FIRE FIGHTING PUMPS
PUMPS
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’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 to be 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 revolution pump 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 mainly 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.
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.
hey 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
Vertical Turbine Pump
A vertical turbine pump is the only type of pump allowed by NFPA 20, Standard for the Installation of Stationary Pumps for Fire Protection that can start with negative suction pressure or take water under a lift condition such as from a below grade source such as a river or subgrade tank. These pumps can be used with raw water sources such as ponds, lakes, and rivers. Vertical turbine pumps come in a wide range of capacities and pressures, and they can be used with diesel and electric drivers.
In-Line Pump
In-line pumps are useful where space is limited. These can be driven by both a vertical or horizontal shaft (end suction type). Vertical shaft types, which are the most common, have the driver located directly above the pump. These are typically one of the less expensive units and take the least amount of space but, they are also one of the more expensive to repair. Pump maintenance and repair can be difficult because the motor must be lifted off and removed to gain access to the pump, unlike a split-case unit. With these pumps, the suction flange and discharge flange are on approximately the same plane. In-line pumps have a limited capacity of typically no more than 1,500 gpm (5,678 L/min), and they can only be used with an electric driver which limits their potential applications
End Suction Pump
An end suction pump has a discharge outlet perpendicular to the suction inlet. These pumps are typically limited to a capacity of approximately 1,500 gpm (5,678 L/min). Compared to horizontal split-case fire pumps, they are more compact and require less installation space in a fire pump room where available space is a concern. End suction pumps can be used with either an electric driver or a diesel driver.
Multistage Multiport Pump
Multistage Multiport pumps use a single-driver that can be either an electric motor or a diesel engine that connects to a pump with multiple impellers in series in a single casing driven by a horizontal shaft. The casing has multiple ports, or discharge outlets, delivering different pressures - each port has increased pressure from the consecutive series impellers.
Using multiport fire pumps could result in:
Fewer pumps required Less pipe work and fewer valves, as one pump could eliminate the need for some control valves and pressure reducing devices No requirement for water storage tanks on intermediate floors Lower structural loads and associated costs as only one pump may be required Energy conservation because less electricity and/or fuel will be consumed. Less pollution is also a potential benefit. Ultimately there are several different pumps that can be used in a variety of situations. When your system demand exceeds what your water supply can provide it’s time to look at what a fire pump can do to help bridge that gap