Which code is primarily used for welding in pressure vessels?

The primary code used for welding in pressure vessels is ASME Section VIII. This section provides the rules and guidelines for the design, fabrication, inspection, and testing of pressure vessels that are intended to be used in various industries, including oil and gas, chemical processing, and more. It establishes requirements for the materials, welding processes, and qualifications of welders, ensuring that the pressure vessels can safely withstand the pressures and temperatures they will encounter during their service life.

ASME Section IX, while relevant to welding, specifically addresses welding and brazing qualifications rather than the overall design and construction of pressure vessels. It lays out the criteria for testing and qualifying welders and welding procedures but does not encompass the comprehensive details required for the construction of pressure vessels themselves.

API 650 pertains to the fabrication of above-ground storage tanks, particularly for the petroleum industry, and does not cover pressure vessels directly. Similarly, ISO 9606 focuses on the qualifications of welders but is not specific to pressure vessels. Therefore, ASME Section VIII is the appropriate code for welding in pressure vessels because it integrates all necessary aspects of design and safety for this application.