Modern Mining March 2016

PRODUCT News

Mill motor rehabilitated for New Zealand gold project

Marthinusen & Coutts recently performed an extensive rehabilitation of an old 2 985 kW salient pole synchronous mill motor that had not been in use for over 10 years. The project was commissioned by international mining company Newmont for the Waihi opencast gold mine in New

Zealand. Marthinusen & Coutts took on the project after initially agreeing to retrieve themotor fromwhere it had been left lying in the veld at the site of the old Crocodile River gold mine at Hartebeespoort Dam near Skeerpoort, Gauteng. “We were first awarded a contract to assess the condition of the motor to establish what sort of state it was in and to then quote for repairing it,” says Craig Megannon, GM at Marthinusen & Coutts. “Not surprisingly we found it to be in a poor state. Apart from the fact that it had been left abandoned for so many years, it is a very old motor. It was manu- factured in Japan in 1970 and had since been deployed at mining operations in Australia, Argentina and South Africa. “Repairing it has involved an extensive amount of work and included complete remanufacture of parts that we found to be beyond repair,” Megannon says. The rehabilitation contract was awarded in October 2014 and was completed at the Capital Equipment Group (CEG) of Invicta Holdings Limited. “These robust excavators, which are now available in Southern Africa, are fitted with special features to ensure optimum efficiency and extended service life in harsh local operating conditions. “Design features for the African mar- ket include a Tier II mechanical engine for reduced operating costs, a heavy duty boom and arm, as well as standard hydrau- lic piping for hammer applications. These machines also have an improved H Class bucket and are supported by Doosan with a 2-year/ 4 000-hour warranty.

end of October 2015. The repairs that were done included rewinding of the rotor and replacement of the stator core with lamina- tions manufactured by Electrical Machines’ Laminations & Tooling business unit. Parts that were replaced with re-manufactured parts included the journals, slip-rings, brush gear and coupling. “We also modified the stator design to increase the stator copper thickness and reduce the overall temperature rise, which we found to be the main limiting factor in the stator in its original form. We did the design using advanced software we recently acquired for this type of special- ised work,” he explains. Machine Monitor, an Australia-based third par ty engineering company, observed andmonitored the entire rehabil- itation process and testing at Marthinusen & Coutts’ Cleveland plant throughout the duration of the contract on Newmont’s behalf. Marthinusen & Coutts, tel (+27 11) 607-1700 “This series features a range of new tech- nologies that deliver effective control over the machine’s power and also simplify main- tenance procedures. As a result, efficiency and machine durability are increased, pro- ductivity is improved and operational costs are lowered.” The 21,5-t operating weight of these excavators is enhanced by new specifica- tions that include a 0,92 m³ bucket capacity, a digging depth of 5 755 mm, a digging reach of 8 950 mm and a digging height of 9 750 mm. The engine rated power is 110 kW at 1 900 rpm. Maximum engine torque is 61,5 kg.m/1 400 rpm. Doosan, tel (+27 11) 974-2095

Marthinusen & Coutts’s test technician, Suresh Gunpat, with the 40-pole synchronous mill motor during the series of tests conducted on it on completion of the rehabilita- tion process.

New generation excavators from Doosan introduced Doosan’s newest generation hydraulic exca- vators – the heavy duty DX225LCA series – have been designed for greater operator comfort, improved fuel efficiency, enhanced productivity and minimal maintenance requirements.

“There are currently 360 20-t Doosan DX excavators in operation in the local market and we expect the improved DX225LCA series to further consolidate Doosan’s position as a leading supplier in this size class of equipment,” says Chris Whitehead, National Sales Manager, DISA Equipment (Pty) Limited, trading as Doosan, part of the

42  MODERN MINING  March 2016