stainless | copper | technology

Outokumpu is one of the world’s largest mill suppliers. Our grinding

expertise combines the most advanced design, analysis and testing

technologies to help you select the best mill for your grinding needs.

A wide variety of designs is available to suit your requirements in either

green-fi eld projects or existing operations. As your partner, we provide

the fi rst key element of a total minerals processing solution.

Grinding technologies

The key to successful concentration

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The Outokumpu factorThe Outokumpu factor is the competitive advantage we give our customers by helping them enhance the performance of their processes, products and services. It is a factor our customers rely on to help them overcome even the most demanding challenges; a hidden asset that helps them win.

Solid grinding experienceOutokumpu’s experience and know-how in grinding, fl otation, separation, dewatering and automation allows us to supply you with single units of equipment or turn-key deliveries to mining and industrial minerals plants. In grinding, we have inherited an established lineage of over 100 years from Morgårdshammar, Scanmec and Nordberg.

All these brands are now incorporated into the Outokumpu Group. Our state-of-the-art designs are developed from these years of experience – yesterday’s practical experience is used in today’s designs to produce premium technologies, to exact specifi cations. Our grinding mill range includes semi-autogenous (SAG) mills, autogenous (AG) mills, ball mills, pebble mills and rod mills. All are available in various designs and sizes in order to fully satisfy our customers’ requirements.

Optimum mill type and size The correct sizing of grinding mills requires in-depth knowledge and experience in crushing and benefi ciation processes. Our metallurgists and application engineers are acknowledged experts in these fields. A deep understanding of parameters such as Ball Mill Work Index (BWI), Rod Mill Work Index (RWI) and Crushing Work Index (CWI) is necessary to determine the optimum mill design for a given application. Size distribution in feed, product and materials behavior are also important considerations.

The fi rst part of the sizing process involves standard application calculations. The calculations determine the power that must be applied to the mill in order to grind the ore, at the specifi ed feed rate, from one size distribution to another. Using our combined expertise in grinding and specially-developed sizing programs, we are able to make these calculations and recommend the correct mill type and size for any given application.

Ore testing for that extra edgeFirst-hand knowledge of the material to be processed is essential for the successful design and operation of any mill. Outokumpu has test facilities for material mineralogy and liberation analysis as well as complete minerals processing facilities at our own R&D center. In cases requiring additional data, we can rely on our close relationships with some of the foremost test centers around the world.

Trunnion-supported SAG/Ball mill circuit operating at Rio Narcea, Spain.

A full range of mills for wet and dry grinding

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The demands of hard-rock mining and industrial minerals operations require the availability of a wide variety of grinding mills. AG and SAG mills are currently the industry standard for primary milling. Outokumpu can provide you with high-aspect or low-aspect AG/SAG mills to meet any milling requirement.

In grinding, a wet process is the most commonly used, as most of the downstream operations – flotation, magnetic separation and leaching – are wet processes. However, there are dry processing applications for which dry milling is the necessary grinding method. Whether wet or dry applications, we can provide you with the right grinding solution.

AG and SAG millsAutogenous and semi-autogenous mills are designed for primary grinding of run-of-mine ore or primary crushed ore. These two types of primary mills are the most commonly used and we are highly experienced in providing the full size and power range right up to the very largest.

Ball millsBall mills are usually used for secondary and tertiary grinding. Ball mills are the secondary mills most often used in the preparation of the material for the following concentration process.

Rod millsRod mills are mainly used for the primary grinding of crushed ore in the size range up to –50 mm for soft materials and –20 to 30 mm for harder materials and for the preparation of feed for secondary ball mills. Pebble millsPebble mills are mostly used for secondary grinding, where minimization of both processed mineral contamination and operating costs are of high importance. Pebble mills are also used where the ore is capable of forming suitable pebbles. The application range is similar to that of ball mills.

Shell-supported SAG mill operating in Mexico.

Mill designs for every requirement

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Our grinding mills are sized, designed and built for rugged duty and operation in the harshest of environments. Different applications call for various mechanical confi gurations and designs. Our capabilities and expertise cover both trunnion-supported mills and shell-supported mills. Both designs are complemented by an optimized drive solution, selected for the exact conditions to be encountered.

Mill bearingsThe type of support bearing is selected on the basis of the mill size, intended duty and environmental conditions at the installation site. We offer mills supported on a variety of bearing arrangements: hydrodynamic and hydrostatic journal, spherical roller, hydrodynamic and hydrostatic multi-pad type bearings.

Mill support bearings Journal bearings

Journal bearings in Outokumpu’s trunnion-supported mills are hydrostatically lubricated during start-up and stopping as well as hydrodynamically or hydrostatically lubricated during operation. The journals are easily removable and bearings for both ends of the mill are identical and reversible.

The journal or bearing sleeve material is either bonded white metal or centrifugally cast bronze. The journal supports the trunnion surface through 120° of rotation. Swivel support allows the bearings to self-align as mill loading changes. The housings (base and cap) are machined from steel plate.

Our hydrodynamic journal-bearing lubrication systems deliver conditioned high-pressure oil at the sleeve center to lift the mill for start-up. The systems also deliver low-pressure oil at the edges of the sleeve to provide hydrodynamic lubrication for reliable, continuous, bi-directional operation. Low and high-pressure standby pumps and standby oil fi lters are standard features of our journal-bearing lube systems. Small reservoirs, integral with the bearings, provide suffi cient oil for the mill to be safely stopped in the event of a power failure.

Spherical roller bearingsSpherical roller bearings can be used for mills with trunnion diameters up to 1.8 m. The benefi ts associated with spherical roller bearings are high load-carrying capacity, short trunnion length and simple lubrication. Due to the short trunnion, the bending moment on the head is small, resulting in reduced stress and lower deformation of the head. The free (non-fi xed) bearing is mounted on rocker-type pedestals, which accommodate the thermal expansion of the mill-rotating assembly.

Spherical roller bearings are lubricated by means of a small motor-driven or air-driven grease pumping system, making them especially well suited to remote locations and harsh environments where routine maintenance is diffi cult.

Shell-supported SAG mill and shell-supported ball mill operating in East Africa.

Multi-pad type bearingsLarge mills can be supplied with multi-pad type hydrodynamic or hydrostatic bearings. Several individual pads are mounted onto the trunnions or shell at each end of the mill to provide a very high load-bearing capability and maximum tolerance of trunnion deformations.

Each pad is mounted on a hydrostatically lubricated ball and socket support. These supports are machined from high-strength steel and fi tted with a white metal bearing surface specially designed to suit the trunnion or shell diameter. As with our journal bearings, high-pressure oil is delivered to the center of each pad to lift the mill for start-up, and low-pressure oil is delivered to a slot at the ends of each pad to provide hydrodynamic lubrication for operation.

To allow for rapid erection and alignment, each pad is supported on a pedestal containing an integral hydraulic jacking cylinder and lock ring. The jacking cylinder ensures easy alignment and equal load sharing between pads.

Shell-supported millsOutokumpu’s shell-supported mills are more compact, occupy less fl oor space and require simpler foundations than comparable trunnion-supported mills. This is an important advantage, especially for indoor installations in severe climates and offers considerable cost savings.

Shell-supported mills are supported by bearings mounted directly to the shell, thereby yielding substantial advantages. Because the end plates of the mill do not support the structure, the feed and discharge openings may be sized to meet process conditions without being limited by bearing diameters. The overall span of the mill is less, which results in lower forces acting on the mill structure. For this reason, shell supports are being increasingly specifi ed for very large, heavily loaded mills.

Our shell-supported mills use multi-pad type bearings, where the journal surface is machined into the specially reinforced end sections of the shell structure. A thrust surface is part of the fi xed end journal and special hydrodynamically lubricated shoes are used to resist the axial thrust of the mill-rotating assembly. The ring gear on shell-supported mills is normally

Shell-supported open-ended SAG mill operating at Murrin Murrin in Western Australia.

mounted on to a flange, centrally located on the mill shell, away from the ends. This enables the remaining components of the mill drive train to be brought closer to the mill, which in turn allows for smaller foundations and lower installation costs.

Shell-supported pebble mill operating in Scandinavia.

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Mill drivesMost mills are driven by ring gears, with a 360° fully enclosing guard. The ring gear casting material is either nodular iron or steel, usually with helical type teeth, which makes them reversible, allowing the use of both fl anks throughout their operational life. The drive may be mounted at either the feed or the discharge end of the mill. Whilst mills rated up to 10,000 kW can be driven by a single pinion, dual pinions are mostly used for mill applications above 6,000 kW.

Both high-speed induction type or low-speed synchronous type drive motors are available. High-speed motors require an intermediate gearbox. Smaller mills up to 500 kW are also available trunnion-driven. Large mills exceeding 13,500 kW normally use gearless drives.

Mill linings Outokumpu offers a complete range of mill linings suitable for specifi c conditions. Lining materials include unalloyed or alloyed cast steel, cast iron, solid rubber, rubber-steel composites or ceramics. Wave or lifter bar linings can be supplied, depending on the application.

The ring gears on shell-supported mills are placed away from the ends.

Feed arrangementFor primary mills, a feed chute incorporating a “rock box” is usually provided. Large feed chutes can be supplied on wheeled carriages, which roll back away from the mill or roll away laterally on tracks, to provide access for mill inspection and liner replacement. Ball, rod and pebble mills are supplied with spout feeders and replaceable liners supported by a wheel-carried steel structure. Other available feed arrangements include screw-type, vibrating drum and scoop-type feeders.

Discharge arrangementWe provide a wide variety of discharge arrangements, such as overflow, peripheral, grate and open-ended. Ball, rod and pebble mills typically have overflow or grate discharge arrangements with trommel screens. Ball, rod and pebble mills with

This open-end SAG Mill (scrubber) at Murrin Murrin in Australia is lined with rubber.

peripheral or open-ended discharge arrangements are generally only used for specifi c processes. SAG and AG mills typically have grate discharge arrangements with or without trommel screens. SAG and AG mills with open-ended discharge arrangements are more efficient than grate discharge arrangements.

Advanced design analysisOutokumpu mills are designed using the latest 3D computer-aided design (CAD) and drafting techniques. Designs are fully verifi ed with the latest fi nite element analysis (FEA) tools and techniques, which predict peak stress levels in the mill structure and the ultimate life of the mill’s structural elements.

Torsional analysis of the drive train can also be conducted, ensuring the mill operates at speeds away from harmonic frequencies. For mills utilizing journal or pad-type bearings, our lubrication design analysis predicts the minimum thickness of the bearing fl uid oil fi lm.

Energy-efficient, cost-effective technologiesThe selection of an appropriate mill confi guration depends on the feed size distribution, the desired product size distribution and other physical properties which define the relative hardness, integrity and abrasiveness of the material. By applying our cutting-edge technology and solutions, you contribute to energy saving and environmental protection.

Our aim is to optimize your initial investment costs as well as the life-time operational costs. Therefore, effectively balancing capital and operating costs requires an experienced, practical understanding of effi cient energy we and optimum mill life-span confi guration.

To ensure premium quality product service and support, Outokumpu mills are backed by our worldwide sales and service network. Our specialists ensure that your mill is properly installed prior to commissioning and the process performance is verified after commissioning.

After commissioning, your local Outokumpu offi ce provides: Ongoing support with promptly

delivered replacement parts Other mechanical services, including

complete mill reconditioning Complete process evaluations and

performance diagnostics Liner wear measurements and profi le

development Maintenance inspections Alignment checks Gear reversals Service contracts

Worldwide sales and service support

Additional technical support is provided by our regional Grinding Business Centers, and Outokumpu’s global design offi ce in Oslo, Norway. Our Grinding Business Centers are located in Denver, USA; Smedjebacken, Sweden; Johannesburg, South Africa; and Perth, Australia, which is also the headquarters of our grinding business.

Quality assured

Outokumpu mills meet the highest quality standards for design, manufacture and supply. Regional business centers are either in pursuit of, or have already received, ISO 9001 certifi cation. Once a contract is awarded, a quality assurance plan is raised in the regional Outokumpu Grinding offi ce. This plan outlines the critical steps in the design and production process and lists the applicable documentation and physical inspections for each step.

We work in close co-operation with our global network of experienced, qualifi ed subsuppliers to produce the mill’s main components as close as possible to the installation site. Engineers from our international mill business centers perform progress inspections to verify compliance with applicable specifi cations and standards. The results are recorded and form a part of the mill installation record, which we maintain for the life of the installation.

www.outokumpu.com

3011EN

. Libris, Helsinki, Finland. A

pril 2004.

E-mail: info.technology@outokumpu.com

Outokumpu is a dynamic metals and technology group. Focusing on our core competences, that is, extensive knowledge of metals and metals processing, we aim to be leaders in all of our key businesses: stainless steel, copper and technology. Customers in a wide range of industries use our metals, metal products, technology and services worldwide.