Modern Mining February 2023

MOTORS AND DRIVES

M&C and ACTOM Turbo Machines share in generator GO success Electric motor repairers, Marthinusen & Coutts (M&C) and ACTOM Turbo Machines successfully performed the General Overhaul (GO) of Sasol’s Secunda gas turbine driven 147 MVA (120 MW) generator.

S asol uses a feed stream of natural gas piped from Mozambique to drive the 2 × 147 MVA turbines and generators. A major General Overhaul (GO) was performed after about 100 000 hours runtime, the company said. Mike Chamberlain, M&C’s marketing & commer cial executive who project managed the GO, said M&C was appointed lead contractor on the GO for the 147 MVA generator and took direct responsibil ity for all the electrical work involved, while ACTOM Turbo was charged with the responsibility of execut ing all the mechanical work. The core portion of the contract was carried out during a 34-day shutdown period late last year, when the generator’s 34 t, 9 m long, 1 m diameter rotor was

removed and transported to M&C’s Benoni Power Generation workshop for removal of the rotor’s coil retaining rings, inspection and cleaning of the windings and overhangs, plus high-speed balanc ing of the rotor, before being returned to site for reinstallation. “At the same time testing and cleaning of the stator windings were carried out on site, and loose wedges were repaired. We also did in-situ Partial Discharge and Tan Delta testing, as well as end winding resonance frequency tests on the 11 kV stator,” said Chamberlain. The GO procedures were completed with the reassembly of the generator on site and perfor mance of a test run witnessed by the client.

ACTOM Turbo Machines removing the 147 MVA rotor from the stator.

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28  MODERN MINING  February 2023