Allianz Global Corporate & Specialty. Safety. Wind turbines. Cause investigation and consulting services. Allianz Center for Technology

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1 Allianz Global Corporate & Specialty Safety Wind turbines. Cause investigation and consulting services. Allianz Center for Technology

2 Cause investigation. An overview of our services. Frequently investigated wind turbine components. Rotor blades Rotor bearings Transmission bearings Gears Generator bearings Electrical components Cause investigation. Manufacturing defects Design loads Operational behavior Design and engineering Inadequate monitoring Labor investigation. Computational analysis. Stress analysis Gear load-bearing capacity Control of gear corrections Bearing life Thermal behavior Serviceability certification Finite-element analysis (FEA) Consulting services for manufacturers and operators. Load and vibration measurement Design and engineering Production consulting Fire engineering Condition monitoring Operating and safety systems Fractography Chemical analysis Oil analysis Light and scanning electron microscopy Stress analysis Non-destructive testing Load and vibration measurement. Torque and bending moments Component displacement and strain Shaft, bearing and nacelle vibration Noise Pressure Temperature

3 Broken rotor blade. Cracked rotor shaft caused by bearing failure after approx. 50,000 hours of operation. Spalling caused by the rolling elements and raceway fatigue after 30,000 hours of operation. Wind turbine damage. The Allianz Center for Technology (AZT) has been investigating wind turbine damage and incidents for insurance companies, manufacturers and operators. Although most of the components of wind turbines are used for industrial applications and power plants, wind turbines operate under dierent conditions, and this results in dierent problems. Wind turbine damage. The most significant dierence between gas and steam turbines on the one hand and wind turbines on the other hand is that the force of the wind is so irregular. As a result, the drive train of a wind turbine is subject to much greater dynamic loads. Virtually all components of a wind turbine are subject to damage, including everything from the rotor blades to the generator, transformer, nacelle, tower and foundation. Rotor blades. Fiberglass rotor blades represent the most vulnerable components of a wind turbine. Lightning or contact with the tower can result in extremely serious damage, but design errors and manufacturing defects can also cause problems during normal operation. For example, blades can develop cracks at the edges, near the hub or at the tips. In addition, bolts also break if they can t withstand the load. Rotor bearings. Spalling on the raceways of rotor shaft bearings can result in cracked rings, and in some cases revolution of the inner rings around the shaft causes cracks in the shaft that can result in a total loss of the turbine. Transmission bearings. The raceways of the roller bearings (usually self-aligning roller bearings) of the low-speed shaft can develop spalling over the entire circumference of the raceway, and excessively high temperatures can damage the bearings of the high-speed shaft. Raceway damage can negatively aect the transmission of forces to gears. Gears. In the course of our investigations, we frequently encounter scuing along the line of action as well as unsatisfactory tooth contact patterns. Highly loaded conditions result in chipping or micropitting. Generator bearings. Generator bearing slippage and wear can ultimately cause inner rings to rotate around the shaft to the point that rotor makes metalto-metal contact. Electrical components. Defects in the electrical system can also result in the outage of a wind turbine. In the course of our investigations, we often find damaged generator windings, short-circuit and over-voltage damage to controllers and electronic components as well as damage to transformers and wiring.

4 Cage wear after 4,000 hours of operation. Flank damage, detected after 7,000 hours of operation. Cause investigation. Our core activities include cause investigation. Our expertise is the product of decades of research in virtually all areas of industry. We use advanced non-destructive testing methods to examine rotor blades. The methods employed include penetration tests and visual inspection with the use of miniature cameras or endoscopes as well as ultrasonic inspection. We can also determine the cause of damage to mechanical components on site. For example, we use endoscopes for the visual inspection of planetary gear transmissions, take oil samples and make impressions. However, we usually examine damaged components in our materials laboratory, where we can take full advantage of our resources and the expertise of our specialists. Our specialists for the analysis of electrical systems also apply their experience and expertise to cause investigation when it comes to wind turbines. They can identify the cause of damage to generators, rectifiers, transformers and controllers. In order to reduce the vulnerability of wind turbine components, we cooperate closely with manufacturers and operators. The more information we have on the technology or chronology of a damaged wind turbine, the easier it is for us to determine the primary cause of the damage. This helps avoid costintensive repairs and downtime. Cause investigation also includes computational analysis. For example, we use finiteelement analysis when conventional methods prove inadequate. This approximative approach is used to compute structural and characteristic values as well as temperature gradients.

5 Damage prevention. The activities of the AZT research facility are intended to reduce the frequency of damage to major components and thereby extend the service life of wind turbines. As a result, our activities go beyond cause investigation. We provide objective, vendor-independent assistance and support for all parties involved to increase the availability of windturbines and cut costs. Load and vibration measurement. In view of the special nature of the forces to which wind turbines are exposed, it is necessary to investigate wind turbine behavior under actual operating conditions in order to identify operating situations that can lead to damage. In particular, it is necessary to determine whether the specified design loads correspond to actual reality at the respective location. We use advanced measurement technology to carry out these investigations. Long-term measurement enables us to determine sitespecific loads on the drive train such as torque and bending moments or shaft, bearing and nacelle vibration. In addition, special measurements also make it possible to determine the causes of damage that regularly aect specific production series. Design and engineering. On the basis of the results of damage analysis and a knowledge of running behavior, we are able to make detailed recommendations for the design and engineering of individual components. In order to increase operational reliability, our recommendations can also exceed the guidelines of certification institutes. Production consulting. We can evaluate individual production processes and inspect or monitor the entire production process in order to preclude manufacturing defects and enhance quality. This is especially important in the case of rotor blades, which represent some of the most cost-intensive components of wind turbines since production is so involved. Fire engineering. There s very little firefighters can do in the case of a fire at a height of 60 to 100 meters. If a wind turbine is not equipped with an automatic extinguishing system, a fire inevitably means a total loss. Falling parts or debris also represent a danger to the surrounding vicinity. AZT has been involved in the development of extinguishing systems and technology for decades and can also provide eective support in the area of fire engineering. Condition monitoring. Our experience and expertise also enable us to evaluate online condition monitoring systems. We have developed a catalog of specifications for condition monitoring systems that includes specifications for systems, operators and manufacturers of wind turbines. It contains information on parameters that cover everything from signal recording and processing to analysis as well as limit monitoring and trend analysis. Operating and safety systems. AZT examines safety systems. We develop damage scenarios and provide wind park operators with support in the area of Failure Mode and Eect Analysis (FMEA). Measurement system on a 600-kW wind turbine with rotor and generator shaft torque measurement and measurement of drive train vibration.

6 Allianz Risk Consulting GmbH Allianz Center for Technology Fritz-Schäer-Strasse Munich Germany Phon e info@allianz-azt.de Allianz Risk Consulting Wind turbines / E