The overhaul included extensive work on both the stator and rotor. With the mechanical work finished, the focus shifted to ensuring that the turbine could run reliably once it was restarted. Even small misalignment between the turbine and generator could lead to increased bearing loads, vibration, and long‑term reliability problems.
Getting the turbine ready for restart
Large turbine‑generator sets operate under demanding conditions, and installation accuracy is essential. After the overhaul, the shafts had to be aligned precisely to ensure smooth operation when the machine returned to service. Any deviation at this stage could introduce mechanical stress into the drivetrain and increase the risk of vibration or premature component wear.
Aligning the turbine-generator set
The alignment was carried out on a 237 MW Mitsubishi steam turbine-generator set using the Easy‑Laser XT770 laser alignment system. Magnetic brackets with offset extensions were installed so the measuring units could be mounted securely on the shafts.
The shafts were rotated using a crane, while digital inclinometers ensured that each measurement was taken at the same angular positions during each rotation. Using the Multi point program, three complete measurement cycles were performed to confirm repeatability and ensure reliable alignment data.
Setting up the alignment equipment on a large diameter shaft is not a problem using the brackets that are included in the system.
Accounting for thermal growth
Measurements were carried out under cold alignment conditions. Because machines of this size expand as they reach operating temperature, thermal growth had to be taken into account. In the XT Alignment software, thermal growth compensation values were added based on data from the machine’s technical drawings. This ensured that the turbine and generator would be correctly aligned not only during measurement, but also under real operating conditions.
Accurate alignment within tolerance
After completing the measurements and adjustments, the turbine‑generator set was aligned within tolerance and the final report was reviewed together with the maintenance manager and the team. It had been a demanding job, but the successful result, achieved through close cooperation between PEAK and the customer, made the effort worthwhile.
Why precise turbine alignment matters
Steam turbines are high‑speed machines and precise installation and maintenance is essential. Accurate shaft alignment plays a key role in plant availability, machine lifetime, and safe operation. For power plants, careful alignment is therefore not just a maintenance task – it is a key factor in ensuring stable and reliable power generation.
