Bolt projectile from failed final drive | Resources Safety & Health Queensland Skip to content
Print notice
Alert Banner

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.


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:

Supervisors must:

Coal Mine Workers must:

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

Authorised by Peter Newman - Chief Inspector – Coal

Contact: Pat Hurley, Inspector of Mines , +61 7 4936 0141

Issued by Resources Safety & Health Queensland

Safety: This information is issued to promote safety through experience. It is not to be taken as a statement of law and must not be construed to waive or modify any legal obligation.
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.