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The importance of continuous haulage technology has been steadily increasing in recent years. This is due, in part, to the natural depletion of the massive blocks of coal best suited to the economics of longwall mining. In fact, much of the underground coal that remains available for mechanized recovery requires the use of a continuous haulage system - with its inherent mobility and flexibility - for economic removal. This makes the optimization of continuous haulage systems an important issue for all mining operations.

Continuous haulage systems typically include a continuous miner followed by a series of short, chain bridge-type conveyors, as well as a section belt that contains extremely low conveyor structure, commonly referred to in the industry as Long-John or Low-Low structure. These systems have evolved dramatically over the past 20 years, and are a credit to innovative engineering and the industry's technical expertise. There are, however, areas of the continuous haulage system's performance that leave room for improvement. The most notable would be a better solution for the functional relationship between the Low-Low structure and the outby conveyor system, which has long been a source of frustration and expense.

Currently, with most continuous haulage systems, a common conveyor belt travels the Low-Low structure and the outby conveyor system. This approach, however, places extreme demands on the conveyor belting and leads to belt damage or the early replacement of belting. Because of its height dimension, the Low-Low structure uses steel slide-bars instead of rotating components, such as idler rolls. This creates significant drag and belt misalignment within the conveying system. Ultimately, the drag from the Low-Low will either limit the practical length of each conveyor, or require the application of additional outby conveyors.

A new method, the Continental Crawler-Mounted Transfer Station (CMTS), developed by Continental Conveyor & Equipment Co. and a continuous haulage operator (Lone Mountain Processing's Huff Creek mine), decreases drag and allows the miners to drive longer panels with the same equipment. It employs an innovative crawler-mounted transfer station that eliminates the problems associated with belt drag and misalignment and makes periodic mining-system moves faster and easier.

The concept behind the CMTS is simple. By isolating the high-drag, belt abusive Low-Low section of the belt from the main outby panel belt, the drag generated by the Low-Low conveyor is eliminated as a factor in outby belts. With the CMTS, relatively short belts and low horsepower drives are used in the Low-Low section, separate from the outby conveyor.


The Continental CMTS incorporates the drive and take-up pulleys for the Low-Low conveyor, as well as a tail pulley for the main outby section conveyor into a fully articulated mobile transfer. This arrangement is made possible (and practical) through the use of a proprietary technology that ensures that the Low-Low belt and the outby belt train properly, regardless of the angle between these two belts. This represents a significant capability that is clearly one of the most advanced features of this important mining breakthrough. The CMTS, with its mobility and alignment capabilities, provides an active, yet efficient, transition between these very different haulage lines, and in doing so improves the economics and performance of this area of continuous haulage technology.

After each system advance or move the onboard powered alignment mechanism is actuated. This mechanism, when actuated, allows the Low-Low drive pulley to rotate around a horizontal axis and find its natural alignment position literally within seconds. (Conceptually, it operates much like a steering wheel and trains the belt away from damaging steel surfaces.) At this point, the transfer station, incorporated into the CMTS, is aligned and is 100% ready to accept full-production volumes.

The system is completely steerable in all directions and it is self-contained, with all hydraulics and drive systems, including the take-up system, integral to the unit. For operator convenience, the CMTS is controlled, aligned, and moved using either a remote joy-stick or hand-operated hydraulic actuation valves.

According to David Webb, Huff Creek's general mine foreman, "Belt damage and splicing has always been a problem on continuous haulage systems, the CMTS has almost eliminated that problem.

"In the past, we have had to be real particular about keeping our Low-Low structure on the centerline, during advance and retreat, to keep the belt from rubbing the sides," Webb said. "Continental's crawler-mounted transfer station helps us keep the Low-Low structure in alignment. It allows us to steer the Low-Low structure and will retreat and advance so that when we do get our belt move made, we are on-line when we get there. With the hydraulic feature on the head movement to align the CMTS drive, you can line the belt up in the Low-Low. It actually gives you more flexibility. You don't have to be on the centerline and it can still run straight. The CMTS drive has allowed us to drive an 8,000-foot (ft) panel by using only one drive, which normally in the past, it would take at least three to drive that far," Webb said. "Our belt availability has increased an enormous amount, since we installed the CMTS unit."


To reap the best possible benefits from the technology, the Huff Creek team also added a belt-storage unit to speed adjustments to belt length, and a belt-splicing system to make the addition and removal of belting extremely efficient.

The belt storage unit has 660 ft of storage (enough for three belt moves). In this application, the belt storage unit is used to both store belt for advancement and to receive belt back into storage for retreat. (Conveyor belt is installed and extracted in 500-ft lengths.)

The splicing system, a Pinch Roll Drive and Hydraulic Belt Clamp, are used in conjunction with the storage unit, to add belt to the storage unit for advancement, or to extract belt from the storage unit on retreat.

The Hydraulic Belt Clamp can be engaged within seconds and replaces a manual belt clamp, which was slow, heavy, and time consuming. (The Pinch Roll Drive is used to extract belt from the storage unit when needing belt slack to pull a belt pin, or to extract belt out of the storage unit into a belt winder or lap it on a flat car.) This system was developed and proven for longwall panel belts and is now being used on continuous haulage panels.

At last, Continental believes the industry has advanced solutions they can count on for the costly problem area of continuous haulage, and it's safe to say that most mining organizations will be taking full advantage of these new technologies, sooner rather than later, to reduce mining costs and improve operating efficiencies.

Continental and SMARTveyor are registered trademarks of Continental Conveyor & Equipment Co.

All-Electric is a trademark of Continental Conveyor & Equipment Co.
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Title Annotation:coal mining
Publication:Coal Age (1996)
Geographic Code:1USA
Date:Jun 1, 2003
Previous Article:Awards.

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