UG-99 lowest ratio

Hi,

I have to review a PVElite calculation. Shell 516-60, nozzles 106 B, 2 barg at 320°C. The UG-99 hydro pressure in the report is based on the ratio (Sa/S = 1.05) of the shell, this means 2.73 barg.

However, taking the ratio of the nozzle into account (Sa/S = 1), the minimum test pressure is 2.6 barg.

How and where it´s possible to persuade PVElite to determine the test pressure based on the lowest ratio?

Michael

Michael,
Have you checked out the Design Constraints page and un-tick / dis-allow the Hyd.Allowable 90% of the Yield?
cheers,
gr2vessels

Yes

Michael

Michael,

The culprit most of the times are the bolt allowables. The bolt allowables do not fall until the design temperature is high. There was an ASME interpretation that indicated that the bolt allowable stress ratio should be used.

In the May build of PV Elite 2008 there is an option to ignore the bolt allowable stress ratio. This new check box is in the Tools menu -> Configuration check box. Here is the help entry for this box,

Consider Bolt Stress Ratio when computing the Stress ratio for ASME Hydrotests

By default PV Elite will consider the stress ratio in bolts of flanges that are designed per Appendix 2 for hydrotests per UG-99 and UG-100. ASME Interpretation VIII-1-83-260 allows this. Flanges that are not calculated (ANSI flanges) are not allowed this exemption. This check box will allow specific control of the use of the bolt stress ratio for calculated custom (Appendix 2) flanges.