No, the welding subcontractor does not have to have certification to ISO 3834. However, when a manufacturer intends to use sub-contracted services or activities (e.g. welding, inspection, non-destructive testing, heat treatment), information necessary to meet applicable requirements shall be supplied by the manufacturer to the sub-contractor. The subcontractor shall provide such records and documentation of his work as may be specified by the manufacturer.

A subcontractor shall work under the order and responsibility of the manufacturer and shall fully comply with the relevant requirements of the part of the standard being implemented (e.g. ISO 3834 parts 2, 3 or 4). The manufacturer shall ensure that the subcontractor can comply with the quality requirements specified.

The information to be provided by the manufacture to the subcontractor shall include all relevant data from the review of the requirements (ISO 3834-2 and Part 3 see 5.2) and the technical review (ISO 3834-2 and Part 3 see 5.3). Additional requirements may be specified as necessary to assure subcontractor compliance with technical requirements.