Raised face vs flat face lugged valves

[p6g2p6]

Hi,
Are lugged valves available in raised or flat face? It seems that every lugged butterfly valve that I come across has a flat retainer ring, but then the lugs are offset, such that the lugs would not come in contact with the flange when they are bolted together. This to me seems that it would be considered as raised face, since the clamping force would only be applied at the sealing face. Do lugged valves exist where the lugs come in contact with the flange, thus creating a clamping force that is distributed across the whole bolt circle diameter?
Thanks.

 

[TugboatEng]

If the valve achieves its class rating as is why would anything need to be changed?

 

[p6g2p6]

TugboatEng,

I'm just curious because I'm wondering if lugged valves can be installed between flat face cast iron flanges. I'm early on in my career, but I've only seen lugged butterfly valves where surfaces of the lugs does not come in contact with the flanges, which I would assume you wouldn't want to install between cast iron flanges because you would risk bending them.

 

[GBTorpenhow]

I'm not aware of a lugged/wafer butterfly valve that would work well with cast iron flanges, a typical cast/ductile iron lugged or wafer butterfly is set up for installation between CL150 RF or FF steel flanges, and the lugs aren't the full width of the valve by design.

I agree that you wouldn't want to use a lugged or wafer butterfly with cast iron flanges. I am not sure even a short pattern double flanged butterfly is available for use with flat faced cast iron if it has a resilient seat/liner as these tend to wrap around into the flange sealing area to serve as a gasket. With cast iron you really want a full faced sheet gasket and two full, flat faced flange surfaces. There are 'long pattern' flat faced flanged butterflies that should work with cast iron flanges.

https://www.nibco.com/nibco-products/valves/butterfly-valves/fc-2765/

 

[p6g2p6]

GBTorphenhow,
Thank you for the advice! This is what I thought, but wanted to confirm. Just out of curiosity, do you know why lugs aren't designed to be the full width of the valve? Is there a benefit to this?

 

[GBTorpenhow]

I am guessing it has to do with making sure that the bolting forces are applied only to the actual sealing face. Squeezing the lug itself with a flange on either side doesn't help seat the gasket. Basically the same reason that flanges have raised faces. You want high stresses (low contact area) on your sealing area/element.

 

[mk3223]

do you know why lugs aren't designed to be the full width of the valve? Is there a benefit to this?

Simply, the fabrication of the butterfly wafer type valve is intended to reduce the metallic material on the valve body but achieve the valve function as required.