The Multotec Group is making steady progress with the implementation of a maintenance contract awarded to the company that covers Debswana’s Jwaneng mine, OLM Process Plants, Orapa No 1 and No 2 plants, Letlhakane Mine treatment plant and Damtshaa mine. Once fully in place, this contract promises to mitigate production delays, reduce costs, decrease ferrosilicon losses and increase efficiency across the board.

Multotec has enjoyed a longstanding involvement with De Beers and Debswana in regard to supply of capital equipment and consumables, as well as servicing. The company also has a close association with Anglo American, which acquired De Beers’ shares in Debswana in 2012. “Diminishing skills, coupled with an increased focus on specialised products, have led to a definite trend in the mining industry towards maintenance contracts,” Derrick Alston, managing director of Multotec Manufacturing, says. “It makes perfect financial and operational sense to optimise maintenance staff on a process plant and enable mine personnel to focus on the management of the mining operation.

“Multotec’s maintenance contract at Debswana is different from the norm, however, owing to the remoteness of its operations. Each of the plants must be overseen by maintenance crews with the necessary skills and expertise to conduct maintenance on a variety of equipment such as wear linings, screen panels, rubber scrubber liners, dense medium and hydrocyclones,” Alston says. “The scope of processing and lining products that Multotec is able to offer is conducive to a smooth integration into the process plant operations. All these activities are undertaken with stringent OSH and security requirements expected of Debswana and Multotec.”

The maintenance contract has been designed on a fixed cost basis with an additional cent per ton variable portion, dependent on the tonnages being processed. Multotec will maintain a stockholding of consumables on each site, eliminating the need for the mine to hold stock and resulting in an overall cost per ton reduction. Alston describes this as a win-win situation that reflects the most appropriate partnership approach with regard to the process plants.

Multotec maintenance crews are now permanently deployed on each mine and these multi skilled teams undertake daily inspections of all equipment related to the contract. These daily checks are carried out in conjunction with the use of the Hawkeye monitoring programme that allows the crews to accurately monitor the condition of equipment. For example, screen panel change-out can be predicted and dovetailed into pre-planned shutdowns to optimise the use of the process plant.

Complete dense medium cyclones are also changed out on the same basis. Multotec teams of artisans and skilled lining installers also install pre-prepared ceramic or rubber lined steel chute work, ceramic lagged conveyor pullets or conduct in-situ repairs in the diamond processing plants.

Hawkeye was developed in-house by Multotec as an innovative means to effectively monitor screen maintenance processes.It is a web based application, accessible anywhere in the world, providing a simple interface for the user to access accurate and efficient records of maintenance activities. These entries are stored in a database and can be called up as required in a number of ways, to identify the actual status of individual screens. An assortment of screen panels are used on the Debswana screens and the Multotec site crews have the necessary level of expertise and experience in screen cloth media to optimise panel selection.

“The configuration of the Debswana plants makes it possible to conduct maintenance on a daily basis, with product flow directed to alternative operational streams,” Alston says. “Key result areas have been agreed upon and the contract performance is being monitored against these areas. A technical committee comprising both mine and Multotec personnel is responsible for month to month management and for addressing issues related to plant maintenance, while a quarterly steering committee of senior management from both companies oversees the activities of both parties to ensure optimal outcome.”

Maintenance contracts are already phased in at the Debswana operations mines to allow appropriate procedures for specific products to be put in place.Initial maintenance started with Multotec wear linings and this includes supply and installation of ceramic tiles and the re-engineering of chute systems to optimise materials transfer and minimise wear. This includes feed chutes, transfer points to conveyors, screen underpans and ceramic pulley lagging.

In the past, several of these plants had used steel or other wear materials to combat corrosion and wear. However, it later became evident that other options such as high alumina ceramics and specially formulated rubber liners would provide a more appropriate wear solution and significantly increase the life of the transfer points and chutes.

The next phase was to undertake the change-out of cyclones and Multotec has now taken over responsibility for cyclone inventory control. Cyclones are monitored using fixed benchmark parameters that allow for proactive condition monitoring and replacement of units to coincide with planned plant shutdowns. In addition, Multotec has replaced opposition products at Lethlakane with its own latest generation cyclones and these are performing extremely well in comparison.

“We’ve an established reference base when it comes to screen maintenance and can point to numerous examples where this has achieved significant savings for other customers in terms of plant operational costs,” Alston continues. “The Multotec maintenance contract model is specifically designed to optimise maintenance costs on an individual plant and there is no such thing as one size fits all.

“Our people are highly skilled and adept at monitoring the condition of our process equipment and, through the use of Hawkeye, they are able to generate accurate management data that allows for proactive screen panel replacement. As with all the other maintenance areas, this replacement is scheduled to coincide with planned shutdowns or carried out on process streams that are offline.

“The fundamental objective of the maintenance contract is to avoid unscheduled shutdowns caused by breakdowns attributed to poor maintenance. One of the most important aspects of this particular maintenance contract is the overall plant efficiency and optimisation of diamond and ferrosilicon recovery.”

More than 70 Multotec employees have been permanently deployed to implement maintenance across the Debswana operations, with a country manager reporting to the Multotec managing director Africa responsible for the Botswana operations. The Multotec office in Gaborone provides support, underpinned by additional technical support from Multotec process engineers and product specialists based in South Africa.