Which valve must be present between the safety valve and the boiler?

In boiler systems, the correct configuration requires that there be no valve between the safety valve and the boiler. Safety valves are critical components designed to prevent overpressure in a boiler system, ensuring that excess pressure is released immediately under unsafe conditions. If there were a valve present, particularly a shut-off valve or any other kind of valve, it could potentially restrict the flow of steam or water during an emergency situation. This could lead to dangerous conditions, including boiler explosions or catastrophic failures.

Safety valves must be directly connected to the boiler to allow for immediate and unrestricted release of pressure. The valve's functionality depends entirely on being able to open and relieve pressure without any obstruction. Therefore, having no intervening valves maintains the required safety protocols and guarantees the safety device can operate effectively when needed.