Liquid Penetrant Testing (PT) – Level 1 Certification Course - Defect Types and Discontinuity Recognition
PT shows visual indications on the surface, but not all of them indicate a flaw.
| Type | Description |
|---|---|
| Relevant | Caused by actual flaws; must be evaluated and reported |
| Non-relevant | From geometry or acceptable surface features |
| False | Created by improper technique, contamination, or lighting |
✅ Correctly identifying indication types is essential for accurate inspection.
These are real, flaw-related indications that typically exceed code limits and may lead to part rejection.
Sharp edges, consistent shape
Often linear, rounded, or clustered
Located in critical stress areas (e.g., weld toes, threads, edges)
Appear consistently on re-inspection
| Common Examples | Flaw Type |
|---|---|
| Bright straight line | Crack |
| Small tight cluster | Porosity |
| Crescent near hole | Fatigue crack |
📌 Must be evaluated per acceptance criteria (e.g., CGSB, ASME, API, etc.)
These are real penetrant responses that are not associated with unacceptable flaws.
Thread roots
Keyways or sharp corners
Machining marks
Casting seams or parting lines
Geometry changes (e.g., fillets, weld toes)
| Feature | Indication Behavior |
|---|---|
| Sharp thread edges | Linear traces in same pattern |
| Weld toes | Curved, consistent edges |
| Bolt holes | Circular border glow |
🛠️ Good surface preparation and interpretation help avoid over-reporting these.
These are artificial indications caused by poor technique, contaminated materials, or environmental errors.
| Cause | Resulting Issue |
|---|---|
| Poor cleaning | Residual oil causes smearing |
| Over-application of penetrant | Dye pools in surface texture |
| Inadequate rinsing | Excess penetrant glows |
| Uneven developer | Splotchy background |
| Low light intensity | Misinterpreted patterns |
| UV light reflection | Halos, ghost images |
🛑 False indications lead to unnecessary part rejection or rework.
| Pattern | Likely Interpretation |
|---|---|
| Straight, sharp, bright line | Crack (relevant) |
| Blurry, large smear | Excess penetrant or rough surface |
| Repetitive dot chain | Porosity (relevant) |
| Line follows geometry edge | Non-relevant geometry |
| Cloudy glow, no sharp edge | False or background |
✅ Re-inspect under optimal light with different angles for confirmation.
| Best Practice | Benefit |
|---|---|
| Clean thoroughly with proper solvent | Removes contaminants |
| Use correct dwell and emulsification times | Ensures proper penetration |
| Apply developer evenly | Reduces blotting artifacts |
| Maintain correct light intensity | Improves flaw visibility |
| Verify indications with multiple angles | Confirms or rules out flaws |
Part ID and area inspected
Type and shape of indication
Length, width, and orientation
Exact location on part (e.g., near weld toe, hole edge)
Photographic evidence (if required)
| Field | Description |
|---|---|
| Part Number | WLD-235-AL |
| Inspection Area | Weld toe, bottom flange |
| Indication Type | Linear, 7 mm |
| Evaluation | Reject per CGSB Table 3 |
| Inspector | H. Nejjahi – PT Level 1 |
| Reviewed By | Supervisor Level 2 – Initials: JT |
Relevant indications come from actual flaws and require evaluation
Non-relevant indications are caused by part geometry or acceptable features
False indications result from poor inspection technique or contamination
Accurate interpretation and documentation are critical for quality assurance
Reducing errors requires proper technique, training, and attention to detail