Gate valve, wafer parallel slab type 1

[Andrii]

Hello, dear colleagues

For a big crude oil park (a lot of 48” valves) we have chosen gate valves slab wafer type. They are comparatively less heavy and not so big as others. We do hope they are also less expensive.

But. I have found only one manufacturer for this type of valve. And I wonder, maybe there is a reason almost nobody produces them.

Does anybody have experience in using this valves?

 

[racookpe1978]

One problem with wafer valves is repair and line draining (to allow repair of the pipe the valve is attached to.

A flanged gate valve is attached to the flanges on both sides of the valve. Sounds obvious, right? You close the valve, you isolate the oil in the pipe behind the valve.

But consider a wafer valve clamped between two flanges with bolts going across the valve through both flanges - it can ONLY work (isolate the pipe pressure and prevent the oil in the pipe from leaking out or leaking through the valve ONLY IF IT IS ATTACHED TO BOTH SIDES OF THE VALVE.

So how do you work on one of the pipes or on the flanges or on the valve or remove one side of the pipe attached to the valve? You can close the wafer valve but you cannot move it or loosen it or remove either pipe without further isolating both 48 inch pipes on both sides of the valve.

 

[LittleInch]

You can either use threaded lugs or studs if the design allows to prevent this, but as racooke says, most people don't think it is worthwhile, especially at those sorts of sizes.

something else to consider - I recall seeing a safety moment where use of the long bolts to clamp your valve in place can cause real issues with excessive leaking in the event of fire as the long bolts expand much more than the shorter normal studs.

It would be interesting to know if there is any real cost saving once you consider the installation issues, longer stud bolts in most instances and the maintenance difficulties noted above.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[Andrii]

Thank you all.

Safety first, so we have dismissed the idea. We can choose for conventional gate valves (parallel slab type) or triple eccentric butterfly valves.