A fire pump is any type of purpose-driven pump used within a fire protection system. It can be driven by diesel engines, electric motors or even steam and is used to provide increases in water pressure to meet the design requirements of a fire protection system. Fire pumps do not create a water supply. Instead, they create pressure from an existing water supply, such as a city supply line or a storage tank, by converting mechanical energy into hydraulic energy.
Fire pumps are necessary when the water supply available does not generate the necessary hydraulic pressure required to meet demand of a fire protection system such as automatic sprinklers and standpipes, or even foam systems. An example would be a high-rise building where the pressure from a city supply line is not great enough to overcome gravity to reach the top of the building. In this instance, installing a fire pump is done to provide a boost to get the necessary pressure to the top. It is important to remember to have a steady supply of water so that the fire pump may operate correctly.
When it comes to best practices for fire pump design and installation, the National Fire Protection Association (NFPA) 20 Standard for the Installation of Stationary Pumps for Fire Protection provides the guidebook. NFPA 20 provides guidance for fire pumps and their installations but does not provide listings and defers to the authority having jurisdiction (AHJ) as the entity with the final say on installations. The AHJ could be the local fire chief or it could be the insurer—it depends on locale.
With regard to listings, groups such as Underwriters Laboratories (UL) and Factory Mutual (FM) provide UL Listings and FM Approvals on products that meet their testing requirements along with their own individual publication standards, UL448 and FM1311. NFPA 20 does not provide listings or approvals but acts as the guide for best practice. If a fire pump has the UL and FM stamp of approval, the manufacturer has gone through the most stringent requirements to be able to provide their pumps for fire protection, giving peace of mind that the pump will operate when it is needed.
NFPA 20, UL and FM provide guidance on the basic requirements fire pumps must meet to be considered as such. Each fire pump must be tested and meet the following requirements before it can be shipped, with a certified factory test curve being provided.
The first requirement is to have a rated duty point, which consists of the rated flow (gallons per minute [gpm]) and the rated pressure (pounds per square inch [psi]). Second, the fire pump must be able to meet 150% of the rated duty gpm while maintaining at least 65% of the rated duty point pressure. Third, the dead head, or churn pressure (pressure at no flow), must not be more than 140% of the rated duty point pressure. It should be noted that FM also requires a constant rise to shut off, which means the pump pressure must always be increasing as pump flow is reduced.
Finally, the driver of the fire pump, whether it is an electric motor, diesel engine or steam turbine, must be sized to meet the full horsepower demands of the fire pump, even if it means flowing beyond the 150% required duty point. The best way to ensure that the driver is sized correctly, and conforms to UL and FM requirements, is to review the certified factory test curve.
Look at the horsepower curve on the factory-certified test report and ensure that the power curve peaks and then begins to fall. This peak represents the highest amount of power the pump requires and the driver must be sized to meet that requirement. If the power curve is continuing to rise, the pump has not been tested to the full requirements of UL and FM, and the motor could be undersized and in violation of UL and FM.
An example of these requirements would be a fire pump UL Listed and FM Approved for 1,000 gpm at 100 psi, using an electric motor. The 150 psi at 65% point would be required to flow at 1,500 gpm while maintaining a minimum pressure of at least 65 psi. The 140% churn pressure must be less than 140 psi at 0 gpm. The pump curve (Image 1) shows a constant rise to shut off from the rated point to churn. The horsepower curve shows a peak of 86 brake horsepower (BHP) at 1,600 gpm, signaling that pump power peaks at 160% and requires a 75-hp electric motor. Many UL fire pump motors allow for a 1.15 service factor, so for this instance, a 75-hp motor provides 86.25 BHP.
Overall design and operation of fire pump installations have not changed much in the past few decades, save for some innovation on controls and other incremental improvements. However, recent developments in the industrial internet of things (IIoT) space have led to offerings that are changing the information users can glean from the fire pump and the entire fire protection system, leading to safer, more informed systems.
Up until recently, users only knew if the fire pump was on from a remote alarm but had no idea what it was actually doing. Was it flowing water or running at dead head? Was overall flow increasing over time in a fire event or had it plateaued, signaling the fire had been contained? How often was the pressure maintenance (jockey) pump running, and was there a potential leak in the system? What is the pump room temperature and is the system at risk of freezing?
Recent weather events in Texas caused many systems to freeze and break, leading to costly replacements—temperature monitoring and alerts could have helped with early action and prevention.
These were all unanswerable questions before IIoT remote monitoring solutions came to the forefront for fire pump systems. Now they are readily available, making for a more informed fire protection manager.
Fire pumps are used to increase the pressure of water sourced from a municipal underground water supply piping network, or a static supply (e.g., tank, reservoir, lake). A fire pump is a centrifugal- or positive displacement- pump that has been tested and listed by a third-party testing and listing agency, such as UL or FM Global specifically for fire service use. The main standard that governs fire pump fixed-place installations in North America is the National Fire Protection Association’s NFPA 20 Standard for the Installation of Stationary Fire Pumps for Fire Protection.[1]
Fire pumps are powered most commonly by an electric motor or a diesel engine, or, occasionally a steam turbine. If the governing model building code requires backup power independent of the local electric power grid, a fire pump using an electric motor may utilize an emergency generator when connected via a listed transfer switch. Fire pumps installed on fire trucks and boats are powered by the engine of the vehicle/vessel.
Utilizing a control panel with pressure sensors, fire pumps automatically start when the pressure in the fire sprinkler system drops below a pre-designated threshold. Given the incompressibility of water, fire suppression system pressures drops significantly and quickly when one or more outlets open. Examples would be fused (opened) fire sprinklers, fire hose valves connected to a standpipe, or automatic control valves opened by release panels.
Fire pumps are utilized when determined by hydraulic calculations that the existing water supply cannot provide sufficient pressure to meet the hydraulic design requirements of the suppression system. This usually occurs if the building is very tall, such as in high-rise buildings (to overcome hydraulic head losses created from elevation differences), in systems that require a relatively high terminal pressure at the fire suppression outlets (to provide sufficient water droplet penetration of a fire plume), or in systems that require a large discharge of water (such as storage warehouses). Fire pumps are also needed if fire protection water supply is provided from a static source which provides little or no pressure. Some situations may be compounded by all of these factors, requiring large water supplies and powerful fire pumps.
Common types of fire pumps used for fire service include: horizontal split case, vertical split case, vertical inline, vertical turbine, and end suction
A jockey pump, also known as a pressure-maintenance pump, is a small pump connected to a fire suppression system near the fire pump and is intended to maintain pressure in a fire protection piping system. These pumps recover pressures lost from gradual, slow pressure declines in a system due to temperature changes, trapped air escapement, or very small leaks. The jockey pump is essentially a portion of the fire pump’s control system. A jockey pump is sized for a flow less than one sprinkler in order to ensure a system pressure drop significant enough to start the main fire pump. Jockey pumps are typically small multistage centrifugal pumps, and do not have to be listed or certified for fire system application. The control equipment for jockey pumps may however carry approvals. Jockey pumps should be sized for 3% of the flow of the main fire pump and to provide 10psi more pressure than the main fire pump (As per Code IS 15105 : 2002)
In the United States, the application of a jockey pump in a fire protection system is provided by NFPA 20. They are inspected per NFPA 25 “Inspection and Testing of Water-Based Fire Protection Systems”.
Fire pumps are an essential part of many water-based fire protection systems. They are used to increase the pressure (measured in psi and bar) of a water source when that source is not adequate for the system it’s supplying. These are commonly found in buildings that tend to have a high-pressure demand such as high-rises or storage warehouses. This blog will review the different types of fire pump options available to designers.
There are many types of fire pumps available. It is important to select the correct type of pump for the installation project to avoid excessive costs, and to avoid excessive pressures that might damage your system. If all the factors are not taken into consideration it could result in a pump installation that does not achieve the necessary pressure requirements which could require a new pump tobe installed.
There are two main categories of pumps: positive displacement and centrifugal.
Positive Displacement Pumps
Positive displacement pumps are characterized by a method of producing flow by capturing a specific volume of water per pump revolution and pushing it out through the discharge line. A bicycle tire pump is an example of a positive displacement pump we commonly see. Positive displacement pumps create very high pressures but have limited flow volume compared with centrifugal pumps. These are not as common because they have a specialized use, primarily with water mist and foam-water systems.
Centrifugal Pumps
Centrifugal pumps are the most common fire pumps and are used with most systems. With centrifugal pumps, pressure is developed principally by the action of centrifugal force or spinning. Water in centrifugal pumps enters the suction inlet and passes to the center of the impeller. The rotation of the impeller, in turn, drives the water by centrifugal force to the rim where it discharges. Centrifugal pumps can handle large volumes of water while providing high pressure boosts.
The following are different centrifugal type pump configurations:
Horizontal Split-Case Pump
With a horizontal split-case pump, the flow is split and enters the impeller from opposite sides of the pump housing. As the name implies, this is a pump installed with a split casing that can be opened for pump maintenance access and is connected to the driver by a horizontal shaft.
They are very reliable, come in a wide range of rated flow and pressure capacities, are easy to maintain due to their relatively easy split-case access, and can be used with both electric and diesel drivers. However, these also typically need the most space of all types of fire pumps.
In India, the pump manufacturers generally adhere to the TAC (Tariff Advisory Committee) guidelines, although pump manufacturers also obtain listings with UL or FM Global. For the purpose of installation & maintenance of fire-fighting pumps, Bureau of Indian Standards has published IS 15301 which is being followed throughout India