Question 7 of 7: Accident Case Analysis — Die-Rigging Keeper-Pin Shear
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
Notes on this paper
National Exams — May 2014 — 11-CS-2 Engineering in Society: Health and Safety. Closed book; approved calculator permitted. Any five of the seven questions constitute a complete paper; all questions are of equal value. Answers are written in point form but fully, as instructed. Complete answers to all seven questions follow.
Immediate cause — the chain was rigged against the keeper pin instead of the proper die notch/lifting point; when the crane took up the slack, the load sheared the keeper pin, which flew and struck the worker's head.
Root/contributing causes (multiple-factor):
Improper rigging — load applied to a component not designed to bear it (keeper pin), not the rated lifting point.
No verification — the die setter did not double-check his rigging; no independent inspection before lifting.
Communication/coordination — the co-worker signalled the lift while the die setter was turning away and not clear; no confirmation that rigging was correct and everyone was clear.
Position (line of fire) — the worker was within range of the stored energy of the tensioned chain/pin.
Procedure/training — no enforced safe-rigging procedure or lift-signal protocol; training gaps.
(ii) Corrective Actions
Safe rigging procedure — attach only to designated, rated lifting points (die notches/eyes); verify before lifting; use correctly rated slings/chains with adequate safety factor.
Independent check — require a second person or supervisor to verify rigging before load is applied ("no lift until checked").
Signalling protocol — one designated signaller; the operator lifts only on a clear signal, and only after confirming all personnel are clear.
Keep clear / line of fire — stand clear of the load and tensioned rigging before any load is taken up.
Training — rigging, signalling and crane-safety training for all involved.
(iii) Follow-Up Actions
Investigate and document (root-cause analysis); report as legally required.
Implement corrective actions; write/update the safe-rigging and signalling procedure.
Retrain riggers/operators; verify compliance through inspection/audit of lifts.
Review similar lifting operations plant-wide for the same risk; monitor for recurrence.
Support the injured worker's care and return to work; share lessons learned.
