The field problem
Commercial Mall — New Administrative Capital
LV/MV earthing loops using exothermic welding produced intermittent continuity.
Some joints were visibly deformed; others looked acceptable externally.
why the obvious answer can be misleading
Visual appearance alone could not establish internal fusion quality. Investigation identified incomplete mold filling, poor powder distribution and use of a smaller charge than required for the joint/mold. Internal voids could therefore remain hidden inside an apparently closed weld.
Why it failed
Visual appearance alone could not establish internal fusion quality.
Investigation identified incomplete mold filling, poor powder distribution and use of a smaller charge than required for the joint/mold.
Internal voids could therefore remain hidden inside an apparently closed weld.
Follow the engineering
Switch between the field condition and the engineering concept. Trace the path and examine what changes.
Inspect the engineering detail
What changes
Treat the exothermic joint as a manufactured electrical component: verify conductor preparation, mold condition, correct charge, full cavity filling, ignition procedure and post-weld inspection.
Correction & verification
Treat the exothermic joint as a manufactured electrical component: verify conductor preparation, mold condition, correct charge, full cavity filling, ignition procedure and post-weld inspection.
Suspect joints require electrical verification and replacement rather than cosmetic repair.
Verification recorded in the case
- Continuity retesting must demonstrate a stable loop after defective joints are replaced. A resistance reading at one instant is not enough when the original symptom was intermittent continuity.
- Record as-built topology and connection points.
- Repeat the measurement or functional test under a defined condition.
- Confirm continuity and mechanical integrity of the corrected path.
- Document instrument/setup, environmental condition and test method.
- Close the NCR/case only when evidence supports the conclusion.
References & project context
References are reproduced from the PIS casebook. Select the governing edition and project acceptance criteria before using them for a design. The diagrams explain the concept, rather than define construction dimensions.
IEC 62561 component requirements where applicable; project-approved exothermic-welding manufacturer instructions; earthing continuity requirements.
PIS reviewed field handbook · PIS-CS-003
The engineering lesson
Exothermic welding is not automatically maintenance-free or reliable; process control determines joint quality.
Take the lesson into your next design review.