NDT Methods

Understanding primary NDT techniques:

Surface Methods:

Visual Testing (VT):
- Direct or remote viewing
- Basic inspection method
- Low cost, immediate
- Limited to visible defects

Liquid Penetrant Testing (PT):
- Capillary action detection
- Surface-breaking defects
- Any non-porous material
- Simple, portable

Magnetic Particle Testing (MT):
- Magnetic field disruption
- Surface and near-surface
- Ferromagnetic materials only
- Fast, portable

Volumetric Methods:

Radiographic Testing (RT):
- X-ray or gamma radiation
- Through-thickness imaging
- Permanent record (film/digital)
- Internal discontinuities

Ultrasonic Testing (UT):
- Sound wave reflection
- Through-thickness capability
- Portable, no radiation
- Versatile applications

Specialized Methods:

Eddy Current Testing (ET):
- Electromagnetic induction
- Surface and near-surface
- Conductive materials
- Fast, automated possible

Acoustic Emission (AE):
- Detect stress waves
- Growing defects
- Real-time monitoring
- Pressure testing

Phased Array UT:
- Multiple element probes
- Electronic steering
- Imaging capability
- Advanced applications

Method Selection:

Consider:
- Defect type sought
- Material properties
- Geometry access
- Sensitivity required
- Code requirements
- Cost and time

Comparison:
- RT: porosity, volumetric
- UT: planar, thick sections
- MT/PT: surface cracks
- VT: all visible

Detailed method understanding:

Ultrasonic Testing:

Principles:
- Sound waves travel through material
- Reflect from discontinuities
- Time and amplitude analyzed
- Flaw size and position determined

Equipment:
- Transducers (various angles)
- Ultrasonic flaw detector
- Couplant (gel, water)
- Calibration blocks

Techniques:
- Contact testing
- Immersion testing
- Through-transmission
- Pulse-echo

Applications:
- Weld inspection
- Forging examination
- Thickness measurement
- Bond testing

Radiographic Testing:

Principles:
- Radiation passes through material
- Absorption varies with density/thickness
- Image shows internal features
- Permanent record

Sources:
- X-ray tubes
- Gamma (Ir-192, Co-60)
- Selection by thickness

Applications:
- Weld internal soundness
- Casting examination
- Assembly verification
- Corrosion detection

Considerations:
- Radiation safety essential
- Geometric considerations
- Film or digital capture
- Interpretation skill

Magnetic Particle Testing:

Principles:
- Magnetic field in part
- Leakage at defects
- Particles gather at leakage
- Visual indication

Methods:
- Continuous (field during application)
- Residual (field before application)
- Dry or wet particles
- Visible or fluorescent

Equipment:
- Yokes, prods, coils
- Magnetic particles
- UV light (fluorescent)
- Demagnetization

Liquid Penetrant Testing:

Process:
1. Clean surface
2. Apply penetrant
3. Dwell time
4. Remove excess
5. Apply developer
6. Examine

Types:
- Visible or fluorescent
- Water washable, solvent removable, post-emulsifiable
- Sensitivity levels

Limitations:
- Surface defects only
- Clean surface required
- Material compatibility

NDT personnel and procedure requirements:

Personnel Certification:

ASNT SNT-TC-1A:
- Recommended practice
- Employer-based certification
- Levels I, II, III
- Written practice required

Levels:
- Level I: Perform testing, limited interpretation
- Level II: Setup, interpret, report
- Level III: Develop procedures, train, qualify

NAS 410:
- Aerospace standard
- Employer-based
- More prescriptive than SNT-TC-1A
- Aerospace industry

ISO 9712:
- Central certification
- Third-party examination
- International recognition
- Periodic recertification

ASNT Central Certification:
- ACCP program
- Industry-recognized
- Portable between employers
- Levels I, II, III

Training Requirements:

Experience Hours:
- Vary by method and level
- Code specified minimums
- Documented experience
- Supervised practice

Training Hours:
- Classroom or OJT
- Method-specific
- Code requirements
- Continuing education

Examination:

Content:
- General knowledge
- Specific method
- Practical examination
- Code/specification

Standards:

Procedure Standards:
- ASTM E standards (methods)
- ASME Section V (boilers/pressure)
- AWS codes (welding)
- Aerospace specifications

Acceptance Standards:
- ASME Section VIII (vessels)
- AWS D1.1 (structural)
- Aerospace specs
- Customer requirements

Quality System:
- Written procedures
- Equipment calibration
- Personnel qualification records
- Audit compliance

Building an NDT career:

Career Paths:

NDT Technician Level I:
Entry level:
- Supervised testing
- Data collection
- Basic interpretation
- $40,000-$55,000

NDT Technician Level II:
Independent operation:
- Setup and calibrate
- Full interpretation
- Report writing
- $55,000-$80,000

NDT Level III:
Expert/supervisor:
- Procedure development
- Training and qualification
- Technical authority
- $75,000-$110,000

NDT Engineer:
Engineering role:
- Method development
- Integration with design
- Advanced applications
- $80,000-$120,000

Work Environments:

Shop/Manufacturing:
- Production inspection
- New fabrication
- Consistent conditions

Field/Service:
- In-service inspection
- Travel involved
- Varied conditions

Third Party:
- Independent inspection
- Multiple clients
- Variety of work

Research/Advanced:
- Method development
- Specialized applications
- Advanced equipment

Getting Started:

Entry Path:
- Technical education helpful
- OJT available
- Start Level I
- Progress through levels

Method Selection:
- UT most versatile
- RT good for welds
- MT/PT simpler entry
- Multi-method valuable

Advancement:
- Multiple method certification
- Level III achievement
- Specialization options
- Management path

Industries:
- Aerospace (stringent)
- Oil and gas
- Power generation
- Manufacturing
- Transportation
- Construction

NDT offers stable career with clear progression and growing demand.