Flexibility in crushing & screening
By Helen Wright11 September 2012
In order to be flexible enough to meet the changing demands of modern quarries and construction sites, the latest crushing and screening equipment must be efficient, often mobile, and offer optimum performance and economy at the same time.
The trend for increased use of recycled construction materials is also putting new pressures on crushing and screening machines, which are expected to be robust enough to handle a range of materials at high outputs.
Energy consumption is another key issue - contractors expect to see higher efficiency in the latest machines, but not at the cost of productivity.
There has been a flurry of new launches that demonstrate manufactures are rising to these challenges. On the screening side, manufacturers have focused in particular on increasing adaptability.
For instance, Metso's latest edition to its Lokotrack series - the two-stage ST2.4 mobile screen - can handle a wide range of materials, from processing recycled materials to pre-screening of coarse gravel or fine classifying and processing of natural sands.
The Lokotrack ST2.4's top deck screen box size is 1.5 m by
3.6 m. It features a 74.9 kW Cat C4.4 diesel engine and it is
14.2 m long during transport, with a height of 3.4 m and a width of 2.9 m. It weighs 23.5 tonnes with a belt feeder, and 26.5 tonne with an apron feeder.
The new screen offers lower fuel consumption thanks to improved hydraulics and automation, and is also said to be easy to transport and set up. Kimmo Anttila, product manager for Metso mobile screens, said the ST2.4 could be set up from trailer to screening in minutes.
"You just set up the screen angle, lift the feeder up and start screening," Mr Anttila said.
Terex Finlay also focused on versatility and adaptability with its new 684 tracked mobile inclined screen, which sports three full size screen decks, each 4.3 m by 1.7 m. Powered by a Caterpillar C4 82 kW air cooled diesel engine, the 684 is a compact and said to be easily transportable.
In fact, Finlay said the machine could configured for transport in less than 30 minutes thanks to its four hydraulically folding discharge conveyors.
Meanwhile, Powerscreen's new Warrior 1400X tracked mobile screen features reduced engine running speed and enhanced hydraulics that Powerscreen says provides a -15% reduction in fuel consumption compared to its predecessor.
The screening angle on the 1400X has also been increased by +50%, and stockpiling capacity on the machine's conveyors has been increased by +25% to +30%. Fitted with the chassis riser and telescopic side conveyor options, the fines and mid-grade stockpiling capacity has been increased to more than double that of a standard Warrior 1400.
Maskin Mekano also focused on minimising operating costs and maximising output when developing its new mobile screening plant, the Ls 903. It contains a three-deck screen-box with a screening area of 1.2 m by 4.4 m per deck and features four onboard hydraulically foldable conveyors. Maskin Mekano said the Ls 903 consumed no more than 4 litres of diesel per hour.
Another manufacturer which has focused on maximizing screening output is W.S. Tyler, whose new XL-Class vibrating screens are the largest it has ever produced.
The XL-Class offers screening surfaces of up to 390 ft2 (36 m2), allowing it to replace up to two inclined screens in virtually the same footprint and produce up to 15000 tonnes per hour.
The new screen is also flexible enough to tackle a range of materials. It was developed to handle copper and iron ore, but the manufacturer said the machine was suitable for almost any application requiring above average production rates.
Indeed, the XL-Class has also proven successful for oil sands, according to W.S. Tyler. This material must be processed in temperatures ranging from -40°C in the winter to +30°C in the summer - with this extreme temperature fluctuation, the oil sands' physical properties change from rock-like formations when frozen to a plastic-like state in high summer temperatures, the company said.
The XL-Class machines use Finite Element Analysis (FEA) technology, which detects high vibration and stress points. This allows W.S. Tyler to set up each screen's stroke, speed and other variables to perform at peak efficiency and ensure it can handle high capacities.
More heavy-duty screening plants have been introduced by Deister, whose new portable horizontal screeners are available in 6 ft (1.8 m) by 20 ft (6.1 m) and 8 ft (2.4 m) by 20 ft (6.1 m) models.
The machines are said to be a highly-mobile and versatile, well-suited to being transferred from site to site. Built around the Deister heavy-duty horizontal triple-shaft vibrating screen, a number of options are also available including either a 42 in (1.1 m) or 58 in (1.5 m) screen feed conveyer, spring loaded belt scrapers, a receiving hopper for crusher return, a four leg hydraulic levelling package and optional hydraulic cylinders to fold the conveyor and adjust the discharge height.
Improving the materials used to make screens is also an area of focus for manufacturers. The new OptimumWire woven wire screen media from Major Wire, for instance, is said to provide up to +40% longer wear life compared to traditional woven wire.
OptimumWire is manufactured with a high carbon and high manganese content, providing ductility, hardness and tensile strength. Each screen is woven with a tight tolerance to movement within the crimp or weave, which can prevent the wires from rubbing against each other during use.
For larger wire diameters, OptimumWire is manufactured from hard-drawn wire, unlike most traditional woven wire that MajorWire said was made of "rod" that varies in diameter throughout its length and can create inconsistent crimping. Hard-drawn wire is consistent throughout, providing proper crimping and weaving as well as increased durability.
OptimumWire is available in a variety of crimp styles, while wire diameters range from 0.05 in (1.2 mm) to 0.8 in (19 mm) with openings from 0.1 in (3.2 mm) to 6 in (152 mm).
Meanwhile, maximising productivity in a compact and economical footprint are also challenges on the crushing side, where the ability to reliably and consistently produce high quality final product is a central requirement.
Cemco aimed to incorporate these needs when developing its new Turbo 80 VSI vertical shaft impact crusher, which it says is capable of processing a variety of aggregate materials and industrial minerals.
The Turbo 80 offers a mid-sized option that can process materials up to 4 in (102 mm), making it well-suited to the aggregates, energy production, mining and recycling industries. Powered by a 400 hp (298 kW) engine, it weighs 19000 lbs (8.6 tonnes) and can produce up to 275 tonnes per hour.
The V-Twin, twin drive design of the Turbo 80 offers higher output of up to 600 hp (448 kW), weighs 25000 lbs (11.4 tonnes) and can produce up to 350 tonnes per hour.
The final product size produced by the Turbo 80 is controlled by a combination of rotor size and type, rotor speed and other configurations, all determined by each individual customer's needs. Cemco pointed out that the ability to produce a consistent final product, and to be able to change the size at a later date is also well-suited to meeting ever-changing US Department of Transport specifications.
Meanwhile, Dieter Dorstmüller, general manager for Austrian compact crushing and screening equipment manufacturer DSB Maschinenbau, highlighted the fact that recycling of used construction materials is increasingly important to contractors.
"Recycling and therefore the requests for crushing machines have changed over the last few years. High power and enormous output are an absolute must. In addition, sometimes the working area is really cramped - only compact and powerful machines will serve the buyer's purpose," he said.
DSB has introduced a new drive system for its Innocrush range of mobile crushers. Called the Innodrive, the new system features direct power transmission, no wear parts and is said to be maintenance free.
Rockster also focused on maintenance when developing its new R700S compact crushing machine, which is built around the R70 impact crusher and can produce up to 150 tonnes per hour. The R70 allows for variable adjustment of the upper and lower swing-beam without using any tools, while accessibility to the crusher chamber has also been made easier.
The smallest model of the Rockster range, the R700S measures 9 m long, 2.4 m wide and 3.1 m tall, and weighs 19.3 tonnes. The plant also features a pivoting return/stockpile conveyor that can be folded in and locked for transport.
But if space is at a premium, you can't get much more compact than a crushing attachment - tools which have traditionally featured lower output than a stand-alone compact crushing machine.
However, Bav Crushers claims advances in its excavator mounted crushing attachments have driven their performance up to levels where it believes, "it is now difficult to justify the significantly higher cost of small mobile tracked crushers".
The manufacturer's BAV-CB range of crusher buckets now covers excavators from 2.5 tonnes to 25 tonnes. The buckets feature removable grids which enable two grades of output to be achieved - fine grade up to 50 mm or coarse grade between 0 mm and 100 mm - and powerful hydraulic jaw action, which is a twin-ram system on all but the smallest model.
Replaceable tungsten carbide teeth give aggressive penetration and are also said to be quick, cheap and simple to change.
"The BAV CB range offers an intermediate processing option, between the primary demolition tools, like the BAV Alligator Crusher attachments and stand-alone, recycling machines like the BAVTRAK tracked crushers," the company said.
From attachments to heavy duty machines, with so many new options available for all types of customer demand, manufacturers of crushing and screening equipment are working to deliver increased versatility and productivity to the sector. And it is clear from the number of new products launched in the last few months alone that this is a dynamic and fast-moving industry that is ready and willing to respond to new challenges.