Coal Inspectorate | Alert | No.415 V 1 | 29 July 2022
Bolt projectile from failed final drive
What happened?
During routine servicing of a Caterpillar D11T Dozer, the machine was being relocated out of the workshop when the right-hand final drive locked up and subsequently failed, splitting the outer case.
Two bolt heads sheared off (projectiles) from the outer casing of the final drive, travelling approximately 4.6 metres, and impacting into a nearby toolbox (Fig 1).
How did it happen?
The machine locked as it began reversing and was unable to move forward or backwards. The operator jacked the machine up to see if it would rotate. During this attempt to move the track backwards, the right final-side drive casing split (Fig 2), ejecting the bolt heads (Fig 3).
Key issues
The technique to remove the plugs contributed to the incident. The plug was struck prior to being loosened and removed using an impact wrench.
The Inspectorate has identified defective magnetic plugs in some final drives and has been working with Hastings Deering to identify the defective part numbers and communicate to industry.
The magnet in these defective plugs can separate from the plug body due to insufficient crimping at manufacture. If the magnet separates when installed, it can cause extensive component damage, which may cause the planetary retaining bolts to shear and become projectiles.
Recommendations
Treat all plugs as suspect, especially if the plug has been replaced with a new magnet since January 2021. Under no circumstances should the plugs be struck prior to being loosened. The use of an impact wrench is not recommended.
Site Senior Executives (SSEs) must:
- Ensure the mine site has access to and has actioned - Hastings Deering Customer Information Bulletin - HDCIB 2022 Bulletin 09_Revisin 1_Defective Magnetic Plugs
Supervisors must:
- Ensure the mine site has access to and has actioned - Hastings Deering Customer Information Bulletin - HDCIB 2022 Bulletin 09_Revisin 1_Defective Magnetic Plugs
- Ensure that all defective plugs are identified and replaced as soon as possible.
- An exclusion zone should be implemented when performing maintenance activities to ensure that Coal Mine Workers are not in close proximity.
- Ensure that under no circumstances are plugs struck prior to being loosened. The use of an impact wrench is not recommended.
Coal Mine Workers must:
- Adhere to Hastings Deering Customer Information Bulletin - HDCIB 2022 Bulletin 09_Revisin 1_Defective Magnetic Plug
- Never strike a plug prior to attempting to loosen it. The use of an impact wrench is not recommended.
- Ensure that you remain within the established exclusion zone, out of the line of fire, as a mitigating critical control.
Investigations are ongoing and further information may be published as it becomes available. The information in this publication is what is known at the time of writing.
We issue Safety Notices to draw attention to the occurrence of a serious incident, raise awareness of risks, and prompt assessment of your existing controls.
References and further information
Contact: Pat Hurley, Inspector of Mines , +61 7 4936 0141 QldMinesInspectorate@rshq.qld.gov.au
Issued by Resources Safety & Health Queensland
Placement: Place this announcement on noticeboards and ensure all relevant people in your organisation receive a copy, understand the content, findings and recommendations as applicable to their operation. SSEs should validate that recommendations have been implemented.
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