During lifting operations with the main crane, a buffer plate fell from the crane boom. It fell approximately 10m, weighing 70 kg and was 90cm x 40cm. It landed inside the barriered off area on the back deck; there were no personnel nearby. Clearly this could have been a potential fatality had someone been struck by the plate. The purpose of the buffer plate is to be a buffer between the jib and the boom so the steel is not damaged.
What went wrong? What were the causes?
- The immediate cause was found to be that the bolts holding the buffer broke due to metal fatigue;
- The root cause was found to be inadequate or insufficient planned maintenance/inspection. Fatigue in the bolts had been allowed to develop over several years in operation as there had been no proper inspection of the bolts. It was not possible to see damage to the bolts during the visual inspections of the crane which were regularly carried out.
What lessons were learnt? What actions were taken?
- The bolts used subsequently to re-attach the buffer plate were increased in size from M12 to M14;
- Secondary securing of the buffer plate was installed to prevent it from falling;
- On all the members’ vessels with similar cranes, the planned maintenance system was modified to include maintenance/inspection of the buffer plate including bolts;
- A DROPS check of all cranes was made in order to assess for potential dropped objects during operation.
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