At what pressure below the lowest safety valve setting are boiler safety valve gags placed on safety valves?

Gags are used on boiler safety valves when the boiler is not in service or when maintenance is being performed. The gags prevent the safety valves from opening under pressure, ensuring that the system is securely contained during these activities. The correct pressure range for placing gags on the safety valves is between 100 and 200 PSI, as this range is below the lowest safety valve setting for most systems. This ensures that the valve will not inadvertently open and release steam, which could present safety hazards during maintenance procedures.

Using a pressure below the lowest safety valve setting minimizes risks while allowing for regular inspections or repairs. The other pressure ranges presented do not fall into the safe operating range typically used for gags, as they may exceed the lowest safety valve setting, which increases the risk of unwanted valve operation. Therefore, the selection of the 100-200 PSI range reflects adherence to safety protocols and standards in preventing accidents during maintenance operations.