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Fire pump
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A fire pump usually refers to a pressure-increasing component of the water supply for fixed-place fire suppression systems such as fire sprinklers, standpipes, and foam systems. Fire pumps are also a critical component integrated into fire trucks and fire boats, and serve a similar purpose boosting water supplies for firefighting hose operations.
Description
[edit]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.
Fire pumps, circulation relief valve
[edit]Each pump shall have a circulation relief valve listed for the fire pump service installed and set below the shutoff pressure at minimum expected suction pressure. Exception: This rule shall not apply to engine-driven pumps for which engine cooling water is taken from the pump discharge.[2]
Jockey pump
[edit]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".
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 Archived 2017-10-05 at the Wayback Machine which is being followed throughout India.
References
[edit]
Wikimedia Commons has media related to Firefighting pumps.
- ^ "NFPA 20: Standard for the Installation of Stationary Pumps for Fire Protection". Nfpa.org. Archived from the original on 2011-09-18. Retrieved 2011-12-15.
- ^ https://www.fmglobal.com/assets/pdf/fmapprovals/1319.pdf FM Global, Standards for Fire Pumps
"Chapter 9 - Fire Protection Systems". International Code Council. Archived from the original on 3 November 2015. Retrieved 30 December 2015.
Fire pump
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Introduction
Definition and Purpose
A fire pump is a specialized high-pressure pump engineered to deliver water to sprinklers, standpipes, hydrants, or related distribution systems during emergency fire events.[5][6] These pumps are integral to water-based fire protection setups, ensuring reliable fluid supply under demanding conditions.[1] The primary purpose of a fire pump is to boost system pressure sufficiently to counteract friction losses in piping and elevation gains, thereby achieving the necessary flow rates and pressures for effective fire suppression—typically ranging from 40 psi up to 250 psi or higher depending on the installation.[2][7] This capability is essential in scenarios where static water sources, such as municipal supplies, cannot provide adequate head to reach remote or elevated outlets.[8] Fire pumps find critical application in commercial buildings, industrial facilities, and high-rise structures, where inherent limitations in public water pressure render standalone municipal feeds insufficient for comprehensive protection.[2][5] In these environments, they maintain system integrity by automatically activating upon detection of a pressure drop, often triggered by the opening of sprinkler heads or other demand points, ensuring rapid response without manual intervention.[5][9] Fire pumps are available in various configurations to suit different system needs.[1]Historical Development
The development of fire pumps has roots in 17th-century innovations spurred by urban fires like the Great Fire of London in 1666, which led to manual pumping devices for more effective water delivery beyond buckets.[10] Early hand-operated force pumps, adapted from ancient designs, evolved into 18th-century models like Richard Newsham's 1720 manual pump, capable of delivering up to 400 liters per minute over 40 meters.[11][12] In the 19th century, steam-powered fire engines marked a mechanized advancement, with the first practical steam pumper developed in 1829 by John Braithwaite and John Ericsson in England.[13][14] Horse-drawn models proliferated from the 1840s, including American Silsby units in the late 1800s that achieved 600 gallons per minute, though requiring 6-12 horses and 10-15 minutes to start.[15] Stationary fire pumps for building protection emerged in the early 20th century alongside the expansion of automatic sprinkler systems in high-rises and industrial facilities. The transition from steam to electric and diesel drivers occurred in the 1920s-1930s, with motorized centrifugal pumps standardizing capacities at 400-600 gpm for reliable, fixed installations.[16][17] Key standardization came with the National Fire Protection Association's (NFPA) early efforts, including the 1915 first edition of NFPA 20, which established requirements for stationary pump installation and testing to ensure interoperability and safety.[18] By the 1950s, automatic pressure-sensitive controls on electric and diesel stationary pumps minimized response times, supporting broader fire protection automation.[3] Since the 2000s, stationary fire pumps have integrated with smart building systems for real-time monitoring of pressure and flow via sensors and IoT, enabling predictive maintenance.[19] Electric models increasingly draw from renewable sources like solar or wind-powered grids, reducing emissions in sustainable designs.[20]Types of Fire Pumps
Centrifugal Fire Pumps
Centrifugal fire pumps operate on the principle of converting kinetic energy into pressure through the rotation of an impeller, making them the most prevalent type used in fire protection systems due to their efficiency in handling large volumes of water.[1][21] The design features a volute casing that houses a rotating impeller, typically constructed from corrosion-resistant materials to withstand the demands of fire service. Water enters the pump axially through the suction inlet at the impeller's eye, where it is accelerated radially outward by centrifugal force as the impeller spins, exiting at the periphery with high velocity and converting that energy to pressure within the volute.[22][21] This rotodynamic mechanism allows for smooth, continuous flow without the pulsations seen in other pump types.[1] The working principle is characterized by a performance curve that illustrates the relationship between head (pressure) and flow rate, with head decreasing as flow increases.[21] A key metric is the total dynamic head (TDH), calculated as $ H = h_s + h_f + h_e $, where $ h_s $ represents static head, $ h_f $ accounts for friction losses, and $ h_e $ denotes elevation head; this equation ensures the pump delivers sufficient pressure to overcome system resistances.[22] These pumps are engineered to meet NFPA 20 standards (2025 edition), providing rated flow at 100% capacity with shutoff pressures between 101% and 140% of rated pressure, and capable of handling overloads up to 150% of rated flow at 65% of rated pressure.[23][21] Advantages of centrifugal fire pumps include their ability to achieve high flow rates, ranging from 25 to 5,000 gallons per minute (gpm), making them ideal for demanding fire suppression scenarios.[21] They are suited for continuous duty operations with lower maintenance requirements compared to other designs, thanks to features like dynamically balanced impellers and robust casings that support long bearing life (at least 5,000 hours L-10).[1][21] Certification by UL and FM ensures reliability across a broad range of pressures starting from 40 psi.[21] Specific applications leverage various configurations for optimal performance. Horizontal split-case pumps, with their impeller mounted horizontally and casing split for easy access, are commonly used in buildings requiring high accessibility and a wide range of flows and pressures.[1][22] Vertical turbine pumps, featuring a long shaft connecting the impeller to the driver, are employed for drawing water from below-grade sources such as tanks or wells, complying with NFPA 20 restrictions on suction lift.[1][21] Limitations include suboptimal performance at low flow rates, where efficiency drops and the pump may operate away from its best efficiency point on the performance curve.[22] Additionally, they are susceptible to cavitation if suction pressure falls below the water's vapor pressure, potentially damaging the impeller, particularly with lifts exceeding 15 feet.[22][21]Positive Displacement Fire Pumps
Positive displacement fire pumps operate by trapping a fixed volume of fluid within the pump and mechanically displacing it to create flow, distinguishing them from velocity-based centrifugal pumps through their ability to maintain consistent discharge pressure independent of system demand.[1] These pumps are governed by standards such as NFPA 20 (2025 edition), which outlines requirements for their installation in fire protection systems, though they are less prevalent than centrifugal types due to their specialized nature.[22] Design variants of positive displacement fire pumps primarily fall into two categories: reciprocating and rotary. Reciprocating types, such as piston or plunger pumps, use a back-and-forth motion of a piston within a cylinder to draw in and expel fluid, effectively trapping and displacing discrete volumes.[22] Rotary variants, including gear, screw, and lobe designs, employ rotating elements to capture fluid between meshing components or lobes and force it toward the discharge, providing a continuous but cyclic displacement action.[1] These configurations ensure precise volumetric control, making them suitable for applications where fluid viscosity or pressure consistency is paramount.[24] The working principle of positive displacement fire pumps relies on enclosing a fixed volume of water or suppressant per cycle or revolution and propelling it under pressure, resulting in near-constant discharge pressure regardless of flow rate variations. In piston pumps, for example, the generated pressure $ P $ is determined by the formula $ P = \frac{F}{A} $, where $ F $ is the force applied to the piston and $ A $ is the piston's cross-sectional area, allowing for high-pressure output through mechanical leverage.[25] To mitigate inherent flow pulsations from the cyclic displacement—particularly in reciprocating models—pulsation dampeners are integrated to absorb pressure spikes and deliver smoother output.[26] Key advantages of positive displacement fire pumps include their excellence in high-pressure, low-flow scenarios, where they can achieve pressures exceeding those of centrifugal pumps without significant efficiency loss, and their self-priming capability, which enables operation even when the suction line contains air.[22] These traits make them ideal for handling viscous fluids like foam concentrates without cavitation issues.[1] In fire protection, positive displacement fire pumps find applications in specialized systems requiring steady, high-pressure delivery, such as foam-water and water mist suppression setups, where low-flow rates must maintain consistent atomization.[22] Gear-type rotary variants are particularly common for metering foam concentrates in these contexts.[27] Despite their strengths, positive displacement fire pumps have limitations, including higher mechanical wear on moving parts due to direct fluid contact and friction, which necessitates more frequent maintenance compared to centrifugal alternatives.[22] Flow pulsations can cause system vibrations if not addressed by dampeners, and they require relief valves to prevent dangerous overpressurization during blockages, as their design allows pressure to build indefinitely without built-in limits.[24] Overall, their complexity and limited flow capacity make them less common for general fire pump installations, reserving them for niche high-pressure needs.[1]Fire Pump Nameplate and Certified Performance Curve
Per NFPA 20 (e.g., Section 4.11 in recent editions), the fire pump must have a permanent, corrosion-resistant nameplate including the manufacturer's name, model/serial number, rated capacity (flow in gpm), rated net pressure at that 100% flow point, rated speed, and certification marks (e.g., UL/FM). The nameplate provides the official rated duty point (100% flow and corresponding pressure) but typically does not include full details like churn or 150% values. The manufacturer's certified shop test curve (required by NFPA 20 Section 4.5) is a detailed graph from factory testing, plotting net pressure vs. flow from churn (zero flow) to at least 150% of rated capacity, often with brake horsepower. Key performance envelopes:- Churn (shutoff/no-flow): Pressure typically 101–140% of rated (maximum 140% at rated speed to avoid overpressurization).
- 100% rated flow: Must match the nameplate's rated net pressure.
- 150% rated flow: At least 65% of rated pressure to ensure overload capability.
Key Components and Accessories
Drivers and Controllers
Fire pumps are powered by dedicated drivers that ensure reliable operation during emergencies, with electric motors serving as the most common type due to their compatibility with standard building electrical systems and lower initial costs.[2] These motors must be listed for fire pump service and comply with NEMA MG-1 standards for continuous duty, typically operating at 60 Hz with a service factor not exceeding 1.15 to handle the pump's rated load without overheating.[23] For vertical turbine pumps, vertical hollow-shaft motors are required to manage thrust loads, featuring bearings rated for at least 15,000 hours of life.[23] Diesel engines provide an alternative driver for enhanced reliability in scenarios involving potential power outages, as they operate independently of the electrical grid and achieve high uptime rates, such as 99.9% reliability.[28] Listed for fire pump use per NFPA 20, these compression-ignition engines must deliver a 4-hour horsepower rating at least 10% above the nameplate to account for derating factors like 3% per 1,000 feet of altitude above 3,000 feet or 1% per 10°F above 77°F.[23] Fuel systems require a minimum 12-hour supply at 100% pump capacity, stored in dedicated tanks with at least 1 gallon per horsepower plus 10% for expansion and sump, ensuring uninterrupted operation.[23] While steam and gas turbines are permitted as drivers in niche applications where steam or gas infrastructure exists, they are uncommon due to higher complexity and site-specific requirements.[2][23] Controllers regulate the activation and performance of these drivers, featuring UL-listed designs that enable automatic starting within 20 seconds upon detection of low system pressure via dedicated switches or sensing lines.[23] They monitor critical parameters such as engine speed, oil pressure, coolant temperature, and electrical faults like phase loss or voltage drops limited to 5% during operation, triggering audible and remote alarms for issues including overheating or low battery charge.[23] For diesel-driven systems, integrated battery chargers—powered by AC or the engine generator—must restore full capacity within 24 hours and support at least 12 cranking cycles, with two independent sets of batteries each capable of six 15-second starts at 40°F.[23] Controllers also include manual override options and interfaces for building management systems to signal pump running status or troubles, ensuring sequenced operation without thermal overload protection on electric motors to prioritize continuous fire protection.[23] Selection of drivers and controllers depends on power reliability needs, with electric motors favored in areas with stable utility service to minimize fuel storage demands, while diesel engines are chosen for high-risk sites requiring grid independence and at least 12 hours of on-site fuel.[28] On-site standby generators can supplement electric drivers, with fuel supply requirements per NFPA 110 for emergency systems.[23] All components must be housed in NEMA Type 2 enclosures or better, located within sight of the pump for accessibility.[23]Supervision and Monitoring in Fire Alarm Systems
Fire pump controllers interface with the building's fire alarm control panel (FACP) to provide supervisory signals for conditions that could impair the pump's readiness or operation. These signals are particularly important when the pump room is not constantly attended, as required by NFPA 20 (Standard for the Installation of Stationary Pumps for Fire Protection). NFPA 20 specifies that controllers must transmit remote indications of three primary conditions via separate, supervised circuits:- Pump or engine running — Activates when the pump starts operating, often treated as a supervisory signal to alert personnel of pump activation (e.g., due to system demand).
- Controller main switch off-normal — Indicates when the controller's selector switch is not in the automatic position (e.g., off or manual), which could prevent automatic startup during a fire event.
- Trouble on the controller or engine — A combined signal for various faults, such as controller issues, engine derangements, loss of power (electric pumps), phase reversal/loss, battery/charger failures (diesel pumps), low oil pressure, high temperature, overspeed, or other malfunctions.
Jockey Pumps
A jockey pump is a low-capacity auxiliary pump, typically centrifugal in design and rated between 1 and 10 gallons per minute (gpm), that operates intermittently to maintain system pressure in fire protection setups by compensating for minor leaks or pressure drops when no water is flowing.[29][30] This unit ensures the fire protection system remains pressurized without engaging the larger main fire pump for routine adjustments, adhering to requirements outlined in NFPA 20, Standard for the Installation of Stationary Pumps for Fire Protection.[23] In operation, the jockey pump activates automatically when system pressure falls below a preset threshold, usually set 5 to 15 pounds per square inch (psi) higher than the main pump's churn pressure— with a minimum differential of 10 psi—to avoid overlap and ensure sequential activation.[29][30] It pumps until pressure stabilizes at the upper setpoint, then shuts off, repeating this cycle as needed without a specified limit on starts per hour, unlike the main pump.[31] This setup prevents water hammer and maintains readiness for emergency demands. Sizing of the jockey pump is determined by estimating the system's leak rate, including allowable leakage from piping and normal pressure fluctuations, with capacity calculated as Q_j = estimated leak rate + safety margin to restore pressure within 10 minutes.[29][30] For aboveground systems, this often equates to 3 to 10 gpm or less than the flow of a single sprinkler head; for underground mains, it is the greater of 1 gpm or 1% of the main fire pump's rated capacity (e.g., 15 gpm for a 1500 gpm main pump), per NFPA 20 guidelines.[31][23] The primary benefits of a jockey pump include extending the operational life of the main fire pump by minimizing wear from frequent startups and ensuring the system remains at optimal pressure for immediate response during fires.[29][31] By handling small pressure losses, it reduces energy consumption and maintenance needs associated with unnecessary main pump cycling. Installation typically involves an electric-driven unit with a dedicated controller, separate from the main pump's system, including an isolation valve on the suction side, a check valve and isolation valve on the discharge, and a ½-inch (15 mm) sensing line connected downstream of the check valve to monitor pressure accurately.[30][29] The pump must be listed or approved for fire service use, with churn pressure plus suction pressure not exceeding the system's rated limits to prevent over-pressurization.[31]Circulation Relief Valves
Circulation relief valves are essential safety devices in fire pump systems, primarily designed to prevent overheating in centrifugal fire pumps during low-flow or no-flow (churn) conditions by recirculating a small volume of water back to the pump suction or a safe discharge point. These valves ensure continuous cooling of the pump internals, such as the impeller and casing, when the system demand is insufficient to dissipate heat generated by the pump's operation, thereby avoiding dead-heading where all flow is blocked.[32] According to NFPA 20, the valve must provide sufficient flow to cool the pump at no discharge, typically a small quantity that bypasses excess pressure without significantly impacting system performance.[33] The design of circulation relief valves features pressure-activated mechanisms, often utilizing a spring-loaded diaphragm or pilot-operated configuration to respond automatically to rising pressure.[34] These valves are listed for fire pump service and installed on the discharge line immediately before the check valve, with discharge piping directed to the pump suction, a drain, or the atmosphere to prevent recirculation issues.[33] Sizing follows NFPA 20 guidelines: a nominal 0.75-inch (19 mm) diameter for pumps rated up to 2500 gpm, and 1-inch (25 mm) for those between 3000 and 5000 gpm, ensuring adequate flow without excessive discharge.[35] The pressure setting is calibrated below the pump's shutoff (churn) pressure at the minimum expected suction pressure—typically above maximum suction pressure but well below any main pressure relief valve setpoint—to activate early and maintain safe operation.[32] In operation, the valve remains closed during normal flow conditions but opens automatically when pressure approaches the churn point, recirculating water to protect against heat buildup in centrifugal pumps, which are particularly vulnerable to impeller damage from sustained no-flow scenarios.[36] NFPA 20 mandates their use on all centrifugal fire pumps unless the engine cooling water is drawn directly from the pump discharge, and they are especially critical for diesel-driven pumps with heat exchangers where discharge is piped back to suction.[33] For variable-speed electric pumps, the valve must open at minimum speed to ensure cooling during partial operation. Many designs include test ports or bypass features for verification during maintenance, allowing operators to confirm actuation without full system testing.[37] Circulation relief valves are predominantly automatic in fire pump applications, though manual variants exist for specific non-standard setups; however, standards require automatic operation to ensure reliability without human intervention.[35] Without these valves, fire pumps face significant risks, including rapid overheating that can cause mechanical seal failure, cavitation, and premature component wear, ultimately reducing the system's lifespan and reliability in emergencies.[36] Proper installation and setting prevent these issues, with NFPA 20 emphasizing their role in maintaining pump integrity during churn conditions equivalent to over 1000 gpm capacities where heat generation is pronounced.[33]Design, Installation, and Operation
Sizing and Selection
The sizing and selection of a fire pump begins with a hydraulic analysis of the fire protection system to determine the required flow rate in gallons per minute (gpm) and pressure in pounds per square inch (psi), guided by the occupancy hazard classification as defined in NFPA 13. Light hazard occupancies, such as offices or schools with low combustibility, typically require a minimum design area of 1,500 square feet at a density of 0.10 gpm per square foot, resulting in flows around 150–500 gpm depending on the system area.[38] Ordinary hazard occupancies, like warehouses or light manufacturing with moderate combustibles, use densities of 0.15 gpm per square foot for Group 1 or 0.20 gpm per square foot for Group 2 over similar or larger areas, often yielding 500–1,000 gpm.[39] Extra hazard occupancies, such as those involving flammable liquids or high-piled storage, demand higher densities up to 0.30 gpm per square foot over smaller design areas like 2,500 square feet, potentially requiring 1,000–1,500 gpm or more.[38] If multiple hazards exist, the pump is sized for the highest demand scenario.[40] The 2025 edition of NFPA 20 includes updates to sizing considerations, such as clarifications for variable speed drive pumps and suction conditions.[41] The total head $ H $ required from the pump, expressed in feet, is calculated as $ H = \frac{P}{0.433} + Z + h_f $, where $ P $ is the required pressure at the most remote outlet in psi, $ Z $ is the elevation difference in feet from the pump to that outlet, and $ h_f $ accounts for friction losses throughout the system.[42] The factor 0.433 converts psi to feet of head, as 1 psi equals approximately 2.31 feet of water head.[43] Friction losses $ h_f $ are computed using the Hazen-Williams equation:
where $ Q $ is flow in gpm, $ C $ is the pipe roughness coefficient (typically 120 for new steel pipe or 100–140 for others), $ D $ is internal pipe diameter in inches, and $ L $ is pipe length in feet; this empirical formula is mandated by NFPA 13 for water-based fire protection systems.[38] These calculations ensure the pump delivers adequate net pressure at the rated flow, with a minimum of 100% churn (no-flow) pressure up to 150% of rated flow per NFPA 20 requirements.
Key selection factors include matching the pump's performance curve to the system's demand curve, where the operating point intersects at or above the required head and flow without exceeding 150% of the pump's rated capacity to maintain efficiency and reliability.[42] Redundancy is incorporated by pairing the main fire pump with a jockey pump, which automatically maintains system pressure against minor leaks (typically sized at 1% of the main pump's flow and 10–40 psi above normal pressure) to prevent unnecessary main pump startups.[44] Driver type selection depends on power availability: electric motors for sites with reliable utility power, diesel engines for backup or remote locations to ensure operation during outages, as specified in NFPA 20.[45] Centrifugal or positive displacement pumps may be chosen based on the application's flow characteristics.[2]
Hydraulic modeling tools, such as software programs like Elite FIRE or FHC, facilitate these calculations by simulating pipe networks, applying NFPA formulas, and generating compliance reports for complex systems.[46][47] Spreadsheets can handle simpler cases, but professional software is recommended for accuracy in larger installations.[48]