Low cost butterfly valves without the rubber lining

[p6g2p6]

Hi,
I am looking for a 24" butterfly valve for a low to medium pressure service. Every valve I have been quoted has been the resilient seated style with the rubber lining extending out onto the flange face. I'd prefer a valve with no rubber on the flange faces, however it seems that the only valves of that style (high performance) are extremely expensive and have ridiculous lead times. Should I keep looking or am I wasting my time trying to find a cheaper butterfly valve with steel flanges? Also, why is it that the cheaper ductile and cast iron butterfly valves only come with the rubber lining? The valve we are replacing is a double flanged ductile iron butterfly valve and there are full face gaskets installed so I am assuming that it is not rubber lined. This valve is 50 years old, but are these not common anymore?

 

[LittleInch]

Define "low to medium pressure". My low might be your very high and vice versa.

What's the issue exactly?

Is it actually flanged or a wafer design?

 

[GBTorpenhow]

You are maybe looking for an AWWA C504 "seat-in-body" type design? Try Mueller, Pratt, Dezurik, etc.

 

[Danlap]

I vouch for GBTorpenhow over 'seat-in-body'. Man, that's really old design and challenging to installed. DeZurik, that is one brand that I never forget since 20 years ago.
You've touch three different topics:
- Seat in body (what you've currently installed) vs EPDM rubber line --> both are considered as double offset butterfly valve (not zero offset nor triple offset), thus in theory both design have similar performance expectation.
- cheap(er) price? its more common nowadays to use EPDM (sleeve) rubber line which is easy to install, hence production cost can be reduced significantly. I've installed seat-in-body several times years ago, the process requires machining of seat insert, installing (original seat), multiple process of vulcanization, testing, and even machining the rubber seat (EPDM or HNBR) afterwards (shall initial test fails).
- Rubber line doesn't need gasket? This was the general perception before 2000's, but not anymore since the birth of Kammprofile (or similar).
Seating stress from higher to lower Spiral Wound Gasket > Rubber > Kammprofile. Now we always install Kampro for rubber line valve, and sometimes even for in between metal to metal Raised Face. It seals perfect.

IMHO, use rubber line valve, make your life easier. But please before tighten the flange to half open the valve, to prevent 'bulging' on the EPDM.
Seat-in-body is good design and 'was' once last for years. Is it value for money? Not necessarily.

Regards,
D