3.4.1 — Safety Devices
Safety valves and safety-related devices exist to prevent pressures and operating conditions from reaching dangerous levels. They protect people first, equipment second, and product/process continuity third. This hierarchy must never be reversed.
Pressure Relief Valves and Rupture Devices
Relief devices open (or rupture) at a set condition to prevent the protected component from exceeding its safe pressure limit. A relief event is a symptom, not a standalone problem — the underlying cause must always be found.
Never cap, plug, or isolate a relief device in a way that defeats protection. Never “reset” a relief event by simply replacing the device without investigating the cause — blocked condenser airflow, closed valves, overcharge, non-condensables. Where discharge piping exists, ensure it remains unobstructed, properly supported, and directed to a safe location per applicable requirements.
High/Low Pressure Cutouts (Safety Controls)
Pressure controls used as safety cutouts stop the compressor when discharge pressure rises too high or suction pressure falls too low. Setpoints are application-specific and must be verified against equipment design limits and refrigerant saturation conditions.
Diagnosing Nuisance Trips
Before adjusting setpoints after a trip, confirm whether the control is responding correctly to a real condition. Common examples:
- High-pressure trip — dirty condenser coil, failed condenser fan, closed discharge service valve, or non-condensables in the system.
- Low-pressure trip — low refrigerant charge, restricted metering device, closed liquid line solenoid, or very low load conditions.
Widening a setpoint without understanding the root cause hides a real problem and increases risk of equipment damage or refrigerant release.