rshanks

clauses 5.11 and 6.2 in d1.1 are probably the closest you'll get regarding equipment maintenance; calibration is quite another subject.

the d1.5 is a bit more wordy in clause 4.31. but that is the bridge code, not building.

you may want to inquire of the welding machine manufacturer as to their specifications for routine maintenance and calibration. "calibration" is an interesting word, especially around welding machines. there is much debate about it. is it "calibration" or "verification"? if the machine cannot be "calibrated" then is the meter that "verifies" the machine output what gets "calibrated"?
before you invest a lot of time and monies, make sure you talk to the machine manufacturer, especially about "calibration"

and if that leaves you with questions, send an inquiry to AWS. maybe we'll get an official interpretation on it in the Journal!

ziggy