PED Valve Ports

[fred01]

I want to get PED for some valves (pressure accessories) but I am a little conjused over the port fittings. The valve uses SAE threads (3/4-16 UNF-2A) in accordance with ISO 725.
The problem is that the port fittings we use are rated by the manufacturer to 6000psi (412bar) and compliant with ANSI B1.1 and yet when I check the measurements of the fittings it also complies with ISO 11926-3 (Light duty stud ends) which are rated to a maximum of 4580psi (315bar). They do not comply with the ISO 11926-2 (Heavy-duty stud ends). The difference being the thread engagement.
I need to rate the valve to 5000psi (350bar). For PED can I accept the manufacturer's rating of 6000psi?

Fred

 

[Cockroach]

No, you favor the lower rating, 4580 psig maximum operating pressure. If you went to 6000 psig then you are violating the ISO 11926-3 specification.

In general the fitting is the weakest part of the design, the weakest link drives the specification ratings.

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada