Hi,

Please refer to API 602, there are a lot of variances: wafer, lug, category A, category B, double flange (short and long pattern). and sometimes manufacturer use a ball valve body.
So yes, it is highly advisable to measure actual sizes on site, even though you will ask the same valve manufacturer.

Regards,
MR

https://nosuchvalve.com
All valves will last for years, except the ones that were poorly manufactured; are still wrongly operated and or were wrongly selected

http://www.eng-tips.com/faqs.cfm?&rat1=2&f...

Agreed.
It seems that you want to replace the old valve without any piping modification to minimize the work. It's always a good practice to measure the space of the current valve dimension, and confirm it with the vendor for the new valve to be purchased. So, you have one less thing to worry about.

Hello,

Popular butterfly valve standard is API-609. There are different face-to-face dimensions depending upon valve type. Concentric disc type, double offset type, etc. NPS 24 and smaller butterfly valve face-to-face dimensions have been standardized for over 30 years, but you must confirm with the manufacturers to be certain.

Thanks bcd,
for the correction of my API typo. It is indeed API 609.

Regards,
MR

https://nosuchvalve.com
All valves will last for years, except the ones that were poorly manufactured; are still wrongly operated and or were wrongly selected

http://www.eng-tips.com/faqs.cfm?&rat1=2&f...

By changing valves the most important thing is cost/lifetime: be sure to buy valves with at least the same technical quality and references at the original. The cheapest to buy are not always the most economical.

And of course: control measurement of building length at site! Are all valves of same dimension at site equal of building length / type / construction details?

By replacing a too short valve may be compensated by extra sealing or metal rings/extension pieces, while longer valves might (by certain overlength) stress the pipeline to much.