Brad,
Your suggested practice makes an overwhelming assumption that by opening
and closing the hydrant quickly that the flow will stabilize enough
during that momentary opening and give your equation a proper reading of
the available flowing pressure. While your proposed solution does not
address a possible closed or damaged valve in the supply (as others have
suggested) it _*directly*_ contradicts the procedures in NFPA 291 §4.5.7
which notes that the water should allowed to flow for a sufficient time
to clear all debris and foreign substances from the stream.
Now that I've shared this I'll also note that you're welcome to make a
public input to the -291 committee Aut-Pri, for their consideration, as
is any member of the public. Speaking as one who has had any number of
PI's rejected over the years I caution you to be prepared for a similar
response.
I would also share the wisdom a mentor of mine a long time ago shared
with me regarding conducting water flow tests at a hydrant. I believe
his quote was "don't measure with a micrometer when you're making cuts
with a chainsaw."
sincerely,
*Ken Wagoner, SET*
*Parsley Consulting
500 West Mechanic Street
Harrisonville, Missouri 64701-2235*
*Phone: (760) 745-6181 *
*Visit the website
<https://linkprotect.cudasvc.com/url?a=http%3a%2f%2fwww.parsleyconsulting.com%2f&c=E,1,Y5zKJKPEh1mBEBqSR-VE9cUKl5y-eyP8BpvmE_5j9ZqW2eJbNphYzrCMBZ-2YuX6d-RRkHI4gQ1FV-cvOeCfRC58uZS9NiToZv2mx7909oCqLvCW_n5hDHeK&typo=1>*
On 9/7/2022 11:34 AM, Brad Casterline wrote:
I like seeing how far water shoots out the hydrant nearest my base of
riser.
Say that is 10 ft, and the butt is 3 ft high. From The Law of Falling
Bodies I know if I drop water straight down from 3 ft it will be going
v=SQRT(2gh) when it hits the ground, and the Time of Flight, t=v/g.
v=(2*32.2*3)^.5=~14 ft/s.
t=14/32.2=.43 s.
If the water goes straight out 10 ft in ~half a second it is going 20
ft/s.
If the butt is nominal 2.5", smooth and well rounded, (like yours truly):
((2.5/24)^2)*pi=~.034 ft^2, times .9=.031 ft^2,
times 20 ft/s=.68 ft^3/s,
times 7.48 gallons per cubic foot, times
60 seconds per minute= 305 GPM.
So if all I can get is a Purveyor Representative with a hydrant wrench
and authorization to quickly, fully open the hydrant and just as
quickly, fully shut it down, I'll take it!
Brad Casterline
**
*From:* Greg McGahan <[email protected]>
*Sent:* Tuesday, September 6, 2022 9:10 AM
*To:* Discussion list on issues relating to automatic fire sprinklers
<[email protected]>
*Subject:* [Sprinklerforum] Re: [EXTERNAL] Hydrant flow tests
How many flow tests have you seen that underperformed due to a closed
valve, broken valve (appeared to be open), disconnected piping that
was never reconnected etc?
Personally? Too many to not be concerned about solely relying on models.
My two cents worth (adjusted for inflation).
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