Pardon my ignorance, but can you elaborate on the term "plated disk?'
Sounds like a legitimate issue, and having a description or examples would
help me in writing specifications. Thanks!
Christopher Born, P.E.
Director, Fire Protection Engineering
Clark Nexsen, P.C.
Norfolk, VA
----- Original Message -----
From: <[email protected]>
To: <[email protected]>; <[email protected]>
Sent: Thursday, January 27, 2011 2:06 PM
Subject: Re: Butterfly vs. Gate valves
You don't want to get me started on this subject - but here goes anyway.
I
will try to be nice. First, there are poor quality products out there in
both categories. I will relay an experience of mine.
One of our sprinkler systems needs to be modified for a design change.
The
butterfly in the riser was closed but water was still at the remote point
of the sprinkler system. The 2-inch drain was wide open and flowing but
could not keep water out of the system. To do the work required closing
the valves out on the main to allow replacing the riser valve. I have
that
riser valve under my desk and am using it as a foot rest. It was 6 years
old at the time of failure. It might have failed before then and we
didn't
know it because it hadn't been called upon to perform. It failed because
it had a plated disc. Any butterfly valve with a plated disc is designed
to fail. Galvanic corrosion between the plating and the base material is
the cause. They are listed this way but I don't know why. We won't
install one. This one had holes eaten in the disc that allowed so much
water to flow that a 2-inch drain was overwhelmed.
We had this same kind of valve in our underground and interior fire
mains -
the plated disc kind - that failed after only a few years of service.
Again, holes eaten in the disc. It cost a couple million dollars to
replace all 110 underground and 24 interior valves. We single-sourced the
replacement valve to get a good one. 20 years later most of them are
still
drop tight.
Gate valves can have their problems too. Depending on the quality of
water
the inside can crud up on you and cause the valve to not seal well. This
happens progressively over time. If in a riser, generally the 2-inch
drain can handle the flow by. But, eventually, it will not seal well
enough and the valve will have to be replaced.
In the end you get what you pay for. If you want a butterfly valve in
the
riser specify a high-quality one and definitely not one with a plated
disc.
If you want a gate valve, most are probably ok but expect them to leak a
little after being in service but not to the point of overwhelming the
2-inch drain, at least for their normal expected lifetime. Of course,
all bets are off if you get a poorly made one.
John Hoffman P.E. | Fire Protection Engineer | Facility Engineering
Services, KCP, LLC - Burns & McDonnell Engineering | National Nuclear
Security Administration's Kansas City Plant | Operated by Honeywell FM&T |
2000 E. 95th St | Kansas City, MO 64131 | ph 816-997-7213 |
[email protected]
From: "Chris Cahill" <[email protected]>
To: [email protected]
Date: 01/27/2011 09:29 AM
Subject: Butterfly vs. Gate valves
Sent by: [email protected]
Anyone have evidence or reasoning why a BFV would be more prone to leaking
past the seat when closed than a GV.
I hadn't heard this before. But in the last week or so have heard from
several independent sources the same concern. I'm try to figure out if
there is something to it or passed down urban legend.
I've never had a real preference. BFV a little cheaper and tampers are a
little easier to deal with and take up a little less space in our typical
valve rooms. But if they leak more often maybe I can form a preference.
Chris
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