Self Supported Roof Slope?

[JAG11512]

How do I determine the slope of a self supported cone roof? Will it always be 2" in 12" or can it be different?

 

[IFRs]

It can be different and almost always is. Shallower slopes have thicker plates. You have to use good engineering judgement.

 

[JAG11512]

Do you know of any books that go in depth on Storage tank roof designs?

Thanks.

 

[JStephen]

API-650 includes a section for calculating thickness of self-supporting roofs; you work through it backwards to find the minimum slope.

Note that API-12D, 12F, and UL-142 all have different slope requirements from API-650.

 

[LCeballos]

I am agree with IFRs and JStepehen. Paragraph 5.10.5.1 says:

"Self-supporting cone roofs shall conform to the following requirements:

theta <= 37 degrees (slope = 9:12)
theta >= 9.5 degrees (slope = 2:12)"

Regards.

 

[JAG11512]

Would this be the same for a tank thats 19ft dia. and 32ft high? If 2:12 is acceptable for this tank than thats what i would like to use.

 

[IFRs]

Depends on the thickness but I think you can stay under 1/2" (API max). Run the calcs and see!

 

[Duwe6]

2:12 at 19-ft should be in the neighborhood of 3/16 to 1/4" roof thickness.

 

[IFRs]

Depends on the loads but in general I'd agree that 3/16 to 1/4 would ordinarily do it for you.