By Bob Moser

With 1,285 operational turbines (accounting for nearly 2GW), E.ON Climate & Renewables North America knows a thing or two about wind turbine O&M. “Maintenance on this equipment can be overwhelming. If there's a problem that happened during the warranty period, you have to find it before the end of warranty, so you're not strapped with the cost of repair for parts that failed prematurely,” says Judah Moseson, manager of operations support services for the E.ON Climate & Renewables North America.

But the cost of third-party warranty exit inspections can be prohibitive, begging the question: is it worth it? The answer is "yes".

Many operators say the cost of a third-party inspection – upwards of US$2,000 per turbine for a comprehensive exam – is worth the windfall in savings they may reap from squeezing any final costly repairs into their warranty agreement.

With gearbox or blade failure potentially costing 25% to 50% of a turbine's original price, owners that try an end-of-warranty exam by themselves may lack the objective, contextual eye that a third-party specialist brings to the machinery.

Following an end-of-warranty inspection, owners then have to face the warranty provider. Having a third-party available to present damage findings often eliminates any contention the warranty provider can come up with against repair.

“We're unbiased, we don't have skin in the game after this inspection,” says Merritt N. Brown, vice president of Rev1 Renewables, a 10-year-old utility engineering firm that branched into wind energy inspections in 2009. “If that owner does decide to go with a third party afterwards (for future maintenance), they'll have an objective view of those turbines.”

Leveraging post-warranty O&M contracts

End-of-warranty inspections can be a key negotiating tool as well for operators juggling multiple offers for future maintenance. If an operator isn't sure if they want to renew a warranty with their original equipment manufacturer or sign with a competitor, getting inspected by an independent can serve as a bargaining chip.

Inspections should focus first on parts of the turbine that would be the most costly to repair. A blade expert should inspect blades visually, with the aid of a telescopic or high-powered camera. Infrared analysis is a potential add-on, helping inspectors find hot spots on control panels or spliced areas in tower cables, and to analyze transformers.

A boroscope should be used for an internal inspection of the gearbox. This is usually limited to looking above the oil line, but draining the box of oil to look throughout would be ideal (yet costly). Keep eyes peeled for any sign of a leak, Moseson says, like with hydraulic fluid or oil lubricant. Loose electrical connections and suspect wiring can and should be included in warranty repairs.

While blades and gearboxes are the initial focus, inspectors should go down the tower to examine any aspect of the turbine tower. Inspectors should also stop and listen to the machine, in an effort to catch any abnormal noise when the blade pitches or unit yaws.

“These noises could lead to damage that you wouldn't see easily,” Moseson said. “So you can report a bad noise, too.”

Good track record?

The main motivation for end-of-warranty inspections is for operators to see if common issues are found on multiple turbines. “If I climb a turbine and its clean, then all the turbines are probably like that, and have been cared for uniformly,” Brown said. “But if one isn't clean inside, those kinds of small details will paint a broader picture of inadequate care.”

Look for inspection companies that offer experience with the specific make and model that you own. Operators with experience in end-of-warranty inspections warn that some inspectors simply grow out of touch with certain turbine manufacturers.

Your third-party inspector should also look through a turbine's previous service reports from the warranty period, to see if service was completed on time and the unit was examined uniformly every time. Those reports may also clue inspectors to deeper integrity issues with the turbine, like if a certain component had to be replaced frequently during the first few years of operation.

With inspection results in hand, owners and operators can judge whether they got the proper value out of the warranty service they'd been paying for. Across the board, service from an OEM is usually more expensive than from a third-party maintenance company.

“The OEM's willingness to correct punchlist items from a third-party inspection is a good indicator of whether they're taking ownership of their performance during the warranty,” Brown said. “They'll do this if they're smart, because they want to renegotiate your warranty. But the best way to be in good position to renegotiate is to do good work during the warranty period.”

Inspection results give operators a baseline for wear on the unit heading into post-warranty use, and help plan future maintenance accordingly. “Even if something isn't broken or worn to a point that it warrants a warranty claim, you still gain better understanding of your machine,” Moseson said. “You understand better where items are in their life cycle.”

To respond to this article, please write to: Bob Moser

Or write to the editor: Rikki Stancich