Welding is performed at the plants according to certified welding technology (WPS and WPQR) in the fabrication shops, which are equipped with beam stands and welding machine lines of various modifications, enabling performance of different welding types and methods. A welding manual is prepared for each project, specifying the welding technology, process parameters and interim and final control conditions for weld seams, according to ISO 3834-5. Weld seams are subject to visual and instrumentation control.