For a mid-sized plant, processing over 200,000 tonnes of waste per year, keeping downtime to a minimum is essential to maintain efficiency. Operating a comprehensive, preventative maintenance program is crucial to operating a cost-effective plant. However, unforeseen maintenance issues will occur; in these situations, it is the speed of response and the quality of the repair that will determine the success of the repair project.
A waste-to-energy plant owner in the UK experienced an unexpected failure of the site's sole generator, which meant that the heat generated by the incinerator could no longer produce energy. Keen to resolve the issue quickly, the maintenance manager called in Sulzer engineers, who arrived within two hours, to carry out an initial inspection to determine the cause of the failure.
The results showed that the stator had suffered from a coil shorting to earth on the turbine side of the winding, as well as suspected damage to the stator core. The plant operator had to move fast. The order was given to remove the generator from the site for further investigation of the core and rotor which were not accessible without a full dismantle.
With time such a critical factor in this project, the generator was dismantled overnight to allow the rotor, stator and coils to be tested. Apart from the need to rewind the stator, the tests also showed that the rotor required further investigation as the insulation resistance tests did not meet the acceptance criteria of 100 MΩ.