I suspect their use of the term LAMINAR FLOW is being applied too
casually. It actually occurs only at very low flows. In a 1 inch
pipe its maximum is around 1 gpm. I assume the concern was excessive
turbulence (whether real or probably just imagined since listed
assemblies can be much closer).
Roland
On Feb 8, 2007, at 3:13 PM, Thom McMahon wrote:
I believe the distance was 5 pipe dia., this came originally from
those pesky Mech. engineers, and was to allow the turbulence from
the valve to subside, into a more laminar flow, which at the time
was considered necessary for the operation of vane water flow
switches. Since we want to measure any flow (as low as .7 gpm or
less for some MFG.'s) Turbulent flow actually is more likely to
activate the vane switch than laminar flow at those low flow rates,
hence the very short distance from the valves to the FS in the
riser assemblies, and floor control assemblies.
I believe I have correctly re-stated the info given to me by the
Potter rep. at the last convention.
Thom McMahon
Firetech, Inc.
2560 Copper Ridge Dr
Steamboat Springs, CO 80488-2136
Tel: 970-879-7952
Fax: 970-879-7926
----- Original Message ----- From: "Roland Huggins"
<[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Thursday, February 08, 2007 4:00 PM
Subject: Re: WATERFLOW SWITCHES
once upon a midnight dreary, the listing required vane type water
flow switches to be a minimum distance away from the main
drain. Although, if the same switch was part of a listed
shotgun riser assembly, it could be installed much closer to the
main drain. I haven't looked lately.
Truth can be stranger than fiction.
Roland
On Feb 8, 2007, at 11:38 AM, <[EMAIL PROTECTED]>
<[EMAIL PROTECTED]> wrote:
FYI The distance from a fitting or valve is only a "should" not
a shall. There are no UL or NFPA requirements regarding
distance. There are a number of riser assemblies on the market
that put the switch closer than the stated 24" from a valve or
drain. If the switch works during the test after installation
it's a good installation.
Mike Cabral
---- Steve Leyton <[EMAIL PROTECTED]> wrote:
Look at the tech data sheet for the switch. For Potter Signal
products in the installation guidelines ...
Steve Leyton
Protection Design & Consulting
-----Original Message-----
From: Loren Johnson [mailto:[EMAIL PROTECTED]
Sent: Thursday, February 08, 2007 11:06 AM
To: Sprinkler Forum
Subject: WATERFLOW SWITCHES
Forum:
Can anyone direct me to where it indicates that a
waterflow switch for a wet pipe system has to be so
many inches away from the control valve or an
elbow/tee?
I seem to have seen this somewhere before, but now I
am unable to locate it. I thought it was in a pre-
vious edition of 13, but I'm not sure.
Thank you.
Loren Johnson - CFPS, CET
Fire Protection System Consultant
The Hitchcock Company
Peoria, IL
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