SAFETY IN LONGWALL MINING

[Music] down through the centuries coal has been one of the primary energy sources used to fuel the world's industrial operations as industrialization and the demand for coal increased better mining methods were needed [Music] this increasing demand for coal led to greater technical advances in mechanized mining methods [Music] potentially the most productive and safest method of mining being used today is the long wall system [Music] long wall mining is relatively new to most american coal operators in contrast to other major coal producing countries which mine practically all their coal by this method the long wall method is believed to have originated in england near the end of the 17th century and has since become the most widely accepted mining method there and throughout all europe basic long wall mining equipment consists of either a planer or plow type cutting machine that slices off the coal as it is pulled along the face or a shearer type cutter that travels along the face cutting the coal as it goes coal cut by the shearer falls onto a mobile face conveyor called the pam line [Music] [Music] [Music] hydraulic chucks or shields support the roof and are individually advanced as the coal is cut [Music] the long wall mining system differs from conventional mining in that the coal seam is removed in one operation by means of a long working face or wall from which the name long wall is derived the coal is mined in a continuous line cutting across a coal face which may be several hundred feet in length [Music] there are two basic systems of long wall mining the advancing and the retreating system in the long wall advancing system of mining the coal is extracted from the face starting from the shaft and advancing through the coal deposit toward a boundary or other limit lines in the long wall retreating system narrow developing headings are driven through to the boundary or limit line of the coal seam and then the coal is extracted by long wall faces retreating back in the direction of the shaft as the mining machine makes a pass across the face cutting a width of coal the pan conveyor and roof supports are advanced immediately behind it toward the new face as this happens a void is left behind the supports the roof is allowed to collapse or cave in filling this void [Music] the fallen material is called gob [Music] a double ranging drum shearer is shown in action here it is especially effective in high seams of coal and where the coal bed varies in thickness and composition the spiral drums are equipped with an internal water spray system as well as externally mounted sprays to more effectively control dust [Music] the broken coal that falls from the face is picked up by an armored flexible conveyor or heavy scraper chain conveyor that also serves as a track for the shearer this conveyor carries the coal along the face to the head gate entry and dumps it onto a gate chain conveyor or stage motor which then feeds it to the entry belt conveyor [Music] from here the coal will be delivered in the mine cars or conveyors which will transport it to the surface a very important part of the long wall mining system is the powered self-advancing roof supports the most common type in present use are the chalk roof supports the chalk system shows much improvement over conventional roof control methods but a number of disabling injuries have been caused by loose rock falling between the canopies striking the worker unexpectedly in many long wall operations today shocks are being replaced by a newer shield type support this assembly of steel hydraulic supports is moved forward as an integral unit by means of a hydraulic ram coupled to the face conveyor proper alignment of long wall support and conveyor is important failure to keep the distance between the support tip and coal face to a minimum can cause bad roof conditions to occur in the face area [Music] the shield type of self-advancing roof support provides an added safety factor in that it isolates the worker from the god [Music] there is less dust or rock falling down between the supports and because they are fully enclosed they prevent virtually any spalling rupturing or caving of the gob into the working area improved shield supports provide better overall protection from fall of ground and offer other important safety features not provided by earlier conventional shocks for example rocks falling from the roof as shields advanced are deflected by the canopy or gob shield the travel way under the shields will also have fewer obstructions and since the overhead canopies are of solid construction with no gap between adjacent shields the worker is safer and feels more secure long wall mining methods usually create more dust than other methods and methane emission rates are increased special attention to the application of water and ventilation is required to control these hazards current methods employed to control coal mine dust and methane include the use of cowls to help confine the dust [Music] proper positioning of water sprays and proper application of a sufficient quantity of air air can be directed up one entry across the face and out the return entry or through the gob into the bleeder system long wall miners have methane monitors mounted on the machine itself or at the tailgate to warn the operator or shut it down if methane emissions reach a dangerously high level also the operator is required by law to make gas tests periodically at intervals not to exceed 20 minutes the urgent problem of supplying our nation's increasing fuel needs has resulted in a search for high productivity methods of mining long-wall mining may be one of the solutions a growing number of coal mines in the united states today have operating long walls and many of them report that the system has not only improved productivity but has also helped reduce the accident frequency rate [Music] despite the fact that long wall mining is potentially the safest technique available in actual practice up to now its overall safety effectiveness has not been appreciably better than other mining methods therefore the hazards involved in long wall mining must be identified and eliminated or guarded against if the workmen are to be effectively protected and the safety of the mining operation improved to help prevent accidents from roof falls shields are equipped with hydraulic controls placed safely beneath the support this allows the miner to advance the unit while remaining under the protection of the shield at all times when compared with conventional chalk systems of roof support workmen are much safer with a long wall mining system using shields as the primary means of support but experience has shown that there are still hazards involved with the use of shields and that the potential for an accident is always present for instance there's the possibility of pinch points causing foot accidents [Music] these and other accidents sometimes occur during the advancing of supports or when moving the long wall equipment to another panel some typical ones are hydraulic hoses can suddenly break [Music] jacks can pull loose and fall on a worker ropes and chains of come-alongs can break and workers can get muscle strains pinched fingers and be hit by falling crib blocks while constructing cribbing moving supplies across the long wall face is difficult due to limited space between the hydraulic legs and the pan line disabling back injuries twisted knees and muscle strains due to tripping slipping and falling frequently occur on long wall mining sections this emphasizes a need for greater alertness on the part of minors to prevent these injuries [Music] clean up and repair activities along the pan line can also involve mine workers in hazardous situations [Music] the worker may be subjected to possible falls of the face or roof from between the tip of the canopy and the face after the long wall miner has passed roof hazards are often present in front of the supports before they have been moved up for this reason the roof support should be advanced as soon as possible to keep newly exposed unsupported roof to a minimum proper safety procedures must be taken to control the roof when working on the pan line additional support may be required such as hinged face shields or if the equipment does not have hinged face shields hydraulic props may be used [Music] [Music] installation of additional roof support is often necessary at the gate entry cribbing roof bolts or hydraulic props such as these can be used this extra support helps protect miners who have to work in this belt head area from fall of ground accidents accidents can happen during repair and maintenance activities the equipment on long walls is massive and space is usually limited especially between the conveyor and shields [Music] workmen may be struck by hoses or machinery and they may bump into or be caught between the equipment [Music] the danger of working with and around electrical equipment especially in cramped underground quarters is another hazard that workmen must be aware of recent accident statistics show that well over half of the injuries on long wall sections occurred to minors with less than two years experience at their regular jobs they could turn it on and you'll be careful greater emphasis must be put on the miner's training before he starts his regular job to better prepare him to do his job not only effectively and efficiently but in the safest way possible improvements are continually being made in long wall mining equipment permissible fluorescent lights that mount on the shield supports have been developed to provide illumination for the entire length of the line improved communication systems have made it easier more efficient and safer for the long wall mining crew to operate or work together santa clara the face conveyor stand clear [Music] the system can also be used as a warning device to let everyone in the long wall mining section know when the chain conveyor or shearer is going to start up this is vitally important for the safety of the crew members [Music] [Music] as our country's need for coal continues to grow the trend to use long wall mining methods continues to find increasing application in our coal mining industry long wall mining offers the advantages of higher production and efficiency and the potential to provide our nation's miners with a safer work environment [Music] so