Does the B16.34 design standard applies to resilient seated valves?
Yes but they are not required to necessarily have full flange rating.

I agree for ball valves : i have found some manufacturers. But for the same manufacturers, none claims to be conform to B16.34 : this is the origin of my doubt.

I don't have much experience with soft seated butterfly valves as I don't really ever purchase these.  Typically, if I require a butterfly valve for a process service, I default to a triple offset, metal seated, high performance valve and these are typically available to ASME B16.34.

I understand that the most common standard for resilient seated butterfly valves is API 609 and that under API 609, it is not mandatory that the valve meet all the requirements of ASME B16.34.  API 609 only references  certain parts of ASME B16.34 (e.g., pressure temperature ratings) and not all of the requirements.

API 609 is a listed component standard in Table 326.1 of ASME B31.3 and so these valves may be used in ASME B31.3 piping systems. I assume that the end user has specified the ASME B16.34 compliance as mandatory and so all I can suggest is that you go back to them and tell them that you have been unable to locate a compliant valve and would they prefer (1) that you switch to an alternative valve type (e.g., triple offset metal seated butterfly valve, ball valve, etc.), or (2) that they accept API 609 as an alternative to ASME B16.34.

PS: in the future it would be helpful if you would provide such additional details in your original post.  There was no mention of "butterfly valves" until your 4th post.

For butterfly valves, resilient seated could be a no offset (a.k.a. rubber lined or concentric type) or a double offset with a plastic seat.  Doubt you will be able to find a concentric type complying with B16.34.  The way this type of valve is fabricated and the typical materials of construction are not suited to B16.34 compliance.  Mostly this type of valve meets AWWA standards for water distribution systems.  For the double offset type, there are plenty of manufacturers making product compliant to B16.34.  Jamesbury, Fisher, Xomox are the biggest brands.

Also, a word of caution.  When you see the words "design to B16.34" is literature, it does not mean full comformance to B16.34.  When a manufacturer states only design, that normally means the dimensions, materials, and marking.  The valve testing does not follow B16.34.  So they cannot state full compliance, only design.

MORE NEWS