Whilst working with one of our key European clients with the general maintenance of a BRUSH 2-pole generator in a H2S environment, we were also asked to inspect a 3rd party manufactured 2-pole turbo rotor that was experiencing earth fault problems - it was found that the coils had experienced heavy corrosion between the soldered connections.
BRUSH undertook the project to rewind the rotor and improve the protection against the H2S environment. To reduce outage time, it was decided to re-utilise the existing copper.
The rotor coils were carefully removed from the rotor so not to cause undue stresses and deformation to the coils. Both the rotor body and the rotor coils were then thoroughly cleaned to remove dirt, debris and the old insulation. Everything was fully tested to prove all components were "fit for purpose" according the BRUSH Aftermarket quality management programme.
The rotor was then rewound with the existing copper whilst applying new insulation and medium frequency brazing for the connections. The slot wedges were also cleaned and re-fitted with suitable insulation and packing to prevent significant movement during the rotors normal operation. A protective epoxy top coat was also applied to the coils to give extra protection to the rotor from the H2S environment. After passing electrical testing both retaining rings were re-fitted with new under cap insulation.
The rotor was then balanced and an over speed test of 110% was performed which was witnessed by the client at our test facility.