Maximum impact

The latest generation of mobile crushing and screening equipment brings together the newest developments in crushing technology, screening media and computer diagnostics. One area that has seen considerable development in recent years is computer diagnostics, both on- board and in remote application.

The newest mobile cone crusher from Sandvik Rock Processing, for example, is the CM4800i - the “i” in its name stands for “intelligence”. According to the company the CM4800i is a “flexible” secondary crushing unit featuring its high capacity H4800 Hydrocone crusher.

A Sandvik spokesman told iC that, “the CM4800i is the perfect choice for any contractor looking for a highly flexible and mobile secondary unit with a short payback time. Several running options will be available as standard and the CM4800i can operate independently or in a processing system with other units. Incorporating the CM1208i primary crushing unit, for example, gives an intelligent control system that optimises the entire production process.”

Like the CM1208i, the CM4800i's control system allows for sequenced start-ups, close-downs and fault tracing. The operator has an overview of the machines operation giving full control of the process. A computer monitor, with user-friendly icons and symbols, is incorporated into the control system. Material flow is controlled automatically, although there is also a manual override. In multi-stage crushing setups, the system can communicate with the succeeding units.

Features include automatic crusher control, protecting the crusher from damaging overloads, increasing production, the highest possible degree of reduction, improved product distribution and better product shape.

Enhanced crushing

Terex Pegson has also extended its product range with the introduction of three new crushers - the 1165 Premiertrak, the Metrotrak HA (see box story p.35) and the 1412 Trakpactor.

The 1412 Trakpactor is a track mounted primary impactor designed to be simple to operate and maintain. It can be used for both quarrying and recycling applications and has an output capacity of up to 550 tonnes/hour. It is fitted with a Hazemag AP-PH 1214/Q impactor with four reversible and replaceable blowbars.

One key feature is the hydraulic apron locking facility, including hydraulic overload protection. This, claims the company, eliminates apron bounce, maximises reduction, and provides consistent product size with less oversize than conventional spring-loaded impactors as well as additional protection from metal waste.

The 1165 Premiertrak track-mounted single toggle jaw crusher is designed for processing quarried hard rock and construction and demolition waste recycling applications, and has a throughput of up to 350 tonnes/hour. A new hydraulic adjustment system has been developed to allow crusher settings to be made quickly and easily over a wide setting range.

Key to the design is its easy and rapid set-up and use. It is also available in a hydraulic release version, the 1165 HR, designed for applications where steel may be encountered in the waste stream.

Another new tracked jaw crusher comes from Komatsu. The company's 31.5 tonne BR380JG-1 uses the same track undercarriage as its excavators and is designed with a “high commonality”, which should help guarantee product availability.

The BR380JG-1 incorporates Komatsu's HydrauMind hydraulic technology. The system supplies the optimum amount of oil through load sensing and pressure compensated valves, which sense overloads and automatically slows the feed.

At the business end of the machine its KCJ4222 jaw crusher is powered by a 180 hp (134 kW) Komatsu SAA6D102E-2 engine, giving a production output of 55 to 265 tons/hour (50 to 291 tonnes/hour).

The BR380JG-1 also features a real-time monitoring system that displays and monitors all of the machine's components in order to alert the operator to problems.

New screens

Like crushers, one trend in screens has been towards compact, versatile units capable of working in a number of environments, such as quarries, construction sites or construction & demolition waste recycling stations.

Powerscreen International's mobile Chieftain 2100 Triple Deck, for example, is capable of an output of up to 500 tonnes per hour (depending on mesh sizes and material types) and features a 20 x 5 ft (6 x 1.55 m) triple deck screen unit for optimum efficiency in screening quarried materials.

It features heavy-duty, low ground pressure crawler tracks and is both agile and manoeuvrable around the site. The design and construction provides maximum access for easy maintenance and serviceability, while operational efficiency and mobility make it “a truly versatile screening unit for large-scale applications such as quarries”, said a company spokesman.

“This new machine is designed and built for high volume processing of aggregates, coal, crushed stone and demolition debris,” added the spokesman.

Also new from Powerscreen is its Horizon 6203. At 18.55 m long and 4.75 m high in working mode it is designed for large volume processing of crushed stone, sand and gravel, recycled concrete and asphalt. Capable of up to 800 tonnes/hour throughput of four specific sized products, the plant features a 6 x 1.83 m horizontal triple-deck screening box with a high productivity geared triple shaft oval stroke screen.

Its four stockpiling conveyors can be hydraulically folded for transport, giving a travelling width of only 3.2 m. Once on site, set- up time is swift, just a few hours, and, according to the company, the low ground pressure, heavy-duty crawler undercarriage provides “an agility and mobility around the job-site that belies its size and capacity”.

The 8.2 m³ direct feed hopper is equipped with impact bars and rollers and has Hardox 400 steel side and back plates, which can also be hydraulically folded for transport.

The horizontal 20 x 6 ft screen box (6 x 1.83 m)is triple deck geared, triple shaft and features an adjustable forward and elliptical throw (oval stroke). The elliptical stroke is adjustable from 15 mm up to a maximum 19 mm and is also angle adjustable from 30° to 60°.

“These screen motion variations allow operators to adapt the plant to specific applications and the elliptical stroke produces high resistance to pegging and blinding, with high energy characteristics to loosen fines,” said a Powerscreen spokesman.

The four attached stock-piling conveyors are all angle adjustable, hydraulically folding and have variable belt speed control. The feed conveyor also features variable speed control for optimum material feed performance.

Screening media

Crushing rock is only part of the process when it comes to supplying aggregates. Just as important is the right screening media system, and with the huge number of companies that make screening systems, it is hardly surprising that there is such a diverse range of consumable screening media available on the market.

Claes Larsson, Metso Minerals' media product line manager told iC, that Metso hopes to change all that with its new Trellex range. The heart of the system is what the company describes as 'upgrade strips' - polyurethane adaptors that mount onto a screen's existing rails. Different variants are available to match the range of fixing systems in the market, but they all have the same top profile, which matches the company's new range of modular polyurethane and rubber screening media modules.

These modules are produced to fit the four standard widths, and are easy to change by hand - they simply snap in and lock to the top rail of the adaptor strip. This is a very user-friendly system compared to some, where changing screening media could take days if they are fixed in by pins that would need to be drilled out.

The panels are also very light because they do not contain any steel. The bottom part is a 'structural' polyurethane that provides strength, while the top part is a wear-resistant polyurethane for screening.

At first glance, this would seem to be adding to the problem by introducing yet another fixing system into the market place. However, Metso Minerals makes the point that after the one-off expense of the upgrade strips, an entire screening plant, or even an entire company will have standardised its replacement needs, regardless of the diversity of its fleet of screening equipment.

Mr Larsson said, “Customers can use us as their sole supplier, which is becoming an increasingly important issue in these days of ever-larger organisations.”

Dam project

Besides screening media Metso also make screens and crushers of course. Two of its Barmac VSI (Vertical Shaft Impact) crushers have recently been used at The Ridges Basin Reservoir dam, part of the Animas-La Plata Project, which aims to provide water for Southern Ute and Ute Mountain Indian tribes and water districts in the states of Colorado and New Mexico in the US.

The dam is over 80 m high and stretches for about 400 m from one canyon wall to the other. It is an earth filled embankment structure requiring about 990000 tonnes of washed and dry processed filter materials. The whole plant will process approximately 2.3 million tonnes of raw feed in approximately two years of operation.

The borrow area is a sand and gravel deposit with the base rock being granite. Due to concerns over the presence of 'soft' materials in the borrow, considerable attention was given to how the material would degrade during processing, stockpiling, and placement in the dam.

To alleviate these concerns, a dry attrition drum scrubber was placed in the primary stage of the 1050 tonnes/hour primary plant to produce a multiple pass degradation process.

All 0-6.3 mm material from the primary scalping process was rejected. A closed circuit Nordberg HP400 cone crusher was used to process an average of 450 tonnes/hour of material to the secondary stockpile.

Two Barmacs, with an average processing capacity of 450 tonnes/hour and using the cascade function, were selected in the secondary section due to their ability to upgrade the finished material quality and produce superior cubical products at high tonnage rates. The Barmacs were fed a 0-44 mm cone crusher product and operated in a closed circuit.

According to Rob Englehart of Weeminuche Construction Authority (WCA), “We did study the use of multiple cone crushers to meet the required production rates and gradation requirements but by ignoring cone crushers and installing only Barmacs, we were able to achieve the same required design production rates for sand and washed gravel, an improved gradation curve and good product shape with less crushers.”

WCA also realised from test data on the material that rock-on-rock crushing was superior to the shoe and anvil design in terms of estimated wear costs, parts change-out time and waste.

VSI's are a critical component as they provide an excellent shape on all product sizes and aid in the removal of soft particles or rock. It is absolutely essential the finished products do not have slivers, shards and soft particles that break down during the hauling, spreading and compacting at the dam placement.

Any excessive degradation leads to having to produce the material at the coarse edge of the specified gradation curve to compensate for break down, which leads to higher production waste factors and removing of out of spec materials from the placement, which is obviously very costly.

Working well

The installation has met the design specifications. WCA is currently right on track with their estimate in wear costs.

Capacity through the crusher is being achieved with room to spare, according to Mr Englehart, which balances very closely with the designed plant flow throughout the down stream portion of processing.

The Barmac rotor design allows for the easy replacement wear parts. The height of the rotor allows for access to the parts and minimal plugging through the port area.

The side door minimizes down time when working on the rotor. The upper and lower wear plates wear extremely well.

The Barmac cascade feature also worked well. WCA targeted a 60% sand and 40% washed aggregate production balance, the cascade allowed for coarser crushing through the cascade while providing shape and keeping the rotor full to produce the finer sand sizes without a heavy recirculation load.

Mr Englehart also found that cascade was required to get the extra 9.5 x 6.3 mm product size needed while keeping both the sand and washed aggregate in spec. “It's also an easy way to keep from having crusher overflow and spill problems,” said Mr Englehart.