Wind turbine inspections play a vital role in enhancing operational safety, optimizing performance, and maximizing the longevity of wind energy equipment.
By identifying and addressing potential blade defects, such as cracks, erosion, or lightning strikes, inspections ensure the safe and reliable operation of turbines. Regular inspections also contribute to efficient performance by detecting issues that can impact energy production, such as blade damage or misalignments.
Early detection of component problems, including gearbox or bearing issues, through inspections allows for timely maintenance, preventing major failures and costly repairs. Moreover, wind turbine inspections extend the operational lifespan of the equipment, ensuring a higher return on investment for wind energy projects.
Compliance with industry regulations and standards is also ensured through inspections, maintaining the credibility and reputation of wind energy initiatives. By implementing comprehensive inspection programs, the wind industry can enhance safety, optimize performance, and ensure the long-term success of renewable energy projects.
Inspection stages for wind turbine
Wind turbine inspections are not solely reserved for monitoring the operation of a turbine. The following lifecycle stages also benefit from continued monitoring:
- During and Post Manufacturing
- Transporting The Component to The Work Side
- Building The Turbine in The Field
- Inspect For Warranty Claims
- Operational Performance of The Turbine
- Preventative Maintenance and Damage Assessment
Critical components of a wind turbine
Wind turbines rely on essential components like:
- blades,
- nacelle,
- generator,
- tower,
- main bearing,
- and gearboxes.
Those components collectively ensure their optimal operation and energy production.
Inspection frequency
Wind turbines undergo routine visual inspections on a monthly, quarterly, or semi-annual basis.
Critical components necessitate more comprehensive assessments at specific intervals.
Adhering to regulatory mandates is imperative, and condition monitoring systems facilitate timely inspections.
Traditional vs modern inspection approaches
Traditional rope access methods for inspections are costly, time-intensive, and potentially hazardous.
Modern drone-based inspections offer efficiency, cost-effectiveness, real-time data, and the ability to scrutinize interior turbine components.
Rope access method
Rope access technicians perform the traditional inspection of wind turbines through Ultrasonic Testing, Thermography, X-Rays etc. These highly trained individuals utilize ropes and tethering systems to scale wind turbines for visual inspections, maintenance, and repair.
Turbines are turned off for manual inspections, and the blades are stopped in the six o'clock position. Once the team ascends the tower, they look for damage and knock on the blades to determine the condition of the materials.
Drawbacks of wind turbine rope inspection are as follows:
- Requires highly specialized inspectors to work on higher altitudes.
- Highly expensive and involves lots of documentation approvals.
- Turbines are shut off for hours resulting in loss of income and energy.
- Operating at high altitudes is dangerous and time consuming.
- Knocking on blades is not a sound method of determining the structure's strength.
- Wind noise and weather conditions make inspections difficult.
- Damaged wind turbine equipment puts workers in danger.
Modern inspection method using drones
The utilization of drones for wind turbine inspections offers a secure, efficient, affordable, and precise means of gathering data.
- While rope-access and other conventional approaches can require 3 to 6 hours to inspect a turbine, a drone can accomplish the task in under 1 hour.
- By offering a comprehensive perspective of the turbine's condition and detecting potential concerns that may go unnoticed during visual inspections, thermal drones can enhance wind turbine inspections.
Utilizing drones for visual inspections aids in identifying surface defects and evaluating external wind turbine components, enabling timely corrective maintenance.
Advantages of drones for wind turbine inspection are listed below:
- High efficiency with improved data collection times.
- High-resolution images that identify defects the human eye can't detect.
- Drones are used at both onshore and offshore wind farms.
- The operational expense of drones is significantly lower than traditional methods.
- Workers are not in danger at high altitudes and in cramped working environments.
- Real-time data is viewed on a ground control station.
- A wind turbine inspection drone is capable of inspecting the interior of blades.
Visual inspection using drones
A surface inspection uses visual techniques such as cameras, drones, or the human eye to identify any issues. The following flaws are detected visually:
- Surface cracks
- Leading-edge erosion
- Lightning strikes
- Bird strikes
- Delamination
- Leading or trailing edge splits
The benefit of regular wind turbine inspections of the surface is performing corrective maintenance. Catching defects early on allows for repairs that prolong a component's life without reducing energy production.
Visual Inspection can also be supportive to:
- Inspect the external components of the wind turbine, such as the tower, blades, nacelle, and foundation, for any signs of damage, corrosion, wear, or other visible issues.
- Check for loose or missing bolts, fasteners, or covers.
- Look for oil leaks or other fluid leaks from the gearbox, hydraulic systems, or other components.
- Inspect electrical connections, cables, and wiring for any signs of damage or wear.
Thermal imaging for inspection of wind turbine
Thermography is instrumental in evaluating rotor blade conditions and identifying potential issues, contributing to prolonged functionality and performance.
Thermography operates on the fundamental principle of observing the thermal behaviour of an object that is not in thermal equilibrium with its surroundings. This thermal disequilibrium triggers heat transfer processes within the object following energy input. Various factors, including geometric attributes like thickness and shape, as well as material properties such as density, specific heat capacity, and thermal conductivity, influence these transfer processes.
In a wind turbine, rotor blades play a crucial role in converting wind energy into electrical power. As these composite components endure significant stress during manufacturing and operation, maintaining their stability is vital.
By utilizing infrared thermography, wind turbine manufacturers and operators can thoroughly assess the condition of the rotor blades, ensuring optimal long-term functionality and performance.
Shearography on wind turbine
Shearography, a non-destructive testing technique, excels at detecting defects in turbine blades, offering heightened sensitivity and real-time inspection capabilities.
It is a laser-based interferometric method that utilizes the principles of holography to analyze the surface deformation of an object under stress. In shearography, a laser beam is directed onto the surface of the turbine blade being inspected.
The laser light is split into two beams, a reference beam, and an object beam. The object beam is directed onto the surface of the blade, and the reference beam is directed onto a reference surface. Both beams are then recombined, creating an interference pattern.
When stress is applied to the turbine blade, either through thermal loading or mechanical loading, the surface of the blade deforms slightly. This deformation alters the interference pattern produced by the recombined beams. By analyzing the changes in the interference pattern, shearography can detect and identify defects or anomalies on the surface of the blade.
By using shearography, inspectors can identify various types of defects in turbine blades, such as
- Delaminations,
- Disbonds,
- Cracks,
- and other structural abnormalities
Advantages of shearography are:
- High Sensitivity: Shearography can detect very small deformations on the surface of the blade, allowing for the detection of minor defects that may not be visible to the naked eye.
- Non-Contact Method: Shearography is a non-contact technique, meaning it does not require physical contact with the blade surface. This eliminates the risk of damage or contamination to the blade during inspection.
- Real-time Inspection: Shearography provides real-time feedback and imaging, allowing inspectors to immediately observe and analyze the results during the inspection process.
- Full-Field Inspection: Shearography provides a wide-field view of the blade surface, enabling the detection of defects across the entire surface area, including curved or complex geometries.
Phased Array Ultrasonic Testing (PAUT) for turbine blade inspection
PAUT stands for Phased Array Ultrasonic Testing. It is a non-destructive testing (NDT) technique used to inspect materials and structures for defects, flaws, or abnormalities. PAUT utilizes ultrasonic waves to assess the integrity and quality of the inspected object
PAUT can be used to inspect the internal structure of wind turbine blades for:
- Delaminations,
- Disbonding,
- Voids or foreign inclusions.
- It allows for accurate detection and characterization of flaws within the composite material used in blade construction.
This method is applied for:
- Turbine foundation bolt inspection - PAUT can be employed to inspect the bolted connections within the wind turbine tower. It helps in identifying potential issues such as loose or damaged bolts, corrosion, or fatigue cracks, which can affect the structural integrity of the tower.
- Turbine nacelle components inspection - PAUT can be utilized to inspect critical components within the nacelle, such as gearboxes, bearings, and shafts. It helps in identifying defects or anomalies that may impact the performance or reliability of these components, allowing for timely maintenance or replacement.
- Turbine structure inspection - PAUT can assist in conducting general structural inspections of wind turbine components, including assessing the condition of structural elements like beams, brackets, or support structures. It helps in identifying defects or degradation that might compromise the overall structural integrity.
Other NDT techniques for flaw detection
Diverse non-destructive testing methods, including Dye Penetrant Testing, Magnetic Particle Inspection, and Radiography Testing, are employed to identify surface or internal defects in wind turbine components.
Industry codes and standards
Several industry codes and standards, such as IEC 61400-12, IEC 61400-23, ISO 18436-2, and ISO 10816, govern wind turbine inspections, guaranteeing safety, reliability, and performance. Complying with these standards is essential, alongside adherence to manufacturer guidelines.
Here are some commonly referenced codes and standards for wind turbine inspection:
- IEC 61400-12: This standard, published by the International Electrotechnical Commission (IEC), provides guidelines for the inspection and measurement of wind turbine power performance. It covers procedures for measuring power performance, wind conditions, and associated uncertainties.
- IEC 61400-23: This standard focuses on the electrical systems of wind turbines and provides guidelines for the inspection, maintenance, repair, and testing of electrical equipment. It covers areas such as protection systems, control systems, and grid connection.
- ISO 18436-2: This international standard outlines the requirements for the qualification and certification of personnel involved in vibration condition monitoring and diagnostics. It applies to individuals performing vibration analysis and diagnostics during wind turbine inspections.
- ISO 10816: This series of standards defines procedures and criteria for the measurement and evaluation of mechanical vibrations. While not specific to wind turbines, it can be applied during inspections to assess the condition of rotating machinery components, including bearings and gearboxes.
- ISO 16079: Condition Monitoring and diagnostic of Wind Turbines.
- Manufacturer's Guidelines: In addition to the industry standards mentioned above, it's important to refer to the specific guidelines provided by wind turbine manufacturers. These guidelines outline inspection protocols, maintenance requirements, and safety considerations specific to their equipment.
It's worth noting that the applicable codes and standards may vary depending on the country, region, or specific project requirements. It's essential to consult the relevant local regulations and industry best practices when conducting wind turbine inspections to ensure compliance and safety.
Integrity assessment of turbine civil structure
Assessing the civil structure integrity of wind turbines is pivotal to ensure safety, serviceability, and load-bearing capacity.
Wind turbine foundation and substructure inspection methodologies encompass:
- Design review of wind turbine foundation & substructure - Comprehensive assessments entail collecting design documents, specifications, maintenance history, and project dossiers.
- On-site visual inspection of sub structure and foundations - ACI 201.1R and ISO 13822 for concrete and steel structures are deployed to detect cracks, defects, and potential vulnerabilities.
- Topographic and settlement survey
- Health assessment of sub structure & foundations by non-destructive and destructive techniques - Methods like Ferro Scanner, Schmidt Hammer, Ultrasonic Pulse Velocity, Magnetic Particle Inspection, and Tensile tests facilitate assessing the integrity of reinforced concrete and steel structures in wind turbines.
- Repair recommendations/ restrengthening / retrofitting
Conclusion
Wind turbine inspections are critical for ensuring safety, operational efficiency, and the longevity of equipment. They play a crucial role in identifying defects and facilitating timely maintenance, thereby mitigating the risk of major failures and minimizing downtime.
Adhering to industry standards and regulations is essential to maintain the credibility of wind energy projects.
These inspections take place at different stages, including manufacturing, construction, and operation, and involve the use of non-destructive testing (NDT) techniques. Embracing modern drone-based inspections offers enhanced safety and efficiency.
Furthermore, the integrity assessment of civil structures involves comprehensive visual inspections and essential chemical and mechanical tests for steel structures.
Regular inspections are strongly recommended to ensure sustained energy production and contribute to a greener future. By prioritizing proactive inspections and adhering to best practices, the wind energy industry can continue to deliver reliable and environmentally friendly power generation.
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