To isolate a dual pressure relief valve while the system remains in service, which valve type should be used?

• A. Gate valve
• B. Three way valve
• C. Ball valve
• D. Check valve

Answer: (B)

To isolate a dual pressure relief valve without taking the system offline, you need a valve that can redirect the flow around the valve while keeping the process running. A three-way valve can do this by providing a bypass path. In one position it routes flow through the normal line around the relief valve, and in another position it connects the supply to a bypass so the relief valve can be isolated and serviced without interrupting service to the rest of the system. Gate valves or ball valves can shut off flow, but using them alone would interrupt the process and don’t provide a built-in bypass path. A check valve prevents reverse flow but does not offer a way to bypass or isolate the relief valve while keeping the system in operation.