All welding variables procedure specification are provided in article IV. It is separated for each welding procedure application from table QW-252 through QW-256.

Base metal are assigned P number in QW-422 and base metal qualification in QW-424, main purpose of P-Number to reduce number of welding procedure qualification if material are the same weldability, chemical and mechanical.

Find ASME BPVC Section IX latest edition here or other sections here.

Example: PQR qualified on ASTM A106-B to ASTM A234 WPB

  • Base metal are in P-Number 1 and Gr-Number 1, see table QW-422.
  • So, WPS shall qualify for the same base metal P-Number such ASTM A105, API 5L Gr. B or ASTM A36,…
    If CNV requirement, the Gr-Number shall be essential variables. So, above WPS shall not be qualified for ASTM A105 or ASTM A516 Gr. 65 (Gr-Number. 2).
  • This WPS does not qualify for ASTM A182 F316L (P-Number 8) because of different base metal P-Number.

Base metal used for procedure qualification shall detailed in the table QW-422. In case of material do not list in table QW-422, so it consider to be unassigned metal.
Any change P-Number shall be required to requalification WPS.

Assigned metal number: listed in table QW-422
Unassigned metal number: not shown in table QW-422.

We need to know about base metal used for procedure qualification coupon (LIFT COLUMN) and base metal qualification (RIGHT COLUMN) as detailed in table QW-424.1.

The same an assigned P-Number

Left column: One metal from a P-number to any metal from the same P-number.

Right column: Any metals assigned that P-Number.

Ex. PQR qualified for ASTM A106-B to ASTM A106B (P-No.1), the welding procedure shall qualify for ASTM A105N/ A234-WPB, A516 Gr. 60 to ASTM A105/ EN 10025-2 S235JR of any the same P-number , vice versa. This PQR shall not qualify for ASTM A106-B (P-No. 1) to ASTM A312 TP316 (P-No. 8).

The different an assigned P-Number

Left column: One metal from a P-number to any metal from any other P-number.

Right column: Any metals assigned the first P-Number to any metal assigned the second P-number.

Ex. PQR qualified for ASTM A106-B (P-No.1) to ASTM A312 TP316 (P-No.8), the welding procedure shall ONLY qualify for P-No.1 to P-No.8 and vice versa.

This PQR shall not qualify for P-No. 8 to P-No.8.

The unassigned P-Number to any P-Number

Ex. PQR qualified for API 5L Gr. B (P-No.1) to AISI Gr. 4130 (Unassigned P-Number), the welding procedure shall ONLY qualify for P-No.1 to AISI Gr. 4130 and vice versa.

This PQR shall not qualify for P-No. 1 to AISI Gr. 4137, 4140, 4145Hmod due to different the unassigned metal.

The unassigned P-Number to other unassigned P-Number

Ex. PQR qualified for AISI Gr. 4140 (Unassigned P-Number) to AISI Gr. 4130 (Unassigned P-Number), the welding procedure shall ONLY qualify for AISI Gr. 4140 to AISI Gr. 4130 and vice versa.

This PQR shall not qualify for AISI Gr. 4140 to AISI Gr. 4140 or 4145, 4137 due to different the second unassigned metal.

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