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Anonymous Poster

Backflow Prevention

11/14/2010 1:12 PM

Hi, we had a minor accident involving a corrosive chemical. It got past a check valve and into our nitrogen system destroying several brass fittings.

Any ideas on what would do a better job of preventing backflow? Could a pressure regulating valve work? The valve I am thinking about would sense a drop in pressure and close until that threshold is reached again.
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Tornado
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Technical Fields - Technical Writing - New Member Engineering Fields - Piping Design Engineering - New Member

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#1

Re: Backflow Prevention

11/14/2010 4:28 PM

There are several types of backflow preventers, starting with a single check valve, then a double check valve, and finally an RPZ (reduced pressure zone) backflow preventer. I'm not sure what is available in stainless, but at least the downstream check and service valves need to be corrosion resistant.

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PWSlack
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#2

Re: Backflow Prevention

11/15/2010 9:32 AM

Double-block-and-bleed works well: two isolator valves with a third valve locked open to drain from a branch.

Spade-off between flanges downstream of the check valve works even better.

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MrGeneRall
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Location: Austin, TX
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#3

Re: Backflow Prevention

11/15/2010 1:55 PM

Sorry to hear of such a problem.

Kind of curious as to what kind of situtation would lead to such a scenerio.

Were you using N2 to drive a diaphragm pump? or for Oxygen displacement?

You may need to take two steps back and consider the current design of the system in question.

Can you provide any more details of the problem?

I would think that if the N2 pressure were greater than the system which introduced the corrosive chemical, the chance of a backflow could be mitigated.

Please provide more details if possible.

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