Weld Inspection

Visual inspection is the foundation of all weld quality evaluation:

What to Examine:

Weld Profile:
- Size (throat, leg length for fillets)
- Shape (convex, concave, flat)
- Reinforcement height (butt welds)
- Undercut and overlap
- Face and root appearance

Surface Discontinuities:
- Porosity (gas pockets)
- Cracks (surface-breaking)
- Undercut (groove melted in base metal)
- Overlap (weld metal over unfused base)
- Spatter (acceptable amount varies)

Dimensional Requirements:
- Weld length
- Location and spacing
- Leg size consistency
- Throat dimensions

Workmanship:
- Arc strikes outside weld area
- Incomplete fusion visible at surface
- Excessive grinding
- Proper cleaning

Tools Required:
- Weld gauges (fillet, undercut, hi-lo)
- Straightedge
- Tape measure
- Flashlight
- Mirror (for limited access)
- Magnifying lens (typically 10x)
- Temperature indicators

Inspection Conditions:
- Adequate lighting (minimum 50 foot-candles, 100+ preferred)
- Proper viewing distance and angle
- Clean weld surface
- Inspector vision requirements (annual eye exam)

Documentation:
- Inspection reports
- Non-conformance reports
- Photographs when required
- Traceability to WPS and welder qualification

Weld inspection requires thorough knowledge of applicable codes:

Major Welding Codes:

AWS D1.1 - Structural Welding (Steel):
- Buildings, bridges, structures
- Defines inspector qualifications
- Visual acceptance criteria tables
- NDT requirements by connection type

AWS D1.2 - Structural Welding (Aluminum):
- Aluminum structures
- Similar format to D1.1
- Aluminum-specific requirements

ASME Section IX - Welding Qualifications:
- Boilers, pressure vessels, piping
- Welder and procedure qualification
- References other sections for acceptance

ASME B31 - Piping Codes:
- B31.1: Power piping
- B31.3: Process piping
- Different categories with varying requirements

API 1104 - Pipeline Welding:
- Cross-country pipelines
- Stringent qualification requirements
- Specific inspection criteria

Acceptance Criteria Concepts:

Workmanship Standards:
- Minimum quality for production
- Based on code requirements
- May be exceeded by contract

Fitness-for-Service:
- Engineering evaluation of discontinuities
- Consider actual service conditions
- May accept welds rejected by workmanship

Critical vs. Non-Critical:
- Codes often distinguish by loading
- More stringent inspection for primary members
- Category affects NDT extent

Reading Code Tables:
Understanding acceptance criteria tables:
- Discontinuity type (undercut, porosity, etc.)
- Size limits (length, depth, diameter)
- Location restrictions (root, face, etc.)
- Accumulation rules (total in given length)

NDT methods supplement visual inspection:

Liquid Penetrant Testing (PT):
- Detects surface-breaking discontinuities
- Apply penetrant, developer reveals indications
- Works on any non-porous material
- Simple, inexpensive, portable
- Limitations: surface defects only, surface prep critical

Magnetic Particle Testing (MT):
- Detects surface and near-surface defects
- Magnetic field reveals discontinuities with particles
- Steel and iron only (ferromagnetic materials)
- Can find subsurface defects
- Faster than PT for ferromagnetic materials

Radiographic Testing (RT):
- X-ray or gamma ray examination
- Reveals internal discontinuities
- Permanent film record
- Excellent for porosity, inclusions
- Safety requirements, expensive
- Less sensitive to crack orientation

Ultrasonic Testing (UT):
- Sound waves detect internal defects
- Highly sensitive to planar defects (cracks, lack of fusion)
- Portable, no radiation hazards
- Real-time results
- Requires skilled technicians
- Phased array technology advancing rapidly

NDT Personnel Certification:
- Level I: Perform tests under supervision
- Level II: Interpret results, supervise Level I
- Level III: Develop procedures, train others

Certifications per:
- SNT-TC-1A (employer-based)
- ASNT Central Certification Program
- ISO 9712 (international)

The AWS Certified Welding Inspector credential is industry gold standard:

CWI Requirements:
- Vision requirements (near and far acuity, color perception)
- Experience requirements (varying by education level)
- High school: 5 years welding-related experience
- Associate degree: 4 years
- Bachelor's degree: 2 years
- Pass three-part exam:
- Part A: Fundamentals (open book)
- Part B: Practical (hands-on inspection)
- Part C: Code book (code-specific exam)

Exam Preparation:
- AWS seminars and study materials
- Practice visual inspection
- Know code navigation
- Understand fundamentals thoroughly

Career Opportunities:

In-House Inspector:
Manufacturing or construction company:
- Inspect production welds
- Qualify procedures and welders
- Interface with customers and auditors
- $55,000-$85,000

Third-Party Inspector:
Inspection services company:
- Work for multiple clients
- Travel frequently
- Variety of projects
- $60,000-$90,000

Contract Inspector:
Independent contractor:
- Higher earning potential
- Business management required
- Irregular work flow
- $70,000-$120,000+

QA/QC Manager:
Leadership of quality function:
- Manage inspection team
- Develop quality systems
- Customer interface
- $80,000-$120,000

Industries:
- Structural steel fabricators
- Pressure vessel manufacturers
- Pipeline contractors
- Shipbuilding
- Aerospace
- Nuclear

Advanced Certifications:
- Senior CWI (SCWI)
- Certified Welding Educator (CWE)
- NDT Level II or III
- Specialized codes (D1.5 Bridge, D17.1 Aerospace)

Professional Development:
- Stay current with code revisions
- Expand NDT capabilities
- Develop specialty expertise
- Network through AWS sections