material requirement of external attachments directly welded to shell( wind girder heating pannels)

[inammanj123]

Hi,
Good day,

It is a general practice that we use curb and wind girders of A36 material, even if the material of shell is A 516 Gr 70.As per my knowledge, API 650 is not saying anything about material of external attachments which are directly welded to shell. I have a tank of material A 516 Gr 60N, and there contrace heating system coming on the tank, and that Cotrotrace heating panel is of A 516 Gr 70N. to my understanding, if curb angle and wind girder can be of different material, than surely there should problem of welding other attachment, like heating panel, bosses etc.

Regards,
Inam

 

[JStephen]

Yes, wind girders would normally be A36- see 4.10.2.1 where the list of items that require consideration of toughness are shown, and wind girders are not among them.
Should be no problem welding A516-70N to the wind girder. They may use that material as a matter of course so that they can weld it to shells. If welding stainless and carbon steel, differential expansion may be an issue, though.

 

[inammanj123]

there is no 4.10.2.1 clause in latest edition.Kindly check again

 

[JStephen]

Sorry, Section 4.2.10.1.

 

[inammanj123]

But clause 4.10.2.1 is related to MDMT and impact testing requirement. In 5.7.2.3 API clearly says that all reinforcing plates need to be of same material, so the normal practice is that all pad including that ladder and platform all of same material, but API is not very clear about material of attachment which are direct welded to shell.
For example can i weld a 35 mm thick A36 anchor chair top plate to 516 Gr 70 shell?

 

[IFRs]

In contrast to your statement, I read the standard to say that 5.7.2.3 does not require repads to be the same material as the tank shell. They can be, or they can be any appropriate compatible material listed in certain tables of equal or greater strength as the tank shell. You can not use out-of-the-box A36 repads on an A516-70 tank shell because A516-70 is stronger than A36 and it may not have the required toughness at the DMT. However, you can use A36 anchor chair top plates welded to an A516-70 shell because the strength requirement does not apply ( 5.7.2.3) and it is compatible for welding assuming you have a weld procedure for this combination.

My (internet opinion only)