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Flange calculation in hydrotest conditions

Flange calculation in hydrotest conditions

Flange calculation in hydrotest conditions

(OP)
I submit flange calculation according to ASME VIII div 1 Appendix 2 with stress analysis for operating and gasket seating conditions (to get approval for CE marking). The notified body replies that there is too high stress in hydrotest conditions. I know that hydrotest conditions calculation is considered only with European standards and the safety factors for allowable stresses aren't the same as for the operating and gasket seating conditions. In ASME VIII-1 no indications for calculation with hydrotest conditions. So the notified body hadn't to consider this calculation.
Have you any remark.

RE: Flange calculation in hydrotest conditions

I agree with you: ASME VIII Div.1 is an accepted standard for PED, it is up to the fabricator to choose the standard, and once it is chosen the only thing to do is to follow it fully till the final acceptance tests.
I've never calculated a vessel where the flanges were insufficient in hydrotest, but there are situations where, even under ASME, it is necessary to consider hydrotest stresses: an example is the hydrotest in horizontal position of tall vessels.
If you need to get out of a difficult situation, you may take the limit set forth in Div.2 for hydrotest stresses, that is 90% of the minimum yield strength at test temperature. I would be surprised if this proved to be the dimensioning condition for the flanges.

prex
motori@xcalcsREMOVE.com
http://www.xcalcs.com
Online tools for structural design

RE: Flange calculation in hydrotest conditions

(OP)
Prex,

I am sure that there is no calculation required for hydrotest conditions in Appendix 2 of ASME VIII-1. I don't know if it is required in other parts of this division.
In the european standards, the safety factor is about 1.05 while for operating conditions is 2.5.
I am in my 7 file (category III and IV) CE approved vessel according to 97/23/EC.

If someone knows where in ASME VIII-1 hydrotest conditions calculation is mentionned.

Prex, your link doesn't work.

Regards,


RE: Flange calculation in hydrotest conditions

As I already told, I agree with you: Div.1 requires no calculation for hydrotest conditions, flanges per App.2 included.
However, on the rare occasions where such an evaluation is necessary, the limit of Div.2 is customarily used.

prex
motori@xcalcsREMOVE.com
http://www.xcalcs.com
Online tools for structural design

RE: Flange calculation in hydrotest conditions

I don't know anything about PED requirements but would the industry segment affect it? For example, API 6A flanges require design calcs for hydrostatic test conditions.

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