pad thickness and material 1

[mdischarge]

Hi every body,

I would like to know why all the reinforcing pads attached to the shell should be as thick as shell or less with the same shell material?

thanks

 

[dtn6770]

I'm not aware of such requirements. Re-pad thickness should be fair game recognizing the limits of reinforcement cited in UG-40. And the only stipulation placed on re-pad material is that it have an allowable stress value equal to or greater than that of the shell material, UG-41 (a). You don't get extra credit for re-pad material having an allowable stress greater than the shell material.

Those are ASME Section VIII, Div. 1 references.

 

[chaulklate]

There isn't an actual restriction on the thickness of repads other than not violating the maximum thickness for welding for the material in question. I've heard what you are talking about before and use it as a rule of thumb for guidance, not a hard fast rule as I have more than once used repads thicker than host. I have colleagues who have mentioned it helps avoid "local hard spots" that supposedly don't flex as consistently as the rest of the system.

 

[Shmulik]

thread794-156800

 

[deanc]

See Appendix L&G

 

[mammut74]

My reply is not replying why the re-pad should have the same thickness (local stiffness, etc), but why it is beneficial for the fabricator: I will have less steel wastage, because the pices from a cutting hole for a 24" mayway on the shell, I can use to reinforce a small nozzle on the shell and even heads. Bear in mind that heads can come up to be thinner than the shell required thickness. as I can have a 1 piece formed SE 2:1 head (100% joint effeciency) vs. a shell with different joint effeciency.

Kai