How to Size a Fire Fighting Water Pump

Fire fighting water pump is a vital part of the fire protection system, providing the necessary pressure to support sprinklers and standpipe systems. Choosing the right fire pump is key to making sure the building is adequately protected from fire hazards and provides enough water flow to handle any situation that may occur in a building. Fire pumps must be sized and selected to be able to deliver the required capacity at the desired discharge pressures, while also meeting local fire codes.

The first step in selecting a fire fighting water pump is to perform a hazard analysis for the building. The hazard analysis will determine the most demanding area of the fire protection system, which can be used to size the fire pump. For example, in high-rise buildings a typical method for sizing fire pumps is to use the standpipe demand determined by NFPA 14: Standard for the Installation of Standpipe and Hose Systems which requires the first standpipe to provide 500 gallons per minute (GPM), and then 250 gpm for each additional standpipe in the building, up to a maximum of 1000 gPM.

Once the hazard analysis is completed, the next step in sizing a fire pump is to select a pressure booster, which will provide the required pressure boost needed to supplement the incoming fire water supply. The selection process for the pressure booster will be based on three points: churn, rated flow, and 150% of the rated flow. This will ensure that the pressure is generated at the required levels to meet the building demands, and also allow for the expected peaks in flow that could be experienced during normal operations.

In addition to ensuring the proper sizing of a fire fighting water pump, it is important to understand the different types of fire pumps and their operating principles, types, driver options, and applications. This knowledge can help pump operators move from being simply a “knob puller” who sets predetermined figures on a gauge to becoming efficient engineers who know how to properly use and operate the fire fighting water pump to ensure that the fire protection system works as it should.

Another consideration when sizing a fire fighting water pump is the type of hose that will be connected to it. Hose sizes are available from 3/8″ to 1 1/2″, with the majority of fire departments using a 1 1/2″ hose. This hose is easy to maneuver and manage, and offers the ideal balance between volume and managementability. It is also important to choose a hose that matches the fire pump’s discharge port size, as well as considering any potential temperature monitoring and alerts that may be part of the system, such as those recently installed by several Texas cities after freezing conditions resulted in costly repairs.

In addition, it is critical to understand that when sizing a fire fighting water Pump, you must take into account friction loss. Friction loss is the energy lost in pressure when water flows through the hoses, couplings, and other fittings. The amount of friction loss will depend on the hoses and their condition, but in most cases this can be minimized by using hoses made with higher quality materials and avoiding loose or worn components.

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