A WPS says your shop can weld under those conditions. But it doesn't cover every combination of thickness, position, base metal, and joint type — only the combinations within its qualification range, which is defined by the variables recorded in the supporting PQR.
Three misconceptions about qualification range show up repeatedly in audit findings:
- "Our PQR was on 1-inch plate, so we're covered from thin material up to unlimited." — Sometimes true, sometimes not.
- "We're qualified 1G, so we can weld flat groove welds anywhere." — True, but 1G covers only flat position.
- "A groove WPS covers groove welds — we need a separate PQR for fillets." — Not true under AWS D1.1.
Getting qualification range wrong puts production welds outside the WPS's coverage, which is the same compliance exposure as having no WPS at all. The weld may look good and pass NDE, but the qualification chain is broken.
See: WPS essential variables vs. nonessential variables: the distinction that drives requalification
Thickness qualification range for groove welds
AWS D1.1 defines the qualified production thickness range for a groove weld WPS based on the PQR test plate thickness. The general rule under D1.1:2025:
- PQR test plate ≥ 3/8 in (10 mm): WPS qualifies unlimited maximum production thickness.
- Minimum production thickness: typically the lesser of 1/8 in (3 mm) or the PQR plate thickness.
This means a PQR run on a 1/2-inch test plate qualifies the WPS from roughly 1/8 inch up to — and including — 4-inch plate, 6-inch plate, or heavier, for the same process, position, and base metal category.
The "unlimited maximum thickness" provision is one of the most useful aspects of D1.1 groove weld qualification. A single well-designed PQR campaign covers the full production thickness range without multiple PQRs at different thicknesses.
Exceptions to unlimited thickness:
- CVN-required WPS: When CVN (Charpy V-Notch) impact testing is part of the qualification, Table 6.8 supplementary essential variables apply. These can restrict the qualified thickness range — toughness is sensitive to heat input and plate mass. Do not assume unlimited thickness on a CVN-required procedure without checking Table 6.8 limits.
- High-heat-input processes: Some process-specific rules constrain thickness coverage more tightly. ESW and EGW, for example, follow Table 6.7 rules rather than Table 6.6.
Rule library based on AWS D1.1:2025; verify against your governing edition.
Position qualification range for groove welds
Position coverage in AWS D1.1 follows a hierarchy: qualifying in a more demanding position covers the less demanding positions beneath it, but not all others.
For groove welds:
- 1G (flat): covers flat groove welds only
- 2G (horizontal): covers flat and horizontal groove welds
- 3G (vertical): covers flat, horizontal, and vertical groove welds
- 4G (overhead): covers flat and overhead groove welds — but not vertical
The practical takeaway: 3G and 4G together cover all four groove positions. To achieve full position coverage, a shop runs two test plates — one in 3G, one in 4G — and the resulting WPS documents cover all production groove weld positions.
A 1G-only qualification, common in shops that historically did only flat-position work, creates a significant gap. Adding a vertical or overhead production weld is an essential variable change that exposes unqualified positions.
Fillet weld coverage — use your groove WPS
Many shops maintain a separate fillet weld PQR when they don't need one. AWS D1.1 allows a groove-weld qualified WPS to cover fillet welds of any size in the same base metal and process category. There is no separate fillet weld size limit flowing from the groove PQR.
This is a significant benefit worth structuring your qualification campaign around. If you qualify groove welds in demanding positions, your shop covers:
- All groove weld thicknesses from minimum to unlimited
- Flat, horizontal, vertical, and overhead groove welds (via 3G + 4G)
- All fillet weld sizes and positions (via groove-weld coverage)
That is broad coverage from two test plates and one PQR campaign.
When would you need a separate fillet PQR?
Rarely. One scenario: a shop that welds only fillet welds and wants to avoid the cost of a groove test plate. Under D1.1, a fillet-only qualification is permitted. But if your shop does any groove work — and most structural shops do — the groove WPS covers fillets and a standalone fillet PQR adds nothing.