A fire pump is an important piece of equipment for many buildings and can play a key role in a standpipe system when it's needed to quickly pump water under high pressure to a fire sprinkler head or hose line. It's critical that a properly specified and installed UL Listed or FM Approved fire pump is ready to perform when called upon in an emergency.
Several factors should be considered when selecting the correct pump for a particular application and installation. Some of the most common considerations include:
Power Sources for Electric Motor-Driven Fire Pumps
Obviously, the most crucial aspect of any fire pump is the power source that will drive it. It's imperative that the power source(s) meet NFPA 20's requirements for an emergency generator set for a standpipe pump. This includes minimum ratings, maximum continuous duty rating, and the required surge capability.
The next factor to consider is the type of fire pump required. Single-stage pumps are better for low flow rates and lower discharge pressures while two-stage fire pumps are designed to deliver higher flow rates at more discharge pressures. Finally, one-stage and two-stage pumps can be powered by either electric motors or diesel engines. It's also important to understand the piping systems that will be connected to the fire pump. For example, if the pump will be used to supply water through long lays of small diameter hose (wildland), a single-stage fire pump is probably the best choice.
In addition to the piping and pressure requirements, the design and specification of the fire pump must also meet NFPA's minimum operating conditions. The primary rating point, secondary rating point, and shut-off points must be met on the fire pump curves. The primary rating point expresses the overall system's 100% Q at a given pump capacity and is used to select and specify the fire pump model and horsepower. The secondary rating point is a 150% Q at 65% P and is the pump's normal test flow point.
Lastly, a fire pump must have sufficient residual pressure to ensure that the piping and all fittings can maintain a system pressure after the fire pump has shut off. The required residual pressure varies from code to code. The minimum required residual pressure is 25 psi in New York City, 65 psi in Chicago, and 100 psi in the International Building and Fire Code.
Once the fire pump is commissioned, it must be tested on a regular basis to ensure that it's still operating within its design specifications. This is done by opening the 2-1/2-inch fire department valve outlets and measuring both the motor and pressure. These measurements must be taken at the primary and secondary rating points to meet NFPA 20 requirements. While weekly inspections can be performed by in-house personnel, a qualified professional should conduct the annual tests and flow test to make sure that the fire pump is meeting all its requirements. This can help identify problems such as a clog or other simple problems that can easily be corrected before they cause serious issues when an emergency occurs.
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