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Fire pumps are an essential component of water-based fire protection systems. It is vital that they are designed and installed properly, otherwise fire protection systems may not function correctly in the face of a fire emergency. And nowhere is the reliability of fire pumps more critical than high-rise buildings, where the evacuation of the building occupants may not always be feasible if a fire breaks out.
The 2016 edition of the NFPA 20: Standard for the Installation of Stationary Pumps for Fire Protection includes new rules that specifically address fire pumps installed in high-rise buildings, with the intent of standardizing fire pump design in these types of structures to ensure an appropriate level of reliability. Among the new requirements are updated provisions for fire pumps arranged in series.
Elevating fire protection The construction of high-rise buildings around the world has been on the upswing in recent years, with skyscrapers stretching to ever-dizzying heights. The world’s tallest building, the Burj Kahlifa in Dubai, stands at 2,716 feet, and the Jeddah Tower, currently under construction in Saudi Arabia, will reach 3,280 feet upon its completion in 2020.
When buildings exceed 400 to 500 feet, higher floors are often beyond the pumping capacity of fire departments, which could result in loss of life or property in the event of a fire. Taking that into account, the NFPA 20 Technical Committee on Fire Pumps developed specific provisions regarding the fire pump and water supply arrangement. Under the new requirements, even if a single piece of equipment becomes impaired, the full fire protection demand of the building can still be met.
One of the most significant changes in fire pump design for high-rise buildings is that fire pumps operating in a series can no longer be located on different floors. The practice of vertical staging — placing the second and third fire pump in series on higher floors —requires that the discharge pressure from the lower pump be sufficient enough to feed the pumps on the higher floors. Consequently, if the fire pump at the lowest level fails, the rest of the fire pumps in series will also fail for lack of adequate suction pressure.
Under the new NFPA 20 provisions, fire pumps in series must be installed in the same pump room. This modified fire pump design increases the reliability of the overall fire pump operation. When the pumps are located on the same floor, failure of a lower level pump will no longer result in cavitation and damage to the higher-level pumps that it feeds. In the updated arrangement, if the first pump in series fails, there would still be significant enough pressure to the other pumps in series to pressurize the system. NFPA 20 220.127.116.11 states that no more than three pumps shall be allowed to operate in series as a part of a series fire pump unit.
Additional advantages More reliable fire pump operation isn’t the only reason for requiring fire pumps in series to be in the same pump room. The new requirement also ensures firefighters can respond and assess pump operation during a fire in accordance with NFPA 20 standards. In addition, it simplifies fire pump maintenance and restoring fire pumps in the event of an emergency during maintenance. It also simplifies fire pump testing, which results in lowered testing costs.
Most importantly, locating fire pumps in series in the same pump room provides additional protection to firefighters by reducing fire department connection complexity and providing additional options for firefighters to pump water into building sprinkler systems.
When multiple pump rooms are acceptable Although there are considerable benefits to requiring fire pumps in series to be housed in the same room, the NFPA 20 Technical Committee acknowledges that there are exceptions. The 2016 edition of the NFPA 20 clarifies five conditions under which fire pump units are permitted to be in separate pump rooms:
· Arranging fire pumps so that all pumps operating in a series can be manually stopped or started from all pump rooms housing the series fire pumps
· Displaying the suction and discharge pressures from all pumps operating in series in all pump rooms housing the series fire pumps
· The presence of alarms and signals that sound in other pump rooms for all pumps that are part of the series fire pump unit
· Standard compliant interconnect control wiring between the controllers in different pump rooms
· A standard compliant pump room communication system
The readiness and reliability of fire protection systems is critical — particularly in high-rise buildings. The clarified criteria for fire pumps arranged in series in the latest edition of NFPA 20 helps ensure these types of pump arrangements are installed correctly so they can communicate as intended — and ultimately avoid potential pump failure or damage.
Brian Buscher is a global marketing manager for Xylem’s A-C Fire brand with expertise in centrifugal pump systems for fire suppression in industrial and commercial facilities. He has served as alternate on the NFPA 20 Technical Committee on Fire Pumps for the last three years. Buscher holds a bachelor’s degree from Northeastern Illinois University. Any comments/opinions made are the author’s own and not those of NFPA.