All You Need to Know About Fire Pumps: Types, Applications, Sizing

We know fire protection engineering is a critical element of safety, yet it can be challenging trying to understand all aspects, especially when it comes to fire pump selection. Hence why this blog covers the basic things you need to know about fire pump design, types, applications, and sizing. Here, we'll provide comprehensive information from our experienced professionals and industry experts to help you make informed decisions.

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Fire Pump Working Principle

Pumps are divided into two broad types: positive displacement and centrifugal.

• Positive displacement pumps: These produce flow by capturing a specified volume of water in each pumping cycle before pushing it out of the discharge line. A familiar example of such a pump is the bicycle tire pump.
  Although they create extremely high pressures, they are limited in their flow volume compared to centrifugal pumps. Therefore, they are more specialized and less common in many applications - typically, they are used in fire sprinkler system engineering.

• Centrifugal pumps: The most prevalent type of fire pump generates pressure by spinning water. When the water enters the pump's suction inlet, it is rotated by the impeller and pushed to the edge of the pump, where it is discharged. The centrifugal force created by the impeller yields large water volumes at high pressures.

Common Types of Fire Pumps

These standard fire pumps provide a steady flow of water to fire hoses and sprinkler systems to ensure that a fire is extinguished quickly and safely.

Horizontal Split-Case Pumps

A horizontal split case pump has a distinct design that significantly increases its functionality: the flow is split at the center of the pump housing and enters the impeller from both sides. Hence the name "split-case." Advantageously, the pump can be used with both electric and diesel drivers.

HSPs are known for being reliable, having various capacities in rated flow, pressure, and space, and, most importantly, they are relatively easy to maintain due to their split cases. The only limitation of this type of pump is its size; typically, this kind of fire pump requires the most space/

Vertical Turbine Pumps

Vertical turbine pumps are the only pumps approved by the (The National Fire Protection Association) NFPA 20 to operate under negative suction pressure. They are well-equipped to move large volumes of liquid from natural bodies of water such as rivers and subgrade tanks.

These types of pumps have a turbine-style impeller vertically positioned in a drive shaft assembly, connected to a motor at the surface; thus, it can draw liquids from deep depths and lift them to the surface. Vertical turbine pumps operate with diesel or electric drivers in several capacities and pressures.

In-Line Pumps

In-line pumps are an attractive option when space is limited. They come in two varieties - vertical shafts, which are the most common and are the least expensive to purchase but the most costly to repair, and horizontal shafts (end suction type).

Vertical pump drivers are located directly above the pump. Maintenance and repair of a vertical in-line pump are complex since the electric motor must be lifted off and removed to access the pump, unlike a split-case pump. They are also limited to 1,500 gpm (5,678 L/min) capacity and can only be powered by an electric driver.

End Suction Pumps

End suction fire pumps are an ideal choice for fire pump rooms with limited space as they need less installation space than the traditional horizontal split-case fire pumps. These pumps generally feature a capacity of 1,500 gpm (5,678 L/min), and their discharge outlets are at a right angle to the suction inlet.

They are available with either an electric motor or a diesel engine, and they can efficiently pump through a range of pressures and flows for clean water applications. In addition, installation and maintenance are both simple processes due to their design.

Multistage Multiport Pumps

Multistage multiport fire pumps are high-pressure pumps used in applications requiring multiple booster stages to increase water pressure for fire-fighting systems in industrial and large commercial buildings. The casing is fitted with multiple ports or discharge outlets, each delivering a different pressure level due to the consecutive positioning of the impellers along the horizontal shaft.

They are typically connected to a fire sprinkler system to increase the water pressure in the system as needed to meet the NFPA 13 or other local codes for building fire protection. Multistage Multiport pumps use one driving source, such as an electric motor or diesel engine, to power a series of impellers inside a single casing.

Types of Pump Drivers

Generally, diesel and electric motor drives are the most popular fire pump drivers, although there are others:

• Diesel engine drivers provide a reliable and economical operating system, mainly used in remote locations that don't have access to an electric power supply.
• Electric motor drivers are the most common, requiring minimal maintenance and providing efficiency.  
• Turbine drivers usually work like jet engines for higher capacity and pressure requirements.  
• Hydraulic motor drivers are relatively expensive but offer superior performance and require less energy than most other drivers.  
• Steam drivers are less common but require no electricity or other external fuel source and, therefore, are used as a power source in remote locations.

How to Size a Fire Water Pump?

Follow these steps to select the correct fire pump sizing:

1. Determine the total water flow rate required for the building or site based on the water demand for the fire sprinkler system, hose reels, foam systems, sprinkler tanks, and any other fire protection system or application requiring water.
2. Calculate the minimum flow rate around the system, which is the flow rate required to meet the main fire protection system requirements. The flow rate should meet the pressure requirements of the system's longest and most critical pipe runs.
3. Determine the number of fire water pumps required, usually based on a maximum flow rate for each fire pump.
4. Select the appropriate pump size. Consider the fire pump's: flow rate, impeller size, number of impellers, type of impeller, size of suction line, size of discharge line, and drive.
5. Have the system certified by a third-party inspector. This is important as it will ensure your system complies with local and national codes.

Get a Professional Fire System Sprinkler Design

Fire pumps are an essential part of the fire protection system and come in many varieties and sizes. Properly sizing a fire pump is essential to ensure that the system can meet the system's pressure and flow requirements and that the fire protection system can deliver the necessary water to extinguish a potential fire.

At MNA Quality Consulting, we provide qualified fire protection engineering services, giving you peace of mind that your sprinkler system is correctly sized and installed. Our Calgary fire protection consultants allow us to size fire pumps correctly and ensure your fire sprinkler system meets the relevant regulations.

Don't just trust anyone with your fire protection system — reach out to us today!