B16.5 Flange working pressures

[pipe15]

I was under the impression that the B16.5 flange working pressures were absolute limits which could not be exceeded. However, looking at ASME III article NC-3000 section 3658.3 there are factors from 1.1 for Level B to 2.0 for Level D events. The section says that the pressure shall not exceed the factor times the rated pressure.

So, it appears that the B16.5 pressure limits are only for Level A events.

I do not see the same guidance in ASME B31.1. So, are flanges in B31.1 service limited to the pressure values listed in B16.5?

thanks
Mark

 

[BigInch]

Not sure about B31.1. B31.3, 4 and 8 permit temporary overpressure under certain circumstances, time limits, etc. B31.4 and 8 permit up to 10% overpressure above system design pressure (assumed <= to the flange rated working pressure for discussion purposes here), if the overpressure event is in a sequence which will eventually return to maximum design pressure or less, ie not a permanent situation.
You probably need to read B31.1 a little more closely.

Independent events are seldomly independent.