Is it acceptable to place a shutoff valve between the relief valve and the boiler?

Placing a shutoff valve between the relief valve and the boiler is considered unacceptable for several reasons rooted in safety and proper function of the heating system. The relief valve plays a critical role in safety, as it is designed to open and release steam or water when pressure exceeds safe limits within the boiler. If a shutoff valve is installed in this location, it could be closed inadvertently or fail to open, thereby preventing the relief valve from functioning as intended during an overpressure situation. This could lead to dangerous conditions, including boiler explosions.

Furthermore, the codes and standards that govern boiler and pressure vessel safety explicitly prohibit such installations to ensure that the pressure relief system remains fully operational and accessible at all times. This helps safeguard both equipment and personnel from potential hazards associated with excessive pressure buildup. Maintaining an open path for the relief valve is essential for the reliability of the boiler system and ensures compliance with safety regulations.