standards for butterfly valve

[cak30887]

Which standards has to refer while designing a double offset butterfly valve?
Pl. Mention design and testing standards.
Also for calculating valve torque for a double offset butterfly valve, what factors has to be consider like bearing torque, seating and unseating torque, packing torque, is there any standard for these calculations?

 

[reverman]

MSS SP-68, and API 609 are the two main design standards

 

[cak30887]

Thank you sir ...