Which valve is designed to automatically relieve excess pressure from the boiler?

The safety valve is specifically designed to automatically relieve excess pressure from the boiler. Its primary function is to ensure that the pressure within the boiler does not exceed safe operating limits. When the internal pressure rises to a predetermined level, the safety valve opens automatically, allowing steam or pressure to escape. This function is crucial to prevent potential catastrophic failures, such as explosions, which can occur if excess pressure is not properly managed.

In contrast, the check valve is used to prevent backflow in a system, ensuring that the flow of fluids occurs in a single direction. The main steam stop valve is used to control the flow of steam from the boiler to the system, providing a means of starting or stopping the flow, but it does not have a function to relieve excess pressure. The on-off valve also serves the purpose of controlling flow but lacks the safety mechanism necessary for managing pressure surges. Thus, the safety valve is an essential component of boiler safety protocols.