In a recent major overhaul of a 70 MVA turbine generator set, Marthinusen & Coutts, a division of ACTOM (Pty) Ltd, contracted with South 32’s Metalloys to take full responsibility for entire drive train refurbishment.
Working in collaboration with business unit ACTOM Turbo Machines, Marthinusen & Coutts completed the work successfully within six weeks. The electrical generation plant is at Metalloys’ manganese plant in Meyerton, Gauteng.
According to Mike Chamberlain, Marthinusen & Coutts’ marketing executive, this achievement showcased the capacity of the divisions to take full control of large mechanical and electrical refurbishments. Chamberlain highlights that the customer did not want to split the responsibility for the complete generator and turbine drive train between separate contractors.
“Marthinusen & Coutts and ACTOM Turbo Machines’ capabilities enable us to control the entire process, offering peace of mind to customers, coupled with optimised cost efficiencies,” says Chamberlain. “This also reduces customers’ risk and managerial effort in dealing with multiple suppliers.”
The scope included a complete inspection of the turbine rotor and internal components, as well as runout and dimensional inspection on the rotor. Inspections incorporated glass bead blasting and non-destructive testing of many components.
High-speed balancing of the 13 tonne rotor was conducted, and turbine rotor journals were repaired. White metal bearings were relined, and the thrust bearing was modified to improve fitment in the bearing casing. Positive material identification tests were conducted on all the studs, nuts and shaft seals. A complete 3D scan was done of the centreline to allow reverse engineering drawings.
At is repair facility in Cleveland, Johannesburg, Marthinusen & Coutts also performed a number of inspections, tests and repairs on the rotor. Dimensional inspections and electrical tests were conducted, as well as non-destructive testing such as the phase array test. Slip rings were ground, the diode wheel was inspected, and the diodes were tested.
ACTOM Turbo Machines inspected and refurbished the auxiliary mechanical equipment. This included lubrication and control oil systems, pumps, coolers, and white metal bearings on ID and FD fans. ACTOM Turbo Machines project manager Hannes de Jager notes that an overhaul of this magnitude and scope would usually take over two months.
“The excellent working relationship we had with Metalloys’ technical staff, and the cooperation we got from them certainly contributed to completing the work as quickly as we did,” says De Jager. Starting the inspections, tests and repairs in July, the team completed the overhaul by mid-August.