This standard covers the gas and arc welding of butt@ fillet@ and socket welds in carbon and low-alloy steel piping used in the compression@ pumping@ and transmission of crude petroleum@ petroleum products@ fuel gases@ carbon dioxide@ nitrogen@ and where applicable@ covers welding on distribution systems. It applies to both new construction and inservice welding. The welding may be done by a shielded metal arc welding@ submerged arc welding@ gas tungsten arc welding@ gas metal arc welding@ flux-cored arc welding@ plasma arc welding@ oxyacetylene welding@ or flash buttwelding process or by a combination of these processes using a manual@ semiautomatic@ mechanized@ or automatic welding technique or a combination of these techniques. The welds may be produced by position or roll welding or by a combination of position and roll welding. This standard also covers the procedures for radiographic@ magnetic particle@ liquid penetrant@ and ultrasonic testing@ as well as the acceptance standards to be applied to production welds tested to destruction or inspected by radiographic@ magnetic particle@ liquid penetrant@ ultrasonic@ and visual testing methods. The values stated in either U.S. customary units (USC) units or metric units (SI) are to be regarded separately as standard. Each system is to be used independently of the other@ without combining values in any way. The figures depicted in this standard are not drawn to scale. It is intended that all work performed in accordance with this standard meets or exceeds the requirements of this standard. While this standard is comprehensive@ it may not address all issues that may arise. The absence of guidance or requirements is not to be considered prohibitive to a particular activity or approach that is based upon sound engineering judgment. For example@ other industry standards@ reliable engineering tests and analyses@ or established industry practices may provide useful reference to establish sound engineering judgment.