What type of valve is permitted for the interconnection of standby fuels?

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

Answer: (C)

Interconnecting standby fuels calls for a valve that can route flow from one of two sources to a single downstream line while keeping the other source isolated. A three-way valve does exactly that: it has three ports—two inlets from each fuel source and one outlet to the system—and you can position it to connect the desired source to the line while closing off the other. This setup prevents cross-flow between sources and avoids backflow, which is essential for safe standby-fuel operation.

Two-port valves like gate, globe, or ball valves are designed to shut off or allow flow in one line. They don’t provide a built-in means to select between two sources and direct one of them to the system without using additional valves or piping, which can create cross-connections and extra leakage paths. The three-way valve is specifically suited for interconnecting standby fuels, offering a single, safe means to choose and feed the system from the appropriate source.