What is the largest pipe size for threading a safety valve onto a steam drum of a high-pressure boiler?

The largest pipe size for threading a safety valve onto a steam drum of a high-pressure boiler is 2.5 inches. This size is significant due to the requirements of pressure and safety regulations in boiler systems. In high-pressure applications, the dimensions and fittings are critical for ensuring that the safety valve can function effectively within its designed parameters.

A 2.5-inch connection allows for adequate flow and minimizes the risk of pressure buildup that could occur if the diameter were smaller. Furthermore, safety valves must be sized properly to handle the volume of steam that may escape in the event of an overpressure condition, ensuring that the system remains safe and compliant with industry standards.

Option selections beyond 2.5 inches, such as 3 inches and 4 inches, do not apply in this scenario because they exceed the typical sizing limits established for safety valves on steam drums, thus potentially compromising the valve's effectiveness and the boiler system's safety protocols. Therefore, 2.5 inches emerges as the optimal choice for maximum efficiency and safety.