Modern Mining January 2018

PRODUCT News

Weba provides solution for Chilean copper mine

material was being presented to the con- veyor was causing impact damage and excessive spillage. The spillage had to be controlled using extremely hard skirtings under such tension that this had been causing extreme damage to the conveyor resulting in frequent belt replacement. “It is not uncommon for us to see this type of issue which arises from inadequate plant design,” Nienaber says. “When the transfer points do not receive the requisite attention during the design of the plant, numerous problems can occur during operation.” As a transfer point specialist, Weba Chute Systems is a strong advocate of their involvement at the start of a project. “This approach ensures that the transfer points are engineered for the particular plant, with the advantage that material transfer will be optimised and wear and impact issues such as those found at Carmen de Andacollo could be mitigated from the beginning.” Where operational plants experience issues with transfer points, Weba Chute Systems sends in its technical team to con- duct a full design assessment. According to Nienaber, this is a criti- cal step in the process as it will ensure

that the solution provided takes all fac- tors into account. He explains that the previous chute was essentially just a box structure and this was problematic as the material flow was not controlled and it directly impacted onto the conveyor from the screen. To add to this situation, the receiving conveyor design was also compromised. “We were able to design a new transfer point solution that would accommodate the shallow flow angle required in this application,” he says. “By custom engineer- ing the chute, we were also able to design it in such a way so as to feed the material onto the conveyor in the direction of belt travel. This then eliminated the issues asso- ciated with the previous direct impact.” The design of Weba Chute Systems also allows for absolute control of the material and, in this application, has been config- ured to force a concentrated stream from the screen decks onto the conveyor. Due to the compromised general arrangement between the screen and conveyor, skirts are still required to eliminate spillage. To provide further protection against sliding abrasion, the chute has been lined with high alumina ceramic tiles. Mark Baller, Weba Chute Systems, tel (+27 11) 827-9372

Weba Chute Systems has successfully engineered a new transfer point to replace an under-performing chute at Carmen de Andacollo in the Coquimbo region of Central Chile. Carmen de Andacollo is an open-pit copper operation; Teck has a 90 % inter- est in the mine with Empresa Nacional de Mineria holding the balance of shares. The new chute system transfers mate- rial from a double deck screen feeding oversize material from both decks to a conveyor. Material throughput is 2 000 t/h with a lump size of minus 85 mm. Alwin Nienaber, Technical Director at Weba Chute Systems, explains that in the previous installation the manner in which The design of Weba Chute Systems has been configured to force a concentrated stream from the screen decks onto the conveyor.

All WEG electric motors are VSD compatible The benefits of variable speed drives (VSDs) are making this technology a popular choice among users of electric motors; now, with the introduction of the WEG Insulation System Evolution (WISE®) to all WEG motor lines, customers have full assur- ance that all WEG motors are VSD-compatible. “Not all standard electric

quencies, the voltage pulses – combined with the cable and motor impedances – may cause repetitive conditions of over voltage or voltage overshoots at the motor connection terminals,” he notes. “This may degrade the motor insulation system and reduce the motor’s useful lifespan.” To ensure that this does not occur in WEG motors, the WISE® insulation systemhas been developed through the use of enhanced materials in the production of the motor insulation. These materials include VSD‑compatible wire, insulation film, impregnation mate- rial and suitable cables. WEG has also specially developed its LackTherm varnishes for the insulation systems of its electric motors, which are applied to the 99,9 % pure copper wire during the enamelling process. These LackTherm varnishes have excellent dielectric strength, flexibil- ity, hardness and chemical resistance, as well as strong adhesion properties. During the impregnation process, the stator coils receive layers of high‑solid resins and water‑based coatings which are environ- mentally‑friendly and free from harmful solvents – as required by the ISO 14000 guidelines. “This process allows any WEG motors to be used with VSDs, as the WISE® insulation system ensures that the motor windings are protected against voltage peaks and voltage variations,”says Steyn. Zest WEG Group Africa, tel (+27 11) 723-6000

motors are suitable to be used with VSDs,” says Fanie Steyn, Manager Rotating Machines at ZestWEG Group.“The motor insu-

WEG WISE® insulation systems for electric motors.

lation systems are susceptible to insulation damage caused by the harsh switching frequencies and voltage peaks generated by VSDs.” Steyn explains that VSDs use power transistors – typically insu- lated-gate bipolar transistors or IGBTs – for the switching process. To achieve the high frequencies necessary for switching, the transis- tors have to turn ‘on’ and ‘off’ to conduct current repeatedly at high speeds. This results in voltage pulses with a high dV/dt, or rate of voltage change over time. “When squirrel cage electric motors are fed by these high fre-

70  MODERN MINING  January 2018