Fire Pump Design And Installation Considerations

When the water supply is insufficient to maintain the pressure required to keep the water flowing to every sprinkler head in the building, fire pumps are an essential part of the sprinkler system. 

The fire pump intakes are linked to either an on-site tank or reservoir or subterranean public water supply piping to deliver water at a higher pressure to the sprinkler system risers and hose standpipes. Along with considerations of Fire pump design and installation, also consider to buy fireproofing accessories

When the water pressure in the system falls below a predetermined level, fire pumps are turned on. This might occur, for instance, if one or more sprinkler heads are subjected to heat beyond the threshold at which they were intended to function or if additional firefighting connections are opened, which lowers mainline pressure.

This page will give an overview of the many types of fire pumps in use today and explain the elements taken into consideration when choosing a pump, even if the design and installation of fire pumps must be done by qualified fire protection professionals.

Does a Fire Pump Get Needed for Your Sprinkler System?

There are sprinkler systems without need for a fire pump. The majority of commercial buildings, however, have those installed since the pressures required to guarantee sufficient flow to every component of the system typically surpass the capabilities of a typical public water supply. 

A fire pump is always needed when the sprinkler system is connected to a static water source.

The National Fire Protection Association (NFPA) 13 Standard for the Installation of Sprinkler Systems has numerous references to fire pumps because they are an essential component of so many sprinkler systems (e.g., pump room requirements, testing, etc.).

The National Fire Protection Association (NFPA) 20 Standard for the Installation of Stationary Pumps for Fire Protection, on the other hand, contains the specifications that are particularly relevant to the actual design and installation of fire pumps. 

Furthermore, NFPA 22 Standard for Water Tanks for Private Fire Protection has further installation and maintenance guidelines for onsite tanks that may be included with your system.

Many Kinds Of Fire Pumps And Their Uses

Pumps For Positive Displacement

By continuously sucking a defined volume of water into the internal chamber of the pump and compressing it before releasing it via the discharge valve, positive displacement pumps generate flow pressure. 

These pumps are less frequent since they are usually exclusively employed with foam-water or water mist systems, and their flow capacity is more constrained than that of centrifugal pumps.

Centrifugal Pups

The most prevalent kind of pump utilized in commercial buildings nowadays is the centrifugal fire pump. 

With an internal impeller, this kind of pump uses centrifugal force to generate pressure. When the pump is turned on, water flows into the impeller’s core, where it is forced through the valve by forceful rotation of the impeller at a high speed, which creates pressure.

There are various varieties of centrifugal pumps; these are discussed here along with some factors to take into account when choosing a fire pump for your structure.

Selecting the Appropriate Kind of Pump Driver

The two most widely used types of fire pumps nowadays are those powered by diesel engines and electric motors.

When feasible, electric-driven pumps should always be used instead of hydraulic ones because electric motors are more affordable and smaller, requiring less mechanical components. They also have less of an adverse effect on the environment. 

Electric-driven pumps can be powered by a generator, utility connection, or another source that has been authorized by your AHJ.

When the electricity grid is unstable or unable to support the load of an electric-driven pump, diesel-driven pumps are usually utilized. They are also utilized in situations like these, when a generator is not available for emergency electricity.

Diesel-driven pumps are subject to additional rules compared to electric pumps because of the extra processes involved in managing the fuel system, cooling, exhaust, vibration, etc.

How to Size Fire Pumps?

Typically, the sprinkler system design process determines the required fire pump size. The first step in constructing a sprinkler system is to perform a hazard analysis in order to identify the occupancy classifications. 

These are based on the anticipated fire risks in various building sections. The number of sprinkler heads needed is determined by this analysis. 

Additionally, while the quantity of sprinkler heads fed is a crucial consideration for sizing a fire pump, the size needed is determined by the area of the sprinkler system that requires the greatest hydraulic demand, which may or may not be the area with the greatest number of sprinkler heads.  

Finding the system’s most hydraulically demanding area involves a very complicated computation that needs to be carried out by trained fire safety specialists. Among the variables used to calculate it are:

  • Distance: The amount of water that needs to go laterally to reach the farthest sprinklers depends on the footprint of the building.
  • Elevation: The number of floors in the building must be considered by the designer. Higher floors will require greater pressure to deliver water to sprinklers because of gravity.
  • Classification of Occupancy: It’s critical to identify any risks within the building that would need using more water to put out a fire, as well as their location. For this reason, it is necessary to perform the hazard analysis prior to fire pump sizing. 

Because quantities expressed in GPM cannot be easily converted into PSI, correctly designing the fire pump and fireproofing accessories also helps. 

The quantity of water that flows through a sprinkler system is measured in gallons per minute (GPM), but fire pumps are usually rated using pounds per square inch (PSI), which is a pressure range.

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