Can one fabricator's WPS be used by a different shop on the same project?

No. A WPS belongs to the organization that qualified it — it is supported by that organization's PQR and signed by their authorized representative. Shop A's WPS cannot be used by Shop B. Each shop must submit procedures supported by their own qualification records.

What should the pre-approval WPS package from a subcontractor include?

At minimum: the WPS itself, all supporting PQRs, the welder qualification matrix tied to each WPS, and evidence that the procedure covers the essential variable ranges required for the project (base metal groups, filler metal F-numbers, positions, thickness range, PWHT if applicable).

How often should welder qualification status be re-verified across subcontractors?

Under AWS D1.1 Clause 6.4.1, welder qualifications lapse after 6 months without welding with a given process. The prime contractor's QC plan should require subcontractors to re-submit updated welder matrices at least every 6 months, and at each new work phase where welders are reassigned.

What happens if a subcontractor changes filler metal mid-project?

A filler metal change may or may not be an essential variable depending on whether the F-number changes. If it does, the existing WPS is no longer valid for that work without a new PQR. The prime contractor's WPS change-control procedure must require written notification and pre-approval before any essential variable change in production.

Managing WPS across multiple fab shops: EPC contractor QC

EPC contractors overseeing multiple fab shops face a recurring trap: each shop's WPS looks valid in isolation but fails project requirements together. Here's the QC framework.

Managing welding documentation on a project where one general contractor or EPC manages five fabrication shops is a different problem from managing it in a single shop. Each subcontractor has their own WPS library, their own PQRs, their own welder roster, and their own opinion of what counts as a complete procedure package. The prime contractor's QC team sits above all of it and must ensure that every weld on the project is supported by a qualified, project-approved procedure — even when the shops are working in parallel on different phases.

The failure mode is almost always the same: WPS review happens once at mobilization, the packages look acceptable, and nobody re-checks until an owner's inspector walks the floor three months later and finds welders using procedures that don't cover the material or position they are actually welding.

Why multi-shop WPS management fails

The most common reasons:

Pre-approval was thorough but static. The prime approved WPS packages at the start of the project based on the scope at that time. Scope changed, new base metals were added, and the shops submitted new procedures informally — or not at all.

Each shop's WPS was reviewed in isolation. Shop A's procedure covers 3/8-inch plate, Shop B's covers 1-inch. The project design then specifies a 1-inch-to-3/8-inch transition joint. Neither shop's WPS covers that combination — the prime didn't catch it because they reviewed each package separately.

Welder qualification tracking was delegated entirely to the subs. Each shop tracks their own welders. The prime has no centralized view, and nobody notices when a welder who was qualified on SMAW in month one has been on a GMAW crew since month two without re-qualifying.

WPS revisions during production went unreported. A shop changed filler metal to resolve a procurement issue, updated their internal WPS, but never notified the prime. The revised WPS went to the field without pre-approval from the owner's inspector.

See WPS responsibility: who owns the procedure, the fabricator or the EOR? for a primer on the contractual chain before the project starts.

The pre-approval package: what to require from each shop

Before any shop welds a single production joint, require a complete procedure package and review it against the project scope — not against generic acceptability. The package must include:

WPS documents: Each WPS with WPS number, revision, date, supporting PQR number(s), and authorized signature. Each WPS should be current — not a photocopy of a document from a project five years ago.

Supporting PQRs: The PQRs that underpin each WPS. Verify that the PQR base metal P-number and group number, filler metal F-number, thickness range (per QW-451 for ASME IX or Section 6 ranges for AWS D1.1), and position qualification all match production requirements.

Welder performance qualification records (WPQs): The roster of welders who will work on the project, with their current qualification records. Verify process, position, and thickness range. Confirm that qualification dates are within the code's active-use continuity window — under AWS D1.1, qualifications lapse after 6 months without welding that process (see AWS D1.1 welder continuity 6-month rule explained).

Cross-reference matrix: A table mapping each joint type in the project scope to the WPS that covers it, the supporting PQR, and the qualified welders. This matrix is the most useful single document in the pre-approval package — if the shop cannot produce it, they probably haven't done the analysis.

Mapping WPSs to project scope

Before approving a package, perform a gap analysis: compare the project's joint schedule (base metals, thicknesses, positions, processes) against the WPS qualified ranges.

Common gaps:

Thickness: The production joint is 1-1/2 inch plate; the qualified thickness range tops out at 1-1/4 inch. Requires a new PQR or an additional test coupon.
Position: The shop's WPS is qualified for flat and horizontal only. The project requires vertical (3G) welds in the field.
Base metal group: The shop tested on A36 (AWS D1.1 Group I). The project specifies A572 Gr. 65 (Group II). The WPS essential variable table may require separate qualification.
PWHT: The project specification requires stress relief after welding; the shop's WPS was qualified without PWHT. PWHT is an essential variable — the existing WPS does not apply.
Supplementary essential variables: The owner's spec requires Charpy V-Notch testing. The shop's WPS doesn't address CVN supplementary essential variables (AWS D1.1:2025 Table 6.8). The shop needs a new PQR with impact testing.

Document every gap in writing and require the shop to resolve each one before welding starts. Gaps discovered after production begins are exponentially more expensive to resolve — you may have to accept with engineering disposition, reject and re-weld, or perform NDE that wasn't planned.

Rule library based on AWS D1.1:2025; verify against your governing edition.

Welder qualification tracking across subcontractors

The 6-month continuity rule under AWS D1.1 Clause 6.4.1 is a rolling clock. A welder who qualifies in January and then transitions to another process in March may lapse their original qualification by September — on a long project, this happens constantly.

Establish a transfer-of-information cadence with each subcontractor:

At mobilization: Full welder qualification matrix, showing process, position, thickness range, and last-welded date for each qualifier.
Monthly (or at each phase boundary): Updated matrix. Any welder whose last-welded date on a given process is approaching 6 months must re-demonstrate or be removed from work requiring that qualification.
At welder additions: When a shop adds welders mid-project, the qualification package must be reviewed and approved before that welder touches production joints.

Some primes require shops to physically stamp production welds with a welder ID (see welder ID stamp and production traceability), which makes it possible to trace any joint to the welder and their qualification record. This is common practice on heavy structural and bridge projects; on commercial construction it is less uniform, but implementing it during multi-shop projects makes audit response significantly faster.

Managing WPS changes mid-project

In a multi-shop project, WPS changes are inevitable. Filler metal lots run out and substitutions come from different manufacturers. Base metal arrives with a different heat that tests to a slightly different chemistry. A subcontractor tries to save time by adding a process they think is covered.

Establish a written WPS change-control procedure at the start of the project and require every shop to sign it. It should specify:

Any change to an essential variable requires written notification to the prime QC manager before the change is made in production.
Essential variable changes require review and pre-approval, and may require a new PQR test coupon.
Nonessential variable changes may be made by WPS revision without a new PQR, but the revised WPS must be submitted to the prime and the old revision removed from circulation.
Emergency substitutions (a filler metal shortage on a night shift) require a documented field engineering review, not a verbal approval.

Without this procedure, you will discover changes after the fact during closeout documentation assembly — when you are trying to compile the record package for the owner and find that a third of the welds on Levels 3-5 are supported by a WPS that was never pre-approved for the change made in month four.

See subcontractor WPS acceptance under AWS D1.1 for the specific acceptance review checklist.

Audit readiness for owner and third-party inspectors

When the owner's inspection agency arrives, the prime contractor should be able to produce, for any joint in the project:

The WPS number that governs that joint
The current revision of that WPS
The supporting PQR(s)
The qualified welder who made the joint (from welder stamp or production record)
The current qualification status of that welder

If any of those five items is missing or inconsistent, the prime is in a vulnerable position. Owners and third-party inspectors do not accept "the sub has it" as an answer — the prime is accountable for the complete documentation record regardless of who holds the paper.

A software-managed welding QC system lets the prime maintain a read-only view of each sub's active WPS library, welder qualification matrix, and PQR status in one place. When a shop's qualification document ages toward the 6-month boundary, an alert goes to the prime's QC manager — not just to the sub. That single visibility improvement eliminates most of the surprise findings that show up during owner audits.

See how the platform handles multi-org welding procedure libraries and welder continuity tracking on our pricing page — the Pro and Shop tiers are designed specifically for the documentation load that multi-shop EPC projects generate. See also building an audit-ready welding procedure library for the document organization principles that make the audit response fast.