I came across a specification requirement I've never seen before.
The specifications called for "sprinkler systems that require a fire pump to meet sprinkler requirements, all sprinkler pipe sizes shall be based on the Pipe Schedule method. This is to provide maximum sprinkler operation when the fire pump is not available, and minimizes the size of the fire pump. This also provides the possibility that with future water infrastructure improvements, the fire pump would no longer be required." A few questions about this - first, if the Pipe Schedule method could be used, wouldn't a fire pump not be necessary in the first place? Second, has anyone ran into something like this before and designed their system that way? For large facilities the only cost savings that comes back with having a fire pump is better pipe sizing. If that goes away, I could see the fire pump being a major cost burden above and beyond what it already is to the owner. Posted anonymously for discussion. Discuss This | Submit Your Question | Subscribe
2 Comments
10/8/2019 10:27:17 am
When sizing fire sprinkler systems piping, I try to optimize the system by increasing pipe size in segments with significant pressure loss to create system 'head-space'. This minimizes pump size and pressure demand requirements on the supplying mains.
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Salvatore Izzo
10/8/2019 11:37:36 am
This specification is flawed for several reasons. First, the fire pump is required because of a pressure deficit based on several design variables. The pump is needed to meet the given sprinkler demand pressure (and flow). If the fire pump is not available, the demand will not be met. The conservatism built into the pipe schedules are not intended to meet such a performance requirement. Second, minimizing the size of the fire pump may be demonstrated by hydraulic calculation only, not by using a pipe schedule design. Third, NFPA 13, Section 19.3.2.3, 2019 edition permits the use of pipe schedule systems in only certain circumstances. And fourth, no one is going to spend the money on a fire pump with the notion that someday it might become obsolete because of water infrastructure improvements.
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