Thickness before and after forming

[Fario]

Hi all,

Does exists any table, papers, tips of fabrication or suggestion in any norm (ASME VIII D1 or another) that says about of difference between thickness before and after forming?, for example 10%, 15%, 20% plus than design thickness, my question is about formed heads.

Cheers
D.Marshall

 

[Jano6924]

In ASME VIII-1 take a look into UG-79.

Regards.

 

[metengr]

Only that you must be at or above the minimum design thickness after forming the head. Specifying thickness prior to forming to ensure after forming thickness is above the minimum is left up to the design/fabrication organization.

 

[Don56]

Fario
Thinning is minimal when shells are rolled. Heads are a different story. How much they thin depends on the forming method, shape, starting thickness, size and material properties. There is not table or published rule of thumb. Contact the manufacturer.

 

[SnTMan]

A previous discussion:

http://www.eng-tips.com/viewthread.cfm?qid=160977

Regards,

Mike

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

 

[Fario]

guys...thanks

I just wanted to know a little about how much thickness more is relatively common in the industry (order of magnitude). I see in the StMan link's says a guy "1/16" for head thicknesses 1/2" thick and under and 15% for head thicknesses above 1/2"", this is OK for me, since it is only for general culture not for to design, however the most important of their comments is to contact the supplier and it is his job to accomplish my nominal thickness after forming.

Thanks again..

D.Marshall

 

[racookpe1978]

Right - It is HIS JOB to give YOU the correct minimum thickness after forming.

So, if YOU have questions, go measure it after forming. Reject ALL heads not meeting your minimum thickness . Don't try to guess what will be required as they roll and distort the head during forming. And, truthfully, you really don't care what the rest of the thicknesses of the head were before forming. Unless a rocket or missile pressure vessel when final vessel weight is a critical requirement.