The cost difference between prequalified and qualified-by-test WPSs is large enough to drive procedure decisions. A 30-WPS library that's 100% prequalified costs zero in lab fees. The same library 100% qualified by test costs $45,000–$120,000 to set up.
Most shops sit somewhere in between. Here's how to decide where.
Prequalified path
Cost: $0 in lab fees. Just engineering time to write the WPS.
Speed: Days, not weeks.
Constraints: every variable must fall inside AWS D1.1 Clause 5 limits.
- Process must be SMAW, SAW, GMAW (with short-circuit restrictions), or FCAW (with electrode restrictions)
- Base metal must be in Table 5.3 (Group I or II carbon steels listed)
- Filler must be matched to base metal per Table 5.4
- Joint detail must be from Annex B
- Position and progression must be within prequalified limits
- Electrode diameter must be within position-specific limits
When it fits: structural carbon-steel work with standard joints and standard fillers. Most ordinary fab shop production.
Qualified-by-test path
Cost: $1,500–$4,000 per PQR (lab fees + witness time).
Speed: 2–4 weeks per PQR.
Constraints: essentially none, as long as you can weld a test coupon and the lab can test it.
When it fits: anything outside Clause 5. Specifically:
- GTAW (not prequalified under D1.1 at all)
- Non-listed base metals
- Filler classifications not matched to base metal in Table 5.4
- Non-Annex-B joint geometries
- Production parameter ranges wider than Clause 5 allows
- Project specifications that mandate qualification regardless of Clause 5
Cost breakdown of a single PQR
For a typical AWS D1.1 PQR on plate:
- Welder time + base metal + filler: $200–$500
- Witness inspector time: $200–$600
- Lab tests (tensile + bend): $800–$1,500
- CVN tests (if required): +$400–$800
- Macroetch (if required): +$100–$300
- Engineering time to compile PQR: $200–$500
Total: $1,500–$4,000.
That's a one-time cost. The PQR supports WPSs for the procedure's lifetime — often decades.
Decision tree
For each procedure you need:
- Does Clause 5 cover it? Process, base metal, filler match, joint, position all inside the limits? → Prequalified. Done.
- Does Clause 5 cover most of it but not all? → Consider qualifying by test for the gap and prequalifying for the rest. Some shops keep a single PQR per process that supports a range wider than prequalified, plus a stack of prequalified WPSs for everything inside Clause 5.
- Does Clause 5 not cover it at all? (GTAW, exotic base metal, non-listed filler) → Qualified by test. Budget for one PQR.
When qualification beats prequalification on economics
Three cases where qualifying by test is actually cheaper than prequalifying:
- Heavy production with tight parameter latitude. If welders need wider heat-input range than prequalified allows, qualify a wider PQR-supported WPS. The lab fee amortizes over millions of welds.
- Multi-process hybrid WPSs. GTAW root + SMAW fill on small-diameter pipe. GTAW isn't prequalified; you have to qualify. While you're at it, qualify a wider range.
- Future-proofing for AISC seismic work. CVN-required jobs need supplementary essentials under Table 6.8. A purpose-built PQR for AISC 341 demand-critical welds opens future bids that prequalified WPSs cannot.
The library a typical structural fab shop carries
For a fab shop doing standard structural carbon-steel work:
- 8–12 prequalified WPSs covering SMAW, FCAW-G, FCAW-S, SAW for the common processes × thicknesses × positions
- 2–4 PQR-supported WPSs for procedures outside Clause 5 (GTAW root pass, AISC seismic, etc.)
- 1–2 maintenance / repair WPSs for field work
Total library size: 15–25 WPSs, total qualification cost: $5,000–$15,000 in lab fees, all up.