Different Grade Steels on Storage Tanks

[Leinster]

Is there any problem with having 2 different grade steels on an API 650 Storage Tank?

We want to weld a bottom course of A537 and all other courses of A283 and want to know if there could be any detrimental effects caused by this?

I understand that they may distort at slightly different rates however is there anywhere where this is permitted or rejected in API 650 or any other engineering standards or specifications?

 

[IFRs]

If you are using the variable point design method the bottom two courses may have to be calculated using the same design strength. See API 650 section 5.6.4.5. Otherwise it is pretty common to do what you describe.

 

[Leinster]

Many thanks..

As this is not directly addressed in API 650 is there any other storage tank standard that specifically states that 2 shell courses can be of different grade steels?

 

[JStephen]

The example in API-650 Appendix K uses two different strength steels.

Section 14.3.2.4 of AWWA D100-11, "In the interest of economy, upper courses may be of weaker material than used in the lower course of shell plates...", etc.