By Torsten Lemm
Conveyor belts can do more than just transport unit loads or bulk cargo from point A to point B. They form the backbone of efficient production processes, particularly when faced with current economic challenges such as raw material shortages and synchronized global value-add chains. Conveyor belts and conveying equipment are thus a central influencing factor for companies’ competitiveness. To maintain their peak performance over the long term, regular maintenance is a must. Timely replacement of worn components can effectively prevent a sudden failure of the conveyor belt, but a project at Chile’s Los Pelambres copper ore mine, however, demonstrates how an economic loss due to such failure can be avoided. There, two of the heaviest-duty conveyor belts in the world—with a total length of 23 km (14.3 miles)—were replaced without production disruption.
Conveyor belt systems nowadays form an integral part of both raw material extraction and modern production. They optimize transport routes, make complex logistics processes more efficient and bridge short or medium distances for transportation of material. The demands on conveyor belts can be many and high; in addition to high expectations and requirements for conveying performance and load-carrying capacity, factors such as low wear and maintenance costs and a high degree of production safety play an important role. From an operator’s standpoint, a major goal is to have conveyor belts run as efficiently as possible over a long service life and avoid downtime to the greatest possible extent.
Each industrial sector assesses the characteristics of conveyor systems differently. Conveyor belts in the raw materials industry, for example, need extremely high levels of tensile strength and operational safety as well as extreme resistance to wear to be able to cope with the load caused by the transported materials over long distances. To meet differing operator requirements, custom-made and flexible system solutions are required, matched to the particular location, type of use and range of tasks involved, and to the repair or maintenance of these systems.
For conveyor systems used in raw material extraction applications, the belt and other components must be changed after a certain operating time. Conveyor systems used in opencast mining are exposed to particularly difficult conditions that affect the structure of the belt and limit its life expectancy—but extraction of natural resources, often in areas that are geographically exposed, is currently very lucrative. High demand from economically emerging nations and the resulting scarcity of certain resources and associated price increases are transforming conveyor-system projects that only a few years ago were classed as unprofitable, again attractive.
In many of these instances, the materials and equipment used are often exposed to extreme temperatures, higher levels of insolation (solar radiation exposure) or high humidity levels. With the help of specialists who have the necessary know-how and knowledge, professional maintenance and trouble-free exchange of worn components such as conveyor belts, drive and redirector drums and carrier rollers can be guaranteed. Even large conveyor belts that run round-the-clock, are kilometers long, or carry particularly heavy materials can be successfully exchanged using proven techniques and innovative approaches.
An example of this is the recent replacement of two conveyor belts at Antofagasta PLC’s Los Pelambres copper ore mine, located in Chile’s Coquimbo Region, 240 km northeast of Santiago. This opencast mine lies in the Andes at an altitude of 3,300 m (10,800 ft). More than 8,000 mt/h of copper ore are transported by steel-cord conveyor belts to a site at 1,800 m altitude for further processing. This arrangement involves downhill transport gradients of up to 10% for the conveyors.
Together with the mine operator, REMA TIP TOP developed an approach that would enable replacement of both conveyor belts without extended downtime, the goal being to keep production losses to a minimum during the maintenance work.
“The normal method of changing a belt, making a splice and pulling it in roll by roll would have meant downtime of over nine weeks,” said Jan Severing, reliability engineer at REMA TIP TOP. “Taking into account the copper price then of at least $6,000 per mt, an immense production loss of around $250,000 an hour threatened.”
To keep production loss as low as possible, a REMA TIP TOP team created a technical solution that permitted both belts to be simultaneously exchanged in parallel with the running operation.
Both old belts were replaced by new ones directly on site. In the first phase, half of the belt length was vulcanized together for each belt. The kilometer-long belt loops made in this way were positioned in pits made for this purpose and later attached to the existing belt. This process was then repeated for each second belt half.
A smoothly progressing sequence of steps is necessary in critical projects such as this that directly affect production operation; accordingly, and taking into account the weight of around 44 mt per belt length and the length of the splice, 13 people were permanently assigned to each belt. By having trained personnel operate in two shifts, and through the high degree of work efficiency and the use of state-of-the-art materials and tools, both conveyor belts were simultaneously and successfully exchanged. The specialist team worked on the Los Pelambres project from October 2010 to March 2011.
“In addition to the requirements regarding quality and work protection, the efficiency of the work processes was also right at the top of the priority list for this project,” said Michael Labbé, REMA TIP TOP Latin America Spa.
“This meant that we had to find and use tools and machines that were state-of-the-art for time-consuming work such as rubbing down of cover plates, stripping and brushing off the steel cord or filling of steel-cord interstices. The assembly/vulcanization process, however—with 10 heating plates and 48 beams—could not be accelerated through the use of machines, but here, the fitters were actually even faster than using a crane.”
The Los Pelambres project illustrates that, for the maintenance of conveyor systems, flexible approaches tailored to the area of use are required. A relatively high work and materials effort in situations such as this can quickly provide a good return, because the production process is subjected to only short conveyor system downtime periods that are carefully planned.
Torsten Lemm is sales and product line manager–industrial, for REMA TIP TOP GmbH.