Brad,
That section of -291 has been in the document at least since the
'88 edition. It used to be section 2-9, and was relocated and
renumbered in a subsequent edition.
*Ken Wagoner, SET
*Parsley Consulting***
*350 West 9th Avenue, Suite 206
*Escondido, CA 92025-5053
*****Phone 760.745.6181*
Visit our website <http://www.parsleyconsulting.com/> ***
On 6/20/2014 8:45 AM, Brad Casterline wrote:
Whaaaa...? Where has 291 been all my life?!?
I think I'll propose adding that if one has neither a gage OR a pitot, how
to do it with a comb and a ruler.
-----Original Message-----
From: Parsley Consulting [mailto:[email protected]]
Sent: Friday, June 20, 2014 10:20 AM
To: [email protected]
Subject: Re: to Pitot or not to Pitot?
Roland,
Excellent description of what the intent of -291 describes in
section 4.9. As our mutual friend Joe Hankins used to say "Don't
measure with a micrometer when you're going to cut with a chainsaw."
*Ken Wagoner, SET
*Parsley Consulting***
*350 West 9th Avenue, Suite 206
*Escondido, CA 92025-5053
*****Phone 760.745.6181*
Visit our website <http://www.parsleyconsulting.com/> ***
On 6/20/2014 8:04 AM, Roland Huggins wrote:
NFPA 291 says use a Pitot but IF a pitot is not available then a butt
gauge will provide APPROXIMATELY the same results. Unless one broke the
bloody thing, if one doesn't have a pitot I suspect they shouldn't be out
there. Nonetheless, the velocity pressure in the discharge stream equals
100% of the pressure whereas the gauge pressure is just the normal pressure
(that being total pressure minus velocity pressure) prior to the water
outlet but it shouldn't be seeing the pressure loss associated with the
water going through the outlet. Since the pitot reading is recommended to
limit the velocity (not exceeding 30 psi on the pitot), it may not be a lot
of difference. Combining this with the exacting precision associated with
many pitot readings, it could be the TC felt it was close enough (like using
hand grenades).
Roland
Roland Huggins, PE - VP Engineering
American Fire Sprinkler Assn. --- Fire Sprinklers Saves Lives
Dallas, TX
http://www.firesprinkler.org
On Jun 20, 2014, at 6:05 AM, Brad Casterline <[email protected]>
wrote:
Yesterday's flow test thread, along with talk of "because that is the way
we
have always done it" reminded me of something I have been wanting to post
since last Christmas-- I was 'calculating' flow tests and looking for any
info that might help and I discovered something that surprised me, that
being NFPA 13 (2007) A.23.2.1 (2). For the flowing hydrant we can either
attach a second gage or use a pitot. I have always used a pitot because
that
is the way the person who taught me had always done it.
No question here, just thought I'd throw this out there on a Friday
morning.
thanks,
Brad Casterline, NICET IV
Fire Protection Division
FSC, Inc.
P: 913-722-3473
[email protected]
www.fsc-inc.com
Engineering Solutions for the Built Environment
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