In accordance with § 1 (1) of the Law on Energy Management (EnWG), operators of long-distance gas pipeline networks are encouraged to design pipeline-bound sup-plies of gas to the general public in a way which is as safe, inexpensive, user-friendly, efficient and environmentally-compatible as possible. The generally recognised rules of technology must be observed in complying with these demanding supply tasks (see § 49 (2)). This can be assumed when the technical rules of the Deutsche Vereinigung des Gas- und Wasserfaches e. V. (DVGW – German Technical and Scientific Association for Gas and Water) are applied. This article concerns "welding on gas pipelines under pressure" maintenance tech-nology outlined in the DVGW worksheet G 466-1, Maintaining high-pressure gas pipelines made of tubular steel for operating pressure > 5 bar. Apart from the DVGW worksheet G 466-1, the DVGW worksheet GW 350 "Welded joints on steel pipelines in gas and water supply – Manufacturing, testing and evaluation" is also of relevance for this maintenance technology. Welding on high-pressure gas pipelines under pressure or even in operation repre-sents one of the most demanding and risky maintenance technologies. In accord-ance with DVGW worksheets G 466-1 and GW 350, only sufficient competence on the part of the operator and/or pipeline construction company as well as preparatory tests and plans can ensure that work is carried out safely and the welded joints dis-play mechanical properties in line with the respective requirements. As a result of an 8-year research project conducted by ONTRAS Gastransport GmbH in collaboration with renowned universities and institutes, this article shows how safety can be evaluated in advance by means of technical welding simulation of welding work on high-pressure gas pipelines in operation and what mechanical prop-erties are displayed by the weld seams. ONTRAS Gastransport GmbH therefore avails of a tool for carrying out this maintenance technology with maximum safety and quality.