Wafer type butterfly valve

[NDS_21]

Hey
Greetings!
I'm in a confusion regarding something I read on internet. Can anyone explain me how a wafer type butterfly valve safeguards against bi-directional pressure differential to avoid any back flow in systems that have been manufactured for uni-directional flow?
I mean I know wafer type are designed with this purpose only but I don't get that how is this accomplished. So it would be great if I receive some explanation.
Thanks in advance.

 

[LittleInch]

Nope. Read that four times and still can't work out what you're on about. A sketch or a bit more explanation would help.

If something is preventing back flow then there will be a pressure difference.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[mk3223]

Do you mean that the "uni-directional flow" is for the process flow control purpose, and the "bi-directional pressure differential" for blocking flow purpose?
Consult with your valve manufacturer for how it works.

 

[NDS_21]

I read some of the information which related to wafer type butterfly valve on online website.They provided following things on their website:
A wafer butterfly valve's function is to retain a seal to protect against dual-directional pressure differential in the flow of fluid. In other words, the wafer version of butterfly valves was designed to hold a tight seal, safeguarding against bi-directional pressure differential in order to avoid any backflow in systems that have been manufactured for uni-directional flow.
This is accomplished by using a tightly fitted seal, such as an O-ring, gasket, precision machined, along with a flat valve face on the downstream and upstream sections of the valve.

When I read this things i don't get any idea from this information.So it would be great if I receive some easy explanation related to this information.
Thanks in advance.

 

[LittleInch]

Basically it means that they have designed the valve to work equally well in sealing flow in either direction through the valve by not having angles or wedges or lips in the sealing face and instead having a flat disc and then the sealing surface pressures against it.

they usually give you some sort of sectional view of the seal face if you dig deep enough.

In general, AFAIK, you are really only looking at the more simple concentric centerline butterfly valves for this type of sealing. the offset valves are uni directional in sealing.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[NGiLuzzu]

See also, for instance:

• thread408-435592 within this Forum;​

•

https://youtu.be/0tnFqy-lOaM

Of course, as long as the face-to-face dimension is sufficient to realize the desired valve trim design, the valve body ends style (wafer, lug, butt-weld or double flanged) has nothing or little to do with the internal flow and pressure features…

Hope this helps,​

’NGL​

 

[NDS_21]

Thanks to make things clear in my head.

 

[gerhardl]

Yes but no. The valve-world is wide and a multitude of BFL valves, for instance double eccentric valves for water, even in larger dimensions, are constructed for tight sealing in both directions.