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:: Multotec Range Of Trommels Proving Increasingly Popular
Multotec Manufacturing, a company in the Multotec Group, can rightfully claim to be one of the largest suppliers of trommel screens to the mining industry. The company has received significant orders from all the major platinum an gold producers in southern Africa, and its trommels are also hard at work in various other mining applications throughout southern Africa.
Trommel screens were long regarded as unsophisticated disposable items attached to end of mills and scrubbers. This is no longer the case. Modern technology means that they are designed to last for a number of years. The structure is rubber lined to prevent erosion of the steelwork, while the surfaces are now equipped with replaceable screen media. Flanges are machined to ensure seamless contact with the mill trunion flange to prevent undue stress in the joint.
Trommel screens are, in fact, very complex steel structures that have to cater for uneven loads discharged from mills and scrubbers. As the units rotate, the product discharges through an arc of no more than 25° of the circumference creating a preferential load bearing zone and keeping the frame under constant stress.
Multotec has, over the years, with the assistance of finite element analysis, developed methods of designing trommels in-house to cater for these requirements. The company is ISO 9001 listed and uses extensive quality assurance procedures in the manufacture of trommel screens to ensure a high quality product is produced.
With the advent of large SAG and ball milling processes, trommel screens have become more prominent in processing plants. Mills have increased in size to cater for higher through-puts, significantly increasing the size and complexity of trommel screens as well.
In 1982 Multotec started supplying trommel screens using modular polyurethane panels onto trommels previously fitted with woven wire screen cloth. The use of replaceable modular polyurethane panels on a substantial steel structure has reduced plant downtime, resulting in improved plant throughput and reduced running costs.
Multotec trommels can be designed to take modular polyurethane panels or bolt-down type panels. Modular polyurethane panels with integral scrolls or wear bars can be fastened to the trommel frame with the company’s well-proven pin and sleeve attachment system. The choice of modular or bolt-down type panels is based on economics. On large trommel screens, over 3.0 metre in diameter it is often more economical, from the structural design, to use bolt down panels rather than the modular type screen panels.
Multotec Manufacturing product manager, Anthony Yell explains that the polyurethane panels are injection-moulded and rolled to achieve the correct radius to suit the steel frame, with scrolls being hand cast and welded onto the panels.
The polyurethane panels manufactured by the company are available in a wide variety of apertures and panel thickness, and are very effective against sliding abrasion experienced in milling applications.
“The modular design of the Multotec systems makes the trommels user-friendly. During operation the feed-end of the trommel usually sees more wear, and the customer can easily replace the affected panels when they’re at the end of their effective life, rather than the complete set of panels thereby reducing running costs.
Scroll and weir bar panels form an integral part of the trommel screen and are available in a variety of heights, pitches and number of starts.
“The scrolls force material to move from the feed-end of the trommel to the discharge end and the longer the trommel is the more important the scroll. If longer retention times are required we can install rows of weir bars to retain the material in the screening area or a combination of both scroll and weirs to feed material forward in a controlled manner at the optimal speed for best process efficiency. We size all the trommels screens ourselves and we give process guarantees," Yell says.
Multotec modular polyurethane panels are available with forward or reverse scroll executions and the layout of the scroll is designed to minimise the number of different panels.
Double trommels are also available, and equipped with a special mounting flange, which is designed to assist with installation and removal of trommel panels.
The Multotec range of self-driven trommels gives the customer the choice of several different options. Self-driven trommels can be hydraulically driven on a centre shaft at the discharge end or driven by a motor and gearbox driving supporting wheels.
Since its establishment in 1973, the Multotec Group has maintained its leading position in the industry by adopting a proactive approach to research and development.
Through Group companies, Multotec Manufacturing, Multotec Process Equipment, Multotec Wear Linings, Multotec Rubber and Mato Products, it supplies a wide range of products to the mining and materials handling industries throughout southern Africa and the world.
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