What is the function of the intake relief valve (IRV) on a fire pump and when should it be used?

What is the function of the intake relief valve (IRV) on a fire pump and when should it be used?

• A. The IRV helps prevent loss of prime by venting suction line air; use during draft priming and whenever suction pressure rises unexpectedly.
• B. The IRV increases discharge pressure automatically.
• C. The IRV vents air from the discharge side only.
• D. The IRV is used to shut down the pump.

Answer: (A)

The intake relief valve on the suction side is there to keep the pump primed by venting air that can get trapped in the suction line. When you’re drafting from a static source, air pockets can form in the suction line and break the water seal, causing the pump to lose prime. The IRV provides a controlled vent so those trapped air pockets can escape, allowing water to fill the suction line and the prime to be maintained. You use it during draft priming to purge air from the line, and you use it whenever suction pressure rises unexpectedly to relieve the line and prevent air from compromising the prime. It sits on the suction side near the pump and does not increase discharge pressure, vent the discharge side, or shut down the pump.

The intake relief valve on the suction side is there to keep the pump primed by venting air that can get trapped in the suction line. When you’re drafting from a static source, air pockets can form in the suction line and break the water seal, causing the pump to lose prime. The IRV provides a controlled vent so those trapped air pockets can escape, allowing water to fill the suction line and the prime to be maintained. You use it during draft priming to purge air from the line, and you use it whenever suction pressure rises unexpectedly to relieve the line and prevent air from compromising the prime. It sits on the suction side near the pump and does not increase discharge pressure, vent the discharge side, or shut down the pump.