Dusty Story

In the mine, like in medicine, prevention is the best way of treatment. It means that it is easier to prevent an explosion than to fight with its consequences, which unfortunately turn sometimes into disasters. Explosion in coal mines happen, as a rule, because of accumulation of combustion agent – natural gas and/or slack – in the air underground. The natural gas and/or slack may explode spontaneously – simply because its concentration in the air has reached the critical value. To learn how much slack is accumulated in the coal mine will help the sensor developed by specialists of the Trapeznikov Institute of Management Problems, Russian Academy of Sciences, this institute is intended to invent various useful devices and management systems.

It should be noted that there are different ways to determine the quantity of accumulated dust, including that of slack. The easiest way is to pass a finger over a smooth surface, in the best case – over the varnished one. The method is demonstrative and tried by centuries, but it is not a quantitative one, and it would not work remotely. Instrument methods can be applied – for example, infrared sensors or piezoresonance sensors, which allow to solve the task accurately within micrograms, but they are unfortunately complicated, sometimes capricious and very expansive.

The sensor designed by the Muscovites ranks somewhere in the middle of the line. It meant that it promises to be sufficiently effective, i.e. automatic, quantitative and reliable, and at the same time simple and affordable, i.e. low-cost. It is called the radio-frequency sensor for quantity of accumulated slack.

The oscillatory circuit is the sensor’s detector element. On the flat substrate made of dielectric, for example, fluoroplastic, two wires – conductors and at the same time electrodes – are laid zigzaging in a specially turned rather shallow groove. This is the very oscillatory circuit, i.e. electromagnetic resonator, the parameters of which – resonance frequency and good quality – depend on characteristics of the environment. And thus they depend on the quantity of slack settled on the plate’s flatness and accordingly on the resonator groove. Sensitivity is determined by geometrics of the line – the distance between the conductors and their length.

Naturally, the sensor’s structure is such that it allows to take into account humidity and temperature fluctuations, although these fluctuations are not too large in coal mines – but precision is above all. Naturally, the authors also designed all necessary units and respective software for the sensor – electronic module converting resonator parameters into electric signal, interface block, computer controlling the system operation.

Probably the only drawback of the system is that it is not wireless. Cables and electric wiring are required to connect the sensor to the controlling computer. The maximum distance between the sensor and the computer is only 100 meters, although this is not little. However, miners would be glad to have such a sensor – during testing in the real mine circumstances the device worked precisely and reliably, the level of slack was measured accurate within almost 100 percent. It means that if mines had been equipped with such devices, at least part of explosions could have been prevented. When it comes to human lives, the opportunity to avoid the death of even one person is invaluable.