This document specifies requirements for calibration, verification and validation of equipment used for control of process variables during fabrication, and control of the properties of equipment used for welding or welding allied processes where the resulting output cannot be readily or economically documented by subsequent monitoring, inspection and testing. This involves process variables influencing the fitness-for-purpose and in particular the safety of the fabricated product. NOTE 1 This document is based on the lists of process variables stated in International Standards for specification of welding procedures, in particular, but not exclusively in the ISO 15609- series. Future revisions of these International Standards can result in addition or deletion of parameters considered necessary to specify. Some guidance is, in addition, given in Annex B as regards requirements for calibration; verification and validation as part of acceptance testing of equipment used for welding or allied processes. Requirements to calibrate, verify and validate as part of inspection, testing, non-destructive testing or measuring of final welded products performed in order to verify confirm product compliance are outside the scope of the present document. The subject of this document is limited to calibration, verification and validation of equipment after installation, as part of the workshops and site operations for maintenance and/or operation. It needs to be stressed that this document has nothing to do with manufacture and installation of equipment for welding. Requirements for new equipment are formulated in directives and product codes (standards), as necessary. Annex C provides information when other parties are involved in calibration, verification and validation activities.