To improve the safety and highly dynamic conditions associated with underground stoping activities, gold major Harmony Gold has implemented an innovative new lighting system in the working faces of its Mponeng mine, near Carletonville, in Gauteng, South Africa.

The Instope lighting solution produces ten times more light than traditional cap lamps, helping underground teams identify hazards earlier, thereby improving workplace visibility and enhancing overall underground safety, reports Mponeng mine rock engineering manager Evert Kleynhans.

Harmony is currently rolling out the technology across 94 panels at Mponeng, which at about 4 km deep, is the world’s deepest mine.

“We believe that illuminating working spaces creates enabling environments, fostering an atmosphere of personal ownership,” he says.

The lower luminance strip light solution works better than a high luminance point source because the latter tends to cast more shadows/contrast and could temporarily affect the sight of nearby employees, which could have “unintended consequences”, says Kleynhans.

Thus far, he says some of Mponeng’s crews have already reported that the LED lights immediately “change the mood” of the stopes. This, says Kleynhans, instils a sense of professionalism and safety, as unsafe conditions are made immediately visible for all to see.

Having lights in the stope faces also assists service departments such as geology, safety and rock engineering in doing their assessments. Initial comparisons showed a significant improvement in quality of work and compliance to mine standards for crews with lights installed at Mponeng mine.

In describing the advancement of a stoping panel, he says the work is “in essence a form of civil construction”, which involves making the area safe, painting of drilling and support positions, support installation, equipping, drilling, charging up and timing.

“It’s a complex process and the higher the degree of quality of these processes, the higher the degree of general safety. Simply put, you wouldn’t want your house to be built in darkness with only cap lamps. Similarly, how then can we expect high quality stopes in the same conditions,” explains Kleynhans.

Complementary Solution

While Harmony has no plans to phase out standard-issue cap lamps, as certain areas of its mines are not illuminated, the company opted to focus the use of the LED light strips on stope faces, owing to this being the area where the most benefit has been realised.

“Cap lamps are a statutory requirement and serve as a redundancy, seeing as no natural light is available underground,” says Kleynhans.

The LED strip lights assist in providing a more enabling environment for employees to better identify hazards such as poor ground conditions, damaged or failing roof support or even unsafe acts by colleagues.

“As a miner, team leader, safety representative or general mining team member, you can observe a wider field of view which does not only focus on your own area, but also those of colleagues located elsewhere in the panel. This then allows for a cooperative and proactive response to hazards,” he explains.

However, implementing an advanced and modern lighting solution in a mine that saw first production in 1986, has come with challenges.

“. . . making major changes to a conventional mining process that’s more than 100 years old is challenging.

“Although a lot of continuous work had taken place behind the scenes, progress was initially slow but has since ramped up [since] the first working place was illuminated in March 2023,” says Kleynhans.

Although the Instope lighting was developed for in-stope use, he says Mponeng’s trackless section has recently adopted it of their own accord.

“This goes to show the perceived value and versatility of these lights: low power, adequate but not blinding light, and easy to install and remove. All features that make these lights user friendly and safe.”

Extending the illumination technology to other areas is also being investigated.

How Integration Works

Installation of Instope lighting is “relatively quick” and can be undertaken by one person in less than 30 minutes owing to the system being designed to be mobile, making it easy for the lights to move with the stoping crews, says Kleynhans.

The light strips are suspended on specially designed clips that attach to the permanent hanging wall mesh.

“An iterative design process was followed to identify and mitigate various electrical and fire hazard risks during the development,” notes Kleynhans, adding that should any damage to the system occur, the problem segment can easily be replaced.

The LED strips are powered by an independent step-down transformer reducing the standard 525 V power supply to 36 V. An added benefit of this unusual voltage is a discouragement of theft. The transformer was co-developed with electrical switchgear company Reef Switchboard Manufacturers to Harmony’s electrical standards. The transformer is installed on a pole in the nearest face winch cubby and moves forward with the face winch as the panel advances, while an armoured extension cable connects the transformer to the LED strip lights.

This system is designed to power up to 40 m of LED strips, which is based on the maximum panel length design.

Further, the distance of the LED strips to the panel face depends on the mining cycle, such as support installation or face preparation to blast. The strips are not designed to be blast proof and as such must be removed and stored away at the end of each shift.