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OILS & LUBRICATION


FEATURE SPONSOR


WIND TURBINE MAIN BEARINGS


A CHANGE IN THINKING PLEASE


Wind turbine main bearings are a critical part of the turbine’s drivetrain. Main bearing health and longevity is key to production and impacts on the condition of other major drivetrain components like the gearbox. It would therefore seem logical that main bearing design should facilitate routine maintenance up-tower to optimise their operational condition. Main bearing grease flushing (MBGF) is available for certain wind turbines, however it is not universal and MBGF is used by many as an operation of last resort, or is not considered at all. Detecting main bearing failures with condition monitoring in the early stages of the failure process is relatively straightforward. As main bearing failure can be a lengthy process, many will monitor the situation, however corrective or preventative action is rarely undertaken. Current thinking seems to be: “There is a failure. Track the failure. Exchange when condition is so bad catastrophic failure and consequential damage is imminent.” Many think there is no real choice and consequential damage in areas like the gearbox planetary stage is not considered at all.


ONSHORE & OFFSHORE WIND TURBINES


When dealing with onshore turbines, crane availability is good and weather windows are frequent. Owners have plenty of time to organise parts and labour. When considering offshore turbines, things become more involved. Availability and cost of suitable jack-up vessels required for major component exchange are at a premium and weather windows fewer. The financial implications of de-rating turbines for extended periods, or shutting down completely to prevent catastrophic failure and consequential damage, are huge. Where MBGF is available it can clearly be shown that main bearing life extension occurs. Also, the earlier in the failure process that flushing is performed, the


Romax Fleet Monitor Vibration Monitoring showing main bearing failure early detection and flushing to prolong bearing life until convenient repair scheduling for a reduced cost of failure


longer the life extension is seen to be. It is almost universally true, however, that MBGF is regarded as an operation of last resort used to nurse bearings through to the next available weather window or the next round of Opex budget allocation. This is strange when compared to how manufacture, up-tower serviceability and O&M strategies of major components have improved over recent years. New turbines come fitted with CMS for the drivetrain. Off-line filtration, particle counters and quality sensors come as


standard and oil is changed as a matter of course when necessary. Gearbox up-tower serviceability, service tooling and service procedures are considered at the design stage. Sump and splash lubrication has been replaced by forced and adaptive lubrication. Keeping components in the nacelle by extending their useful life is one of the best ways to reduce Opex and lower the cost of energy. So what’s happening with the main bearings?


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www.windenergynetwork.co.uk


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