THE MINE Safety Operations Branch of the NSW Department Of Primary Industries has released an official safety warning following the structural failure and collapse of drill rig mast.
The mast on an open cut blast hole drill rig collapsed suddenly when the operator attempted to lower the mast before moving the drill rig off the drill bench.
The authority says that the operator was attempting to lower the mast on a single pass over-burden drill rig before tramming off the bench and up the access ramp. The operator had unlocked the mast locking pins and was lowering the mast when the lower pivot points on the mast failed, causing it to collapse. The drill sustained substantial damage but there were no recorded injuries.
The Department claims that an onsite inspection has concluded that the mast pivot points had failed where the bearing blocks were welded onto two RHS (rectangular hollow support) vertical supports. Further visual inspection of the drill rig identified additional cracking at the base of the bearing block support steel work.
The Department recommends that a visual inspection of the mast pivot points, pivot shaft and supporting structure for any visual signs of cracking or component failure be included as part of the operator’s pre-operational checks, a visual inspection of the mast pivot points, pivot shaft and supporting structure for any visual signs of cracking or component failure. And that more detailed visual inspections on all critical elements as part of all periodic maintenance checks.
The group says that companies should consult with the plant original equipment manufacturer (OEM) about the frequency of non-destructive testing (NDT) of all critical structural elements to include, but not be limited to, mast pivot points, pivot shafts, locking devices and supporting structures. And a copy of all current NDT reports should accompany the plant for review upon request by the operator of the mine before the machine is put into service.
Additionally, firms should consult with the plant OEM to ensure the mast pivot points, pivot shaft and supporting structure are of the latest design. Should the plant require modification, this should be carried out in consultation with the plant OEM. Where modifications have been made, or are required to be made, ensure design changes are assessed by the plant OEM or a suitably qualified person.
Lastly, the authority advises that companies develop ‘exclusion zones’ around the plant whenever the mast is being raised or lowered before tramming or servicing.
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