Partial Replacement of Tank Shell Course - not full height
Partial Replacement of Tank Shell Course - not full height
(OP)
Hi guys, no matter how much experience you have, there is always room for a difficult to answer question... Here it goes:
Existing Tank made of 3 courses, each one about 2 meters in height, the first course thickness is 1", each course made of 3 plates in full length. Material Carbon Steel, no PWHT required.
The tank demonstrates corrosion on the bottom plates, annular ring and 1st shell course, from bottom up to a level of about 800mm, all round.
Client requests (suppose for economic reasons) that the first course to be substituted, but not in its entirety, but for about 1 meter from bottom, at full circumference. In other words, cut the first shell course at 1 meter (progressively), add a new plate of 1 meter width, do that for the entire circumference, and at the end we will have a new shell course of 1 meter height, and a new circumferential weld at 1 meter height.
After checking with API 653, I found no information if this practice is approved or not, I personally do not like it, but Code does not describe it in the foreseen methods, nor forbids it...
Any ideas?
Existing Tank made of 3 courses, each one about 2 meters in height, the first course thickness is 1", each course made of 3 plates in full length. Material Carbon Steel, no PWHT required.
The tank demonstrates corrosion on the bottom plates, annular ring and 1st shell course, from bottom up to a level of about 800mm, all round.
Client requests (suppose for economic reasons) that the first course to be substituted, but not in its entirety, but for about 1 meter from bottom, at full circumference. In other words, cut the first shell course at 1 meter (progressively), add a new plate of 1 meter width, do that for the entire circumference, and at the end we will have a new shell course of 1 meter height, and a new circumferential weld at 1 meter height.
After checking with API 653, I found no information if this practice is approved or not, I personally do not like it, but Code does not describe it in the foreseen methods, nor forbids it...
Any ideas?
Only best result in absolutely necessary time





RE: Partial Replacement of Tank Shell Course - not full height
RE: Partial Replacement of Tank Shell Course - not full height
RE: Partial Replacement of Tank Shell Course - not full height
So, weld clearance is the main issue as I understand... Common practice would be satisfied with a 50mm (2") weld clearance, and I think we do have it.
Just for the record, it was decided by Client to substitute totally the lower course, which of course is a better solution, technically, and especially for us, the contractor...
Once again, thanks!
Only best result in absolutely necessary time