Structural Inspection, Corrosion Assessment and NDT
- Map structural defects against fixed references.
- Assess section loss and select suitable examination methods.
- Recognize unsafe load-path damage and escalate before release.
- Inspection light and mirror — Examine accessible members, connections, overlapping surfaces and water traps.
- Camera — Capture overall views and defect details before cleaning or disturbing evidence.
- Tape measure and marking chalk — Locate defects relative to fixed references and identify mapped inspection areas.
- Cleaning solvent, rags and hand brush — Remove contamination sufficiently for examination without grinding away crack evidence.
- Calibrated caliper and pit-depth gauge — Measure accessible remaining sections and localized pitting where the geometry permits reliable contact.
Start with the trailer's service history, reported symptoms, collision or overload events and previous repair records. Inspect accessible primary members and connections systematically, recording each defect against a fixed datum or identifiable component rather than using vague descriptions.
Look for cracks, buckling, flange distortion, loose connections, fretting, elongated holes, coating disruption and corrosion at water traps or overlapping surfaces. Rust trails and cracked paint are screening clues, not proof of either sound metal or a particular crack depth; clean the area sufficiently for examination.
Measure remaining metal where corrosion or abrasion has reduced a section, using suitable calibrated equipment and sound reference areas or documented original dimensions. Deep pitting and hidden corrosion between joined surfaces can be more serious than the average surface appearance suggests, and allowable loss must come from applicable design or repair criteria rather than a universal percentage.
Liquid penetrant testing detects surface-breaking discontinuities on suitable clean, nonporous surfaces. Magnetic particle testing applies only to ferromagnetic materials, while ultrasonic methods may assess thickness or internal discontinuities when geometry, calibration and a qualified procedure permit; use qualified personnel for the selected examination.
Damage mapping must include adjacent members and the opposite side of the structure because loads can spread damage beyond the visible impact. Stop use and obtain an authorized disposition when a primary load path is cracked, buckled or otherwise potentially unsafe; a negative result from one NDT method does not prove the whole structure is sound.
How It Works
Follow the load path, not just the visible damage
Review service history, reported symptoms, collision or overload events and previous repairs before examining the structure. Loads travel through connected members, so damage mapping must extend to adjacent members and the opposite side rather than ending at the visible impact. Record defects against a fixed datum or identifiable component so later examinations can locate the same area.
Separate screening clues from measured deterioration
Rust trails, cracked paint and coating disruption identify areas needing examination, but they do not establish crack depth or remaining strength. Corrosion reduces the load-carrying section, while deep pits create localized stress concentrations and overlapping surfaces can conceal deterioration. Measure remaining metal against sound reference areas or documented original dimensions, and obtain allowable loss from applicable design or repair criteria.
Match the examination to the material and suspected defect
Liquid penetrant testing detects surface-breaking discontinuities on suitable clean, nonporous surfaces, while magnetic particle testing applies only to ferromagnetic materials. Ultrasonic methods may assess thickness or internal discontinuities when geometry, calibration and a qualified procedure permit; use qualified personnel for the selected examination. A negative result does not establish that the entire structure is sound, and potentially unsafe primary load-path damage requires stopping use and obtaining an authorized disposition.
Step-by-Step Procedure
0/6 doneDiagnostic Chart
| Symptom | Check | Spec / Expected | Likely cause & fix |
|---|---|---|---|
| Rust trails or cracked paint near a structural connection | Photograph the area before cleaning, then remove contamination without grinding away possible crack evidence. Examine the connection and surrounding metal, escalating to suitable NDT when visual examination is insufficient. | Rust trails and cracked paint are screening clues, not proof of sound metal or a particular crack depth. | Possible underlying cracking, corrosion or connection movement; surface appearance alone cannot distinguish them. Basis: General shop practice (not from a downloaded manual) |
| Deep pitting or corrosion at overlapping surfaces | Measure accessible remaining metal with suitable calibrated equipment and compare with sound reference areas or documented original dimensions. Record locations where hidden surfaces prevent a complete assessment. | Allowable section loss must come from applicable design or repair criteria, not a universal percentage. | Localized or concealed corrosion may remove more load-carrying metal than the average surface appearance suggests. Basis: General shop practice (not from a downloaded manual) |
| Buckling, flange distortion or cracking after impact or overload | Map the affected member, its connections, adjacent members and the opposite side against fixed references. Identify whether the damage affects a primary load path. | Stop use and obtain an authorized disposition when a primary load path is cracked, buckled or otherwise potentially unsafe. | Loads can spread deformation and cracking beyond the visible impact area. Basis: General shop practice (not from a downloaded manual) |
| Suspicious damage remains despite a negative NDT result | Have qualified personnel review material suitability, surface condition, geometry, calibration and procedure coverage. Determine whether another suitable examination is needed to assess the unresolved concern. | A negative result from an NDT method does not prove the whole structure is sound. | The defect may fall outside the selected method's detection capability or the area examined. Basis: General shop practice (not from a downloaded manual) |
At the Bay: Diagnose the Case
CASE 1 / 4
Rust trails or cracked paint near a structural connection
- Test
- Compare
- Correct
Select the next check
Basis: General shop practice (not from a downloaded manual). A likely cause is a hypothesis; confirm it with the applicable service procedure before repair.
Common Bay Mistakes
- ✕ Grinding a crack flush and calling the structure repaired.
- ✕ Recording defects without a fixed location reference.
- ✕ Judging section loss from average surface appearance.
- ✕ Releasing the structure solely because an NDT result is negative.
Quick Check
Practice only — not scored.
Plan the Service Sequence
Planning practice only. Follow the applicable manufacturer's instructions, employer safety program and qualified supervision on real equipment.
Plan the first action. Compare the service steps with the bay mistakes.
Source: General shop practice (not from a downloaded manual)