9.2 Clause 5 — Prequalification Requirements

The Prequalification Concept

Clause 5 lets a fabricator use a Welding Procedure Specification (WPS) without qualifying it by destructive test (no Procedure Qualification Record, PQR) — provided the procedure stays inside a tightly bounded envelope the code has already proven. This is unique to D1.1 and saves enormous time and cost, which is why Part C tests it heavily. The classic question form is: "Given these conditions, is this WPS prequalified, or does it require a PQR?"

A WPS is prequalified only if EVERY one of the following is satisfied:

1. Process is one of the four prequalified processes — SMAW, SAW, GMAW, FCAW. (GMAW short-circuiting transfer is not prequalified for CJP groove welds.) GTAW is never prequalified and always needs a PQR.
2. Base metal is listed in the prequalified base-metal table (historically Table 5.3, renumbered in current editions — tab it regardless of number).
3. Filler metal matches the base metal per the matching-filler table (Table 5.4) and meets the correct AWS A5.x classification and strength group.
4. Joint detail matches a prequalified configuration in Figure 5.1 (CJP) or Figure 5.2 (PJP) within all listed tolerances.
5. Minimum preheat and interpass temperature meets the prequalified preheat table (Table 5.8).
6. All other Clause 5 limits are met — welding positions, electrode/flux conditions, technique, and essential-variable ranges.

If any single condition fails, the procedure is not prequalified and must be qualified by test per Clause 6.

Reading the Prequalified Base-Metal and Filler Tables

The base-metal table organizes steels by ASTM specification, grade, steel group, and a preheat category (A, B, C, D...) that you carry forward into the preheat table. The matching-filler table then pairs that steel group with acceptable filler classifications.

Cross-Referencing Preheat (Table 5.8)

Minimum preheat and interpass temperature is a three-input lookup — a favorite cross-reference question:

• Steel category (from the base-metal table),
• Thickness of the thickest part at the point of welding, and
• Process / hydrogen level (low-hydrogen vs non-low-hydrogen filler).

The table returns a minimum temperature (for example, thicker low-hydrogen welds may require 150°F or 225°F [65°C or 110°C]). The trap: candidates pick thickness of the thinner part. The code uses the thickest part at the joint.

Reading a Prequalified Joint Detail

Each Figure 5.1/5.2 entry carries a joint designation (for example, B-U2 or TC-U4b) and specifies the groove type (square, V, bevel, U, J), groove angle, root opening, root face, permitted positions, allowed processes, backing (with/without, backgouge), and thickness range. If the actual fit-up falls outside any listed tolerance, prequalification is void.

Prequalification Is Not Welder or Inspection Relief

A frequent conceptual trap: prequalification only exempts the WPS from procedure qualification (PQR). It does not waive welder/operator qualification (still required per Clause 6), and it does not reduce inspection or acceptance criteria (Clause 8 applies in full). A prequalified joint welded by an unqualified welder is still non-conforming, and a prequalified weld with a crack is still rejected. Keep the three concepts separate: procedure (Clause 5/6), personnel (Clause 6), and product acceptance (Clause 8).

Filler-Metal and Hydrogen Subtleties

The matching-filler table pairs a steel group with an electrode strength level and AWS A5.x classification (for example, E70xx SMAW electrodes for many 50 ksi steels). Two traps recur:

Essential Variables Still Bound the WPS

Even a prequalified WPS must stay inside Clause 5's essential-variable ranges — amperage, voltage, travel speed, electrode diameter, and position limits. If production drifts outside the WPS, the weld is non-conforming even though the procedure was prequalified. On Part C, a scenario that changes the welding position to one not permitted by the joint detail, or swaps to short-circuit GMAW on a CJP groove, breaks prequalification just as surely as an unlisted base metal.

Quick Prequalification Checklist

When the stem asks "prequalified — yes or no?", run this in order and stop at the first failure:

1. Process one of SMAW / SAW / GMAW (not short-circuit on CJP) / FCAW?
2. Base metal in the prequalified table?
3. Filler matched and correct A5.x / hydrogen level?
4. Joint detail matches a Figure 5.1/5.2 entry within all tolerances?
5. Preheat/interpass meets Table 5.8 for the thickest part?
6. Position, technique, and essential variables within Clause 5 limits?

For the Exam: When asked "is it prequalified?", walk the six conditions like a checklist. The most common reason the answer is "no, requires PQR" is a non-prequalified process (GTAW) or a joint detail outside the figure's tolerance.