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Last-chance inspection

Complex rotating equipment like wind turbines demand care and attention to detail throughout their lifetime.

End of warranty check...crucial
End of warranty check...crucial
Even so, they can be expected to suffer some faults or component failures during operation. 

As the warranty period nears its end, it is in the interests of the owner/operator to check the turbine fully, to avoid subsequent service or component replacement costs that would have fallen under the terms of the manufacturer warranty.

Historically, there have been disputes between the parties as to who shoulders the costs and responsibilities for bringing the turbine back to warranted condition.

Some disputes end up before the courts, where it must be determined whether the fault or failure existed during the warranty period.
The ISO/IEC 17020 international inspection standard was developed to accredit independent third-party inspection bodies.

These companies use an agreed inspection process and can provide evidence to help resolve warranty disputes.

A full end-of-warranty inspection comprises dozens of major component checks and even more secondary aspects of a properly functioning wind machine.

It is the final opportunity for the owner/operator to document whether a fault or condition has arisen during the warranty period and as such is the responsibility of the manufacturer..

All components of the wind turbine must be reviewed, including mechanical, electrical, hydraulic, electronic and composite components.

Service and fault logs must also be assessed. The diagram shows key inspection aspects, but the full list covers more than 100 items. 

Test equipment has improved, and a telescopic video can now inspect the internal condition of the gearbox components, for example. Rotor and stator inspections should include measurement of insulation and resistance, between phases and against the windings. 

Some aspects of an end-of-warranty check depend on the knowledge of the inspector. With experience, a review of operation and fault logs can offer key insight into the turbine’s condition.

Experience has also shown that spot-check vibration measurements of the main bearings, the gearbox bearings and stages, and the generator bearings can detect faults and imbalances, which can be critical in determining the turbine’s state. 

Blades and hub joints must be closely inspected, using a cherry picker, crane basket or rope access.

Evaluation at a distance will not detect the blade’s condition.   

Randy Tinkerman is responsible for strategic due diligence at Deutsche WindGuard. With contributions from Gerhard Gerdes, managing director, and inspection engineer Ingmar Sörensen

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