WORLD PROSPECTS
Caterpillar Rock Straight going commercial
The Caterpillar Hard Rock Cutting product group began with a team of three people under predecessor DBT then Bucyrus but has grown to a dedicated team of almost 100 people, with a state of the art training centre; the Cat Rock Flow System now in underground installation at Codelco Andina; the Cat Rock Straight System which has completed trials at KGHM Polkowice; and the Cat Rock Header program, currently at the development stage and effectively a hard rock roadheader, using the same hard rock cutting technology with Activated Undercutting Technology that Rock Straight uses.
The Cat Rock Straight System is being launched officially in June 2016. It is essentially a hard rock longwall producing a smooth panel outline. It is designed for continuous mining of low seam deposits in hard rock conditions, aimed at platinum, gold, chromite and copper mining. It replaces the cyclic nature of mining by blasting which causes constraints on the face advance, extraction rate and financial return on investment. The Activated Undercutting Technology works as the cutting tool causes the rock to burst through percussion. Rather than a constant contact with the rock face, the individual pick very quickly“ hits” the ore, greatly reducing the amount of heat generated. This results in a number of advantages, such as less pick wear, lower energy consumption, less reaction forces and lower stress, enabling the excavation of hard rock using a small and compact machine. Explosives transport is also becoming more difficult in many countries such as Mexico and Colombia, requiring armed escort.
Initial underground trials at KGHM have proven that the technology is feasible. KGHM had experienced several constraints in their underground excavation and wanted to minimise ore dilution and copper ore losses in low seam deposits, reducing the number of personnel in the active area and increasing productivity with continuous technology instead of the cyclic drill and blast operation.
Caterpillar also argues that the main competing technology, disc cutting, also being widely tested in the platinum industry has important weaknesses, such as heavy weight and restricted manoeuvrability of the machines used. The system would also be competing with XLP equipment suites( dozers, bolters, drill jumbos) in platinum, though these machines have had their own issues.
A predecessor of the Cat Rock Straight System was also tested in South African platinum in Rustenberg, but not commercialised, and was known as the ADS
Hard Rock Miner HRM220 specifications
Range of cutting height Installed Power per Cutting Unit Installed Power Electrical System Cutting Depth per Unit Maximum Advance Rate Instantaneous Cutting Rate Operating Voltage
Hard Rock Miner, but was developed under Bucyrus / DBT before the Caterpillar acquisition.
The Cat Rock Straight System combines the use of a hard rock shearer( Hard Rock Miner HRM220), a hard rock apron conveyor( Hard Rock Conveyor HRC30) and hydraulic roof support( Hard Rock Roof Support HRS1220). The miner cuts the hard rock material and loads it onto the apron face conveyor, which transports the ore to the belt conveyor. The hydraulic roof supports protect the miner from roof falls and advance the conveyor in a bank push after each cutting sequence. A sophisticated automation system steers the cutting progress and the advancement of the system. The operator is comfortably located in a protected cabin, and controls the cutting process safely from there.
With the Cat Rock Straight System tailored to operate in low seam heights, it was a good match for KGHM, as most of the copper deposits found in the KGHM licensed areas are flat, with a seam height between 1.0 and 2.5 m. Rock Straight has a minimum seam height of 1.3 m, so in UG2 for example, some waste dilution would occur. In the future, the system may be developed for sub 1.3 m minimum heights.
The initial performance test proved that the Rock Straight System is capable of cutting rock with a compressive strength of up to 200 MPa, with pick wear remaining in a favourable range of replacement. The KGHM panel length was 300 m with a face length of 43 m; and mining rock of 120-150 MPa in seam heights of 1.8-2 m and rock density of 2.6 Mg / m 3. The excavated area covered 9,030 m 2( 210 m x 43 m), with around 45,000 t having been mined.
The longwall shearer component – the HRM 220 – has a robust mainframe with two independent cutting units( each takes a slice so getting double cutting depth in one pass) and
1.3 – 2 m modular architecture to aid
132 kW relocation and installation. In
319 kW higher seam heights, the first unit
100 mm would be elevated doing cutting 6 m / min only and the second unit both up to 175 t / h cutting and helping to load the
1,000 V ore to the AFC. The face length can be up to 100 m while there is
no limit for the panel length, other than the longer it is the more economically that it can be operated by the customer. It is hard to assess the time required for a face move, as this depends on the length of the transport route and the conditions on the route. However, each unit is rather compact in comparison to a coal / soft rock longwall system, which makes the face move comparatively straightforward.
The self-advancing supports are different to coal supports in design but have sensor technology for shield position and roof load with proven PMC-R automation. They can be supplied with or without backside canopies. Currently the KGHM operation involves operators installing artificial timber pillars behind the machine( as in hard rock mining the roof will not cave), every two metres, safely from under the longer canopies. A future option for projects is to use backfill behind the advance. The hard rock conveyor is variable to suit different face lengths and flat to suit low cutting heights. It is effectively a low profile apron face conveyor, carrying the ore on base plates. Any valuable dense ore fines that might form a muck and might be lost is picked up from the flat apron plates by an optional rotating brush system( not necessary at KGHM but designed for PGMs and gold). The mine roof and floor smooth are smooth without cracks or traps to retain dust anyway so anything remaining could be removed by vacuum. Another option is small dozer blades to guide all the ore onto the apron plates.
Remote control operation provides optimal comfort and safety for operators, as the operator is placed in a RSPS( FOPS equivalent) certified cabin with air conditioning.
The KGHM machine is looked after by Cat dealer Bergerat Monnoyeur but discussions are also being held with potential customers in Zambia and South Africa through dealer Barloworld Equipment, and in Kazakhstan through dealer Borusan Makina.
The Cat Rock Flow System, which is a production system for block caving operations, not a cutting system, is now in installation for large scale industrial application at Codelco`s Andina mine in Chile, following initial functionality and system validation trials at Codelco Salvador. At Andina there are four sets of eight dozer type Rock Feeders( RF300), s
4 International Mining | MAY 2016