made in the more general question is: are valves of same class and size, check valves of same class and size and safety valves of the same class and same size have the same dimensions ?
The TOLs should be the same, depending on the make from a mfg who followed the API 6D or CSA Z245.15 code. Vertical clearance is outside the code. Because of pipe layout variation.
that means that no matter the manufacturer, when i bey an equipement : mecanicly i 'll have the same dimensions so i can reinstall it, of course the sizes of flanges, the class has to be the same.
I question the RJ on the 3"-600# side. I am not saying it's wrong, but in that line class you might be better off trying to find RF x RF, unless your client specifications specifically call for RJ.
Yes, sometimes Clients (or employers) won't want you to deviate from what is published in a specification. In that case, you wouldn't.
However, to me at least , 3" 600# RTJ x 4" 150# RF woule be an unusual or uncommon PSV. Depending on the service, I would be looking into the possibility of a spec deviation to get RF x RF, because I could probably find lots of those in a standard size.
I think it´s no problem,
They machine the flange facing whatever you want it to be.
All big companies have pipespecs and it´s very difficult to deviate.
