Fire protection for high-rise buildings includes specific rules for fire pumps.
In contemporary America, fire rates and fire deaths are trending downward due to stronger fire codes, greater public education, widespread use of smoke alarms, requirements for sprinkler systems, and other factors.
In 1974, annual fire deaths in the U.S. were estimated at 12,000. In 2012, they were at their lowest point at 2,855 according to a 2017 report issued by the U.S. Fire Administration.
As the predominant standards-setting organization in the U.S. for fire protection, the National Fire Protection Association (NFPA) has developed more than 300 detailed and complex consensus codes to establish the highest levels of fire defense. Redundancies within each code and across codes are intentional to account for all conceivable scenarios in order to ensure maximum protection.
For instance, these closely related codes, NFPA 13: Standard for Installation of Sprinkler Systems; NFPA 20: Installation of Stationary Pumps for Fire Protection and NFPA 101: Life Safety Code, are commonly applied to high-rise buildings. Tall buildings pose unique fire protection challenges due to population, longer and more complicated exit routes and other risks associated with increased building height.
The good news is that there has also been a downward trend in high-rise fires over the last few decades. According to a 2016 report by NFPA, U.S. fire departments responded to an estimated average of 14,500 reported structure fires in high-rise buildings per year from 2009-2013. That is down from the 2005-2009 reporting period in which high-rise structure fires averaged 15,700 annually. This trend appears to track with growing use of fire prevention systems including wet pipe sprinklers, changes in building codes and standards and improvements in fire-resistive construction. Due to these and other safety measures, fires in high-rise buildings are much less likely to spread beyond the room or floor of origin, according to the NFPA report.
Reliable, code-compliant fire protection systems begin with the consulting engineer or designer, tasked with meeting the overall project objectives and selecting the necessary systems for the project. NICET-certified (National Institute for Certification in Engineering Technologies) professionals who are knowledgeable in each component of the system understand how each component will affect the selection of another component, and how they will all work together.
Without question, the fire pump is one of the most critical pieces of equipment inside a building. NFPA 20: Installation of Stationary Pumps for Fire Protection protects life and property by providing requirements for the selection and installation of pumps to ensure that systems will work as intended to deliver adequate and reliable water supplies in a fire emergency.
By setting uniform standards for both fire pump design and fire protection system design, there is greater safety for both building occupants and emergency responders. The NFPA 20 Technical Committee on Fire Pumps consists of experts representing fire departments, fire equipment manufacturers, listing authorities, government, academia, engineering, insurers, associations, unions and other groups who undertake the years-long process of reviewing current codes and updating codes every three years. During the interim periods, technical bulletins are issued as warranted.
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.
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 unless some very stringent criteria are met to ensure safe operation of all pumps. 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 new requirement 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 22.214.171.124 states that no more than three pumps shall be allowed to operate in series as a part of a series fire pump unit.
Locating fire pumps in series in the same pump room provides additional options for firefighters to pump water into building sprinkler systems and reduces the complexity of fire department connection. In addition, it simplifies fire pump maintenance and restores fire pumps in the event of an emergency during maintenance.
Protection for first responders
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 safely respond and assess pump operation during a fire in accordance with NFPA 20 standards. When responding to an alarm, firefighters go immediately to the pump room to make sure equipment is operating properly. When pump rooms are on multiple floors, it increases the risk for firefighters, who must take elevators or stairways to access pump rooms, which can put them in harm’s way if they encounter smoke, the fire itself or other issues.
The code still permits vertical staging, but only if the NFPA 20 provisions that protect firefighters are incorporated into the design of the fire protection system.
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 NFPA 20 Technical Committee on Fire Pumps is currently considering new provisions for the 2019 update, including further protection for high-rise buildings. The committee is assessing the need for a common means to remotely access fire pump controller data; currently, each manufacturer has a proprietary means. Also, as construction practices evolve and buildings become ever taller, codes become obsolete and refinements must be made to them.
Brian Buscher is a global marketing manager for Xylem’s A-C Fire Pump brand with expertise in centrifugal pump systems for fire suppression in industrial and commercial facilities. He is a principal member on the NFPA 20 Technical Committee on Fire Pumps. Buscher holds a bachelor’s degree from Northeastern Illinois University. Any comments/opinions made are the author’s own and not those of NFPA.
Original article: http://www.plumbingengineer.com/content/nfpa-20-2016-impact