The site Mechanical team were engaged by Mighty River Power (MRP) to undertake the rotor removal and electrical repairs of the stator at Whakamaru unit 3. The stator had developed an earth fault during service, early attempts to repair the stator without the removal of the rotor failed. The 160 ton rotor had to be removed to gain access to the stator windings in the generator. Because of the nature of the repair and the tight time frames, MB Century were appointed the main contractor, coordinating all of the electrical contractors, NDT requirements, oil testing, asbestos management, off site repairs and final commissioning once the unit was assembled.
The Mechanical team commenced disassembly on 24th August, working a split shift pattern to achieve less down time of the unit. The unit was disassembled complete with alignment checks within eight days, allowing electrical contractor’s access for the repair. Once the repair was complete and the Stator high voltage tested, the unit was then assembled and re-aligned. The unit was returned to service on 8th September after extensive testing and vibration analysis. The excellent result achieved within the short time frame was appreciated by MRP.
Since the completion of this work MB Century has been successful in the tender for the full class 4 refurbishment of Unit 1 at Whakamaru commencing January 2010.