Canadian Weld Inspection — CSA W59 Visual, UT, and MPI Requirements

Complete reference for weld inspection per CSA W59-18 for Canadian structural steel fabrication. Covers visual inspection (VT), ultrasonic testing (UT), magnetic particle inspection (MPI), acceptance criteria, inspector qualifications (CWB Level 1/2/3), and NDT frequency requirements for buildings and bridges.

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CSA W59 Inspection Framework

CSA W59-18 establishes three inspection levels:

Visual Inspection (VT) — Requirements

Visual inspection is mandatory for all welds per CSA W59 Clause 12. All welds must pass VT before any NDT is applied.

VT Acceptance Criteria (CSA W59 Table 12.1)

VT Inspection Frequency

Ultrasonic Testing (UT)

Per CSA W59 Clause 13, UT is required for:

1. Complete joint penetration (CJP) groove welds in tension
2. CJP groove welds in bridges (all) — 100% UT
3. Partial joint penetration (PJP) groove welds in dynamically loaded members
4. All welds in fracture-critical members — 100% UT

UT Acceptance Criteria (CSA W59 Clause 13.8)

UT Calibration Requirements

• Reference block: IIW type or equivalent per CSA W59
• Calibration frequency: Beginning of each shift and after battery change
• Sensitivity setting: DAC (Distance Amplitude Correction) curve for the full thickness range
• Probe selection: 45°, 60°, 70° shear wave as needed for weld geometry

Canadian UT Certification Levels

• Level 1: Can perform UT under supervision, cannot interpret results
• Level 2: Can calibrate, perform, and interpret UT results
• Level 3: Can establish techniques, write procedures, and approve Level 2 interpretations

Magnetic Particle Inspection (MPI)

Per CSA W59 Clause 14, MPI is used for surface crack detection in ferromagnetic materials:

MPI Application

MPI Equipment Requirements (CSA W59 Clause 14.2)

MPI Acceptance Criteria

• No linear indications > 1.5 mm
• No rounded indications > 3 mm
• No cracks of any size
• No aligned indications (3 or more in a line at 2 mm spacing)

Radiographic Testing (RT)

Per CSA W59 Clause 15, RT is an alternative to UT for groove welds:

RT Acceptance Criteria

• No cracks or incomplete fusion
• No elongated slag inclusions exceeding t/3 (for t ≤ 50 mm)
• Total slag length per 150 mm: ≤ one inclusion width of t
• No rounded porosity clusters exceeding limits in CSA W59 Table 15.1

NDT Frequency Requirements

Per CSA W59 and project specifications:

For Canadian building structures, the default is 100% VT + spot UT on CJP welds. The Engineer of Record specifies additional NDT requirements in the project specification.

Inspection Documentation

Per CSA W59 Clause 16, the fabricator must maintain:

1. Weld maps: Showing weld sizes, types, and NDT locations
2. NDT reports: Technician name, equipment, calibration, results
3. Repair records: Defect description, repair procedure, re-inspection results
4. WPS/PQR: Welding procedure specifications and procedure qualification records
5. Welder qualifications: Current CWB welder cards for each process used

Standard Inspection Checklist Items

Frequently Asked Questions

What NDT is required for complete joint penetration welds in Canadian buildings? Per CSA W59 Clause 13, CJP groove welds in tension require UT. For building structures, 10-25% of CJP tension welds are typically tested by UT, with the specific percentage specified in the contract documents. For bridges per CSA S6, 100% UT is required on all CJP welds. Surface MPI is typically added for the root pass before back-gouging.

What is the difference between CWB Level 1, 2, and 3 weld inspection? CWB Level 1: Visual inspection of welds and basic measurements, works under supervision. Level 2: Full VT authority, can calibrate and operate NDT equipment, interpret UT/MT results. Level 3: Establishes inspection procedures, resolves disputes, can approve WPS and welder qualifications. CSA W59 requires Level 2 as the minimum for final acceptance inspection on most building projects.

What are the acceptance criteria for fillet weld profiles per CSA W59? Per CSA W59 Table 12.1, fillet weld convexity must not exceed 2 mm for welds with leg size ≥ 8 mm. For smaller welds, the maximum convexity is 1.5 mm. Fillet weld concavity is acceptable provided the effective throat thickness is maintained at the specified minimum. Undercut must not exceed 0.5 mm for structural welds and 0.8 mm for non-structural.

How often should ultrasonic testing equipment be calibrated? UT equipment must be calibrated per CSA W59 at the beginning of each shift, after battery change, and whenever the technician suspects the calibration has drifted. The calibration must be verified against the reference block for: beam angle, sensitivity (DAC curve), distance range, and probe zero offset. A calibration log must be maintained.

Related Pages

• CSA W59 Welding Procedure Specifications
• Canadian Weld Capacity — Fillet Weld Table
• Canadian Weld Symbols — AWS Standard
• CSA Weld Electrode Selection Guide
• CSA S16 Connection Design
• Welded Connection Calculator
• All Canadian References

This page is for educational reference. Inspection requirements per CSA W59-18. NDT personnel must be certified per CSA W178.2. Verify project-specific NDT requirements with the Engineer of Record. Results are PRELIMINARY — NOT FOR CONSTRUCTION without independent PE/SE verification.

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