Provides specific requirements for fusion welding in contracts which require the manufacturer to have a quality system other than ISO 9001 or ISO 9002 and where the documented welding control has a minor importance to the overall integrity of the final construction; specific requirements for fusion welding as guidance to a manfuacturer developing a quality system; and specific requirements for references in application Standards which use fusion welding as part of their requirements or in a contract between relevant parties. This Standard is identical with and has been reproduced from ISO 3834-4:1994.