Which device can be used as a backup to the safety relief valve in ammonia systems?

• A. Rupture disk
• B. Pressure switch
• C. Flow meter
• D. Thermocouple

Answer: (A)

In ammonia systems, safeguarding against overpressure often relies on a rupture disk as a backup to the safety relief valve. A rupture disk is a one-time pressure-relief device that bursts at a predetermined pressure and provides an immediate vent path. It is placed to act quickly if the valve is slow to lift or fails to operate, giving an extra layer of protection before the system pressure climbs too high. After it ruptures, the disk must be replaced, which is why it serves as a backup rather than a primary, reusable relief method. The other devices—pressure switch, flow meter, and thermocouple—are sensing or monitoring instruments and do not provide venting, so they do not serve as backups to relief valves.