What is the only type of valve that can be used before a safety valve?

The type of valve that can be used before a safety valve is a 3-way valve. This is important in high-pressure piping systems because a 3-way valve allows for the diversion of flow and can facilitate maintenance or testing without interrupting the safety measures in place.

In high-pressure systems, safety valves are critical for preventing overpressure situations. The 3-way valve can redirect flow from the safety valve, enabling operators to perform checks or adjustments safely while keeping the system operational. This ability to divert flow is what sets the 3-way valve apart from other types of valves.

Other types of valves, such as 2-way valves, can control flow in one direction but do not provide the redirection capability necessary to maintain safety and operational efficiency. 4-way valves generally function in more complex systems and could complicate the safety operations. Check valves, while important for preventing backflow, do not serve the necessary function of rerouting flow in a way that aids in maintaining or servicing a safety valve.