Getting A Grip On Grinding Gearboxes: Why Such Events Need Not Be Showstoppers

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Getting A Grip On Grinding Gearboxes: Why Such Events Need Not Be Showstoppers As the central component of the drive system, the gearbox has always been a critical interface and constitutes 13% of the overall value of the typical onshore wind turbine.

Nonetheless, the current financial climate has led several major gearbox manufacturers to reconsider the manufacturing process from first principles – from forging to final inspection, according to a report from renewable energy underwriter GCube Insurance.

According to GCube, the trend has contributed to market pressures that have seen some companies face insolvency, which, in turn, has presented a major issue for operators seeking repairs and component replacements following the end of the warranty period.

Using GCube's claims database to categorize all known root causes of gearbox failure, the report analyzes manufacturing defect and cracking of bearing coatings on abnormal blade loads and ineffective lubrication.

With approximately 175,000 geared turbines in operation in 86 countries worldwide, there are around 1,200 incidents of gearbox failure reported each year – one failure per 145 turbines – commonly ranging between $200,000 and $300,000 in insurance claims and, in some unique cases, exceeding $500,000.

Therefore, GCube notes, it is crucial that asset managers take proactive, preventive steps to ensure that this financial and operational risk is managed appropriately.

Key component inspection

Turbine suppliers normally have set inspection dates for the projected lifespan of the gearboxes. Many set three-, five- or ten-year scheduled maintenance visits, but this often exceeds the lifespan of the gearbox itself.

Most gearboxes last around only five to seven years, and GCube has typically received 92% of all gearbox failure notifications after five years.

More frequent inspections earlier on in the lifespan of the gearbox are vital for designing measures to extend the longevity of the gearbox and its reliable performance. Preventive maintenance can be carried out every six months, normally within one day. This includes oil sampling, checking the oil filter for leaks and identifying any unusual noises from the gearbox.

Further internal visual inspection can be undertaken using an endoprobe or fiberscope, for example. It can be beneficial to change the oil after only one month, as some contamination occurs just after initial operation. Initial gearbox operation inevitably grinds particles from the surfaces in gliding contact. These particles may be almost immediately harmful.

‘While GCube recognizes that gearbox incidents are, in some ways, unavoidable and will continue to occur, we must empower our insureds to use our data to raise greater awareness among their asset managers and project teams about the wider macro trends affecting their peer group,’ says Jatin Sharma, GCube's head of business development and co-author of the report.

‘Such trends identify risk, as well as opportunities, which complement the experiences of asset managers and their operating fleet, particularly in newer, more remote geographic markets, such as Chile and South Africa, or as aging assets enter the post-warranty phase of their lifecycle in Europe, the U.S. and Australia.’

To request a copy of the report, click here.

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