WipFrag is a revolutionary new way of sizing rock fragments, designed to replace slow and subjective tape measurements and screening of samples. The system offers a quick, systematic and automatic way to measure not only the average size of the product, but also its uniformity, oversize & fines content and fragment shape.
WipFrag uses simple photographs or video tape images of the rock pile. The stored images are captured and enhanced, by the latest in high-tech hardware. Imaging frame grabbers, high-speed microprocessors and video accelerators are backed by innovative artificial intelligence software that recognizes fragment edges and measures the size and edges of each individual block.
Click here to see a picture of some WipFrag Outputs
The availability of quick and simple fragmentation measurements opens the door to a broad range of applications in mining, quarrying, and control of rockfill construction:
Control of Blasting and Blast Optimization
The objective in blast design is to achieve efficient rock breakage within an excavation while preserving the rock walls intact. It calls for a compromise between the competing objectives of maximum yield and fragmentation, minimum overbreak, underbreak and backbreak, and minimum costs for drilling, explosives, rockbolting and other forms of support. No single factor such as the cost of explosives can be properly evaluated without reliable measurements of fragmentation. The prime objective in blasting for stone production is to achieve the required gradation with a minimum of secondary breakage and screening. A further and often conflicting requirement is to achieve maximum yield with minimum costs for drilling and explosives. WipFrag gives a quick and convenient comparison between the achieved fragmentation and specified tolerances. It measures not only the average size of the product, but also its uniformity and content of oversize and fines.Fragmentation measurements allow optimization of the initial blast design, and subsequent fine-tuning in response to rock quality variations. Blasting models such as the Kuz -Ram equation define quantitatively the three-way relationship between fragmentation (fragment size and uniformity), rock quality (strength and intensity of jointing), and blasting parameters (e.g. specific charge, burden to spacing ratio, degree of confinement). Fragmentation measurements allow fine-tuning of blast design in response to changes in rock strength and jointing. Fragmentation can be maintained at the desired level while economizing on drilling and blasting costs.
Mining at Depth
Mining to ever-increasing depths in hot, highly stressed rock suggests a trend towards smaller stopes and service openings because they are less prone to ravelling, squeezing and bursting, and also are cheaper to mine, reinforce and ventilate. In these small drifts and bored shafts and raises, conveyors are likely to replace LHD, truck and rail mucking systems. To maintain flow of ore will require a finer and more uniform product and more attention to quantitative fragmentation control.
Control of Caving
In caving and longwall mining, rock strength and jointing in the orebody, hanging and footwalls determines the size of undercut required to induce and maintain caving. WipFrag with camcorder input is ideal for caveability assessment and control of dilution. During mining, the size of product can be continuously monitored at fixed camera locations.
Ore Flow in Stopes
Inadequate size distribution, notably an excess of oversized or slabby blocks and/or fines, is a common cause of hang-ups in stopes and ore passes. Fragmentation measurements help to detect and avoid such problems.
Loading and Transport
Oversized blocks and excess fines also are significant factors leading to delays and costs for secondary breakage, loading and transport by scoops, trucks and conveyors. Cost control requires monitoring of fragmentation and of the subsequent breakdown of ore and waste during handling.
Crushing and Screening
WipFrag works equally well at any scale, even microscopic, and can readily be used for quality control of crushing operations. Cameras focused on conveyors can provide continuous process control of crushing and grinding at a sampling rate of up to four images per minute, giving advantages over more conventional methods of granulometry. Systems can be customized for strip chart output and to warn of excedance of gradation or fragment shape tolerances.
Rockburst and Roof Fall Records
Photoanalysis can provide quicker and safer measurements of rockfall and rockburst data. WipFrag observations from a safe distance can be used to record the sizes and shapes of fragment as an indication of energy release, and also the volume and throw of debris, dimensions of the remaining cavity, and damage to support systems.
Rock Quality Changes
Drifts penetrating into faulted, weathered and weakened rock produce a slabby rockpile and a smaller fragment size. Routine blast fragmentation measurements can be used to monitor and give early warning of changes in rock quality and the need for adjustments to opening dimensions and support systems.
In-place Quality of Stone
WipFrag with portable video camera input provides a quick and convenient method for quality control of rockfill, rip rap and armor stone at every stage from quarry source selection through blasting, transportation of stone, embankment construction and monitoring of in-place embankment performance. Video tapes, hardcopy prints and fragmentation statistics provide a permanent record of product quality and help to identify any problems. Inspection costs are reduced with theelimination of slow manual measurements. WipFrag has been used to evaluate rockfill and armorstone stockpiles for breakwater contracts in Canada, USA and Brazil. Measurements can include complete gradations and block shapes, measurements of homogeneity and segregation, and also, with customized software, monitoring of embankment spread and settlement, and the amount and type of stone deterioration.
Performance of tractor-mounted rippers depends on rock strength and jointing. Ripability predictions are commonly based on measurements of sonic velocity, which at best give only a rough indication of rock mass quality. In situ WipFrag measurements of fragment size and shape are ideal for evaluating ripper performance and for diagnosing problems.
Transportation and Placement
Rockfill degradation during handling and placement, is caused either by breakage and rounding of block corners, or by segregation into coarser and finer fractions. In marine works, this segregation creates pockets of undersized materials that are easily eroded, and concentrations of large blocks that are transparent to wave action and provide windows for internal erosion. WipFrag can help diagnose and correct these problems and also the delays and excess costs in loading and handling caused by oversized blocks or an excess of fines.
Fragmentation is a key factor also in quality control of shale embankment construction. Whereas the stability of hard rock fills is ensured by specifying durable rock, shale embankments rely on thorough compaction using sheepsfoot or tamping rollers and lifts of limited thickness. Problems occur if only partial compaction is achieved, as a result of further degradation during the service life of the embankment.
On-Stream Control of Production Machinery
Cameras trained on conveyors can provide continuous process control of crushing and grinding equipment. Interface software can be custom designed to adjust machinery based on particle size measurements and pre-set excedence standards.