Coal Inspectorate | Alert | No.426 V 1 | 02 May 2023
Rare earth magnets
An original equipment manufacturer (OEM) advised of an incident where an underground coal mine worker reported seeing a spark generated when a drill steel came in contact with a rare earth magnet.
As ferrite core magnets and rare earth magnets are used extensively, this Safety Alert is issued to alert industry to a potential safety hazard involving the use of rare earth magnets.
These magnets are commonly found on equipment such as continuous miners, miner-bolters, multi-bolters and longwalls operating in hazardous environments.
How did it happen?
- The rare earth magnet was contained in a polyurethane drill steel holder.
- The magnet was exposed due to wear in the holder.
- An internationally accredited certification body was engaged by the OEM to perform extensive tests on a rare earth magnet. These tests were carried out to IEC 80079.38 Explosive atmospheres - Part 38: Equipment components in explosive atmospheres in underground mines.
- Although the magnet passed the standard tests using mild steel plate, it did not pass these tests when using hardened steel plate.
- This confirmed that a spark is generated when a steel drill hits a rare earth magnet and that this spark will ignite methane.
- A material safety data sheet for the rare earth magnet material states that:
- material is brittle and may chip if not handled with care
- magnets may spark on impact and to handle carefully in explosive atmospheres.
It is recommended that Site Senior Executives:
- advise all coal mine workers of potential hazards associated with rare earth magnet applications, particularly in explosion risk zones (ERZs)
- audit all equipment located in or able to enter ERZs and identify the use, application and robustness of physical protection of rare earth magnets
- visually check all applications of rare earth magnets. If any part of the rare earth magnet is exposed, remove it from service
- review inspection and maintenance regimes for rare earth magnet applications
- risk assess the continued use of rare earth magnets, consider alternative designs and the application of higher order controls.
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.
RARE EARTH MAGNETS ARE EXTREMELY POWERFUL!
- They exhibit very strong magnetic forces attracting them to other magnets and ferromagnetic materials such as iron or steel.
- The strong force between magnets can cause severe injury when fingers and other body parts are pinched between magnets.
- Strong magnets may affect the operation of pacemakers and other implanted medical devices.
- Keep magnetised parts away from mechanical/electrical instruments which may be damaged by high magnetic fields.
Contact: Anthony Logan, Senior Inspector of Mines - Mechanical , 0477 373 213 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.