Crushing & screening choices
By Chris Sleight10 September 2013
There has long been a trend in the crushing and screening sector towards mobile equipment. With the fast set-up and tear-down times possible with modern equipment, and improvements made in transportability, there is great flexibility to be gained from machines that can be used in multiple locations, and which are easy to move around sites to where they are needed.
And after decades of refinement in the design of such machines, they have become well-honed to the needs of the sector.
The latest crushers from Kleemann, for example, are the 300 tonnes per hour Mobicat MC 110 Z and MC 110 R, which have been redesigned from scratch to incorporate a series of new features. These include hopper walls integrated into the chassis and a fully hydraulic crushing gap adjustment, which combine with previous features such as the independent double-deck pre-screen.
Like the company’s Mobirex EVO series, drive variants with direct drive crushers and electric drives for the vibrating conveyors, belts and the pre screen, are now used for the mobile jaw crushers. This helps with efficiency and even loading of the crusher chamber, as does the Continuous Feed System (CFS), which is used to adjust feed conveyor speeds to keep the crushing chamber loaded to the optimum level.
The heart of the machine is the articulated crusher jaw, which on the one hand prevents blocking of coarse material and on the other hand takes all fastening elements of the crusher jaw from the wear area. In addition, the transfer from the pre screen or the feeder trough is designed so that the material can simply tilt into the crushing jaw and convey an even material flow.
IRock’s latest machine is the 2644 wheeled jaw crusher (WJC-2644), which can produce up to 350 tons per hour (318 tonnes per hour). The primary unit features a 36 ft (11 m) long, 48 in (1.22 m) wide discharge belt which offers a stockpiling height of 11 ft (3.35 m) – said to be the highest available in the industry for this class of machine.
The crushing chamber features hydraulic adjustment, from a minimum of 2 in (50 mm) on the closed side to a maximum of 6 in (150 mm) on the open side.
Other features include a 24 in (610 mm) wide grizzly bypass conveyor with an adjustable flop gate, as well as a 40 in (1.02 m) by 14 ft (4.27 m) feeder with a 5 ft (1.52 m) grizzly bar section. These features ensure that material is properly classified and directed to either the side discharge conveyor or the crusher discharge conveyor.
New from Terex Finlay is the 684 mobile screen, comprising two 4.3 m x 1.7 m inclined decks. The screenbox features quick wedge tensioning, access holes and a bottom deck hydraulic tensioning system to reduce the time required for mesh changes.
All three discharge conveyors fold hydraulically for transport which makes for quick set-up and tear-down times. In fact Terex Finlay says this self-contained plant can be ready for transportation in less than 30 minutes.
A 1050 mm wide variable speed belt feeder, with hydraulic gearbox drive, is standard and the hopper has a capacity of 8 m³ capacity. It can be fitted with either a 14 ft (4.27 m) tipping grid or 12 ft (3.66 m) vibrating grid.
But there is also still a strong market for fixed crushers and stand-alone components for crushing and screening plants.
Shanbao, which is part-owned by Sandvik, has unveiled three new crusher units in the last 12 months. The company says it built them specifically for the Chinese market, with a simple yet robust and versatile design.
The high capacity DY single cylinder hydraulic cone series, for example, offers more performance and less weight than the previous PYYX range. It has a wide range of discharge sizes, and Shanbao says it is easy to maintain.
The PV jaw crusher series meanwhile can handle materials with a compressive strength up to 320 MPa and feed sizes up to 600 mm. Key features include a new chamber design to deliver better crushing performance, a fully-welded frame for rigidity and reduced weight, simple mechanical adjustment of the discharge opening and a motor mounted directly to the frame.
Also new is the VI range of vertical shaft impact crushers, which are designed for shaping and sand manufacturing applications. The company says the range offers a large crushing ratio and production volumes, while at the same time being flexible enough to be used in different applications.
W.S. Tyler has launched a 4 ft (1.22 m) wide version of its F-Class vibrating screen. Due to its consistent G-Force, the F-Class is said to reduce blinding and pegging, even when screening sticky material, and is now available in widths from 4 ft (1.22 m) to 10 ft (3.05 m).
The F-Class features a shaft with two eccentrics, which the company says handles material volume spikes without losing momentum. As the eccentric shaft turns, the screen body follows the shaft movement. Counterweights on each screen reduce the amount of vibration transferred to the supporting structure, meaning multiple screens can be placed side by side with minimum investment in heavy structures.
The design also keeps noise to a minimum. The continual circular screening action produces a constant force which maximises screening efficiency and allows the equipment to be effective in both wet and dry applications.
Designed for operations that require a smaller footprint and capacity, the 4-foot F-Class can process up to 300 tons (272 tonnes) per hour while providing accurate sizing. It can screen any material from 3 in (76 mm) down.
Green field plant
Indeed, when it comes to high output facilities, many mobile units would struggle to keep up with the throughputs achieved by static units.
This is illustrated by Metso, which has won the contract to supply a complete crushing & screening plant to a green field quarry being opened by road building contractor Colas in France. The order includes primary, secondary and tertiary stages along with service contracts and extended guarantees.
Metso Mining and Construction sales director for France, Philippe Portevin, said, “Tailored solutions for high-end output, reduced costs with energy-efficient machines and automated treatment are the major benefits we are delivering to our customer with this supply. Colas wanted not just a supplier, but a responsible partner for their investment. We’ve set an ambitious target and we’re confident in achieving it.”
The installation includes a C160 jaw crusher, a HP500 cone crusher, two HP6 cone crushers, more than 12 vibrating machines from TS, CVB and VF range completed with more than 2,000 m of Metso conveyors.
The full engineering scope of the installation includes a truck loading station, automation and power, 2,000 tonne steel structures, plateworks, de-dusting, erection and commissioning for a targeted 1.5 million tonnes/year and equipped with 4 MW of installed power.
But in other applications, where a contractor or quarry operator needs flexibility, mobile machines can be the answer.
This is illustrated by the 100th Warrior 2400 mobile screen manufactured by Terex’s Powerscreen subsidiary, which was delivered to Galfar Engineering SAOG in Oman. The contractor had originally asked local distributor General Engineering Services (Genserv) about a scalping machine, but with outputs of 700 to 900 tonnes per hour required, along with the need for mobility, the recommendation came back for the Warrior 2400.
The initial order for two machines has since grown to six, including the 100th machine to roll off the production line. All six are currently working on the 45 km Phase 1 of the Al Batinah Expressway project, where high quality sub-base is being produced from feed material of a nearby wadi (river bed).
A spokesman for Galfar said, “We are very happy with the performance of our plant - each machine is working for up to 20 hours per day and producing high volumes of material. We find that the machines offer a low operating cost per tonne and we know that we can count on high speed local support from Genserv when we need it.”
The Warrior 2400 screens are configured with a 150 mm punch plate on the top deck and with a 63 mm aperture mesh on the bottom deck, giving three end products. The -63 mm fines are used for base rock on road projects. The mid-size material (63 to 150 mm) is crushed with Terex cone and impact crushers to produce smaller products for re-screening, while the +150 mm material is processed with a variety of jaw, cone and vertical shaft impact crushers to produce other aggregate fractions as well as sand.
The Petaquilla Gold Mine near Panama City, Panama is unusual in that it produces aggregates as well as precious metals. Contractor Panama Development of Infrastructure (PDI) is using a range of Sandvik drills, crushers and screens at the facility for the diverse production requirements.
Equipment on the site includes a Sandvik DX800 drill rig, UJ440i mobile crusher and QA450 triple deck Doublescreen mobile screener, supplied by national distributor Grupo Tecún.
David Baralt, general manager and chief operations officer at Servicios Mineros de Petaquilla said, “We are seeking friendly suppliers, who understand how their products are connected to our production. We strongly believe in Sandvik for the recognised quality of their equipment worldwide.”
The UJ440i jaw crusher is used to process Andesite rock from the quarry, crushing down from 700 mm to 150 mm, at a production rate from 450 to 500 tonnes per hour.
The company also uses a QA450 triple deck Doublescreen, which is able to achieve a production rate of up to 600 tonnes per hour, depending on the material, the feed size, and the required fractions. It can produce four material sizes, plus an oversize from the grid and the high production capability is due to the patented Doublescreen screen box, which features two independent triple deck screen boxes. These have independent drives, that are able to have their amplitudes and screen angles adjusted depending upon application.
And the choice of components such as screening media can be just as important as choosing the right capital equipment, as Sundre Contracting Co. of Sundre, Alberta, Canada found out. The company produces more than 30 different product sizes – from 1.6 mm fine sand to 305 mm screened rock for a range of customers from road builders, concrete plants and even golf courses.
However, the rainy climate and clay material it handles puts demands on its screening media, especially when it comes to avoiding blinding and pegging.
Having had trouble producing aggregates for a road project from clay-contaminated materials using traditional mesh, the company turned to distributor Elrus Aggregate Systems for a solution.
The recommendation that came back was to use Major Wire 7/8 in (22 mm) Flex-Mat 3 Series D Tensioned screen media, and this produced
“The operation went from not being able to produce at all in marginally rainy weather to being able to operate through heavy downpours. We’ve recommended Major Wire’s Flex-Mat 3 screen media before and knew it could stand up to the challenge of screening sticky, clay-ridden material,” said Matt Armstrong, dealer representative at Elrus Aggregate Systems.
The self-cleaning media allows producers to increase open area, create more screening action and eliminate blinding and pegging problems as the wires are able to vibrate independently at different frequencies.
Sundre said adopting the media has allowed production to double on rainy days, which equates to thousands of tonnes of extra production in a single day.
“We make more than 30 different products in our operation, from golf course sand, to concrete and road base aggregates and decorative stone. Flex-Mat 3 helps us screen and wash all products more efficiently and saves us thousands in lost production each year. In addition, we estimate that its increase in open area provides us with up to +30% more screening capacity than before,” said Jason Harder, manager of operations at Sundre Contracting.
This goes to show that getting a crushing and screening system right is about much more than the choice between a mobile or static plant. It is also important to consider seemingly less critical factors such as the choice of screening media.