Fire fighting water pump is a type of purpose-driven fire system pump that increases the pressure (measured in PSI and bar) of an existing water supply to meet the design requirements for a fire sprinkler, standpipe or foam systems. These pumps are typically tested on a regular basis.
These tests can help detect any problems that may be developing such as clogs or low pressure. They can also identify any potential fire safety issues before a fire occurs.
Choosing the Right Pump
A fire fighting water pump is a critical piece of equipment. Choosing the right one means more than just knowing the maximum capacity (gpm). It also requires an understanding of how to choose the pump based on the most demanding factor. This involves knowing the operating principles, types and drivers of pumps, and how to size them based on sprinkler hazard levels and the pressure requirements of the fire protection system.
The most important consideration is the pressure capability of the pump, known as Total Dynamic Head (TDH). The higher the pressure, the more distance the hose can reach to spray water for fire suppression.
Typically, a fire pump is selected that produces a TDH of at least 175 psi, providing enough potential pressure to reach the most critical areas in your building. This is calculated using the manufacturer’s performance curve and comparing it with the system demand flow and pressure requirements. This process is performed at the beginning of a project, ideally as the scope of work is being developed.
Choosing the Right Hose
If a fire fighting water pump is not properly matched to its application, it can be ineffective. For example, if the fire pump is underpowered it can not achieve the necessary pressures to reach the point of discharge for effective mop-up operations. In other cases, the nozzle size can be too small to deliver sufficient water flow for the specific circumstances and requirement.
A good starting point is to understand the different operating principles, types, drivers and applications of fire pumps. This can help in specifying a solution that meets the requirements of the Local Authority Having Jurisdiction (AHJ) and NFPA 20.
Once the fire pump is selected, it is important to perform periodic inspections and tests to ensure the system is in good working order. These inspections can be performed by a licensed professional, and include testing the water flow, pressure and temperature of all components. Identifying problems early, like cavitation and NPSH, can save time, money and equipment damage in the future.
Choosing the Right Nozzle
All firefighters should be able to identify the type of nozzle that is attached to their hose. This knowledge will help them better understand the nozzle’s operation, maintenance requirements and downfalls. They should also be aware of the different types of flow rates, reaction forces and other special features that each nozzle has to offer.
The fire fighting water pump’s nozzle size should be determined by the most hydraulically demanding area of the building. It should also be based on the number of people who will be on the attack line and their ability to physically handle a particular flow rate for a longer period of time.
Another factor to consider is whether the nozzle will be used for water-based or foam-based extinguishing. A water-based nozzle produces a fine mist that displaces the oxygen in a fire, which will extinguish it. A foam-based nozzle, on the other hand, creates an aerated stream that breaks down into small droplets to quickly cool down and protect personnel.
Choosing the Right Size
A fire fighting water pump has to be large enough to meet the pressure and GPM requirements of the sprinkler system it’s installed in. Engineers rely on core standards like NFPA 20, UL Listing, and FM Approvals to guide their choices.
Flow and pressure are interdependent, meaning that as you increase the GPM, the PSI goes down, and vice versa. The goal is to find a balance that matches the GPM required by the building’s sprinkler hazard level and the system’s longest and most critical pipe runs.
Most pumps operate at a fraction of their rated capacity and are only able to pump water up to around 150% of their rated flow (this is called the overload point). The optimum choice for a sprinkler system would be a centrifugal fire pump that operates at a performance curve between 115% and 135% at the system’s hose demand. This is the best combination of a high GPM and an adequate PSI.