In a hot water boiler, what is the minimum pressure differential between the operating pressure and the safety relief valve set pressure?

In a hot water boiler system, maintaining a proper safety margin between the operating pressure and the safety relief valve set pressure is critical for safe operation. The correct answer indicates that the minimum pressure differential should be 25% of the operating pressure.

This requirement is in place to ensure that the relief valve functions correctly and opens at the appropriate time to prevent pressure from building up excessively in the system, which could lead to hazardous situations, including tank ruptures or explosions. A 25% differential provides a substantial buffer to account for fluctuations in operating pressure and guarantees that the safety relief valve is capable of handling unexpected increases in pressure effectively.

Setting the differential too low could result in the relief valve opening too frequently or not at all when needed, potentially compromising the safety of the boiler. Therefore, establishing this 25% margin is a standard practice in boiler design and operation, aligning with safety codes and engineering principles.