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Maximum specific gravity for API tank and minimum thickness for stainless steel API tank3

Maximum specific gravity for API tank and minimum thickness for stainless steel API tank

(OP)
Hello everyone!

I need some help with two topics about API tanks.

1) What is the formula to calculate the maximum specific gravity I can store on a tank? I only find minimum thickness and hydrotest height.
2) Where I can find Maximum Allowable Shell Stresses for stainless steel to calculate minimum thickness? Table Table 4.1 only refers carbon steel, I need calculate for ASTM A-240 GR. 304L.
Replies continue below

RE: Maximum specific gravity for API tank and minimum thickness for stainless steel API tank

Is this an existing tank?
Changing specific gravity is a "change of service". That would affect shell thickness, reinforcing requirements, manway and flush manway thickness, floating roof design, foundation design. See API-653 for requirements. For limitations based on shell thickness, just take whichever design method was used for the shell and solve for specific gravity. For variable-design-point method or shell-analysis-theory, that's probably an iterative approach. If the new specific gravity is substantially higher, you may be able to accommodate it by restricting operating depth.
Stainless steel shell stress for 304L is in Annex S.

RE: Maximum specific gravity for API tank and minimum thickness for stainless steel API tank

(OP)
Yes... it is an existing tank. Mostly of our tanks are multipurpose, sometimes we change the storaged product.
The first one was really a dumb question, already solved, thanks.

The second I already found on 650.

Thanks again.

RE: Maximum specific gravity for API tank and minimum thickness for stainless steel API tank

I'm pretty sure most API 650 tanks are designed for an SG of 1 as a minimum to allow it to be hydrotested with water. This sets the wall thickness in Appendix A.

You need to state in any question which API code as there are a lot of them...

What sort of SG range are you looking at?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Maximum specific gravity for API tank and minimum thickness for stainless steel API tank

Note 1: The allowable stress for product SG of 1.0 is different than for hydrotest SG of 1.0
Note 2: allowable stresses in API 653 are higher than allowable stresses in API 650, which can sometims help

RE: Maximum specific gravity for API tank and minimum thickness for stainless steel API tank

(OP)

Quote (LittleInch)

I'm pretty sure most API 650 tanks are designed for an SG of 1 as a minimum to allow it to be hydrotested with water. This sets the wall thickness in Appendix A.

You need to state in any question which API code as there are a lot of them...

What sort of SG range are you looking at?

Oh sorry... API-650.
No especific range., I just need to know what is the maximum SG for the case we need to storage a product with a higher SG.
I'm also always calculating the maximum fill height, for the case of a different product.

Quote (IFRs)

Note 1: The allowable stress for product SG of 1.0 is different than for hydrotest SG of 1.0
Note 2: allowable stresses in API 653 are higher than allowable stresses in API 650, which can sometims help

RE: Maximum specific gravity for API tank and minimum thickness for stainless steel API tank

Go with what IFRS says. He knows much more than me when it comes to tanks.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

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