Misalignment in wind turbine gearboxes can lead to costly repairs, with expenses exceeding $200,000. Regular alignment using laser tools like Prüftechnik’s RotAlign and OptAlign can prevent failures, reduce downtime, and maximize turbine efficiency.
- Gearbox misalignment, which is caused by environmental stresses and operational wear, causes vibration, wear, and energy loss.
- Laser alignment tools provide safe, precise, and efficient solutions for maintaining turbine reliability.
- Regular alignment checks ensure smoother operations and reduce costly downtime.
The world is increasingly reliant on clean energy harvested by wind turbines. As global leaders race to meet the growing demand for wind energy and continue adding infrastructure, one factor often gets overlooked in clean energy production: the importance of maintaining existing wind turbines.
Wind power is one of the most cost-effective ways to generate energy, with an average levelized cost of just $32 per megawatt hour (MWh) in 2022 for land-based projects. The ability of an individual wind turbine to reach its highest capacity factor and profitability depends in a large part on its maintenance. Wind turbines are expected to last 20 to 30 years after their installation, and during that time, the gearbox is the most costly component to maintain.
Wind turbines can not operate without the gearbox to convert the low rotational speed of the turbine into the much higher speeds required by the generator. While gearboxes do not fail as frequently as other components, repair costs can soar to over $200,000 when they do.
Besides replacing the gearbox itself, crane rental expenses and labor costs can push the price of gearbox repair higher. For offshore wind turbines, specialized help from technicians who sail to the repair site needs to be factored in as well. Add in the lost revenue caused by downtime during repairs, and the cost of wind power increases dramatically when wind turbine gearboxes are not maintained appropriately.
Misalignment: A $200,000 Preventable Failure
The root cause of most gearbox failures comes down to a single factor: misalignment.
In a wind turbine, the gearbox serves a critical role in converting the low rotational speed of turbine blades into the high rotational speed required by the generator to produce electricity. The gearbox acts as a speed multiplier through a series of gears.
The gearbox has to be aligned with the main shaft driven by the wind turbine rotor to ensure the smooth transfer of power and to minimize strain on the gearbox components. It also has to be aligned with the generator shaft. Misalignment can cause vibration, excessive wear, energy loss, higher maintenance costs, and even lead to costly gearbox replacement.
Many factors can eventually lead to misalignment. The very nature of wind turbine installations means they are subject to intense forces from nature which can ultimately shift parts out of alignment. Some causes of misalignment include:
- Environmental factors, such as extreme temperature fluctuations, uneven or excessive torque caused by fluctuating wind speeds, and lightning strikes.
- Operational stresses, like constant vibration from wind loads and rotor movement, which causes fatigue over time and wear and tear on components.
- Maintenance errors, such as not performing precision alignment after the initial installation, poorly secured bolts, incorrect assembly, and improper adjustments.
If misalignment is not caught and corrected it leads to problems like excess vibration, wear and tear on components like bearings and couplings, and energy loss due to friction and increased temperatures.
Over time, this will cascade into catastrophic failure, causing hundreds of thousands of dollars in repair costs. Because of their often remote location, massive component size, and the loss of energy production during downtime, turbine gearboxes come with exorbitant repair costs and financial losses when not maintained properly.
The Challenges of Gearbox Alignment
The design and size of wind turbines make using traditional alignment methods impossible. Because of their very large size and the tremendous amount of torque generated, the gearbox and components are underneath a protective cover, which keeps workers safe while the turbine is rotating. The cover can only be removed when the rotor is secured and the safety pin is in place, ensuring no torque can be transferred to the input shaft.
However, in order for alignment to occur, the cover must be removed from the components to allow access for the alignment fixtures, all while the turbine continues to be able to be rotated. So how can wind turbine gearboxes be safely and accurately aligned with modern tools?
Laser Alignment: The Only Way to Align Wind Turbine Gearboxes
Laser alignment is the only safe and precise way to align both coupling shafts in a wind turbine to the manufacturer’s specifications and keep workers safe. While the same safety challenges apply to laser alignment methods, the unique features of Prüftechnik’s laser alignment technology support alignment while also keeping workers out of harm’s way.
Here is how to use the RotAlign or OptAlign alignment devices for wind turbine gearbox alignment.
- First, normal safety measures are taken to ensure the safety of workers during the alignment process. The rotor is secured, the service brake is applied, and the safety pin is put into place.
- Next, workers remove the safety cover to expose the drive linkage. A laser and corresponding sensor are securely mounted onto the coupled shaft. While the cover is still open, the service brake and locking pin are released. On-site workers move as far away from the shaft as possible.
- With safety measures removed, the wind turns the blades of the turbine shaft beginning the alignment process. SWEEP measurement mode makes it possible to determine the quality of the alignment with a rotational angle as small as 60 degrees. However, a wind turbine may continue turning far beyond 60 degrees, even completing multiple rotations, before it can be stopped again – which Prüftechnik alignment tools are designed to account for. With SWEEP mode enabled, the higher rotational angle will allow even more precise measurements, and multiple turns pose no barrier to the alignment.
- RotAlign or OptAlign calculate the alignment results in just a few seconds. The single sensor with two detector surfaces can calculate the alignment from any position, no matter where they are when the turbine comes back to a standstill.
- Once the turbine is brought to a standstill, with the laser and sensor still mounted, the safety measures are put back into place – rotor brake on and rotor pin locked. After the braking devices are activated, workers can begin the process of realignment. Prüftechnik’s Live Move function allows the alignment results to be tracked in both axes in real-time until the alignment targets are met.
Supporting Wind Turbine Reliability, Now and In the Future
Wind energy has exploded over the past decade. In 2013, global production was at 635 terawatt hours (TWh) and grew to 2,325 just ten years later.
Growth is expected to continue as global reliance on renewable energy increases. Not only has the number of wind turbine installations increased, but the size of the turbines themselves has also gone up.
The size of wind turbines has a direct correlation to their ability to capture energy from the wind. The larger the turbine, the more power a single installation can generate. In 2013, the United States had no turbines with rotors over 115 meters in diameter. Ten years later, 98% of newly installed wind turbines had rotors greater than this, and the average rotor diameter was 133.8 meters. While these improvements allow turbines to produce more energy, they also subject the turbine components to even greater force, which ultimately impacts their alignment.
Misalignment in wind turbines is the root cause of up to 30% of downtime, but regular alignment can greatly reduce this number. Turbine manufacturer recommendations may vary, but at a minimum, turbine alignment should be checked upon commissioning, six months after the initial construction, and once a year thereafter.
Prüftechnik laser alignment tools like OptAlign and RotAlign allow safe, precise alignment for wind turbine gearboxes. Prüftechnik is the global market leader for laser optical alignment equipment, and its world-class alignment tools help teams avoid expensive repairs by ensuring smooth turbine operation and maximum efficiency.
