ASME B31.3 — Process Piping — is the code governing design, fabrication, assembly, inspection, and testing of piping systems in chemical plants, petrochemical facilities, and refineries. For field inspectors on Gulf Coast EPC projects, B31.3 is the most frequently referenced code.
Examination Requirements by Category
- Category D (non-hazardous): Minimum examination, visual in many cases
- Category M (lethal fluids): Maximum examination, 100% radiography
- Normal service: Per Table 341.3.2, typically 5-20% random radiography
- High-pressure (Chapter IX): Enhanced examination requirements
Visual Inspection Criteria
B31.3 visual acceptance criteria are defined in Table 341.3.2 — covering weld reinforcement limits, undercut, incomplete penetration, and surface condition. These differ from AWS D1.1 structural criteria, a common source of confusion on multi-code projects.
Hydrostatic Testing
B31.3 requires hydro testing at 1.5x design pressure with a 10-minute minimum hold. The inspector must verify all joints are accessible, correct test medium and pressure are used, and the system shows no leaks.
Field tip: Always verify piping class and fluid category before determining examination requirements. Category M service has dramatically different requirements than Category D for the same pipe size.
Need 3rd Party QC, CM, or Safety Support?
BIG provides independent quality assurance, inspection, construction management, and safety oversight for EPC projects in Houston and the Gulf Coast.
Request a Quote