Credit: CNC Onsite

The teeth on yaw rings can wear down over time, and they’re necessary components for power production.

“This inspired us to develop a repair method as an alternative,” Søren Kellenberger, sales director of CNC Onsite. “We can now offer a repair service for both onshore and offshore at a fraction of the cost of replacing the entire yaw ring, and that makes it viable to keep perfectly good wind turbines operating for longer.”

The CNC Onsite method requires removing and reinserting machined teeth on yaw rings. Mounted at the top of the wind turbine tower, the toothed yaw ring is a gear that engages with motors mounted on the nacelle to align the rotor blades with the wind.

CNC Onsite estimates that turbines on some 5 to 10% of wind farms will experience damage to their yaw ring teeth during their service life. Typical causes include unpredictable wind events or uneven loads sustained over time.

“The process we apply when creating new yaw ring teeth for a wind turbine is similar in principle to a new dental crown that is first copied precisely then fitted by a dentist using precision tools,” Kellenberger said. “The aim is the same, and it should last for a long time.”

These repairs are conducted inside the turbine tower, so the work can be done in inclement weather.

“As long as it is safe to travel to and access the wind turbine, we can carry out the repairs. So there are far fewer days when we cannot work. This is also good for both work schedules and costings,” Kellenberger explained.

Replacing the yaw ring requires the entire nacelle to be detached using a crane. The system developed by CNC Onsite can usually carry out yaw ring repairs within a few days.

“We’re eliminating the need for manufacturing a new yaw ring and above all the huge logistical effort required to transport a yaw ring to the site, deploy cranes, which is particularly tricky offshore, and replace it,” Kellenberger said. “Such an operation requires a significant number of people and a lot of equipment with all the associated CO2 emissions. With our repair method,this is no longer required.”

The yaw ring repair service offered by CNC Onsite has already been used on a range of turbines in wind parks, both offshore and onshore, since it entered the market in 2019 following many months of endurance tests, proving that the replaced teeth are robust over time.

“The fact that whenever you take down the nacelle there is a potential risk of damage to it and especially to the blades which is another factor that cannot be ignored,” Kellenberger said.

News item from CNC Onsite

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Credit: Parker

The bladder replacement kits are engineered with rubber compounds that Parker formulated specifically for demanding wind turbine applications where long service life is critical to system performance. The proprietary compounds buna nitrile, hydrin, butyl, EPR, fluorocarbon, and Neoprene suit various fluids and temperatures.

Parker’s elastomer bladder materials are manufactured to withstand vibration and reduce gas permeation in extreme temperatures, avoiding pre-charge losses that can lead to poor performance and premature bladder failure when left unchecked.

“With industry-leading Greer and Olaer bladder products, Parker has over 70 years of expertise in formulating proven bladder compounds and making the finest quality bladder accumulators,” said Bob Rajabi, global business development manager, Parker Accumulator and Cooler Division. “Our bladder replacement kits are designed with sustained performance in mind, delivering lower lifecycle costs on expensive systems. Understanding the availability of spare parts is critical for wind farm owners and operators to keep their operations running smoothly, we stock thousands of specialized wind turbine supplies to meet fast lead times.”

Parker’s bladder replacement kits are available in capacities ranging from 2.5 to 15 gallons (10 to 57 liters) with several gas valve types and stem sizes. Parker spare parts are sold globally from authorized distributors and Parker Repair Centers. The new bladder replacement kits offered by Parker Accumulator and Cooler may also be used on corresponding non-Parker manufactured accumulators.

Additional Parker bladder replacement kit features include:

• Dual certified to ASME and PED
• An extended lifetime with increased fatigue resistance
• Operating temperature ranges from -40°F to 225°F (-40°C to 107°C)

News item from Parker Accumulator and Cooler

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The United States is a leader in wind energy — wind generates 7% of the electricity Americans use. But it’s still behind the Europe Union, which receives 12% of its electricity generation from wind turbines. The two markets also show differences in O&M, something that should not be ignored in the still growing American industry.

Blade maintenance is continuously being refined as a fine science, but one of the largest issues is the difficulty in controlling pitch. A sophisticated pitch control system with three high-speed proportional valves accounts for up to 23% of all downtime on wind turbines, more than any other component or subsystem. Pitch control valves independently change each blade’s angle facing the wind, sometimes as often as 10 or 20 times a second, based on incoming signals from a main controller on the wind turbine. These signals are a result of the wind conditions that the turbine is experiencing at a given time. Much like the rest of the turbine, the pitch control valve’s performance and lifetime are affected by the weather conditions around it.

Modern wind turbine energy systems were developed in an industrial scale in Europe, and pitch control subsystems were developed for those unique conditions. These valves need to be replaced three to five times over a wind turbine’s lifetime in Europe, which equates to a five- to 10-year expected lifespan. When the same highly developed European technologies were introduced into the United States around 2007, pitch control valve life was noted to be remarkably shorter than was common in Europe. Valve failures were much more frequent in North America.

Yuken Pitch Control Valve

European manufacturers dominated in the United States until General Electric jumped into the fray with its own technologies, including a different way to address pitch control using electric — instead of hydraulic — devices. No matter which pitch control technology is used, America’s high winds keep pushing products into higher performance and longer life.

It became abundantly clear to wind project owners that normal American wind conditions were very destructive to pitch control valves. When analyzing wind conditions, tornadoes are at the apex, with 100- to 150-mph winds concentrated over small areas. Tornadoes are common in the United States but relatively uncommon elsewhere. Winds in these storm cells can gust at 90 mph over long periods of time and large distances, before reaching tornadic form and intensity. High, variable wind speeds create intense vibrations especially in the blades that feather by design at 55 mph.

Feathered blades in 90-mph winds vibrate violently, resulting in acceleration forces as high as 20 G’s. Valves in European windfarms seldom experience such extreme conditions that are so common throughout the United States. Extreme vibration destroys the delicate balance that exists in any normal proportional valves. The manifold and valves are not in a sealed environment; therefore, they sense the effects of hail, rain, sleet and snow. A few valve manufacturers have addressed these issues — one U.S. company doubled up with a pilot valve, adding power and structural strength. A major Asian manufacturer addressed the same problems by ruggedizing the exterior and strengthening the interior of the valve. Both valves have been successful in addressing the shortened valve life due to vibration. The Asian manufacturer has successfully replaced nearly 4,000 failed valves installed in American wind farms, beginning in 2014.

Yuken Pitch Control Valve Installation

The cost of pitch control valve failures is very high. Nearly one-quarter of all downtime in the industry is attributable to this form of failure. It is expensive for a wind turbine to go off-line for days or weeks. Sending a crew up the nacelle is also expensive. The cost of the valve itself is nearly irrelevant in the overall downtime cost. If this one aspect of O&M represents nearly 25% of all downtime experienced by the industry, its reduction is the highest priority for most owners and O&M crews.

Maintenance costs have to be reduced. Components of the turbine, such as the pitch control valve, need to be reliable and easily installed. “Plug and play” components will provide simple operation and user-friendliness. “Plug and play” for pitch control valves means the valve can be mechanically mounted and bolted down in the same location as the valve it replaces, as well accepting the same electrical plug with the same pin pattern for power and input signals. The replacing valve must be equal in form, fit and function as the originally installed valve.  In addition:

Response Characteristics: A closed loop structure provided by incorporating a differential transformer for spool position detection enables feedback control, achieving high response equivalent to a simple servo valve.

High Accuracy: The valve has a hysteresis of 0.1% or less, achieving high accuracy equivalent to that of servo valves. The 2% overlap type with linear no-load flow characteristics suitable for position and pressure control in machinery equipment.

Safety and Reliability: The valves support a fail-safe function to ensure safe operation in the event of electrical failure. Electrical failures can include power failure, power cable disconnection, etc. Also, with a proportional valve of this magnitude, feedback of the valve’s performance can be monitored by the wind turbine owner or technicians. Steps have also been taken to reinforce the interior and exterior of the pitch control valve in order to provide an extended lifetime for the valve. By doing so, the valve can keep up with severe wind conditions that U.S. wind turbine owners experience.

Overall, with the current short life span of wind turbines, replacement components within them must be constructed to combat the O&M costs placed upon owners. These components, such as the pitch control valve, must also be designed to withstand the harsh weather conditions that come with residing in the United States. The objective for the ruggedized pitch valve is to diminish failure rates and add to the lifetime and reduced O&M costs of the wind turbines. Windfarm owners should look to invest in pitch control valves of this caliber in order to realize these benefits.

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