Double piston effect seat design 1

[waleedarafah]

Could you help me on the following query.

Our ball valve seat design is one seat SPE "Upstream" and the other seat is DPE "Downstream" .
My question is the DPE allow back pressure to pass through valve even the valve in closed position in case the second seat is SPE. (See attached PEFS)

 

[LittleInch]

No. What the spe does is allow any pressure build up of pressure in the ball to relieve back into the trap, however with a second valve it doesn't seem to work.
I would have thought this valve should be the other way around as the key issue is not to allow flow of anything into the pig trap.
I

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[waleedarafah]

Thank you Littleinch
Also the second valve is the same, we understand that thess valves shall be in the other way around.
But i need to know if the back pressure "pipeline pressure" down stream the valves can pass the DPE seat or not

 

[LittleInch]

Not if the seat seals. This also applies to any pressure from "upstream".

However if it does then the spe seat will allow fluid to pass onto the next valve without sealing

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Also: If you get a response it's polite to respond to it.