I understand the limits for what is allowed, but how do you actually determine what air pressure your sprinkler systems needs to be set at?
Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe
2/24/2022 06:18:02 am
2/24/2022 08:05:45 am
By the specific type of valve you are installing for the system type needed. In the past it was a rule of thumb ratio of the clapper size (air) vs the incoming supply (water) but most (if not all) the MFG's have charts specific to their valve.
2/24/2022 08:08:24 am
Like Alex said Its an equipment supplier question. Each dry valve will have a different set of requirements. Make sure you have a properly sized air compressor too. That can be manually calculated or work with the compressor supplier to figure out the fill times and sizing information.
2/24/2022 08:19:00 am
Agree with all of the above. The low-diff ratio valves actually use water to hold back the piston that trips the valve. In years past, a general rule of thumb was 5:1; that is, 40psi of air would retain 200psi of water, 30psi of air would hold back 150psi of water, etc.
2/24/2022 08:22:58 am
Agree based upon the discussion for a dry-pipe sprinkler system. For a supervised pre-action sprinkler system, a different air pressure level must be met.
2/24/2022 08:30:29 am
I read and then re-read the question several times before I understood it was regarding a dry system. Then I saw a squirrel so by the time I got back to it, everyone else very thoroughly answered.
2/24/2022 08:32:39 am
i've never had a problem getting an engineer at my favorite Fire Sprinkler Compressor Manufacturer to check my design for me
2/24/2022 09:26:10 am
NFPA does have a default requirement:
2/24/2022 10:22:36 am
Knowing (at installation) that you want water to reach the inspector's test opening at a certain amount of time, you set the cut-off pressure (of the air maintenance device) at the maximum point (above the recommended dry valve differential ratio) wherein you'll meet that time constraint upon operation of the ITV (with system pressure at its cut-off maximum). Set the cut-in pressure within the most comfortable margins between the dry valve trip point and air maintenance cut-off point.
Leave a Reply.
Subscribe and learn something new each day:
Top May 2023 Contributors
Get 100 Days of Free Sample Questions right to you!
PE PREP SERIES