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NFPA 20 says that if the test header supply main is more than 15 feet from the fire pump, it must be increased one pipe size or hydraulically calculated based on 150 percent of the rated pump capacity.
What form does the hydraulic calculation take? Are we trying to determine if the main can flow 150 percent of the pump rating without running out of pressure? How low a pressure would be acceptable? Is this a one time calculation to size the main or is this a calculation that must be performed during each annual fire pump test? Thanks in advance. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe
11 Comments
Dan
2/15/2023 07:11:30 am
The appendix in the 22' Ed [A4.22.3.4(3)] has a worksheet for this scenario. As the calculation is based off a number (the pump rating) x a % of the capacity of the pump, one calculation is all that is required, and the test must meet this minimum. I've never done this before either...
Jesse
2/15/2023 08:06:21 am
Dan's last comment about making up a placard is an excellent idea. I never thought about how helpful this would be.
Franck
2/15/2023 08:24:13 am
It is always good to give explanations for future reference. That avoids a lot of questions and misunderstanding.
Anthony
2/15/2023 03:55:52 pm
I agree with the others, Dan has this down.
Glenn Berger
2/15/2023 08:46:37 am
I like the placard suggestion made by Dan above. This would be in addition to additional required documentation that is required to be provided.
Mike Morey
2/15/2023 09:07:03 am
I made a spreadsheet for this based on the annex form, whenever we run into one of these I have our guys run it and then put a note on the drawing that sizing is not increased per hydraulic calculation with a safety pressure of X. Ironically I've always said do the calculation because I've literally never had one fail, until a few months ago when i finally found a pump that it didn't work and we did have to do the up-size. That was a very small/low pressure vertical inline.
Kamran Khalid
3/28/2023 03:07:39 am
Can i also get the spreadsheet. I also need it for a project. You can email me. My email is kamranqa@hotmail.com
Alan Barnhizer
4/25/2023 09:21:57 am
I would like to see your spreadsheet as well. Could you share it with me?
Robbie Jacobs
8/10/2023 11:50:30 am
Hello Mike. I know you have been bombarded for this I see, but can I get a copy of your spreadsheet?
Richard H
2/16/2023 11:38:34 am
Mike, Any chance I could get a copy of your spread sheet? I'm still struggling here. Thank you sir.
Andy Peter
4/19/2023 09:13:42 am
The spreadsheet from the annex *generally* makes sense to me. But I cannot reconcile the calculation for required Pitot Pressure P = (Q/29.83CD^2)^0.5 and the table and sample calc that shows the required pitot pressure as 18. Leave a Reply. |
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