Hi nonoy,

If you're welding per AWS D1.1, you can stop a welder if you have a specific reason or reasons to question his ability. Other than that, you might check in the project documents and specifications to see if rejection rates are mentioned.

I don't know of any written requirements, at least not in the structural steel codes. As SW said, you can remove a welder at any time for poor workmanship. I think the maximum reject rates are determined by managers who calculate how much rework can be tolerated for any one person.

Chet

Any acceptable rejection rate has to be an agreement between the client and the contractor. Afterall, repairs cost money and are the responsibility of the contractor.
Some clients require a specific acceptable repair rate. Even on LSTK contracts. Its up to the client.
I am not aware of any code requirements regarding acceptable repair rates. Too much of a liability on the part of the code committee.