Governing thickness of MDMT Head

[Soave]

Dear All

In ASME Section VIII, Div.1 the governing thickness (as defined in UCS-66(a)) used in Step 2 of the Figure UCS-66.2 for formed heads is: the minimum specified thickness after forming? Or is it the thickness of the plate before forming used as the governing thickness?


Thanks

 

[Don56]

Use the minimum specified thickness AFTER forming. See note 1 of figure UCS-66.2.

 

[Soave]

Don56,

I agree with you,and the software PVElite and Compress also use tg (governing thickness) = tn (nominal thickness), but some Authorized Inspector consider as tg the thickness of the plate BEFORE forming. The ASME does not clear about it, can you show an evidence or interpretation that tg = tn in this case? In the ASME 2011a L-9 Example, have this evidence, but this example was excluded in the ASME PTB-4-2013.

 

[TomBarsh]

As Don56 indicated, see Note 1 of Figure UCS-66.2, which states "[tt]...for formed heads, the minimum specified thickness after forming shall be used as tn[/tt]"

http://www.eng-tips.com/

 

[Soave]

The Note 1 of Figure UCS-66.2 doesn't indicate that the tn (nominal thickness) = tg (governing thickness), so it isn't clearly that nominal thickness is AFTER forming for tg (unfortunately).

 

[SnTMan]

Governing thickness for the head is indeed the minimum after forming as per Note 1 until you weld it to something, after which it becomes the thickness of the weld joint, see UCS-66 (a)(1)(a) and Fig UCS-66.3 (a).

This distinction is lost on most software, which contributes to my general mistrust of those outputs.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand