By Susan Kraemer

According to John Covington, Senior VP at South Carolina-based Integrated Power Services (IPS), the key to best practices to save money in the operations and maintenance of wind farms in the US is to handle routine maintenance. That routine, according to the US turbine generator repair firm should include a technician going up-tower once every six months to deal with the basics of lubrication, providing grease for the generator bearings, checking the brush holders and cleaning them - all the standard maintenance that a generator requires.

“Do not skimp out on preventative maintenance,” advises Covington. “Skimping in this area will cost multi times more in repairs.”

Start out right

Covington feels that the first thing an owner or O&M service supplier should do is to get a vibration baseline reading of the generator once it is initially started. “Then you can use that baseline to do condition-based monitoring.” 

He finds that what most of their clients want first is usually a pre-warranty expiration inspection, prior to warranty end. Post warranty they want a good - preferably local - aftermarket service provider for repairs and parts. 

Jesse Elliott, Senior Engineer for Broadwind Services; Midwest, a leading US O&M firm notes a similar reaction. 

“What many clients want first are end-of-warranty inspections,” he affirms. “Then, depending on the results of those inspections, they can prioritise what they want done first, which allows for managing periodic costs of those turbine assets. For example, clients may want oil and filter changes done or a high speed bearing changed out.”

Elliott finds that a common reason for downtime is drive train failure. Other causes include bearing and gear failure, such as breakages in the gear teeth, which are common. Other primary causes for failure is timing and improper gear mesh as a result of premature wear due to poor oil condition. 

“The timing starts to deteriorate,” he explains. "The timing or tooth profile going out of sync due to improper alignment creates a vicious circle, as the timing deteriorates because of the worn gearing. And once the timing starts to go off, that increases wear and tear on the gearing."

The firm aims for maximising accurate preventative maintenance on site and up-tower with the idea of reducing the work required by crane, such as gearbox change-out. One of the critical yet affordable services provided up-tower is the condition monitoring, which captures vibration information.

Repair or replace?

IPS is usually only called in by wind turbine and generator OEMs, site owners or O&M service providers if the turbine has failed or requires serious maintenance work. However, they also provide a vast array of preventative or rather diagnostic technologies, including MCE testing, infrared cameras and vibration analysis. 

Getting a field service crew up in a turbine could cost anywhere from $1,500 to $15,000, depending on the work needed, says Covington.

Therefore, servicing the turbine up-tower is a much less costly option than bringing a generator down, with speedier access and with no crane costs to bring parts down. With this in mind, IPS' field service division has developed a variety of tools and equipment to perform a variety of tasks, like shaft repair, up-tower, and they look for hot spots, the signs of stress, using thermography. 

Bringing a generator down to have it repaired can cost around $35,000. However, sometimes that is unavoidable. “If up-tower repair is not possible and the equipment must come down,” Covington adds, “then we have 17 US service centres that provide a local presence to most of the wind industry.” 

IPS offers upgraded components and retrofits to lengthen the expected life of a wind turbine, including engineered insulation systems for generator rewinds. If a generator fails and has to come down, they can swap it for an exchange wind generator, in order to both minimise downtime and crane cost. 

“Exchanges basically allow us to replace a failed generator with a working generator utilising the same crane,” he explains. "Using the same crane can mean saving as much as $20,000 on crane costs."

Get the best information

Steve Scott, Regional General Manager at Duke Energy Renewables and formerly the CEO of Outland Energy Services, which Duke Energy Renewables acquired in November 2012, believes the best advice he can offer for cutting O&M costs is to make sure that you have the best intel.

“The greatest impact can be achieved through an aggressive Condition-Based Monitoring programme,” he advises. “Making proactive decisions on how to mitigate downtime, based on the data and knowledge collected through that CBM. Any turbine that provides the owner with good data is a good thing, the more the better.”

“Sensors are applied in various locations throughout the turbine and wired to the CBM control system,” says Scott. “They can pick up info from the blade, main shaft, main bearings, gearbox, just the entire drive train; all the rotating equipment. Wherever there’s a bearing is really the focus.”

The typical turbine coming out of warranty and that an ISP services will be ten or more years old and with that in mind, the technology will not be as data-driven. The question here is then, just how good is the data from an older turbine?

“The older technology is less data-driven for sure, but there are systems out there that can be adapted to that technology,” Scott explains. “With the aftermarket CBM systems you can get the same intel off that system as a newer machine. You just have to be a little more creative and work a little harder.” 

Elliott also recommends good intelligence on internal conditions to keep downtime to a minimum. He encourages wind asset owners to have regular borescope inspections - along with frequent oil in the gearbox, of course.

“The borescope is an optic cable that you feed through the gearbox to take pictures of bearings and gears from the inside, so that you can see what’s going on,” he explains. “The ideal is to do a borescope inspection every six months, so we might be able to spot a problem before it becomes a failure.” 

“I have one suggestion when working with an independent service provider such as ourselves,” Elliott suggests. “Actually analyse, for example, a gearbox, and do a triage, if you will, on the entire fleet, and look at the most cost-competitive way of estimating future supply needs. For example, if there are a dozen gearboxes that are still running, but that may need work six months down the road; you look at making a bearing purchase that will cover a quantity of gearboxes, rather than just buy bearings for just one or two at a time.”

Spare parts anyone?

One of the biggest challenges for wind farm owners can be locating replacement parts for the older turbines that are coming out of warranty with the original OEM. 

“Parts access is an extreme challenge," Elliott admits. “Service providers or independent service providers like us, we try and work with OEMs and then also work with resellers, for example the bearing manufacturers and gear manufacturers who are distributors of OEM product.”

To deal with situations where an OEM no longer makes a part that is needed, IPS has an in-house CNC precision parts manufacturing capability that can build a variety of wind turbine parts.

“We have our own spare parts division that specialises in wind turbine spare parts,” says Covington. “We also develop relationships with the OEM’s to serve the market. Our goal is to remanufacture back to OEM specification whenever possible - lead time and cost permitting.”