Generator Inspection

Testing for In Situ Generator Inspection

Generators are crucial components in an industrial power plant and are designed to operate reliably for many years. One of the most expensive parts of a 3-phase generator is the stator, which is where the energy from the magnetic field is converted into electrical energy. The condition of the generator and its core deteriorates over time, increasing the likelihood of failures. Quantitative testing and periodic inspections of the generator core are necessary to avoid unplanned outages.

The common trend is to inspect the generator during a minor outage with the rotor in place. This has a big advantage as it is less labor intensive and is associated with lower cost compared to removing the rotor. Aside from saving time and money during an outage by inspecting with the rotor in place, the results allow for planning of a major outage (e.g. ordering components with a long lead time). Reduced disassembly requirements during the overhaul means less people on site, higher availability of crane and more lay-down space. Possible consequential damage due to rotor dismantling is avoided.
Regular testing increases reliable operation and prevents potentially costly downtime and repairs. Our experts can provide you with information and recommendations regarding:
  • Condition of the generator
  • Routine maintenance/overhaul
  • Long-term condition
If you have any other requirements, like ET of generator coolers, UT on rotor wedges (for built-out rotors), NDT on fan blades, or other, please contact
Robotic Air Gap Inspection (ARGIS)
The condition of the generator and its core deteriorates of time. Removing the rotor to inspect is costly and requires time, manpower and lay-down space. Therefore, air gap inspections with the rotor in place have become commonplace to assess the condition of the generator. With our ARGIS robot (only 15 mm thick), DEKRA is able to inspect a broad range of generators.
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Retaining Ring Inspection (KIRR)
Retaining rings may develop cracks over time due to torsional forces induced by instability of the power grid, start-stops, and stress corrosion cracking (especially with older X55 MnCr(N) 18K material). With the KIRR manipulator, suited for almost all generators, retaining rings can be tested with the rotor in place in just a few shifts.
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Bump Testing
Stator vibrations can loosen the end windings, causing them to vibrate. When natural frequencies of the end windings are close to twice the frequency of the power grid, resonance will lead to rapid wear of the windings. Bump testing will reveal the end windings’ natural frequencies.
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