QG – General Requirements: Scope, Responsibility, and the Variable Model
A qualification standard, not a construction code
Section IX tells you how to demonstrate that a welding, brazing, or plastic-fusing procedure - and the person using it - can produce a joint meeting stated test criteria. It deliberately says nothing about design, service allowances, production preheat, or production acceptance; those belong to the construction code (Section VIII, B31.1, and so on). Question writers exploit this: any stem claiming "Section IX requires 200°F preheat" or "Section IX sets radiography acceptance for production welds" is wrong. Section IX requires only that whatever preheat the procedure states be qualified and recorded.
Who owns qualification
The Manufacturer or Contractor is responsible for qualifying procedures and performance and for certifying the supporting records. An outside laboratory may run the mechanical tests, but the Manufacturer/Contractor still owns and certifies the qualification. The Authorized Inspector may review; the AI does not qualify procedures or welders.
The three-variable model
Every variable in Article II (welding), Article III (brazing), or Article IV (fusing) is classified as:
- Essential - a change forces requalification of the procedure by a new test.
- Nonessential - a change forces a revised procedure specification, but no new test.
- Supplementary essential - becomes essential only when notch toughness is a specified requirement.
Records
The PQR documents the actual qualification test: variables used and results obtained. It is a record, not an instruction, and may be amended only to add data such as supplementary test results. The WPS is the written instruction and must be supported by one or more PQRs. The performance qualification record documents the welder's or brazer's essential variables and the resulting limits of qualification.
Rule of thumb
Ask "which document is now wrong?" A nonessential change makes the WPS stale but requires no retest; an essential change voids the PQR's support of the WPS; a welder-essential change voids the individual's qualification.