🔧 1. Joint Detail and Fit-Up Tolerances in WPS
🔹 Clause 5.21.4.1 – Fit-Up Tolerance Requirements
Fit-up tolerances for groove weld assemblies are critical and must be addressed in the WPS.
Refer to:
-
Figure 5.3 a, b, c – Different fit-up types (with/without backing, with/without backgouging)
-
Tolerance parameters include:
-
Root opening (often ±1.6 mm / ±1/16 in.)
-
Root face
-
Groove angle
-
Alignment/mismatch (hi-lo)
-
⚠️ Out-of-tolerance fit-up (e.g., root opening > 20 mm) is not allowed unless qualified by a PQR — especially for PJP groove welds, where excessive root gap is a nonessential variable turning essential.
📐 2. Essential Variables in WPS (Clause 4 and Table 4.5)
✅ Table 4.5, Line 31 – Groove Type
Change in groove type (e.g., single-V → double-V) requires requalification, unless:
-
It’s a CJP groove weld meeting Clause 3.12, 3.13 (prequalified) or Clause 9.10, 9.11 (tubular connections).
-
Then, any groove detail conforming to those figures (e.g., Figure 3.2, 3.3) is acceptable.
✅ Table 4.5, Line 33 – Fit-Up Tolerances
Changes exceeding tolerance in:
-
Groove angle (decrease)
-
Root opening (decrease)
-
Root face (increase)
🛑 These are essential variables, requiring PQR requalification if exceeded.
🔍 Reference tolerance limits:
-
Clause 3.12 / 3.13 – Prequalified CJP joint tolerances (Figure 3.2 and 3.3)
-
Clause 5.21.4.1 / Figure 5.3 – Assembly tolerance for qualified WPS
-
Clause 9.10 – 9.11.2, 9.24.2.1 – Tubular and special connections
🧾 3. How to Set Up Weld Joint Details in pWPS
a) Select Appropriate Joint Type
-
Use Figure 3.3 for CJP groove weld if prequalified.
-
Clearly indicate:
-
Groove type (e.g., double-V)
-
Backing or backgouging
-
Weld size (PJP) or “CJP” note
-
Joint dimensions and tolerances
-
b) Include Fit-Up Tolerances
Refer to:
-
Figure 5.3 – Tolerance for groove weld assemblies
-
Figure 9.7 to 9.16 – For tubular joint fit-up tolerances
🛠️ Mark allowable:
-
Root opening
-
Groove angle
-
Root face
-
Mismatch
📏 4. Weld Profile Requirements
Refer to:
-
Figure 5.4 – Weld Profiles
-
Convexity limits
-
Undercut, overlap, reinforcement
-
Fillet weld leg size and throat
-
-
Define in pWPS or attach diagram
👁️ 5. Visual Inspection Acceptance Criteria
Refer to:
-
Table 6.1 – Visual Inspection Criteria (CJP/PJP)
-
Table 9.16 – Tubular Structures VT Criteria
Common inspection tolerances:
| Inspection Item | Acceptance Criteria |
|---|---|
| Undercut (static) | ≤ 1/32 in. (1 mm) |
| Weld reinforcement | ≤ 1/8 in. (3 mm) for groove welds |
| Weld size (fillet) | No less than design; oversize usually not restricted |
| Overlap | Not permitted |
✅ Quick Reference Summary
| Element | Clause / Figure | Description |
|---|---|---|
| Joint details | Clause 5.21.4.1 | Fit-up tolerance for groove welds |
| Groove dimensions | Clause 5.21.4 / Figure 5.3 | Root opening, face, angle |
| Fillet/PJP assembly | Clause 5.21.1 / 5.21.2 | Pre-weld joint prep |
| CJP joint detail | Clause 3.12 / Figure 3.3 | Prequalified groove detail |
| Essential variables | Table 4.5, Lines 31 & 33 | Groove type & fit-up change |
| Weld profile | Figure 5.4 | Inspection of weld surface profile |
| Visual inspection | Table 6.1, 9.16 | VT acceptance for CJP/PJP welds |