What is the reseating pressure required for a safety valve?

The reseating pressure of a safety valve is critical in ensuring the safe and effective operation of high-pressure boilers and other pressure systems. The correct reseating pressure is typically set at 96% of the valve's set pressure. This means that after the safety valve has lifted to relieve excess pressure, it must reseat, or close, again at a pressure that falls to this value.

Choosing 96% as the reseating pressure is a compromise that allows for adequate safety while minimizing the potential for nuisance tripping, which can occur if the reseating pressure is set too low. It ensures that the valve does not prematurely close, allowing for a safe pressure relief without excessively frequent activation of the valve. On a practical level, it establishes a reliable performance standard across various regulatory codes and practices, which is why this value is commonly accepted.

Values lower than 96% may lead to the valve not reseating properly at the required operational pressure, while values higher than 96% could risk system safety by allowing pressure to build up beyond safe limits before relieving.

This understanding is vital for those operating high-pressure systems, ensuring that safety devices like valves maintain their integrity and function properly under varying pressure conditions.