It may have changed in the 2010 edition. As of the 2002 edition section 5.11 "...All welding and thermal cutting eqpt. shall be in such condition...to attain the results as desired in the code"
Leaves alot of latitude. Defined - if the machine produces the req'd weld- it's fine.
D1.5 2008(bridges) is another story. Section 4.26 "Eqpt. used to measure variables shall be accurately calibrated. Contractor shall verify at least every 3 months accuray of meters used to display welding varaibles. Eqpt. used for verification shall be certified annually.
Section 6.3.2 "The inspector shall inspect welding and thermal cutting eqpt. used in the work and verify it conforms to 3.1.2" (same as D1.1 5.11) It's up to the contractor not the inspector, to verify meters.