This article is by Randall D Peterson, PE, inventor and president of Softwall Equipment Corporation.
Introduction
The SACUM Conveyor is an extendible, roof mounted, monorail conveyor devised for continually extending or retracting a panel conveyor and its utility systems. The novelty of the SACUM conveyor system is that the entire conveyor rolling and support structure is extended/retracted with assembly/disassembly from the outbye or discharge end of the belt. This unique feature of SACUM keeps the tail-loading end of the conveyor in close proximity to the mining face while progressing both inbye and outbye in advance and retreat.
Conventional panel conveyors and utilities are extended from the inbye or loading end where such activities interfere with production. Commercially available monorail systems are commonly used for retracting utilities in the headgate. However, these systems are still limited by the need to periodically schedule a shutdown to install or remove conveyor structure and utilities. Extending the conveyor and utility lines from the outbye or discharge end places the extension/retraction activities on the opposite end of the conveyor from the actual mining work.
Assembly and function
The SACUM conveyor structure is installed with the conveyor in operation in "assembly line" fashion whereby components are mounted to a converging bottom train. The bottom train is continually moving with progression of the mining face and consists of the channel sections, the return idler and utility undercarriage. Figure 1 is an isometric showing the completion of the conveyor train.
The system is assembled and attached to the bottom train consisting of return idler assembly and utility undercarriage with channel linkage. The return idler of the bottom train converges with the return belt. Troughing idlers are attached, on advance or removed on retreat, just inbye the point where return idlers converge and contact the return belt.
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As the train trams inbye from this point, troughing rollers are fed to the attachment point by a magazine or other device. The train, equipped with troughing rollers, continues movement inbye and troughing rollers converge and contact the top carrying belt. As the train continues movement further inbye, a top hanging structure equipped with bearing wheels and tram drive motor assembly is attached to complete the conveyor train assembly.
The completed train hangs from a monorail which is mounted to the mine roof providing the fixed structure from which the train hangs and upon which the trolley trams for extension and retraction of the conveyor train.
Reserve access
SACUM is an acronym for Surface Assisted Continuous Underground Mining. However, the concept does not have to be used from the surface. Rather, it can be configured for use in any underground mining situation where a monorail can be attached to a mine roof and where the mining operation can benefit from outbye assembly. This suggests several possible access configurations. Among these the following four scenarios are envisioned:
·Surface access - highwall mining, wall-to-wall or longwall punch mining
This is the most direct application of SACUM. Belt and utility lines are extended from the surface directly through the portal to the mining face area. Likewise, troughing idlers are also added on at the surface just inbye the transfer point.
·Surface access - shaft
In this situation, the drive is located on the surface and belting and utility systems are extended there. Troughing idlers are attached to the bottom train at a station underground. The discharge in this case is transferred to a mainline conveyor underground.
·Underground access – mains
In this situation belt and utilities are extended from an outbye station located in the mains for driving and pulling panels off the mains at right angles. A horizontal belt storage unit is required underground due to height constraints.
Anticipated advantages
SACUM has several advantages over conventional panel conveyors. Moreover, these advantages offer new opportunities for mine layout to take full advantage of the continuous mining and hauling capabilities that it offers. The following are advantages are anticipated:
·Shorter shuttle car cycle times
Used in series with shuttle cars or LHD’s, SACUM can reduce the haulage cycle time by maintaining optimal haulage distances from the miner to the loading point. The decrease in haulage delay can improve longwall panel development rates in single pass mining or in place-change mining.
·Continuous production
Production continues without shut down for power and belt moves. Hence there is no need for standby mining sections to sustain production while the move takes place.
·Less face congestion
The underground active face area is not crowded with an accumulation of belting, belt structure, pipe and feeder cable to make the move because these materials and supplies are never taken to the face area. Rather, the move is made from outbye and these materials are queued-up there where there are facilities to handle them.
·Better access to face equipment
The tail of the conveyor can be moved outward to accommodate maintenance vehicle access to mining equipment located on the other side.
·Continuous haulage
Where it is not necessary to turn corners, SACUM can provide continuous haulage directly behind the mining unit. In other cases, the SACUM system can be used in series with continuous haulage and the monorail used to support the discharge end of the continuous haulage unit in both advance and retreat.
·Highwall mining
Where SACUM can be deployed from the highwall, lateral access to ore is provided by the highwall itself. This, combined with extension of the conveyor inbye, can provide a cost effective way to access the reserve with full extraction shortwall or longwall mining systems from the highwall.
·Fewer and better splices
Where the extension facilities can be located on the surface access, large vertical loop storage units can accommodate longer rolls of belt than would otherwise fit in the underground opening so fewer belt splices are required. Moreover, better splices can be made since routine belt splicing can be organised in an enclosed clean atmosphere where they can be vulcanised every time a splice is made.
·Shortwall continuous mining
The long reach capabilities of the SACUM Conveyor combined with mining opportunities having extensive lateral access make SACUM particularly attractive for shortwall mining. In these cases, the provision of continuous haulage and bolting directly behind the miner on development and retreat make it possible to cut high tonnage on development and retreat. Moreover, the same crews and equipment are used for development and retreat so that panel development never gets behind panel retreat. Operating costs are lower because capital equipment and manpower are more fully utilised.
