Proximity Detection and the Last Line of Support

26th October 2017


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The South African coal mining industry led the way for the world when it first installed Strata’s HazardAvert proximity detection systems on underground mining equipment over nine years ago. The technology was created to address the need for safeguarding against crushing and pinning-type accidents between machinery and miners on foot.

Today, the inclusion of proximity detection and collision avoidance systems into mining safety procedures has become a worldwide industry-driven initiative. A number of major South African coal mines utilize these systems on all types of mobile machinery in everyday operations.

HazardAvert was designed to enable automated, two-way communication between miners and mobile machinery by creating “hazard zones” around equipment and detecting when an individual breaches these zones. The electromagnetic zones interact with miner-worn Personal Alarm Devices, or PADs, and the PADs emit warning alarms. If alarms are triggered and no corrective action is taken, or in the event of a sudden emergency, a HazardAvert system that has been interlocked into the equipment will automatically stop the machine to prevent collision. This option is set at the discretion of the mine.

In recent months, a South African coal mine approached Strata to enquire about an alternative function of the proximity detection technology.

The mine was finding that, at times, continuous mining machines were inadvertently advancing too far forward into the coal seam, possibly passing the last line of roof support, and mining beyond the Department of Mineral Resources’ (DMR’s) ventilation recommendations of a 30-metre allowable distance in front of the jet fans (force fans).

Since the jet fans create positive air flow over the machine cutter heads to prevent methane gas build-up, this resulted in a potentially high safety risk. Additionally, the shuttle cars were subsequently being forced to advance into unsafe territories.

In an effort to prevent this situation in the future, Strata engineers reconfigured the proximity detection technology to detect when the continuous miner is too far away from a PAD as opposed to being too close. The system works for this application by attaching the PAD to the jet fan, and as the continuous miner advances forward, the technology detects when the electromagnetic field is too far out of range. At this time, the system alarms and shuts off the cutter head, and the CM must then be reversed.

This configuration can also be applied to shuttle cars, whereby the system detects when a shuttle car is entering an unsafe area and stops its forward movement.

“Initial surface testing was conducted on the 6th of October 2017 and the mining group was extremely happy with the results,” states Ian Cillie, general manager of Strata Worldwide, South Africa. “As soon as the technology is certified for use underground, we will begin the next phase of testing in the mine.”

For more information, please contact us at + 27-12-450-0960 or email

ABOUT STRATA WORLDWIDE – Strata Worldwide was originally founded in 1992 and is headquartered in Atlanta, Georgia, USA. The company has operating facilities in Johannesburg, South Africa and New Castle, Australia, with product distribution worldwide. As a leading provider of products, services and technologies that promote higher levels of safety in global mining industries, Strata’s portfolio of safety products includes proximity detection and collision avoidance systems, wireless communications, tracking and gas detection, emergency refuge chambers and underground roof control.

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Edited by Creamer Media Reporter


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