When replacing a safety valve, what must remain constant?

When replacing a safety valve, it is crucial that the setting of the last valve installed remains constant. The safety valve's primary function is to ensure that excessive pressure does not build up in a boiler or pressure vessel, which could lead to catastrophic failures. Each valve is calibrated to open at a specific pressure setting to provide the necessary safety margin for the system it serves.

If a new safety valve is installed with a different pressure setting than the previous one, it can lead to situations where the pressure exceeds safe limits, potentially endangering equipment and personnel. Therefore, continuity in the pressure setting is essential for maintaining the integrity of the safety system and ensuring that it operates as intended under normal conditions.

Maintaining the same pressure setting when replacing a safety valve helps prevent engineering mismatches that could arise from using a valve with different specifications or settings, which may not be suitable for the system's operational needs.