3rd Class Stationary Steam Engineer License Practice Test

The spring-loaded pop safety valve is the correct choice according to ASME (American Society of Mechanical Engineers) code for use on boilers. This type of safety valve is designed to automatically discharge excess pressure from the boiler, ensuring safe operation by preventing overpressure conditions that could lead to failure or explosions.

Spring-loaded pop safety valves function by utilizing a spring to hold a disc (seal) against a seat, thereby containing the pressure within the boiler. When the internal pressure exceeds the predetermined limit, the force exerted by the pressure overcomes the spring force, causing the valve to open quickly and allow steam or gas to escape. This action not only reduces the boiler pressure but also typically results in a loud popping sound, which is how the term "pop" is derived.

In the context of boiler safety and operation, the use of spring-loaded pop safety valves adheres to the rigorous requirements set forth by ASME standards. This ensures reliability and effectiveness in protecting the boiler and the surrounding environment from dangerous pressure buildup.

The other types of safety valves mentioned do not align with standard practices or requirements for boiler safety according to ASME code, which emphasizes the importance of using approved and standardized equipment to maintain operational safety and efficiency in steam engineering applications.