Monday, January 19, 2015

Coal Mine Safety

Photo taken at The Museum of the Coal Industry
The geologic processes that made coal are similar to the processes that make methane gas. So one of the dangers of mining coal was releasing methane gas. To test the quality of the air, the miners would carry a canary in a cage with them.
Photo taken at The Museum of the Coal Industry
In 1815, Sir Humphry Davy invented a safety lamp. It had a fine mesh covering so the flame of the lamp would not ignite any gases in the mine. The photo to the right is a modern safety lamp. Normally, it would have horizontal lines painted on the transparent part. The height of the flame should be halfway up. If it was higher than that, it indicated there was gas in the air. If it was lower, it indicated that oxygen was below normal.

After visiting The Museum of the Coal Industry where the pictures of the cage and lamp were taken, I noticed an article in the Evansville paper with the headline "Sensors for Safety" on the front page. The picture below was also on the front page.
Photo by Timothy D. Easley with government and company escorts
Dylan Levan reported that the U.S. Mine Safety and Health Administration is requiring continuous mining machines to have proximity detectors because the most common cause of the 40 deaths at all the nation's mines last year involved hauling and mining machinery, including 10 at coal mines. Continuous mining machines have crushed 35 miners since 1984, and MSHA says most of those deaths could have been prevented with proximity detectors. But it has been hard to develop sensors that work in the harsh conditions of an underground mine. The mine operators played an active role in developing the sensors. About half of the 860 CMMs in the country now have them installed.

Note the bar near the top of the photo of this mine that is two miles underground. That is part of a roof support. After the CMM advances the working face, it is backed out and the wire mesh and roof supports are added. A roof support is added by drilling upwards so that a long rod can be inserted in the ground to hold the bar. The nut you see is fastening the long rod to the bar. Two decades  ago most deaths were caused by roof collapses, but those deaths have been reduced so that machines have now become the primary danger.

The article also had a side bar about underground mining. Notice that the walls, floor, and roof are grey, not black. They are sprayed with crushed rock to help mitigate fires. "Coal dust is highly combustible, and in the event of a blast, the rock dust mixes with the coal dust and prevents the spread of flames." In and out ventilation shafts are used to remove the methane gas and keep the air fresh.
Even for a short tour, media members were required to wear steel-toed boots, a hard hat with a light, safety glasses, reflective clothing and a heavy belt with a 10-minute oxygen canister. Before entering the mine, there was ashort training session with exygen breathers and an explanation of mines escape routes in case of an incident.

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