Details please?!
A PRV would originally (if at all) be set, certified and a certificate would be issued and follow the valve. The valve would in some cases be plombed against tampering.
The general conditions for certificate and valve would have to be compared to the rules and necessary certification and approvals required for the local use, both for the valve and the total plant.
Sorry about the roundabout answer, I do not think you will find a general standard, valid all over the world, for all cases.