Guys,
I have not been following this one with too much interest because I have
no experience with it but I am driven to make the following suggestions:
1) It sounds as though you are looking for a valve to seal gas against
dust and grit. And you want it tight. I can not believe you will ever
find such an animal. The closest thing I can think about that might come
even close to work is a diaphragm valve where a rubber diaphragm is
pressed against the top of a wier to effect a seal. If there is not too
much dirt between the wier and the diaphragm, the dirt can be fully
engulfed by the rubber and effect some sort of seal.
2) The only other thing that seals tight is a soft seal against a squeaky
clean seat or two perfectly clean metal seats ground in and lapped to
match each other. Dirt simply means "no seal"
3) I would approach it differently. Why don't you create the conditions
first for a realistic valve to work.
4) I would consider installing two valves, even three if necessary, one on
top of the other. The top one would hold back the dust and grit and the
bottom one would be used for tight sealing of the gas. The top one could
be a butterfly or some fairly ordinary valve suitable for holding back
dirt. Before closing the bottom valve I would ensure that the top one is
closed and then find a way of cleaning the seat of the bottom one before
operation. Perhaps you could blast a stream of gas into the space between
the valves. The moment it is clean you could slam the bottom (gas sealing
valve) shut. You might also be able to arrange the pipework between the
two valves so that the little bit of dirt that does get through the top
valve does not fall on the seats of the bottom one. Maybe two elbows or
something.
5) To open this arrangement, open the bottom one first and then the top
one.
6) Somehow grease does not sound like a good idea to me. Dirt loves to
stick to grease so I think a valve that needs sealant in dirt service is
not a good idea. I would first try the rubber diaphragm valve or a hard
dry teflon seat on a smooth surface as a sealing mechanism for the bottom
valve. Perhaps a ball valve or a teflon coated plug valve. Perhaps even
a teflon coated butterfly valve or a steel butterfly on a hard teflon
seat.
Have fun
Gordon Reddek
"Paul Bowers" <pbowers@pipingdesign.com>
21/03/2004 02:20 AM
Please respond to PipingDesign
To: <PipingDesign@yahoogroups.com>
cc:
Subject: Re: [PipingDesign] Plug Valve
When you say "gas", I assume you mean non-liquid.
If this is true, your incoming stream would be a dirty gas that contains solids, and you have no control over the quality of the incoming gas. Is this correct?
Maybe some other listmember has a solution. If not, I'll send it along to some R&D types I know.
Paul
> Dear Mr Paul,
> The cyclone separator is in the main gas line which enters our
complex. It
> is necessary to remove these dust particles as the gas enters to Gas
> trubines and Process stream further. The purging frequency depends on
> quality of supplied gas. These days the purging is necessary to be
operated
> to remove the dust at least twice in a 8 hour shift.
> To provide more clarity, the arrangement is as below:
> The valve is located just at the bottom of the cyclone separator
(which
> separates dust from gas). We have provided double valve(4" Plug-metal
seated
> and lubricated) to take care of these operations, One always kept
open
> other used for operation, but still end up both passing. Presently we
need
> to inject the lubricant frequntly to arrest this passing. It is not
> practical to inject the sealant everyday. Hope the elite group here
helps
> out.
> Just a thought .. that if the type of valve used is right, then, comes
> addressing the quality of the manufacture too..
> with regards,
>
> >From: "Paul Bowers" <pbowers@pipingdesign.com>
> >Reply-To: <a href="/group/PipingDesign/post?postID=uIFTGJTmLq311Y0o4yehwZdIHwQCFAMlqJq4eGkK9-5T6GmW06v2L7wNtEVhX8UoX93aLpM9wp1idRZDHKKSfMQs">PipingDesign@yahoogroups.com</a>
> >To: <PipingDesign@yahoogroups.com>
> >Subject: Re: [PipingDesign] Plug Valve
> >Date: Sat, 20 Mar 2004 07:42:32 -0500
> >
> >Is periodic purging ever required during operation? I'm thinking
about a
> >duplex arrangement.
> >
> >Paul
> >
> >
> >----- Original Message -----
> >From: "Mohamed Bharuk M." <m.mohamedbharuk@saipem-india.com>
> >To: <PipingDesign@yahoogroups.com>
> >Sent: Saturday, March 20, 2004 7:25 AM
> >Subject: RE: [PipingDesign] Plug Valve
> >
> >
> > > i think u can go for pinch valve( other thanplug valve), because
these
> >are two valve used in abrasive flow conditions.
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[Non-text portions of this message have been removed] Received on Tue Mar 23 19:12:00 2004
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