Which valve arrangement allows maintenance on a relief valve while the system remains in service?

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

Answer: (A)

A three-way valve arrangement is designed to create a bypass around the relief valve, so maintenance can be done without stopping the process. With three ports, you can route flow through the relief valve in normal operation or divert it through a bypass line when you need to service the valve. This lets the system keep circulating or be vented safely while the relief valve is isolated for inspection or repair, preventing a full shutdown.

Two-way devices like a ball valve or a gate valve can shut off flow to the relief valve, but they don’t provide a built-in path to carry the system flow around the valve during maintenance. A check valve protects against backflow but also doesn’t offer a bypass route for servicing the relief valve.