Mine safety fletcher

Share on facebook
Share on twitter
Share on linkedin
Share on email
Share on whatsapp
Share on print

It wasn’t all that long ago that mine safety boiled down to common sense, heightened levels of self-preservation and a small yellow bird. But the days of canaries putting their lives on the line in the detection of coal gas have long gone. However, for all the advances in safety infrastructures major incidents still do occur, with the recent disaster at the Soma mine in Turkey putting a very sharp perspective just what can still happen.

The explosion at Soma, Turkey on the May 13 2014 was caused an underground mine fire, which burned until the May 15, total of 301 people. The cause of what is now the worst mine disaster in Turkey’s history is still under investigation. Unfortunately, mining accidents are scarily common in Turkey. In 2008, deaths per one million tons of coal mined were 7.22 in Turkey – sadly the highest figure in the world and five times that of China (1.27) and 361 times the rate in the US (0.02). Mining accidents are common; in 2012, 78 miners were killed in accidents – a number that rose to 95 the following year.

This level of death paints a rather grim picture that even in developed countries such as Turkey this type of incident can occur and, alas, rather regularly. In less developed countries with far lower and much less stringent health and safety legislation the death tolls are potentially even higher and a lot less well recorded.

Things are definitely getting better compared to the age of canaries and the first safety lamps. At the end of the 19th Century mining was easily one of the most dangerous industrial disciplines with disasters and death tolls that would just not be acceptable in today’s modern environment.

The major issue with mining is that it is heavy and hard; it needs equipment so powerful that the only dependable source of power and movement tends to be assets that themselves create fire risks due to fuel sources or their methods of operation. This is further compounded by natural fuel sources such as dust and gas and it is the management of these varying issues that form the basis of any fire prevention programme.

It is almost impossible to prevent ignition sources, so this means that the machinery fuel itself must be very tightly controlled and segregated, which is why fuel farms and chemical stores are either remotely located or comprise storage structures that make Fort Knox look like a flimsy open house.

Coal dust and methane are the ‘natural fuels’ most often encountered, with methane also being present in non-coal-based. Methane and other gasses are normally dealt with using high-power ventilation systems, which either extract or dilute the gas. A form of dilution is also used to deal with coal gas, where inert dust is added (such as crushed limestone) to remove the explosion risk from coal dust as a layer of coal dust just 0.012 mm thick could cause an explosion if suspended in air.

Advanced detectors are available for methane and other gasses, such as infrared absorption gas detection sensors, which provide gas sensing in the form of suitably ruggedised hardware coupled to low-current signal architectures. Coal dust is approached in a slightly different way, using optical sensors to measure dust concentration and levels. Dust particles produced in underground mines underground range in size from 0 to about 400 µm. The particles are not visible with naked eyes, so their control and measurement need technical equipment. Luckily they are good light absorbers so optical sensors can be highly effective.

Like most establishments, the prevention of ignition sources is the primary preventative measure. Smoking is the obvious no brainer, but when it comes to the vast volumes of electricity consumed, coupled with the incredibly high currents employed, electrical arcing can be a real issues. It is for this reason that many heavy duty motor switches have arc proof enclosures and the associated motors are enclosed with arcing protection. In many instances, the control gear for motors and conveyor systems also require the deployment of high working current, but thankfully there have been many technological developments in the last few years that allow for drives and PLCs to be mounted much further from the operating equipment and hence outside the risk areas. This technology has been spurred on by the oil and gas industry as it strives to reopen certain previously unprofitable wells and then undertake subsea processing; requiring very long cable runs for control signals and power lines.

Should the worst happen and a fire does break out, water is most often deployed as the primary means of fighting. The good news is that due to the depth of many mines the head of water and hence the pressure can be substantial, however there is still need for additional pumping for horizontal tunnels and larger chambers, which require higher pressure. In most instances, the water supply infrastructure is documented to the minute detail in order to ensure enough water can be delivered in enough time to prevent any fires spreading.

Expanding foam is also deployed in many situations and is ideal for filling voids and starving the fire of oxygen. A lot of research is undergoing in the development of more effective foaming techniques, especially with regards to the longevity of the foam and its effectiveness to remain feasible for a long enough time to allow for the subsequent cooling of the filled area.

If they do catch hold, some coal seam fires can burn for years and despite many attempts to put them out they are still burning. Indeed, in China, one fire at a colliery near Urumqi has been burning since 1874! However, even stubborn seam fires may have met their match with the development of the Górniczy Agregat Gaśniczy (GAG), a jet engine unit developed for controlling and suppressing coal seam fires and neutralising firedamp situations. The unit emits carbon dioxide, nitrogen and water vapour at a rate of 25 m3/s in order to lower the oxygen levels, suppress fires and force methane out of the mine by creating levels of less than 1% oxygen. It has been successfully deployed in Australia in 2000 where it extinguished a 54 year old coal fire and in West Virginia, where an Australian team extinguished a two-month-old fire after ten days of continuous operation.

All fire prone areas have the same three common factors fuel, air and ignition. Control of either of these three will result in less susceptibility to fire hazards, but as with so many other cases all three need to be tightly controlled as part of a concerted fire-fighting ethic. In the mining industry, all three are in abundance, so each has to be controlled as part of a holistic fire-prevention plan. Most developed countries have reams of legislation controlling mine operation, but this legislation has to be supported with commensurate levels of common sense and corporate responsibility. Unfortunately, it is the latter that seems to be the weak link in many situations, with organisation putting profit over people. Until this mind set changes, major incidents will certainly happen again and will make the headlines once again all over the world. The technology is there, the procedures are there and the legislation is there… maybe it is the people that need to change.

Subscribe to our newsletter

Don't miss new updates on your email