May 2012

Comminution

 

 

Old made new

Westpro reconditions crushers, mills and other processing equipment worldwide. “We do any that anyone is interested in having done,” says Rob Kaplan, manager of mineral processing. Customers can ship in their equipment or invite a crew to do repairs onsite. Along with quality and good service, says Kaplan, the company offers a short turnaround. “Depending on what you’re looking at, we seem to have a relatively quick delivery compared to some of our competitors.” He points out the company’s services are not restricted to rebuilds: Westpro also custom manufactures equipment ranging from individual pieces to entire processing circuits. Its latest jobs were a rod mill for the potash industry and a pair of ball mills used for lime slaking. 


 

  Near-pure compressive force

The Polycom high-pressure grinding roll uses two counter-rotating rolls, one fixed and one floating, to crush material. According to manufacturer ThyssenKrupp Polysius, it applies near-pure compressive force as opposed to the combination of compressive and less-powerful shear forces in conventional grinding mills. The results contain a higher percentage of fines than crushers produce and coarser particles that have been cracked, easing the job downstream. While high-pressure grinding rolls have historically had trouble with wet and sticky ore, marketing representative Norbert Veit says Polysius has extensive experience with the studded roll bodies suited to these types of material. The hard metal studs also protect the roll body against abrasive material.


Green in, trucks out

This mobile slewing sizing station from MMD Mineral Sizing Inc. enables excavating, sizing and conveyor haulage to take place at the mine face. “The main feature is to eliminate haul trucks,” says Jenny Forsan, logistics manager at MMD Canada. Without trucks’ exhaust and tire impact, she says, mines could run greener. A typical setup would see an excavator loading material directly from the mine face into the sizing station. Sized material would be discharged into a hopper car to travel along an overland conveyor. Repositioned from a control cabin, the sizing station can slew 135 degrees from centre to accommodate different sections of the mine face. It can operate almost continuously, with a maintenance break every two weeks.

 

  Small but mighty

PR Engineering has developed a prototype two-tonne crusher for exploration use. The small jaw crusher is designed to be used in the field, crushing small ore samples for analysis. It will be heavier-duty and more affordable to Canadian customers than lab crushers that are currently available, according to Linda Grieco, director of PR Engineering. “These will outperform what’s on the market now, probably 10 to one,” she says. “Plus, it’s Canadian-made. Other lab crushers come from places like Peru and Brazil. You can imagine what the shipping costs are going to be.” Suited for hard rock applications, the crusher will have a double toggle design, which Grieco says produces less wear than single toggle models.


Rockbreaker with reach

Made for use in large dump pockets, Tramac’s TR rockbreaker boom systems carry 7,000-pound hammers. The booms are custom-built with varying reach measurements, says Gary Hesseltine, boom specialist at Tramac: “With a careful study of drawings or by a site survey, our engineers can make adjustments of base position and boom arm articulation that will allow horizontal and vertical coverage into all required areas of the client dump pocket.” Hesseltine says an arched main boom design offers both superior strength and the ability to work relatively close to the boom’s pedestal base, while critical connection locations are flared and widened to provide extra support. “This is an important element that adds years to the unit’s working life,” he says. 


 

Self-clearing safety

The Telsmith J3858 is a high-capacity jaw crusher, with approximate throughputs of 355 tonnes to 545 tonnes­­­­ per hour at a 100-millimetre setting. Chad McClaskey, marketing manager at Telsmith, says its popularity is due in large part to a remotely operated chamber clearing system. Hydraulic cylinders retract the toggle beam and pitman, allowing large rock chunks to fall. Any remaining stone is crushed to normal size. “By simply using push button controls, the operator can clear the crusher in less than 30 minutes,” says McClaskey. “Not only does hydraulic chamber clearing save time, it provides for a safer work environment since employees no longer have to manually ‘dig’ out the crusher.” The cylinders briefly give way for uncrushable material as well, eliminating toggle breakage.

 

  Reliability boost

Reliability is the highlight of this medium-voltage mill drive. A mill powered by the ACS 1000 will enjoy “fast, accurate, stepless control from zero to full speed” via a patented technology called Direct Torque Control, according to Richard Kraska, product group manager - MV Drives at ABB. Rapid torque response means that the drive responds well to power losses and sudden load changes. Other distinguishing features, says Kraska, are the fuseless design, long-lasting capacitors, and the standard inclusion of an output sine filter that eliminates voltage reflections and common mode voltages. The ACS 1000 controls induction motors of 315 kW to 5 MW. Existing installations can be retrofitted with the drive.

Holistic relining

Russell Mineral Equipment (RME) sells parts of its mill relining equipment individually, but Peter Courtney, key account manager for North America, argues that RME’s entire range is greater than the sum of its parts. “We can offer maximum operator efficiency and safety when the complementary products and services in the RME Mill Relining System are utilised,” he says. “These include Thunderbolt recoilless hammers, T-Mag moil guides, O-Zone liner lifting tools, Russell feed chute technologies, and importantly, spares, service and training throughout the world.” The liner handlers themselves come in models for a variety of mill types; the Russell Twin 8 provides two independent systems for one large SAG/AG mill, operating on eight axes of movement.

 

  Crushing: now in 3D

Gundlach’s roll crushers boast the unique ability to size products in three dimensions. Mike Hamby, vice-president of sales and service at Gundlach, explains that the tooth configuration of a standard roll crusher can determine that particles emerge (for example) 1 inch by 1 inch but they cannot control the third dimension. This irregularity can pose a downstream problem for such products as fertilizers, salts and coking coal pumped as slurry. Gundlach’s crushers use a timed gearbox to control that final dimension. “As those two rolls turn, they turn in a timed relationship to each other,” says Hamby. “Both rollers turn at exactly the same RPM, even if you open and close the roll to change the sizing.”

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