This code covers operations relating to and involving arc welding on ferritic steel and austenitic stainless steel land or offshore pipelines and process plant pipework which contain or have contained a process fluid and which are at least 5 mm thick. It gives details of procedures prior to, during and after all these operations. NOTE 1 Welding on pipes of thickness below 5 mm is not covered by this code although it can be undertaken. The code covers manual, semi-automatic and mechanized arc welding by the following processes or combination of processes: manual metal-arc welding; MIG/MAG welding; TIG welding; flux cored arc welding; non-shielded welding. It is essential that the items listed in clause 3 should be fully documented and followed. Welding operations needing post-weld heat treatment for adequate weld quality are not within the scope of this code. This code is not applicable to a pipeline or pipework that has been fully isolated and decontaminated or has not been commissioned. These are covered by other standards such as BS 2633, BS 4677 and BS 4515. This code does not relate to a pipeline or pipework containing a process fluid or its residuals that will become explosively unstable upon the application of heat or will affect the pipe material by rendering it susceptible to ignition, stress corrosion cracking or embrittlement. NOTE 2 The titles of the publications referred to in this code are listed on the inside back cover.