When are two safety valves required in a boiler system?

In boiler systems, two safety valves are mandated when the heating surface exceeds 500 square feet. This requirement is grounded in safety regulations and engineering principles aimed at ensuring the safe operation of larger boilers, which handle greater pressures and temperatures.

The rationale behind requiring two safety valves for larger heating surfaces is that it provides an additional layer of safety. In the event that one safety valve fails or malfunctions, the second valve serves as a backup, capable of relieving pressure and preventing potential boiler explosion or failure. This is particularly crucial for systems with larger heat loads, where the risk of pressure buildup is higher.

Boilers with heating surfaces smaller than 500 square feet typically can be safely managed with a single safety valve, as they produce less steam and operate at lower pressure differentials. As for the other options, while certain performance metrics and conditions play a role in safety considerations, they do not directly correspond to the specific requirement for dual safety valves as outlined by the design standards governing boiler operations.