This recommended practice, initiated and developed through the joint efforts of API and Process Industry Practices (PIP), provides supplementary guidelines and practices for welding and welding-related topics for shop and field fabrication, repair and modification of: Pressure-containing equipment (such as pressure vessels, heat exchangers, tankage, piping, heater tubes, pressure boundaries of rotating equipment, and attachments welded thereto); non-removable internals for pressure vessels; structural items attached and related to process equipment; and any other equipment or component item when referenced by an applicable purchase document. This document is general in nature and is intended to augment the welding requirements of ASME Section IX and similar codes, standards and practices. The intent of this document is to be inclusive of chemical, oil and gas industry standards, although there are many areas not covered, e.g., pipeline welding (see API Std. 1104) and offshore structural welding (see API Spec. 2Z).