Exeeding pressure rating of flange 1

[cardin]

Hello,

I have a flange rated 150lbs that is welded into a vessel 19Bar (max 50degC). This flange has an allowable pressure of 19,5Bars @50degC. Now i would like to know if it is allowed to exeed the pressure rating with 3 bars (to 22 Bars) for a short period of time (say 8 hours),but no more than 3 times a year?

Asme code (B16.5) says No, but is there a way to allow exceeding this pressure rating? Perhaps people here have some tips on how to proceed in this problem.

 

[BenStewart]

Some thoughts:

1. Could you reassess the flange as per Mandatory Appendix 2 of ASME VIII-1 or equivalent method if the vessel has been designed to a different code i.e. Section 3.8 of PD5500. Note, this would no longer be an ASME B16.5 flange. Be aware though that the p-t rating (19.5bar(g), 50degC) may not even pass the calculation...

2. Complete a BS EN 1591 calculation. This is more sophisticated than MA 2 calculation but more complex to complete.

3. How are the p-t ratings of flanges on the attached piping being justified for this pressure excursion? In ASME B31.3 there are some conditions in part 302.2.4 that may be worth reviewing and something similar may be applicable to the vessel flanges - I recommend you review the vessel design code.

4. There's always FEA - See Part 5 of ASME VIII-2, Annex A of PD5500 or Annex B and C of BS EN 13445. They're generally similar but, in my opinion, Part 5 of VIII-2 is laid out the best.

 

[TGS4]

If it is on a pressure vessel - no. The rules in ASME Section VIII, Divisions 1 and 2 are very clear on this (I am assuming that, due to your pressure, you are not discussing Division 3).

If it is pressure piping, then follow the rules in ASME B31.3 or B31.1 regarding exceeding the design pressure.

The answer may also depend on where in the world you are, and what the regulatory requirements of your local jurisdiction are.

 

[cardin]

It's an ASME vessel, therefore i came to the same conclusion as TGS4, but is was a bit in doubt because there were perhaps some other rules i could use. I did know about the ASME B31.3 rules, but unfortunately this isn't the case. Thank you Ben Steward for your tips in this matter it helps a lot to know this.