Fire protection systems provider Advanced Automated Systems (AAS) is focusing on improving the fire prevention system of conveyors as opposed to most fire-prevention companies that try to prevent the spreading of fires already active on conveyor systems.

AAS has, therefore, finalised the initial tests on its distributed temperature sensing technology, which recognises frictional heating before pyrolysis – the thermal decomposition of materials at elevated temperatures in an inert atmosphere.

This technology is based on the technology of international phototonic specialist LIOS Technology, whose technology is known by the same name. This has been used effectively in transport systems on motorways, and in tunnels and subway systems in Europe and has been improved upon over the past five years by AAS technical director Herbert Schmitz to suit the South African mining conveyor industry.

“We looked at the application in the sense that, essentially, a mine is a tunnel, and we could apply the LIOS Technology to South Africa’s mining spaces.”

Having realised this, Schmitz undertook to conduct testing and development of the product and has now offered the LIOS Technology for implementation in the local market.

Schmitz compiled his research with the assistance of original-equipment manufacturers in the local conveyor industry, and through correspondence with petrochemicals company Sasol Mining group environmental specialist Inus Labuschagne on the research he has previously published on conveyor belt flammability.

Their research shows that conveyor belts do not spontaneously burst into flames and require significant heat energy and time to burn freely. Most conveyor-belt fires are preventable if the correct detection technology is used to measure the environment around the conveyor installation for heat build-up.

The fibre-optic technology of the LIOS system can measure and detect irregularities or fluctuations in temperature well in advance, and proactively notify operators where and when a fire might occur. The fibre-optic sensor cable measures the temperatures in a continuous profile, refreshing measurements every eight seconds.

The LIOS system is integrated with the mine’s control room either through a hardwire to the programme logic controller, or interfaced through an industrial protocol system such as Modbus.

Once an abnormal elevation in temperature on a conveyor system is detected, a message is sent to the control room. The message is received by the supervisory control and data acquisition system and the exact position of the alarm is conveyed to the operator.

If the alarm is not attended to before the situation escalates to a fully fledged fire, a secondary alarm is triggered, which then trips the conveyor system, and escalates the alert to more senior personnel.

“This system not only detects the possibility of a fire but also helps to prevent them,” boasts Schmitz.

In addition, the fibre-optic cable responds to temperature changes faster than conventional thermal sensors, requires no maintenance and is not affected by factors such as humidity, dirt, smoke and radiation.

“There has been interest in the technology and we have eight kick-off projects in the local pipeline already,” adds Schmitz. This is in addition to a South African platinum producer implementing the technology at its concentrator in the North West earlier this year, with a current trial installation being implemented by a large coal operator in Mpumalanga.

Conveyor-belt fires are largely avoidable, but are the cause of a number of this year’s 58 mining-related fatalities reported at the end of July by Minerals Council South Africa.

While current fire protection systems deploy water deluge spray systems to suppress a fire after it has been detected, extinguishing it completely is neither guaranteed nor efficient when dealing with a flaming conveyor belt.

Stamp of Approval

An independent assessment presented at the Mine Ventilation Society of South Africa’s conference, held in Gauteng in June this year, confirmed that the LIOS optical-fibre sensor cable can continually measure the temperature with a high accuracy and resolution over vast distances, making it ideal for conveyor infrastructure.

Schmitz says that conveyors, electrical infrastructure and other mechanical equipment – which all fall under the fire risk areas stated by the Department of Mineral Resources – can all be monitored by one complete system.

“Once the system has been implemented in more volatile environments, we will be able to assess how many fires the system has prevented. Until then, we are sure that we can at least warn of where the dangers lie,” Schmitz concludes.