cold forming of stiffeners 1

[mtvessel1]

When cold forming an 8mm plate, i.e. bending it to effectively form an 90degree angle, the strain on the outer fibres approaches 20%.

PV codes appear to restrict this strain to 3% or 5% but I have a feeling that this is for pressure parts such as dished ends and the like.

The cold formed member is an internal tank stiffener, and therefore does not form part of the pressure containment. Is the limit on the strain still applicable, and can I show 20% is Okay by some means of testing??

 

[metengr]

Mtvessel1;
No. I agree with your position that the cold work limit of 5% applies to product forms that are directly used for the pressure boundary (UG-79 and UCS-79 in Subsection C) of the vessel. I believe for vessel internal hardware you would fall under UG-14 and, as such, there is no limitation on cold work during forming. Based on this information, I would see no need for added testing to prove the design of the internal stiffener member with 20% strain.

 

[deanc]

Think you are on the right track and basicly agree with metengr. However think you should review UG-4(b) and UG-22.

For a good guide see L-5.

Your 90s should be formed across the grain to prevent cracking. Or try a larger radius.