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Coal Inspectorate | Alert | No.400 V 1 | 03 November 2021

Electric motor terminal cover catastrophic failure

What happened?

A 400kW electric pump motor has suffered a rapid pressurisation in the motor body resulting in the motor terminal cover catastrophic failing. It was ejected from the terminal box propelling metal fragments approximately 15 metres. A similar incident occurred in August 2000 (refer significant incident report no. 29).

How did it happen?

A drive-end bearing has over heated due to a lack of lubrication and possible variable speed drive circulating  currents. The temperature rise has resulted in an ignition of the bearing grease. This caused a significant pressure rise in the motor which has then resulted in the terminal cover fasteners failing and the cover being ejected with significant force. There were no electrical faults and the motor continued to run after the event.

Key issues

  1. The bearing had not been receiving adequate lubrication.
  2. The shaft earthing brush was not contacting the shaft.


  1. Mines should review their Safety and Health Management System (SHMS) to ensure maintenance schemes adequately provide for electric motor lubrication and its effectiveness.
  2. Mines should review their SHMS for effective condition monitoring of electrical motors.

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

  • OEM technical specifications
  • Significant Incident Report No.29
  • Similar overpressure events occurred at another site in 2020 although these did not result in the failure of the motor terminal covers but did cause other damage

Authorised by Shaun Dobson - Chief Inspector – Coal

Contact: Greg Napper, Inspector of Mines (Electrical) , 0475 596 318

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.