API 653 Code issue

[blaqesmith]

API 653
12.3.2.5.1 a
A portion of the weld (of any length) may be removed and replaced as long as the replaced weld meets the size
requirements of API 650, Section 5.1.5.7, and the portion replaced does not represent more than 50 % of the
required weld cross-sectional area.

what is meant by portion in red. i am unable to understand "weld cross sectional area" how it will be calculated?

 

[IFRs]

try Google or Wikipedia "cross sectional area" . If you cut the tank in half vertically, separated the two halves and then looked at the exposed corner weld you would be looking at the cross-section of the weld. It looks like a triangle. The area of a triangle is 1/2 times its base times its height. A fillet weld is not exactly a triangle so some additional work is required. You don't calculate is so much as measure it. You measure the fillet weld leg lengths and then compute the area.

 

[blaqesmith]

what is meant by 50 % of required? How to calculate required area?

 

[IFRs]

The size of the weld is specified in API 650 and is based on the thickness of the shell plate and bottom plate under the shell. It is usually a "full-fillet" weld whose legs are equal in length to the thickness of the thinner of the two pieces being joined but can be greater if the shell plate is quite thick. See API 5.1.2.2 for a definition of the size of a fillet weld., 5.1.1.4 for a definition of a fillet weld and 5.1.1.5 for a definition of a full-fillet weld. 5.1.3.3 has the minimum fillet weld size and 5.1.5.7 for the minimum size of the bottom-to-shell fillet weld size.