3.1 Single Qualification Testing & Essential Variables

3.1 Single Qualification Testing & Essential Variables

Under API 1104:2021 Section 6.2, single qualification demonstrates that an individual welder can deposit sound welds under a qualified WPS. The welder welds one test joint — butt, branch, or fillet configuration — and the completed weld must pass visual examination (6.4) plus either destructive testing (6.5) or nondestructive testing (6.6).

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1. Test Positions and the Position Hierarchy

For butt-weld single qualification, the welder makes a butt weld in either the rolled or the fixed position. A fixed-position test pipe may be horizontal (5G), vertical (2G), or inclined at not more than 45° from horizontal (6G). The 22nd edition hierarchy:

• Fixed position qualifies roll. A welder qualified in any fixed position may also perform roll welding within the qualified variables.
• Roll qualifies roll only. A roll-position (1G) qualification does not authorize fixed-position welding.
• 45° inclined fixed (6G) qualifies everything. A welder who passes a butt weld test in the fixed position with the axis inclined 45° from horizontal is qualified to make butt welds and lap fillet welds in all positions.
• A horizontal fixed (5G) or vertical fixed (2G) test qualifies only that fixed position plus roll welding — it does not automatically cover the other fixed positions.

Branch-connection single qualification has its own position matrix (Table 6): the branch test may be run with the branch on the side, top, or bottom of a horizontal run pipe, and the qualified production positions depend on that orientation and the branch/run diameter ratio.

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2. Qualified Ranges: Outside Diameter and Wall Thickness

OD Groups (6.2.2 d)

• < 2.375 in. (60.3 mm): qualifies only OD less than 2.375 in.
• 2.375 in. through 12.750 in. (323.9 mm): qualifies that whole band.
• > 12.750 in.: qualifies OD ≥ 2.375 in. (all diameters at and above 2.375 in.).

For branch-connection welds, the run pipe diameter is not an essential variable.

Qualified Thickness Range (Table 5)

The 22nd edition replaced the old wall-thickness groups with computed ranges based on the thickness t actually tested:

Example: qualifying on 0.375 in. wall covers 0.154-0.750 in. (since 1.5t = 0.562 < 0.750, the 0.750 in. cap governs). Qualifying on 0.500 in. wall covers 0.154-0.750 in. as well (1.5t = 0.750). Qualifying on 0.875 in. wall covers 0.750 in. to unlimited.

For branch connections and lap fillet welds, the run pipe thickness is not an essential variable.

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3. Welder Essential Variables (6.2.2)

A change in any of the following requires the welder to requalify:

1. Welding process — a different process, or a change in the combination of processes (unless each process in the combination was qualified by separate tests).
2. Direction of welding — vertical up ↔ vertical down, or vertical ↔ horizontal progression. (Welding across the 12 or 6 o'clock positions of a horizontal pipe to avoid stacking starts/stops is not a direction change.)
3. Filler metal — a change of filler metal group in Table 4 (WF-1 cellulosic SMAW; WF-2 low-hydrogen SMAW; WF-3 low-hydrogen vertical-down SMAW; WF-4 solid-wire GMAW/GTAW; WF-5 oxyfuel; WF-6 FCAW), or a change involving a classification not listed in Table 4.
4. OD group and thickness range — outside the qualified bands above.
5. Roll ↔ fixed position, or a change in welding position beyond the hierarchy above.
6. Joint design — a change per Note e of Table 1 (major joint type). A welder qualified on a butt weld may also make fillet welds within the qualified variables.
7. Backing — elimination of a backing strip or weld-metal backing.
8. Pass combination — when multiple processes complete a joint, a change in which passes each process welds. A fill/cap process may be used for a complete production weld only if it ran three or more passes in the test; a process used for fewer than three test passes may weld no more than two production passes.
9. GMAW-S restriction — with short-circuiting gas metal arc welding, the welder may use GMAW-S in production only for the same passes welded with GMAW-S in the qualification test.