Haul-truck tyre explosion investigation
At a heavy-equipment workshop serving an open-pit coal mine, a 42-tonne haul-truck tyre is being inflated after a rim repair. A 28-year-old fitter is killed when the lock ring separates. The workshop supervisor was the fitter's brother-in-law and is leading the internal investigation. The incident occurred at 02:10 on night shift; the only witness is a trainee who was told to fetch tools and did not see the inflation. Photographs were taken at 09:00 after the tyre was moved. The maintenance record shows the rim was inspected but not measured; the OEM manual requires a restraining device and a 10 m exclusion zone. The site has a written procedure but no training records for night shift. Production target is 120,000 tonnes that month. The general director asks for the report in 48 hours so operations can resume.
1. Critique the investigation team, evidence handling and timetable. What should be done instead?
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The investigation is compromised at the start. The supervisor is the victim's brother-in-law and is leading the inquiry, which creates both a conflict of interest and a likely bias toward blaming the fitter or protecting the shift. He should step aside from leading the investigation. An independent lead, with a competent person for tyre and rim work and a worker representative, should take over. The family should be treated separately from the investigation, with a single point of contact.
Evidence handling is poor. The tyre was moved before photographs were taken at 09:00, so the original position, the trajectory of the lock ring and the state of the rim cannot be reconstructed from those photographs. The rim, lock ring, tyre and inflation equipment should have been tagged, photographed in place, and retained for examination. The trainee is the only witness but was sent away and may have been coached; the trainee should be interviewed separately and early, without the supervisor present.
A 48-hour report is not credible for a fatal high-energy failure. An interim factual report can be issued to authorise safe resumption of other work, but the final root-cause report needs maintenance records, OEM specifications, rim measurements, training records for all shifts, the production pressure context, and any CCTV or gate logs. The failed parts should be preserved for metallurgical or mechanical examination.
2. Identify likely root and contributing causes using a causal method, and distinguish immediate from systemic causes.
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Immediate causes: the lock ring was not fully seated or engaged; the tyre was inflated without a restraining device; the 10 m exclusion zone was not enforced; and the fitter was in the trajectory zone. These are the direct conditions of the explosion.
Contributing causes: the maintenance record shows inspection without measurement, so a worn or mismatched rim could have been missed. Night-shift workers had no training records, meaning the procedure may not have been understood or followed. The supervisor was on shift and related to the fitter, which may have weakened challenge. Production pressure toward 120,000 tonnes that month may have encouraged speed over the OEM procedure.
Systemic causes: the risk assessment did not treat tyre inflation as a high-energy task requiring a restraint and exclusion zone; the permit or competent-person sign-off was absent; training was not verified by shift; and audits did not detect that the written procedure was not followed. A fault-tree or 5-Whys analysis should trace each path to these management failures. The report should not stop at 'worker error', because the worker was placed in a system that allowed the error to be fatal.
3. Recommend corrective actions and enforcement or communication follow-up. How would you verify that they worked?
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Engineering: provide a restraining device or cage for all tyre inflation, use remote inflation gauges and hoses, and mark a physical exclusion barrier at 10 m. Procedural: a permit-to-work for tyre and rim work, a pre-inflation checklist, measurement of the rim against OEM limits, and a competent-person sign-off. Training: certify all fitters on all shifts, including night shift, and reassess competence by observation. Supervision: ensure a competent person is present for inflation, not just available on call.
Enforcement: prohibit tyre inflation until the restraint and exclusion controls are in place; issue an improvement notice for training and maintenance verification; and consider investigation of the company for failing to manage a known high-energy hazard. Communication: issue a safety alert to all mine and workshop contractors, brief the workforce, and share the findings without waiting for a final report if there is an immediate risk to other sites.
Verification: direct observation of inflation jobs, audit of permits and checklists, records of rim measurements, training records by shift, and a follow-up audit after 30 and 90 days. The measure is not whether a new procedure exists, but whether fitters actually use the restraint and exclusion zone when nobody is watching.