I did a similar calculation for a customer on a bolted body valve. I accounted for the additional axial and moment loads imposed on the body/closure studs through hand calculations.
A way to "comply" is to show that your valve pressure envelope(min. body thickness) calculation takes into account an additional 3mm of corrosion allowance.
This corrosion allowance requirement is typically directly transferred from their Piping specification.
As a vendor, it will also give...
Did you consider the hard wearing properties of a nickel chrome plated carbon steel ball compared to plain SS 316?
Either way, it is always best not to deviate from customer datasheet unless it is a ridiculous request because as a valve vendor you will never know fully all considerations by the...
Vendor should do a post-bake operation for zinc plated fasteners to prevent hydrogen embrittlement.
Have a look at BS 7371 and Shell ES/313 to have a better idea.
ISO 10497/API 607 and API 6FA is generally acceptable as fire safe certification alternatives to one another.
Biggest issue with API 6FA is the valve size qualification range. ISO 10497 allows vendor to fire test an 8" valve to qualify all sizes larger while API 6FA does not allow vendor to do so.