The thesis aims to evaluate, identify and list repair methods for defects on pipelines in the natural gas industry and discusses their impact on safe operation and welding procedure specification respecting all quality requirements for welding in accordance with ISO and STN standards. Welding is a process of fabricating a non-detachable weld by creating interatomic bonds between welded parts in the process of heating, plastic deformation, or by simultaneous application of both at once. The theoretical part discusses welding methods, presents the classification of defects most commonly occurring on gas pipelines and methods for repairing them. The experimental part aims to develop a welding procedure specification (WPS) for various cases of repairing defects on a pipeline. It is a document adhering to one of the acceptance methods which provides required welding variables in a way that ensures its repeatability during production welding. The final part focuses on the evaluation of selected repair methods and the development of a WPS, specified in accordance with technical rules for gas (TPP 702 11) using welding and sleeve