By Sharyn Macnamara

African Mining turns the spotlight on the Sibanye-Stillwater Rustenburg operations –specifically Khuseleka shaft 1, in part 2 of a series of articles discussing the importance and benefits of adequate lighting to miners in underground environments, particularly in light of preventative measures in fall of ground (FOG) incidents.

Join African Mining, incorporating Mining Mirror as we descend to a depth of 986m from surface with Eric Cilliers, acting VP Engineering and Marko le Roux acting engineering manager Sibanye-Stillwater at Khuseleka shaft,1 where the company is trialling lighting solutions to ‘engineer out’ the risk in in-stope illumination. Here the team have uncovered and are in the process of solving some of the challenges. The mantra at Khuseleka is “together we shine,” which is particularly apt in the face of what the industry is trying to achieve with lighting and in this particular case study.

Setting the scene

Left to right: Eric Cilliers, acting VP engineering; Marko le Roux, acting engineering manager Sibanye-Stillwater and Hennie Bodenstein, appointed mine overseer at Khuseleka shaft. All photos by ©Sharyn Macnamara, African Mining

Left to right: Eric Cilliers, acting VP engineering; Marko le Roux, acting engineering manager Sibanye-Stillwater and Hennie Bodenstein, appointed mine overseer at Khuseleka shaft. All photos by ©Sharyn Macnamara, African Mining

En route underground, the team set the scene for us in detail. FOG incidents have historically been number one cause of fatalities in the mining industry in South Africa and the majority of these accidents happen in areas zero to four metres from the stoping face in conventional mines. Miners must rely on their cap lamps for illumination and rockfall hazard identification underground. This lighting is often insufficient, and this forms the crux of the challenge, and has led to underground workface illumination case studies conducted by Minerals Council members to investigate solutions to improve the ability that the workforce has to identify FOG hazards in this area of a mine.

Sibanye-Stillwater has taken a phased approach to in-stope illumination solution seeking in collaboration with the Minerals Council ever since the FOGAP (Fall of Ground Action Plan)2 was adopted by the CEO Zero Harm Forum, and workface visibility was identified as a quick-win project. Sibanye-Stillwater investigated, sourced and purchased LED lighting strips for trials, taking occupational health considerations and MOSH-approved Improved Underground Workface Visibility Leading Practice in 2022 into account. In 2023 these strips were installed in various work faces across several of the company’s operations to determine practicality, robustness and efficiency, and these trials are still in progress.

“Every day we send people down into an ever-changing potentially hazardous environment,” said Cilliers. “For us as leaders to enable our employees to identify hazards to the best of their ability is the way forward. These trialled lighting solutions will lead the way to solutions that will assist with safety and operational excellence and will become industry best practice.” Sibanye-Stillwater intends on making underground illumination and improved underground workface visibility one of their minimum standards.

Illuminating the challenges

Starter box – electrical connection point, more than 50m away from the face. All photos by ©Sharyn Macnamara, African Mining

Starter box – electrical connection point, more than 50m away from the face. All photos by ©Sharyn Macnamara, African Mining

“Due to the changes in face configuration and ground conditions after a blast – the entry examination is the most important period of the cycle and miners need the maximum and safest illumination available at this point to check hang and features on the face, to make the area ready and safe for the drilling team. One of the biggest challenges has been to find a practical solution based on the unique design of each operation. The illumination solution is dependent on the layout of the operation and where the power supply is located – and each operation is different.”

Cilliers explains that the team has achieved quick wins by illuminating underground areas used by trackless mobile machinery (TMM), development ends, travelling ways and cross cuts, which can use a higher voltage LED strip-light illumination. “Sibanye-Stillwater’s modern trackless operations have also rolled out high-voltage, mobile spotlights to assist with the examination of bords where a bord and pillar mining method is used.”

In contrast, Khuseleka case study has proved to be a more challenging environment, primarily due to the fact that the operation utilises a conventional mining method. Conventional stopes are significantly narrower than mechanised stopes, which have an immediate limitation when using low-voltage LED strips, where LED lumen performance is reduced by the length of face as well as the distance to the electrical outlet. Many conventional underground mines in South Africa face the added risk of methane gas entering the stope environment, with the possibility of explosions posing a significant safety concern.

“We cannot use a 110V or 220V system in a potentially hazardous area where there is a possibility of drilling into a pocket of methane which can cause ignition – low voltage i.e., a 32-48V, either AC or DC, is the only option to install close to the face. The maximum length of an LED-strip supplied in this low voltage range is 50 metres and due to the distances from the starter box to the face, there will always be the need for a point of connection, which increases risk because of possible arcing. Between 3 500 – 4 800 lumens or kelvins is the ideal illumination at the face – which is almost a daylight comparative. This cannot be achieved with the current solutions in these environments – even if we could safely connect these strips – due to the fact that, as one extends the length, the light emitted fades and the illumination loses impact. So, we are working on another more practical – quicker charging and lightweight – lighting system, for the miner, which can be easily and safely installed in the morning before the face is examined.”

The LED strip solution system was therefore unsuccessful at Khuseleka, and while the goal is to move to a strip light solution at Khuseleka to achieve constant light, African Mining was shown a robust, mobile spotlight system in action at the face, which has turned out to be more appropriate in the interim. Hennie Bodenstein, appointed mine overseer for Section 420 and the Merensky section 234 on 28 level on the western side haulage, took us to the lowest level at the Khuseleka operation where 75 miners are operating at any one time and benefitting from this alternative. (Watch our video of the difference experienced with and without the spotlights in action.)

Sibanye-Stillwater is working in partnership with suppliers to develop safe, practical solutions to raise the voltage of the stripLEDs for maximum illumination at greater distances to aid miners in their work at the face. Watch this space for developments!

Key technical considerations

 An in-stope lighting solution that offers above 5 000 lumens or kelvins light spectrum is equivalent to midday sunshine and is the best lighting that one could ask for in a mine. These are the current prescribed guidelines: Calming yellow lights are good for residential spaces offering a 2 700 – 3 000 light spectrum, energising white light is recommend for work areas – 3 500 – 4 800 light spectrum, and daylight white 5 000 and above light spectrum is recommended for precision areas such as hospitals or lab research areas.

There are a number of products available in the industry and when selecting a suitable product for underground, it is extremely important to ensure that: there is an OEM certification from industry recognised institutions, together with guarantees; the system is safe, robust, durable and easy to install and remove; it must be energy efficient, for example, the lights are dust and water resistant because dust repellent systems maintain the ‘white light’ and prevent dulling of illumination caused by dust collection.

The benefits of good illumination

Based on solid theory, the mining fraternity is clear – poor lighting is a health and safety hazard. Research estimates that 80-85% of human perception, learning, cognition, and activities are mediated through vision. In fact, the visual system is our most dominantly relied upon sense and when the other senses are impaired, it can take over some of their responsibilities.3 Humans receive about 85% of information through the visual sense and there is a 36% greater chance for accidents in poorly lit areas; and quality of lighting in a workplace influences productivity by 10-50%, while good lighting can decrease errors by 30-60% and improves circadian rhythms4 in a workforce working day and night shifts. A cap lamp has traditionally been the only light source a stope miner had, and with its small arc of vision, often required the miner to move her or his head towards the item they wanted to observe at the face of the rock, which is unsafe practice.

It has also been noted that poor illumination can lead to other safety hazards, including tripping, slipping and falling, derailing of machinery and equipment damage, poor drilling, charging and timing discipline in blasting, and difficulty for miners to estimate shape, size and depth of objects with resultant poor strata control due to insufficient identification of visible geological features like hairline cracks and the opening up of joints.

On the flip side, good illumination can:

  • result in increased visibility of hazards including mobile machinery and others in roadways or haulages
  • lead to better drilling and blasting discipline resulting in better ground conditions
  • improve legibility of safety signage or instructions and identification of sub standards
  • improve observation of deterioration in ground conditions and general housekeeping
  • improve circadian rhythm and concentration and uplift the mood or energy levels of the workforce leading to reduction in fatigue and
  • vitally improve the safety and well-being of women in particular
  • reduce general workforce ailments such as headaches, eye/neck/back strain and lead to a decrease in depression, anxiety and stress linked to underground conditions

References:

  1. The Rustenburg operation consists of three intermediate depth vertical shafts that utilise a conventional mining method at Siphumelele 1, Khuseleka 1, and Thembelani 1 – while the mechanised Bathopele inclined shafts utilise a shallow inclined bord and pillar mining method.
  2. The Minerals Council South Africa’s FOGAP (Falls of Ground Action Plan): The six pillars focus on adoption of leading practices, implementation of research, capacity building of robot engineers, implementation of policies, facilitating zero harm enabling environment and monitoring of FOG safety performance. The action plan, approved in July 2021, included a financial investment of R46-million over five years towards research and development. Adwoa Issaka of the Minerals Council’s MOSH FOG Team said in workfaces and ancillary excavations, employees rely only on their cap lamps for illumination. Cap lamps are inadequate for proper rockfall hazard identification.
  3. https://velvetchainsaw.com/2012/05/23/your-senses-your-rawinformation-learning-portals/
  4. https://sensoryprocessinghub.humber.nhs.uk/sense-visual/