Christian P. Koop
The fire pump is still the single most important component of the modern fire truck, sometimes referred to as the heart of the fire engine or pumper truck.
I also believe it is worth much more than the sum of its parts because without it, firefighters could not put out fires, save lives, and protect property. That is why I believe it should be held in venerable status and be kept in tip-top shape.
This article will cover basic fire pump types in use today, pump maintenance, common problems, key components, and testing required by National Fire Protection Association (NFPA) 1901, Standard for Automotive Fire Apparatus, which establishes that pumps must be able to flow rated capacities.
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1 Shown are sample anodes removed during pump maintenance requiring replacement. (Photos by author.) |
Pumps are rated by gallons per minute (gpm) or liters per minute. The pumps are to be tested at 150 pounds per square inch (psi) at 100 percent of rated capacity, 200 psi at 70 percent of rated capacity, and 250 psi at 50 percent of rated capacity. Additionally, there is another test required by NFPA 1901 that is called the Pumping Engine Overload Test for 750-gpm or larger pumps that consists of pumping at 165 psi for rated capacity at net pump pressure for at least five minutes. Basically, if your rig's engine, drive train, and fire pump pass this rigorous test, then the pump is in great condition. This test should be performed right after the 150-psi 100 percent of rated capacity test. These tests should also be performed annually, which is required by NFPA 1911, Standard for the Inspection, Maintenance, Testing, and Retirement of In-Service Automotive Fire Apparatus.
Pump Types
There are several different types of pumps in the fire service today with various drive configurations that depend on the output ratings of the pumps and the type of firefighting they are specified for. Regardless of the type of pumps you have on your rigs, they require proper care, maintenance, and testing to ensure long and trouble-free lives.
The most common type of fire pump used by the United States fire service today is the centrifugal pump, which is available in both single-stage and multistage versions. Both are nonpositive displacement pumps with main components consisting of an impeller mounted on a shaft housed inside a casing.
The centrifugal pump is a nonpositive displacement pump because unlike a piston-type pump, it does not pump a specific amount or volume of water with each revolution. It works on the basic principle that as water enters the center of the impeller (eye) as it rotates, the water is flung outward by velocity, and the faster it rotates the greater the pressure it creates. Which type is better when considering single-stage vs. multistage is still debated to this day. However, multistage pumps can develop higher pressures than the single-stage or single-impeller pumps, and they allow the pump operator to select either volume or pressure modes depending on firefighting needs. Selecting pump type and size basically boils down to preference and a department's needs based on the structures it protects.
The pump operator or driver is the most important person tasked to ensure the fire pump is properly maintained. I consider this person to be the first line of defense in keeping the pump in top condition. He should operate and test the pump on a daily basis and follow the pump manufacturer's published maintenance checklist. He should exercise all valves and pump controls and keep the valve oper