Is it true that a stop valve cannot be installed between the boiler and relief valve?

A stop valve is a device that can obstruct the flow of water or steam in a piping system. In the context of a boiler system, having a stop valve between the boiler and the relief valve is not permitted because it can create a dangerous situation under certain circumstances.

The primary function of a relief valve is to prevent overpressure conditions within a boiler by releasing excess pressure. If a stop valve is installed between the boiler and the relief valve, it could be closed or malfunction, leading to the relief valve being unable to function properly. This could result in an increase in pressure that might exceed safe limits, potentially leading to equipment failure or catastrophic events such as explosions.

Industry standards and safety codes are designed to protect both the equipment and personnel working with or near these systems. Therefore, it is considered a best practice to ensure that there is no obstruction between the boiler and the relief valve to maintain system integrity and safety, which solidifies the assertion that a stop valve cannot be installed in that position.