Shell course plate thickness

[zsa]

Hello,

Currently designing a tank in which the shell bottom course comes out to 10 mm and all other courses are 6 mm.

Can I use a 10 mm plate for the bottom course and directly use 6 mm for the other courses, or is it a better engineering practice from a fabrication and operation point of view to use an 8 mm course on top of the 10 mm course and then use 6 mm courses above that.

API 650 has no reservations regarding this but a client is concerned about the bulging of the 6 mm course on top of the bottom course.

Thanks

 

[JStephen]

Normally, the two courses would be welded directly together.

 

[BAretired]

I prefer a gentle transition 10...8...6 mm.

BA

 

[JStephen]

Lots of people might prefer it, or might prefer to just run the 10mm all the way up, but most aren't willing to pay for the extra steel to deal with a non-issue.

 

[IFRs]

The 6mm course above the lower course should not be a problem. If the plates are center-stacked the thickness difference is only 2mm each side. Why is bulging a concern? What would cause bulging? Why is the lower course so much thicker?