Maintaining the wind turbine revolution

The fastest-growing segment of the power generation industry is wind, which is on track to expand by over 45 percent in the United States this year, says the American Wind Energy Association. But equipment reliability remains a stumbling block to growth, as operators struggle with ensuring that critical components - such as gearboxes and bearings - remain properly lubricated and maintained.

Blade tips on modern turbines can reach as high as a 40-story building, and their columns may be anchored high on a mountaintop or offshore in the ocean. Even routine maintenance takes extra effort - and may simply not be happening, a recent report indicates.

In an informal survey of 75 wind farm operators in the United States conducted by Frontier Pro Services, many respondents indicated they had fallen behind on scheduled preventive maintenance such as oil changes and gearbox lubrication because of a shortage of qualified technicians. According to Frontier, the survey found many wind farm operations and maintenance teams are so resource-constrained that they can barely keep up with unscheduled breakdown repairs to wind turbines.

Others in the field agree. "The availability of skilled technicians is a major problem," Varelube Systems president Andrew Carney told Lube Report. Costa Mesa, Calif.-based Varelube Systems supplies lubrication and hydraulic systems and other equipment to wind farm operators in California, Oklahoma, Oregon, Texas and Washington. "The second side of that is, they don't want third-party companies to do the work for them. It's a strange situation in that you've got people who've got the capability and willingness to do this kind of job, but you've got the other guys who say ‘no we want to do it ourselves, we want to control it.'"

If oil is not properly monitored and replaced as needed, according to Frontier, bearing and gear wear will lead to more serious and costly damage to the drive train. As an example, the company said that when a $1,500 bearing fails, it can lead to production and revenue losses, including an unscheduled replacement of a $100,000 gearbox and an unscheduled crane cost of up to $70,000 to access the failed components.

"Damage caused by worn out or compromised gear oil can be irreparable," said Frontier Pro Services lead technical advisor Jack Wallace, who has been servicing wind turbines for more than 20 years. "You can really see that it makes no sense to put off needed oil changes." Frontier claims fluid analysis can save the typical wind farm operator hundreds of thousands of dollars in repair work.

Varelube's Carney said he represents two companies that manufacture diagnostics equipment for monitoring oil in wind turbines, but so far has found the wind farm market unreceptive to the concept, citing the cost per unit to add monitoring technology. He disagrees, saying the cost would likely pay for itself after the first two or three gearbox exchanges.

"I'm fascinated someone can go buy a $2 million piece of equipment and absolutely not be interested in understanding what the quality of the oil is in the most expensive item on the machine - the gearbox," Carney said. "They're willing to pay $500,000 to go and replace the gearbox, hire a crane and put it in. But they haven't shown an interest in oil monitoring technology."

According to Carney, it's difficult to get empirical data concerning wind turbine maintenance due to reluctance to share information.

"If you go to a meeting with all the operators, none of them want to admit they had any failures in the first place, and secondly they won't admit what the failures were," he said. "The gearbox manufacturers won't tell you how many gearboxes have failed, and the original equipment manufacturers won't share how many gearboxes have failed or how much money they've put aside. This is one of those nasty little secrets nobody wants to talk about."

Triple R America Co. Ltd. in Toronto, Canada, takes a different tack, offering a continuous oil purification system with a bypass filter designed to help eliminate unexpected failures in wind turbine gear boxes by maintaining oil at five ISO grades cleaner than new fluids.

"We have been working with General Electric the last three years on developing some bypass oil filters for wind turbine gearboxes," Triple R America managing partner David Murray told Lube Report yesterday. "And we have just been given a worldwide vendor number for that product."

Murray said the company's oil purification system, which has no moving parts, aims to protect a wind turbine's gear box and extend oil life without requiring an additional pump or motor. Water and sludge are absorbed by a special cellulose material.

Oil is the lifeblood of the wind turbine gearbox, he said. "If there isn't good lubrication, if there isn't good quality oil, you get all sorts of problems," Murray stated. "Depending on the location, there could be a very high progression of moisture. Moisture and oil are not very good friends, so the filtration is addressing this."

Among the wind farm operators surveyed by Frontier, gearbox failures accounted for the largest amount of downtime, maintenance and loss of power production. Such failures can add up to 15 to 20 percent of the price of the turbine itself, according to Frontier.

"Most gearbox failures are preventable," said Frontier's Jack Wallace. "Most gearboxes fail as a direct result of improper lubrication and lack of routine maintenance. With so many turbines behind on inspections and regular service, there is real cause for concern here."

Richmond, Va.-based Afton Chemical is a marketer of industrial gear oil additives, including for wind turbine applications. Phil Rohrer, Afton's North American marketing manager for general industrial additives, said gear and bearing fatigue are issues in wind turbine gearbox life.

Two characteristics are especially important for additives used in a wind turbine environment, Rohrer told Lube Report: corrosion protection and micro-pitting protection. "From an operator standpoint, long fluid life is important because of the issues involved in servicing each of these individual wind turbines. So, synthetic gear oils are very popular because of their long fluid life."

Rohrer cited an offshore wind farm with a severe marine environment as an example where corrosion resistance in wind turbines is especially important. "You've got a saltwater environment in the atmosphere," he said. "That's another reason fluid life is important - imagine if there's a few hundred [turbines] around the bay and you have to get to each one of them, and then get up to the top of the turbine."

Banning, Calif.-based Frontier provides operations, maintenance and asset management services for wind farm owners and operators. The company conducted its survey through a combination of informal phone interviews and in-person meetings with operations and maintenance technicians, wind farm operators, and wind farm owners during the first six months of 2008.