Fire Water Pumps are an essential part of your sprinkler system, increasing the supplemental water pressure to meet demand. Choosing the right one requires careful consideration and discussion with fire safety professionals.
Annual fire pump flow tests are performed to determine whether the pump is sized correctly. Considerations include churn, rated and peak loads.
Horizontal Split Case
Suitable for use with either electric or diesel driven engines, horizontal split case pumps are best suited to high-capacity deluge systems in buildings, plants and yards. They offer a higher flow range than end suction centrifugal fire water pumps, which typically cannot be used for flows above 1500 gpm. Their durability comes from the fact that they feature a double-suction impeller design, which reduces hydraulic thrust forces and vibration in the pump piping.
They also have an axially split casing, meaning the flange where the pump case splits is in the same plane as the pump axis. This allows for easy access to the pump bearings, shaft seal and impeller for inspection and maintenance. Unlike end suction pumps, these pumps can be easily disassembled and serviced without disturbing any piping connections or the engine or motor.
Due to the large flanges, larger impeller and overall larger size for the split housing seal joints, these pumps have a slightly higher initial cost than end suction fire pumps. However, their durability and ease of maintenance can help offset this. Cooling towers and other industrial processes that require the exchange of high volumes of water at low to mid pressure often use these types of fire pumps. They are also commonly used in irrigation applications to deliver water to crops and turf.
Vertical Turbine
A vertical turbine fire pump is a type of split case pump that uses an electric motor located above ground connected via a long vertical shaft to the impellers at the bottom of the pump. These pumps are commonly used in sprinkler, chemical mitigation and hydrant systems for fire suppression in industrial and commercial facilities.
The electric motor of a vertical turbine fire pump is powered by water that is drawn into the can or suction barrel by gravity. The resulting pressure is then used by the first stage impeller to create suction. This process is similar to how a rotary positive displacement pump works.
Once the liquid leaves the diffuser bowl, it travels up a shaft with internal sleeve bearings that are lubricated by the water that moves through them. The shaft is supported at three- or five-foot intervals by the sleeve bearings to reduce stress and vibration in the system.
The motor is then attached to the shaft and used to drive the impellers in a circular motion. The rotation of the impellers creates an upward force on the fluid and it is discharged through a discharge pipe to your system.
TKFLO’s vertical turbine fire pumps are designed to meet the stringent requirements set by NFPA 20, Underwriters Laboratories and Factory Mutual Research Corporation. They are available in a wide range of capacities, from end-suction models up to 5,000 gallons per minute. They also feature modular bowl assemblies, heavy-wall bowl bearings and oversized shafts for greater reliability.
Electric Motor-Powered Engine
Fire pumps rely on reliable drivers to push water through the fire-hose nozzles used to fight fires. Traditionally, this has meant electric motors or diesel engines that have been proven to be reliably powerful enough to handle the load.
Electric motor-powered engines can be powered by AC power, but they also can use lithium batteries that offer longer running times than conventional batteries, as well as instant starts and no thermal runaway. This is especially important in large spaces such as stadiums, where it can be difficult to reach the vehicle for emergency battery disconnects.
Like other electrical equipment, electric motor-powered engine fire pump systems must be tested and inspected on a regular basis. In most cases, this is performed by the property’s own maintenance personnel, but if they are not trained on how to properly test the fire pumps, Koorsen can perform these inspections and tests, which decreases the risk of a mistake that could potentially damage the pumps or shut them down.
For installations with more than one fire pump, a secondary power source is required, whether it’s an alternate utility feed or an on-site generator. The secondary power supply must be sized to carry the locked rotor current of all of the fire pumps at their full rated capacity, as well as any associated loads. If a backup generator is used, the system must be able to transfer from the normal utility to the generator without opening overcurrent devices.
Diesel Engine
Diesel engine-driven fire water pumps are more reliable than electric motor driven fire pumps. However, they have a higher capital cost. They are used for unattended fire water pumping applications such as sprinkler fire extinguishing systems in industrial and mining enterprises, engineering constructions and high-rise buildings.
They are also good for fire hydrant fire water supply system in oil & gas refineries, petrochemical plants and airports. They are usually located in a separate fire pump house to facilitate refueling operations and the ventilation of combustion exhaust. Diesel fire pumps must be installed in environments that comply with NFPA 20, the engine manufacturer’s requirements and their own specifications.
The fire pump diesel engine must be properly sized by a calculation program and the exhaust system piping must be insulated, guarded and kept short to minimize heat transfer into the pump room and other locations. Failure to do this can result in damage to the equipment or insufficient available power when needed during a fire event.
A common mistake people make when using fire pumps is not providing adequate emergency power to the fire pump controller and diesel engine from an on-site generator. This can cause the pumps to fail at full load and not meet NFPA 20 requirements during a fire event. It is important to make sure the power requirements are clearly defined and understood.