Roof Bolter
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A roof bolter is a hydraulically driven miner-mounted bolting rig used to install rock bolts in mines, tunnels, underground power plants, and storage facilities.
Roof bolting is also a common application in underground coal mines for securing mine roofs to be self-supportive. It is extremely dangerous as an occupation, accounting for nearly 56 percent of injuries in underground coal mining operations.[1] According to U.S. law, all underground coal mine entries must be roof bolted.
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[edit] Features/How it Works
A roof bolting machine works by drilling directly into the rock strata and inserting either conventional bolts or resin roof bolts. Some roof bolting machines may feature a two-stage frame and carriage that enable it to extend and drill to varying roof heights. The machine uses a bidirectional type drill to allow for the drilling of bolts from four feet (1.2 m) to 12 feet (3.7 m) into the rock in addition to the tightening and tensioning of the bolts to a preset torque.[2] Roof bolting machines may also come equipped with an inbuilt hydraulic timber jack that provides temporary roof support during the drilling process. Some roof bolting machines may come equipped with a protective cab or canopy to protect the operator from possible rock falls. The canopy is usually articulated and mounted to the front of the machine to allow for greater vertical movement.
Conventional roof bolting operations in a coal mine worked with the coal mining machine moving forward in the shaft mining the coal until a new portion of roof area was exposed. Mining was then stopped to prevent the risk of rock falling onto the operator carrying out the roof bolting operation. This maximized the safety of the operator bolting the roof but resulted in long breaks that disrupted the production cycle. Attempts were even made to mount roof bolting equipment to roadheaders but with limited success.[3]
More modern roof bolting machinery, however, is automated to completely remove the risk of having the operator be exposed to falling rock while roof bolting is being carried out. The roof bolting machine is operated via remote control from a safe position located away from the unsupported roof area. Automated roof bolters can also double the productive capacity of existing mining equipment by completely eliminating any disruptions in the production cycle.
[edit] Types
In the U.S. roof bolters are designed to provide automated temporary roof support (ATRS). The two types of roof bolters commonly used are:
Single boom – a roof bolt is installed from one machine setting. The machine must then be repositioned to install the next bolt. The area of support is typically five feet by five feet square (1.5 x 1.5 m2), encompassing the bolt location.[4]
Dual boom – is a roof bolting machine that features a bar- or beam-type ATRS system that allows multiple roof bolts to be installed from one machine. The intended area of support is much larger, resulting in typical load capacities of excess of 33,750 pounds (15,309 kg).[5] Double boom roof bolter with a bar-type ATRS system has advantages over single boom roof bolting machines. Far less time is actually spent positioning the machine and with two drill booms instead of just one, the installation process in cut in less than half the time it a takes a single boom roof bolting machine. Dual boom roof bolters are very common for example in the room-and-pillar coal mining method. They are even available as walk-through models in conditions where unstable rib may present a hazard to roof bolter operators. Crawler-mounted roof bolters are also available for working in mines with softer ground conditions.
[edit] Common Manufacturers
[edit] References
- ↑ Walk-Thru Roof Bolting Machine Trainer's Guide. 17-06-2009.
- ↑ Evaluation of Roof Bolting Requirements Based on In-Mine Roof Bolting Drilling. Dept. of Mining Engineering. West Virginia University. 17-06-2009.
- ↑ Evaluation of Roof Bolting Requirements Based on In-Mine Roof Bolting Drilling. Dept. of Mining Engineering. West Virginia University. 17-06-2009.
- ↑ Use of Single-boom Roof Bolting Machines. United States Dept. of Labor. Mine Safety & Health Administration (MSHA). 17-06-2009.
- ↑ Use of Single-boom Roof Bolting Machines. United States Dept. of Labor. Mine Safety & Health Administration (MSHA). 17-06-2009.
