I haven't had any experience doing site calculations before, but I'm curious how it works from a practical standpoint. Fire Flow is required by the International Fire Code here locally, and there's guidance (albeit not formally adopted) in Appendix B of the IFC for a total demand. Additionally, there's hydrant spacing requirements for any particular building, and guidance on how far the hydrants can be from a building.
In order to determine how the hydrants are fed (dead-end vs. looped and size of pipe), are there specific flow and pressure amounts that each hydrant has to be calculated at? Is it similar to a standpipe calculations where each hydrant has to have a specific flow? I'm not performing the design work myself, but I'm just curious how that is typically done and pipe size determined. Posted anonymously for discussion. Discuss This | Submit Your Question | Subscribe
11 Comments
Hector R
5/6/2020 11:54:48 am
Yes, it's done in a similar way as standpipes, hydrants will require 1500 GPM at 20 PSI.
Reply
Nick
5/6/2020 11:58:01 am
Where does the 1,500 GPM per hydrant come from? Am I missing that somewhere?
Reply
Mike
5/6/2020 12:27:24 pm
Piping size is Chap. 7 of NFPA 24.
Reply
Jesse
5/6/2020 12:55:03 pm
Good question. Its not dissimilar to any other volume calc you would do for automatic sprinkler design. I guess the process would depend on which software suite you're using. For a program like AutoSPRINK its pretty simple, but it starts with the fire flow requirement in your local code.
Reply
Franck
5/7/2020 10:49:33 am
1500 gpm per hydrant?
Reply
Jesse
5/7/2020 12:23:29 pm
Absolutely. I spent 19 years as a career firefighter before fire protection engineering. I could count on one hand the number of hydrants that didn't flow at least 1500-gpm. Right now I'm looking at flow test data that flows 86 static, 85 static @ 1007 gpm. You don't think that's not flowing way more than 1500-gpm as the flow curve progresses?
Reply
Bill
5/7/2020 05:40:09 pm
Keep in mind NFPA 13 is for the hose stream allowance, in addition to the sprinkler demand. It has no bearing on the fire flow requirements for a hydrant. The IFC or NFPA 1 give the minimum flow requirements.
Reply
Jesse
5/7/2020 12:24:47 pm
That was meant to say 86 static, 85 residual @ 1007 gpm
Reply
Shaikh
5/8/2020 04:56:44 am
Even i have concern on pressure requirement for hydrant.
Reply
Jesse
5/8/2020 07:38:27 am
Shaikh - I'd look at that specification a little deeper. 20-psi is always our benchmark minimum residual so we don't collapse a main or pull a draught from the suction of a pump. I would speculate that the 100-psi minimum is along the lines of "must maintain a minimum static pressure of 100-psi. So 100-psi static with our rated flow somewhere at a lower pressure, and system not to have a residual pressure lower than 20-psi.
Reply
Muhammad Jawad
12/14/2020 12:48:10 pm
JESSE: How to find out the Gpm of fire system? let's say we have 6 hydrants in one system & 15 in another.
Reply
Leave a Reply. |
Free SignupSubscribe and learn something new each day:
CommunityThank You to Our Top
October '20 Contributors!
Your PostThe ToolkitSprinkler Designer or Engineer?
Get all of our tools, including the Sprinkler Database, Friction Loss Calculator, Fire Pump Analyzer and more: Filters
All
Archives
January 2021
Daily
Daily discussions are open-ended fire protection, fire alarm, and life safety questions submitted anonymously for the benefit of sharing expertise and learning from other perspectives. Anyone can submit a question here:
Exam Prep2020 PE Prep Guide
(Available Now!) PE Prep Series
(Available Now!) 2020 PE Prep Series
Current Leaderboard (Click to enlarge) PE Problems
Visit July-October for daily Fire Protection PE Exam sample questions.
Solutions are posted the day after posting. Comment with your solutions, questions or clarifications. Please note that questions posted are unofficial and in accordance with NCEES rules are intended to be similar to actual exam questions, not actual exam questions themselves. |