Leaf River Cellulose LLC, part of Georgia-Pacific Corporation, is a packaging company based in New Augusta, Mississippi, in the United States. The company operates pulp manufacturing mills producing filter-grade pulp and market pulp, which is used in the manufacturing of different kinds of filters and paper. Leaf River Cellulose offers its products around the world.
The company’s mills have two turbo sets, each having one turbine and two generators. This means that there are four generators. To ensure a disruption-free supply of steam and electricity and to prevent forced outages, the rotor of the generator needs to be rewound on a regular basis and intermittently replaced with another rotor.
The customer only had one spare rotor for four generators. But in 2018 the customer complemented their supply of spare rotors by purchasing a sixth rotor. Before the new rotor could be installed in the generator, it had to be rewound. It also required some modifications to make it compatible with the existing fleet of turbogenerators.
Improvements in design and rewind knowhow of ASEA GTP-type rotors
The rotor in question is of a unique design and one which Fortum eNext knows very well. These ASEA GTP-type rotors – later ABB – were originally manufactured in a workshop in Västerås, Sweden, where Fortum eNext today runs a dedicated workshop for generator maintenance services. Approximately 2000 ASEA/ABB GTP-type generators were manufactured there between 1920–1988; about 500 are still in operation and, as with Leaf River, crucial for customer processes.
“The technology of how these rotors are designed and how they should be rewound and high-speed balanced has been maintained at our workshop. We were thus even able to introduce improvements in both the design and the process of rewinding. This case is a good example of how a good relationship with the customer and the high quality of work always pays off in the service business. This is the fifth rotor that the customer has sendt literally from the other side of the world to be serviced at our workshop. To us, it is a sign that our knowhow is appreciated,” says Senior Product Manager Gabor Csaba from Fortum eNext.
After having accepted Fortum’s offer, the customer put the rotor, weighing as much as 9 tons, on a boat from New Orleans to Stockholm from where it was transported by truck for servicing at the Västerås workshop. After the rewind and high-speed balancing was completed, the rotor was packed and shipped back in time for the coming outage. With this additional rotor, the customer now has two spares; in a future major overhaul, it will be possible to swap both rotors at the same time and, if needed, send both old ones for rewinding.
Repairing promotes sustainability
A generator is a technically complex piece of machinery designed for long life. Therefore, it always makes sense to repair and modernise the existing equipment instead of buying and manufacturing new. As an OEM-independent service provider – and with more than 30 years of experience in generator services – Fortum eNext is uniquely positioned to support power producers with very specialised technical expertise and workshop skills. Our generator maintenance and diagnostics is based on approximately 100 identified failure modes to support the condition-based maintenance of generators. Fortum eNext is one of the very few service providers able to also offer stator rewinds for this type of generator.