Harold Kestenholz
You will receive a variety of answers to your question because:
1. there are many different applications of relief valves; such as:
a. water heaters
b. boilers
c. pressure vessels for chemicals
d. refrigeration machinery
e. etc.
2. Each manufacturer of relief valves specifies on an attached tag the recommended frequency of opening.
3. A manufacturer of a machine may specify the frequency of examination aside from the valve manufacturer’s recommendations.
4. Each person you ask may be from a different vocational background. A plumber may recommend once a year for a water heater. A boiler operator may recommend once-per-week; etc. The answer depends upon the circumstances of their occupation.
This question is similar to asking how many licks you may take of a lollipop. – It depends on the manufacturer and the circumstances.
