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Facility and plant managers know that the goal of a successful fire suppression system is to provide constant, reliable water pressure and flow to the critical sprinklers that comprise the system. In the field, strategically designed fire suppression systems are configured around a site's piping, layout and specific needs-from every square foot of a building to each source of friction loss in the piping. All aspects must be considered for effective fire suppression planning, design and installation.
The White Tanks Regional Water Plant in Surprise, Ariz., which had been planned for operation since 2007, was designed to serve 167,000 homes and treat 80 million gallons of Central Arizona Project water daily. In 2008, a plan and specifications were sent to local providers and contractors. Fire system specialists teamed up to meet the requirements using a standard 1,500 gpm split case fire pump with three inline multistage booster pumps designated to serve as the plant's domestic water and jockey pump.
During finalization of the system's design and pump specifications, a problem was discovered-there had been a small miscalculation in the original design. The amount of NPSHA for the pumps was not sufficient for them to work properly. In addition, the layout of the site was a bit misleading, so the end result would have starved the pumps and caused internal damage and an unreliable fire suppression system.
With the project breaking ground, the layout already constructed and a deadline to meet, the project engineer, general contractor and engineering firm put their ideas and knowledge into motion. The goal was to use the available storage tanks and provide a custom built pump system around what was already onsite. The objective was an effective, functioning fire pump system.
The previous design was completely scrapped and a new concept was hatched. With low NPSHA, choices were limited. Because a fire suppression system was involved, the limitations were even greater. However limited, the choices were simple:
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Reduce friction losses by increasing the pipe diameter.
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Lower the pump suction below that of the water supply and create positive head pressure.
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Use an approved fire pump that requires less NPSHA.
The issue was solved with the following plan:
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Select a different style pump designed to handle low NPSHA applications.
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Lower the suction inlet of the pump below that of the water supply.
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Reduce losses.
 Simply put-the solution was to position vertical turbine can pumps underground. In addition, by using a listed fire pump, the group was able to design and fabricate cans in which the pumps could be mounted. By positioning the cans underground and mounting the pumps into them, the pumps had plenty of positive suction pressure to meet the necessary requirements.
The redesigned system incorporated a fire vertical turbine pump as the main fire pump and three vertical turbine pumps set on variable frequency drives to provide domestic water boost. The system was redesigned from scratch, fabricated and delivered to be fully operational before the plant start-up. This project was unique because vertical can pumps are not commonly used in Arizona for fire pump systems. However, they were the best solution for the application requirements.
In terms of the safety and security of fire suppression systems, the smallest miscalculation can cost lives. A great deal of thought should be given to calculating the most efficient fire suppression system for a specific facility's needs and requirements. Every fire suppression system must also meet all codes set by the National Fire Protection Association.
Michael Marquez is an account manager with Quadna, Inc., which engineers, fabricates and services mechanical systems that move fluids and gases for industrial applications. Tags: Pumps , Vertical Turbine Pumps , Water and Wastewater
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