What is the general sequence to prime a centrifugal fire pump?

• A. Open discharge valves, close priming valve, fill pump, start priming, then open discharge valves.
• B. Open priming valve, discharge valves, then fill with oil.
• C. Start pump at full throttle, then close priming valve, open discharge lines.
• D. Close all discharge valves, open priming valve, fill pump with water, start priming until suction prime, then close priming valve and gradually open discharge lines.

Answer: (D)

Priming a centrifugal fire pump relies on getting the suction line and pump fully filled with water so air is removed and a strong suction can be developed. To do this correctly, you first keep all discharge lines closed. Open the priming valve so water can flow into the pump and up the suction line. Fill the pump through the priming device until the suction path is completely filled and you have a reliable prime. Once the suction is primed, close the priming valve to stop the priming flow, then gradually open the discharge lines to bring the system online. This sequence prevents air from remaining in the suction, avoids losing prime when lines are opened, and helps prevent water hammer as you restore discharge flow.