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Coal Inspectorate | Alert | No.402 V 1 | 18 November 2021

Introduction, inspection and maintenance of gas detecting and monitoring equipment

What happened?

Incidents have occurred whilst undertaking maintenance tasks associated with the gas monitoring systems.

  1. An incident occurred at an underground coal mine where a Longwall CH4 sensor was being relocated from a powered roof support to another location along the faceline. When the sensor was disconnected, the tripping circuit failed to operate.
  2. An incident occurred at another underground coal mine where an ERZ/NERZ boundary sensor went into a fault condition due to the failure of the uninterruptible power supply and the tripping circuit failed to operate.

How did it happen?

Investigation on the first incident found that the designated relay in the gas monitoring controller had not been configured to activate for a failsafe condition. The parameter sheets for the gas monitoring installation stated that the relay should have been configured to activate for a failsafe condition.

The second incident investigation found that another digital address module was still active on the signal line from a redundant gas monitoring station and was transmitting the same address. This prevented the boundary sensor from be able to trip on a fault condition.

Key issues


Mines should review their safety and health management system to ensure:

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 Shaun Dobson - Chief Inspector – Coal

Contact: Mark Lydon, Inspector of Mines (Electrical) , 0436 950 514

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.

All information on this page (Introduction, inspection and maintenance of gas detecting and monitoring equipment -,-inspection-and-maintenance-of-gas-detecting-and-monitoring-equipment) is correct as of time of printing (6 Dec 2021 6:03 pm).