A 40 MW turbine generator was recently repaired on a fast-track schedule, with an undertaking to have the generator back in operation within three months.
The emergency repairs were required after the generator broke down, with damage including failed bearings on the generator train. All four bearings, as well as the rotor sealing elements were found to be damaged. On assessment, additional damage unrelated to the initial failure, was also discovered.
The damage included a crack on the high-pressure (HP) gland section of the main steam casing, while a second, unforeseen irregularity of a malfunction in the starting or auxiliary oil pump, was also discovered. Other irregularities included an incorrect bolt clearance on one of the HP palms, possibly due to a faulty installation.
Mechanical repair company ACTOM Turbo Machines repaired the damaged bearings and reconditioned a spare set of bearings. The sealing segments were replaced with new ones manufactured at the company’s Sasolburg works.
The company notes that the process of repairing the crack in the main steam casing took the team five days, working around the clock.
The repair of the starting oil pump was performed in only two days. This required the manufacture of a new shaft and the reconditioning of the mechanical seals.
Once operations resumed, vibration testing of the generator based at ArcelorMittal South Africa’s Vanderbijlpark Works, confirmed that its performance had significantly improved.