API 650 Shell Vertical 1

[JXWu]

Dear experts,
API 650 storage tanks

My welding process is FCAW-G.
On the shell vertical seams, I am considering a single-vee joint, single side welding with ceramic backing.
Another option is single-vee, double side welding, which means I need to backgouge the second side.

I need advice on which option is better.
Thickness ranges from 7 mm to 13 mm.
With the double side welding, I think I can have a better shrinkage control also weld consumable may be less than welding single side with backing.

Not sure if API 650 allows to use temporary backing for shell vertical seams.

My welders are qualified on double side welding. Does this qualified them to weld on single side joint with temporary ceramic backing?
Thanks.

 

[mk3223]

Suggest to post or search the "Tank" related question in the "Storage tank engineering" forum.
Here are related Posts for references as below,

thread1452-446641
thread1452-402982
thread1452-444302

 

Speaking from personal experience, with large tank construction you will not achieve the dimensional control of fit-up necessary for the successful use of ceramic backing.
Double sided is definitely favoured for managing angular distortion, although at sub-13mm there isn't much difference between single and double, but double-sided is more difficult to fabricate.
Transverse shrinkage is a function of the weld process and procedure but will definitely increase with larger root gaps. Fit-up is at least half the battle.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[Dhurjati Sen]

Dear JXWu,

The second option is most prevalent (at least in the Indian sub-continent and the Middle-East).
However, SMAW is used instead of FCAW.

Regards.

DHURJATI SEN
Kolkata, India

 

[JXWu]

Thanks to everyone for the advice!