Minimum Dimension/height of Complete Shell Course Replacement as per API 650/ 653

[Zaheer_Ahmad_Raza]

We have observed severe pitting (Remaining Thickness approaching Minimum Required Thickness of Top Shell Course) only in top 6" of top shell course of a Tank. Remaining Portion of the Shell Course is health. Now we have to repair that portion of the shell course.

Can we Replace the entire top 12" of the Top shell course as per API 653 Clause 9.2.2 satisfying all the requirements of weld spacing or do we need to replace the entire shell course?

Furthermore, does API 653 limit the extent of build up to be carried out if we decide to build up entire top 6" of corroded shell course?

 

[IFRs]

If you remove and replace the entire circumference of shell with new shell plates 12" tall I think you are OK. You do not have to replace the entire shell course in my opinion. The tank will not suffer or be at additional risk.

 

[Dhurjati Sen]

Replace the corroded portion but remember to cut & replace the shell course from weld to weld.

Weld build up is a poor alternative to the above.

DHURJATI SEN

 

[HTURKAK]

What is the top angle/ comp. ring detail ? What is the roof type ?