In-Situ Machining and Annealing Saves a Generator Crankshaft
Goltens travelled to the plant to complete an inspection of the engine, which had been completely disassembled by plant personnel at the maker's recommendation. Goltens determined that the 450mm diameter journal had surface cracks and excessive hardness (as high as 568HB) from the bearing failure and proposed in-place machining and annealing repair in addition to the overhaul.
After the tender was awarded, Goltens first machined the crankpin to -4.5mm to remove all surface cracks leaving a 250mm x 120mm hard spot. The team then performed the annealing process and reduced the crankshaft hardness from 568HB to a maximum of 300HB. A new radius was cut for the final undersize of -6.0mm, and final machining and polishing were completed with a surface finish of 0.4Ra.
While the annealing was being carried out, Goltens deployed diesel teams to begin the overhaul of components in parallel. The 36,000- hour scope was comprehensive and included the calibration and overhaul of all pistons and connecting rods, honing the cylinder liners, replacing all crankpins and main bearings, and overhauling the cylinder heads. In addition, all cam bushings were removed and replaced, and the vibration damper was overhauled along with the turbochargers and fuel equipment before the engine was completely rebuilt and tested.
Goltens then flushed the engine, completed system checks and commissioned the engine before it was turned over to T&TEC powerhouse personnel.