American Standard Section IX vs AWS D1.1

American Standard Section IX and AWS D1.1 are the two primary welding codes used in the oil and gas industry. American Standard Section IX governs welding and brazing qualifications for pressure-containing equipment (pipes, vessels, boilers), while AWS D1.1 covers structural steel welding (pipe racks, supports, buildings). Understanding which code applies is essential for welding engineers and quality inspectors on EPC projects.

Comparison Table

Aspect	American Standard Section IX	AWS D1.1
Full title	Welding, Brazing, and Fusing Qualifications	Structural Welding Code - Steel
Scope	Pressure equipment (piping, vessels, boilers)	Structural steel (buildings, bridges, pipe racks)
Referenced by	American Standard B31.1, B31.3, Section VIII	IBC, AISC 360, AWS D1.8
WPS required	Yes	Yes
PQR required	Yes (procedure qualification record)	Yes (called PQR or test record)
Welder qualification	WPQ (Welder Performance Qualification)	Welder qualification test per Clause 6
Essential variables	Defined per QW-250 tables	Defined per Clause 5, Table 5.5
Prequalified WPS	Not allowed	Allowed for common joints (Clause 4)
Visual inspection criteria	Deferred to construction code (B31.3, Sec. VIII)	Defined in Clause 8, Table 8.1
NDE acceptance criteria	Deferred to construction code	Defined in Clause 8
Requalification	If welder has not welded with the process for 6+ months	If welder has not welded with the process for 6+ months

Key Differences

Prequalified WPS: AWS D1.1 allows prequalified welding procedures for common joint configurations and processes (SMAW, GMAW, FCAW, SAW) without physical testing. American Standard Section IX does not recognize prequalified procedures; every WPS must be backed by a tested PQR.

Acceptance criteria: American Standard Section IX only qualifies welders and procedures. Acceptance criteria for production welds come from the referencing construction code (e.g., American Standard B31.3 for process piping). AWS D1.1 is self-contained and includes its own acceptance criteria for visual, RT, UT, MT, and PT examinations.

Essential variables: Both codes define essential variables that, if changed beyond a specified range, require requalification. American Standard Section IX essential variables are listed in QW-250 through QW-265 tables. AWS D1.1 essential variables are less granular and rely more on grouping by process and joint type.

P-Number system: American Standard Section IX groups base metals by P-Numbers (e.g., P-1 for carbon steel, P-8 for austenitic stainless steel). AWS D1.1 groups base metals by steel group classifications (Groups I through IV).

When Each Code Applies

On a typical EPC project, both codes are used simultaneously:

• American Standard Section IX: All pressure piping welds, pressure vessel welds, boiler welds, and any component falling under American Standard B31.1, B31.3, or American Standard Section VIII
• AWS D1.1: Pipe rack structures, equipment supports, platform steelwork, building frames, and non-pressure structural attachments
• Overlap areas: Structural attachments welded to pressure piping (e.g., pipe support lugs on pressure pipe) may require qualification under both codes, depending on the project specification

Pro Tip

On EPC projects, verify the project specification for structural attachments welded to pressure-containing piping. Many clients require American Standard Section IX qualification even for non-pressure welds on pressure components. The applicable code is determined by the construction code, not the welder’s preference.

A welder qualified under American Standard Section IX is not automatically qualified under AWS D1.1, and vice versa. Cross-qualification must be assessed by the welding engineer based on the essential variables of each code. In practice, many fabrication shops qualify welders under both codes to maintain flexibility across project requirements.

Read the full guide to piping engineering