Manchin said he would include a ban on the practice — which some safety experts say spreads fires and toxic gases — in the additional mine safety reforms he proposed in the wake of the Sago and Aracoma mine accidents.
Current regulations require conveyor entries to be isolated from primary escapeways but allow belt air to be used at the face under certain conditions. If a mine elects to do this, significant upgrades to fire protection and monitoring are required, including lifelines and additional self-rescuers.
In order to comply with the fire protection upgrade clause, some mines use a dry powder system of fire suppression. While relatively low in cost compared to a water deluge system, it is a one-shot type of application, according to ventilation experts. If deployment of the dry powder does not immediately put out the fire, there is no second chance.
One of the problems is that a detection and suppression system for a conveyor belt would have to be very sophisticated in order to identify the location of the fire and deploy sufficient powder to suppress it.
Furthermore, while detection systems are a requirement in the US, the legislated alarm set point of carbon monoxide monitoring is based on the concentration of carbon monoxide rather than being specific to a particular location. This may mean that the alarm set points are too high in areas where there is a large quantity of air.
The calibration accuracy of the instruments is sufficiently wide to make them relatively insensitive to carbon monoxide as a fire detection device, making the system of limited use in early detection. In addition it has been shown carbon monoxide monitoring systems rarely detect belt fires; people do.
Bottom line: segregation of belt roads is a good idea. According to experts, if a fire is going to start in a coal mine it will most likely be either a conveyor belt or an electrical installation that starts it. This makes a belt road a high probability to be the source of serious mine fires.
If a conveyor fire starts, it is reasonably straightforward to access clean air in the escapeway. However, if that air is then directed to a workplace, the segregation may simply ensure that the products of combustion end up where the majority of people work.
Hence, if intake belt air is used to ventilate the face, additional protection against fire is a requirement in the US. The problem as history has shown is that mines struggle to prevent/detect/extinguish fires on conveyors. It would be interesting to compare the incidence of belt fires in mines equipped with fire suppressions systems with those that are not.
Mines that use belt air to ventilate working faces typically do so because they have to do so in order to get sufficient ventilation. If all mines had to dump belt air to return, this could, in some cases, render their ventilation system inadequate, effectively solving one problem but causing another.
There is more to surviving an incident in a coal mine than escapeways and fire suppression. A future article will consider the various prevention and escape strategies adopted in different parts of the world.
