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NFPA 20 permits the demand for a suppression system to be between 90% and 140% of a fire pump's rated capacity (NFPA 20-2019 4.10.1 and Annex A.4.10.1). The pressure demand must always be less than the pressure supplied by the pump's performance curve along this range.
Does this concept apply to standpipes? For instance, could a 750 gpm pump provide 1,000 gpm demand for standpipes since it would be running at 133% of its rated flow? If it can be done, is it good practice? Posted anonymously for discussion. Discuss This | Submit Your Question | Subscribe
4 Comments
Max
8/9/2019 06:48:27 am
Yes, a 750 gpm pump could supply a 1,000 gpm standpipe demand. The demand is between 90% and 140% of the rated flow of the fire pump.
Ernie Yonkers
8/9/2019 10:44:40 am
Short answer is it's within the standards. I've done it where we could only run a 6 inch line to the building for pump suction
Nic
8/9/2019 11:46:42 am
The FPH essentially tells you this is the way to size your fire pump. See page 15-96 of the 20th edition of the FPH, example 1. The example sizes a 1000 gpm pump to meet a 1400 gpm demand.
Mark H
8/11/2019 05:06:07 pm
Available pressure will be less when flow is above the rated GPM so need to review pump curve to confirm standpipe flow calculations are meeting top of standpipe PSI requirement. Leave a Reply. |
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