Time Calculations
Time Calculations
(OP)
A requirement for hospitals keeps coming up. Inspectors are asking us to ensure that water will get to the area in time for a pre-action system. Often there is quite a bit of distance from the pre-action valve, air-compressor, etc, and the hazard area being protected.
How can I calculate the time for water to reach the hazard in these type of systems?
How can I do it utilizing software?
What can I solve this with fundamentals?
Thanks in advance.
How can I calculate the time for water to reach the hazard in these type of systems?
How can I do it utilizing software?
What can I solve this with fundamentals?
Thanks in advance.





RE: Time Calculations
Do not think it is there.
are you talking about a dry pipe?? and if so the time does not kick in till a certain gallonage system.
RE: Time Calculations
I know this isn't a nfpa13 requirement but rather a an additional requirement from the public health department of my local state.
Any thoughts?
RE: Time Calculations
Travis Mack
MFP Design, LLC
RE: Time Calculations
1. is the requirement in wrinting/ code???
2. what is the requirement??
RE: Time Calculations
What state is this requirement in?
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Fire Sprinklers Save Firefighters’ Lives Too!
RE: Time Calculations
I researched the code, in 2002 in 13 section 7.4.5 the states that the period of time for water to reach the most remote sprinkler is 60sec. for each 400ft of common feed from the main, from the time a heat response element responds. Section 7.4 pertains to combined dry and preaction systems.
From what I understand,the only way to do predict this reliably is with software. (as mentioned by TravisMack)
I wonder if there is a way to determine this from first principles. This could help verify software simulations and submittals.
thanks and sorry for the delay again
desnov
RE: Time Calculations
Unlikely u have one of these things installed, u most likely have a preaction system, so the time thing does not apply.
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Fire Sprinklers Save Firefighters’ Lives Too!
RE: Time Calculations
Don Phillips
http://worthingtonengineering.com
RE: Time Calculations
I'll just take your word for it...
RE: Time Calculations
I also looked up the software and got a quote, the price was somewhere in the range of 5000 USD!
Thanks to all again
RE: Time Calculations
Used to be in Ohio, when they were operating under the Ohio BOCA Fire Code, all dry and preaction systems had to meet the 60 second rule regardless of size. Not all jurisdictions knew about this, but the state fire marshal certainly did, but it was absolutely there and part of law having been adopted by the state legislature.
I had one job near Napoleon, Ohio where I had huge troubles with a 250 gallon dry system. One of those with a static pressure of 90 psi, residual of 20 while flowing 520 gpm. Would work, would calc but when it came to meeting the 60 seconds you had to be real cautious.
Is BOCA still around?
RE: Time Calculations
RE: Time Calculations
RE: Time Calculations
If single interlock preaction systems are designed properly, water will enter the sprinkler piping prior to any sprinkler head operation. NFPA 13 essentially considers the system to be wet with no 60 sec requirement as long as water has filled the system prior to sprinkler head operation.....the inevitable air pockets and minor delay prior to water discharge is ignored by NFPA 13 for the single interlock designs.
Double interlock systems and Combination systems (preaction & dry systems) do have the minimum time requirements discussed on this forum; however, the requirements are different for each.
Sections 7.3 & 7.4 are relatively clear, but you must make sure you apply the minimum time requirements depending on the appropriate system.
RE: Time Calculations
You are correct, I've should have been more clear with this in the post.
Thanks everyone for the comments good feedback.