During validation of PV2009, found Kcor shown for an Ellipsoidal 2:1 (D/2h = 2.0) head is 0.99 instead of expected 1.0.

We did not find ASME VIII-1 Add08 make any changes on this Appendix 1-4 (C).

Q1] Why K became Kcor in PV09 and not 1.0 when D/2h = 2.


Q2] Anybody can help to explain this or it is a bug in PV09?

Background of K value we captured,

We discovered PV08 May Built published report with K value of 0.12. Anyway, computation result is still correct as compare with using K = 1.

PV08 and earlier versions shown K = 1.0 consistently.

Dear SK,

This is not a bug. In the corroded condition, the inside depth of the head increases and the ratio D/(2h) decreases. This will cause the K factor to be slightly less than 1 for a 2:1 elliptical head. Using K = 1 is conservative and this change might help slightly in some cases, but overall makes very little difference unless you are designing right on the edge.

Scott,

I think earlier option Kcorr=1.0 was conservative and was good. There is relation between h and d per Code. h = D/4 for 2:1 ellipsoidal head. When corrosion will take place then also h will be determined by h = D/4 and result will be K = 1. As this is a conservative same is to be followed.

I have seen few cases where with Kcorr = 1, is changing thickness.

Mukesh

Dear Scott,

Most of our clients would like to see K to be 1.0 in PVElite calculation. Otherwise, may comment or query.

From your reply, we know PVElite applied users data D/2h = 2 as new head condition thus Kcor in place for corroded condition.

What if user's intention on D/2h = 2 is corroded condition rather than new? This will help to see Kcor = 1 on calculation report, safe the trouble from client comment/query why not equal to 1 for an E2:1 head.

D and K in Formula Appendix 1-4(c)are refers to corroded values as standard ASME concept. Standard formula in UG-32 (d) treat "k" = 1.

Thank you!

Hi Tan,

The idea is that the Aspect ratio is in the new condition. We proceed with the calculation based on that assumption. However, we understand that this behavior should be optional and we have made that change via a setup parameter. Look for this new option in the first build of the 2009 version.

ok, this is what I have learnt,

It is hard to please all the people all the time. :-)