharge Pressure and Falling High-Stage Suction

A plant runs a two-stage ammonia system: a low-stage screw on a -35°F suction discharging to a horizontal flash intercooler, and a high-stage reciprocating machine discharging to an evaporative condenser. Since a new -35°F spiral freezer was commissioned, the high-stage machine trips on high discharge pressure (195 psig, about 103°F condensing) with 82°F ambient and all condenser fans and spray pumps running.

802 words, about 4 min 3

Ammonia Leak on Night Shift With Ventilation Down

At 02:15 a lone night-shift operator sees the machine-room ammonia detector reading 60 ppm and climbing slowly - roughly 5 ppm every ten minutes. The detector is calibrated.

789 words, about 4 min 4

Condenser Fan Motor Trips Overload on a Hot Afternoon

A 460-V, three-phase, 50-hp condenser fan motor trips its overload after about 15 minutes of running on a hot afternoon. Nameplate: 65 A FLA, service factor 1.15, 40°C ambient.

891 words, about 4 min 5

Compressor Will Not Stay Running: Tracing the Oil-Pressure Rung

The compressor control ladder has four rungs. Rung 1: L1 - STOP pushbutton (NC) - high-pressure cutout (NC, manual reset) - low-pressure cutout (NC) - oil-pressure switch (NC, held closed only when oil pressure is proven; a 90-second timer opens the contact if it is not) - CR1 coil - N.

1,006 words, about 5 min