Eddy Buysse

Engineering Manager

Maintenance Partners

Zwijndrecht, Belgium

eddy.buysse@maintenancepartners.com

The complex generator and steam turbine project has just been completed in the north of Sweden. During the seven intensive weeks, Maintenance Partners carried out a major project for the customer, who has the biggest Kraftliner plant in Europe: Smurfit Kappa Kraftliner in Piteå. The project was divided in three phases: Disassembly on site, works executed in Zwijndrecht, Belgium and assembly on site.

Steam Turbine

The Stal Laval steam turbine was built in the 1970’s and was in need of a major overhaul after years of operation. On site in Sweden, the steam turbine was opened, disassembled and inspected by the 20-head field crew who worked around the clock in teams to finish the job in time. Subsequently, the rotor was balanced and repaired in the Zwijndrecht workshop.

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Generator during varnishing.

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Generator rotor balancing in the Zwijndrecht Workshop.

Turbine installation.

The team also installed a new guide plate, which had been locked for a long time. The new guide plate allows the turbine to run trouble-free for years.

In addition, the steam turbine had the original hydraulic/ mechanic control system installed. The outdated control system was replaced by a new state-of-the-art electronic system with electro-hydraulic converters. Finally, new protections for the over-speed, rotors and stators were installed.

Generator

The 27 megawatt generator was designed and manufactured during the same period as the steam turbine and also needed servicing. In Sweden, precise physical and electrical measurements were made on site and the windings were inspected carefully. The onsite measurements were necessary, because the original manual did not include a lot of detailed information. The measurements showed that the complete stators were badly aged and that the core plates and windings had to be replaced with new ones. The coilshop team designed and manufactured the new stators. In order to perform the required renewals, the generators had to be taken away from the plant to the Zwijndrecht workshop.

In the workshop, the generator stator and rotor were dismantled and thoroughly cleaned. The original core plates were removed from the stator and the newly engineered core plates were impregnated before installation in the existing stator to ensure optimal performance. Replacement coils were manufactured in the coilshop and modern insulation materials were applied to increase the generator’s efficiency. Besides this, the rotor and stator exciters were rewound by the coilshop team.

To ensure the quality, all components were tested electrically. The electrical tests included high voltage testing, surge testing and DLA and tgDelta measurements. Finally a partial discharge test was conducted to ensure the quality of the insulation. All components passed the tests successfully and the generator was ready to be installed again.

The tight schedule allowed just three weeks to perform the complete stator change, rotor overhaul and testing, but the workshop team worked 24/7 to ensure that the stator could return to the Swedish plant on time.

Finished steam turbine and generator.

Installation

After the turbine and generator had been overhauled, both were transported back to the paper mill in Sweden. The field crew reinstalled the overhauled steam turbine, control system and generator in just two weeks.

After testing, the turbine and generator were approved and the go-ahead was given to produce energy for years to come.