This is an important question.  Mining today is a lot more modernized and automated than in the past, yet there are still accidents occurring.  The Impala hoist accident in South Africa in November of 2023 is an example, where there was a tragic loss of life when the hoist winding mechanism operated in the wrong direction.  The hoist was in automatic mode and a request was made to move from Level 20 to Level 17. Instead of heading up to the surface towards Level 17, it rapidly descended at full speed and when the emergency stop button was pressed, the counterweight fouled the headgear arrestors since there was insufficient headroom to operate quickly enough, and the cage bottom collided with the penthouse.  86 people were in the cage where 75 were injured and 11 people died.  As with most accidents there were systematic issues that led to the tragic accident.  Changes had been made to the software, there was no prework assessment and a lack of communication regarding the changes, plus the competency of those involved, according to the findings of the Department of Mineral Resources and Energy of South Africa. It’s easy to forget that mine hoists can carry large numbers of people, similar to a bus.  Therefore, the safety implications are significant.

This is not an isolated case, even in the US, the Mine Safety and Health Administration completed impact inspections in October this year at 15 mines in Alabama, Arkansas, Colorado, Illinois, Kentucky, Louisiana, Michigan, Missouri, Nevada, New York, Pennsylvania, West Virginia, and Wyoming and issued 286 violations.

Given the risks involved, especially with hoists, conveyors and now with driverless vehicles being used both above and below ground, the need for functional safety is more apparent.  Depending upon the level of risk and approach, a combination of risk-based, performance-based, standards such as IEC61508, IEC61511 and machinery standards such as ISO13849 and IEC62061, is required.  Undertaking the proper risk assessment approach and using techniques such as Layer of Protection Analysis (LOPA) can help identify the correct level of mitigation and risk reduction required.  With the level of automation and complexity involved, ensuring the equipment is correctly designed, implemented and maintained, to achieve the given level of risk reduction is paramount.  Ensuring that operators and maintenance staff are properly trained and competent will ensure that failures, such as occurred at the Impala mine, are few and far between. 

In 2024 alone, in the US, there have been a total of 27 fatalities through November, which is unacceptable in today’s modern world.  Although not all of these were automation related, developing the appropriate risk analysis and assessment techniques is paramount for safety critical machinery.  Adopting a more risk-based approach will ensure that automation equipment used in safety and control systems will be properly designed, implemented and maintained.

Here at exida we have been helping mining companies to undertake and implement the IEC risk-based, performance-based standards, such as IEC61508 and IEC61511.  If this blog has generated some interest, then look out for the upcoming webinar on applying Functional Safety in mining applications.