CSIR system helps deep-level mines talk to the surface

Impala Platinum mine in North West Province. (Image: Media Club South Africa)

The system, named AziSA - isiZulu for "to inform" - allows for timely communication that can be processed in a useful form, providing support for decision-making in the often dangerous conditions underground and reducing reliance on sometimes low-skilled workers. South Africa has some of the deepest mines in the world, with some shafts reaching over three kilometres underground.

"Labour-intensive drill-and-blast mining, as conducted on the major South African gold and platinum mines, is often not tightly managed due to the lack of good information about what is going on underground," says the CSIR. The council, established 60 years ago, is one of Africa's leading science and technology research, development and implementation organisations. Its work includes multidisciplinary research, technological innovation, and industrial and scientific development.

AziSA is "a specification for an open measurement and control network architecture that will facilitate decision making". It will operate in underground mining environments in which there is limited power and communications infrastructure.

A group of six South African researchers - Roger Stewart, Steve Donovan, Johann Haarhoff, Van Zyl Brink, Liam Candy and Declan Vogt, from the CSIR Natural Resources and the Environment division - have been working on the system since 2009.

"AziSA is an architecture for how to measure, communicate and store measurements in an underground mining context. It isn't a product as such, more a standardised way of doing things," says Vogt, strategic research manager at the CSIR Centre for Mining Innovation. "Our aim is to provide a way for different equipment suppliers to work together to use the same communication and database infrastructure, saving time and money rolling out their own solutions."

The system will reference "existing open standards, chaining them together to form the various stages of a network, and only adding to the standards when desired functionality cannot be obtained from an existing standard".

AziSA was created to offer "support for low cost, low power and wireless networks, as well as organisation and openness", says the CSIR.

Sensors

The system works with AziSA-compliant sensors that are added to the network with a minimum of human intervention. A sensor refers to a sensing platform, a node on the sensors, with each transducer measuring an aspect of the underground situation. This results in accurate measurements with adequate precision that gives both the time and location of each measurement.

"Sensors are required to be able to identify themselves and make their presence known to the network, send data to an aggregator and respond to instructions from the aggregator (eg to change a detector's sampling rate), perform a health check and detect if these have been tampered with."

The system is sufficiently robust to monitor potentially hazardous conditions and provide for communications even if the link with the outside world is broken.

Sensors would be small battery-powered devices that communicate wirelessly with the aggregators, which would be situated at the nearest power point. Each sensor will have several detectors attached to it, monitoring various aspects of the environment.

"The sensors should be low cost and maintenance free (preferably disposable, with battery life as long as the sensing functionality is required), and would ideally have the capability of determining their own physical position," says the CSIR.

The aggregators transfer the data received from the sensors to some point at which a conventional IT infrastructure will send it on to the shaft, and from there fibre-optic communication is used to convey the data out of the mine to the network controller.

Workplace safety

The system has already been implemented, says the CSIR. "Several relatively small systems have been implemented using AziSA principles. These include systems for monitoring waste and ore separation, safety in the workplace, and the underground environment."

Roll out has taken place at Gold Fields (now Sibanye) in Gauteng, and the Impala Platinum in North West province, and at the New Denmark colliery in Mpumalanga.

The CSIR is optimistic about the system's future use. "It is hoped that CSIR efforts to develop AziSA as an open standard will cause a rapid uptake of the technology on South African mines, and lead to widespread use, with consequent benefits to safety, health and production."