There is no sudden pressure drop with the old "Angle drain Globe Valves"
since they are slow open and close. The newer test and drain assemblies with
90' lever action ball valves could cause a sudden pressure drop, but water
being basically non-compressible anyway, we're not talking a lot of movement
here. In thirty years, I've seen broken vane type flow switches, but in
every case it was not the installed location, but what just happened to try
and flow past it. Rocks, baseballs, nuts and bolts from MJ connections
someone left in the pipe, or my all time favorite a 1/2" ratchet wrench with
the 11/4" socket still on it. (Don't go thereabout flushing! Yes they were
flushed, and we typically found these items after a fire or broken pipe,
from a forklift or something.) The socket wrench was from we believe a tie
in for a new building done a year before about 200LF down the main. (By
Others)
Thom McMahon
Firetech, Inc.
2560 Copper Ridge Dr
Steamboat Springs, CO 80488-2136
Tel: 970-879-7952
Fax: 970-879-7926
----- Original Message -----
From: "Ron Greenman" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Friday, February 09, 2007 9:23 AM
Subject: Re: WATERFLOW SWITCHES
Since you can only use a vane switch in a wet pipe, and since there is
no sudden inrush I think the concern was more with being too close to
the main drain where there would be a sudden pressure drop that could
pull the vane backwards, either damaging the mechanism or pulling the
vane off the shaft.
On 2/9/07, George Church <[EMAIL PROTECTED]> wrote:
Sure you weren't thinking of a DPV or deluge?
There's not a sudden inrush of water above a Alarm check.
glc
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Bill
Minkel
Sent: Thursday, February 08, 2007 6:39 PM
To: [email protected]
Subject: RE: WATERFLOW SWITCHES
I have been told that when the flow switch is too close to an alarm valve
the sudden flow can damage or tear off the vane. Just what I was told
once,
notta clue if it's a valid concern
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Ron Greenman
at home....
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