ASME B16.5 Flange Rating - Allowance 1

[svi]

A certain fabricated skid used an SS flange connection for an instrument connection. The SS flange has a lower max allowable pressure than the rest of the CS class 150 flange rating. The design pressure of the system is marginally over the SS flange rating by a fraction of a bar. Is there any provision in the code that may exempt the use of the SS flange at the marginal excess over the flange rating.

 

[TGS4]

Not to the B16.5 rating. Your Code of Construction may provide an "out", such as performing calculations to ASME Section VIII, Division 1, Appendix 2.

 

[DSB123]

svi,
Think you are asking for trouble using a flange that is not rated for the Design Pressure. If anything happens in operation I don't think you will have a leg to stand on in defence of doing this.

 

[LittleInch]

I think your only real option is to reduce the design pressure to the rating of the SS flange or change out the flange. and then use the overpressure allowance in B 31.3 for the probably very few times the system will actually operate above your new, fractionally lower, design pressure.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way