December 13, 2017

Crushing and screening

By Yvonne Andiva and Torah Onyango             

Crushing is an important mining process which involves the reduction of the particle sizes in an ore body after extraction. Otherwise know now as comminution, the process which actually involves crushing and grinding  has over time undergone several innovations in order to improve efficiency and improve the liberation of valuable minerals some of which we will take a look at in this article.

These processes are highly mechanical, consume large amounts of energy and result in tremendous wear and tear. The best equipment therefore is the one that offers reduced downtime and wear and tear while providing greater production for the same amount of energy

Along with crushing is the equally important screening that enables the separation of different sizes of particles. This can be for a number of reasons such as dewatering or in order to remove dust and smaller particles. There are several types of screens but the most popular is the vibrating screen. In all cases however the screen really consists of a surface with small apertures much like a tea sieve.

Extraction of the highest amount of a valuable mineral with the least energy consumption over an extended uninterrupted period of time is the desired result in any mining process and it all starts with the effectiveness of the crushing and screening process. Choosing the best equipment is therefore vital if the mine is to be profitable and sustainable.

Trommel screens

Stelex Construction Equipment Limited are the only supplier of the original ‘Hercules’ range of heavy duty trommel screens worldwide.

The aggressive ‘tumbling’ action of the feed material within the trommel barrel is highly effective at recovering valuable stone from contaminated overburden or as-dug feed material. This recovered stone can be turned into a saleable product for the customer. This tumbling action is not possible with many other types of equipment leaving the trommel in a class of its own.

The removal of unwanted contamination can also have a positive impact on other equipment within the plant. With this contamination removed it will help to reduce breakdowns and downtime on additional crushers and screens.

A Hercules trommel is designed to last for many years of service with high throughput, high screening efficiency and low maintenance. It is common for this service to be carried out in the toughest of conditions almost anywhere in the world. Another major advantage is that no full time operator is required to run the trommel.

For over 20 years Stelex have manufactured trommels in their own factory in the UK. This experience has helped to develop the machines into a market leader with a range of static and mobile machines from 250-1500 tph to suit a wide range of applications.

In tough economic times customers worldwide can see the advantage of the Hercules trommel as they look to maximise on their precious existing quarry reserves. Stelex are helping customers achieve their aims for the future.

Mobile impact crushers-Trakpactor 250

Powerscreen, designs and manufactures cutting edge mobile crushing equipment for customers in the materials processing industries.Their range of jaw, impact, and cone crushers boast excellent productivity and reliability all of which is supported by their worldwide Customer Support Services.

Powerscreen offer a range of mobile impact crushers suitable for primary and secondary applications including crushing aggregate, reinforced concrete and asphalt. The range includes both horizontal shaft impactors and vertical shaft impactors, both of which are designed to achieve a high ratio of product reduction.

The Powerscreen® Trakpactor 250 horizontal shaft impactor is a compact track mobile crusher designed for small to medium sized operators in the recycling and demolition markets. Capable of processing a wide range of material at a high output, the plant is versatile, easy to operate and fuel efficient due to its direct drive system.

Featuring the Powerscreen® Trakpactor 250 fixed hammer horizontal impactor, the plant offers users both excellent reduction and a high consistency of product shape alongside key features such as hydraulic overload protection.

Powerscreen has extensive knowledge in operating machines in extreme conditions, that is why it is possible to offer machines which can operate in desert or arctic conditions. They are able to provide a complete solution allowing customers to increase throughput potential. This total solution covers front end crushing and screening to final washing, magnetic separation and water treatment.

McLanahan Corporation, established in 1835, has remained a leading provider of custom engineered solutions for mineral processing. Among its capabilities in sizing, feeding, washing, scrubbing, dewatering and classifying, McLanahan provides its customers with an extensive line of crushing solutions

McLanahan patented the first Single Roll Crusher in the late 1800s and now they make four types of Roll Crushers – single, double, triple and quad roll designs – with a wide selection of models for each design. Roll elements in these crushers can be designed to meet almost any application. All McLanahan Roll Crushers have increased efficiency, high through-put for increased production and low roll speeds that minimize dust and fines.

Additionally, McLanahan’s line of Universal Crushers includes Jaw Crushers, Hammermill Crushers, and Primary and Secondary Impact Crushers. The Universal Jaw Crusher is typically capable of a 6 to 1 ratio of reduction when used as a primary crusher. Available in many model sizes, each crusher is designed with a deep crushing chamber for optimum nip, as well as a steep toggle angle for maximum crushing force. The heavy-duty pitman and shaft arrangement offers field-proven reliability and extreme durability.

Both Primary and Secondary Impact Crushers are available in a number of designs. Primary Impactors are capable of offering a high reduction ratio and handling highly cubical products. The Universal VersaCap design is highly adaptive to portable and mobile platforms. The Secondary Impact Crusher is focused on reducing the cost of ownership and is not only competitively priced, but also provides low maintenance cost, making each task easier and quicker.

The heavy-duty, rugged construction of the Universal Hammermill Crusher allows for greater applied forces, achieving higher production rates with controlled product top size and gradation. With numerous models and a wide selection of hammer and grate combinations, McLanahan is capable of providing a custom engineered crusher to fit any application.

CMB International is passionate about crushed rock because their clients depend on it.  With equal focus on rock crushers, screens and crushed rock, CMB prides itself on providing solutions for the effective and efficient production of material with minimum down time.  They understand that these key components are vital for their client’s production capability therefore producing machines that are purpose built, durable, user friendly whilst crucially providing the desired output of high quality product.

CMB are service focused and provide clients with first class after sales care and continued support.  They believe buying a CMB cone crusher, jaw crusher, screen, feeder or any of their product range is an investment over and above the equipment itself as it is also a sound investment into a wealth of knowledge and expertise that will continue to enhance performance and productivity.

The RS225 Rockstar 1350 Cone is the latest addition to the CMB range that also includes the RS150 Rockstar 1000 Cone. The CMB RS225 Rockstar is a modern, state-of-the-art, all roller bearing cone crusher. The crusher features hydraulic adjustment which enables the operator to rapidly change the discharge setting if necessary during crushing.

The proven all roller bearing design features lower power consumption, longevity, easy spares availability and the need for a more compact lubrication system. The product features include; High outputs of excellent product shape, unattended operation, Fast and simple adjustment, Minimal maintenance, Large unobstructed feed opening, and Takes unscreened feed.

The CMB Rockmonster 1100 x 800 jaw crusher features stepless mechanical/hydraulic adjustment enabling the operator to quickly change settings. There are no shims to change or bolts to re-tighten which, streamlines the adjustment procedure.   Welding has been kept to a minimum in the design and the massive front wall and cross beam are special heat treated castings that are bolted and pinned into position, therefore CMB have avoided the substantial stress concentrations often found in welded components.

Derrick Corporation is an American family-owned business, which was established more than60 years ago. Its head office and manufacturing facility are situated in Buffalo, New York. From its South African based office it services the African mining markets. Fine vibrating screen specialist Derrick Corporation and its six-year old African subsidiary are offering technology, equipment and methodologies to classification and dewatering of fines and ultra fines in the mining industry.

The company’s growing success is attributable to its patented technology and cost-saving production enhancing screening equipment. Screening machines are high frequency low amplitude vibratory units that can screen very efficiently down to 45 micron apertures with polyurethane surfaces and down to 35 microns with wire deck technology. The benefits of machines capable of handling and screening fine material at high feed rates, on small footprints (with capacities of between 40 and 500 tph), for both wet and dry applications, are obvious. An example is platinum’s high chrome UG2 ore material where the chrome needs to be separated from the PGM carrying quartz prior to secondary and tertiary milling.

The coal sector, which is frantically evaluating technology that can viably extract fines for upgrading, will also benefit from screening technology that can handle very fine material. Derrick’s patented Stack Sizer – a high capacity, efficient, fine wet screening machine – has become the local flagship product. It provides solutions to African industry’s immediate needs. There are over 1 800 installed and operating across various international mining operations which is sufficient proof of its market attraction.

Thanks to the process performance enhancements, their machines typically have a payback period no longer than one year. Derrick screens are suited to any processing plant, including iron ore, gold, platinum, gold, base metals, silica and mineral sands. African installations include, PGM, gold and diamond mines in South Africa, Gold mines in Namibia and Ghana, Mineral sand operations across Africa, Base metals (copper) mines in the Democratic Republic of the Congo,  Fluorspar mine in Namibia (Okoruso), Iron ore mines – Derrick Corporation South Africa has 60 dry screens installed at an iron ore mine in Mauritania and Uranium mine in Namibia.

Used crushers

CMS Cepcor™ Europe’s largest aftermarket supplier and manufacturer of crusher spare parts and crusher services; Crusher Manganese Steels (CMS Cepcor™) has recently been awarded the Queens Award for Enterprise in International Trade for outstanding achievement in export sales. Founded in 1969Crusher Manganese Steels, marketing their business under the trademark CMS Cepcor™, has successfully grown into a leading aftermarket manufacturer and supplier of precision crusher spare parts, premium manganese wear parts and crusher repairs, servicing the quarrying and mining industries worldwide.

CMS Cepcor™ is the only aftermarket supplier that incorporates one of the most reputable and long standing crushing plant original equipment manufacturers. Whilst CMS Cepcor™ is Europe’s largest aftermarket supplier; it does remain in essence a family run business with traditional values, committed to investment in employees, suppliers and customers alike.

CMS Cepcor™ also purchase used crushers, screens and feeders for stock and they would be pleased to be given the opportunity to tender during the disposal process of surplus equipment including scrap, seized, broken, incomplete or simply mothballed machines.

Horizontal Impact Crushers

ARD Crushing Limited is a newly established company, an amalgamation of industry specialists with experience totaling over eighty years. ARD has sales offices based in the United Kingdom, North America and the Far East.

They manufacture a range of crushing and screening plants and machinery for the quarrying and mining industry. Their products are designed to the highest quality by their in-house team of Engineers and Designers. Manufacturing is carried out in our two factories by specialist Engineers. They can offer consultancy and maintenance packages to all of our Clients to provide you with the confidence that your newly purchased machines will be installed and maintained correctly, helping to prolong the lifetime and efficiency of your investment.

ARD provide an extensive range of spare parts for machines that can be dispatched within 24 hours from one of their distribution facilities. However if you require spare parts for other machines please visit their sister companies Quarry & Mining Services Ltd, FeMax (UK) Foundry Ltd and METVIK Limited who will aim to supply quality engineered products to your requirements.

ARD Horizontal Impact Crushers can be used in both primary and secondary crushing applications of aggregate, and in the recycling industry: crushing of reinforced concrete, asphalt and other construction and demolition materials.

The ARD Horizontal Impact Crusher is fitted with hammers, having four crushing positions to maintain a more constant grading. Hammer types range from manganese, chrome to martensitic ceramic. Maintenance is carried out through inspection doors or hydraulically for a more simple maintenance routine.

ARD’s Horizontal Impact Crusher can be mounted on static, mobile and tracked equipment. Where applicable, the ARD Horizontal Impact Crusher can be easily fitted with a grinding path mechanism allowing you to maximise your control over the grading.

List of contributors

Stelex Construction Equipment Limited

Lee Fletcher

McLanahan Corporation

Andrea Ritchey


Matt Waters

CMB International Ltd

Eric Bennett

Marketing Services Ltd

John Vincent

ARD Crushing Limited

Maria Donovan

Derrick Corporation

Nic Barkhuysen

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