Reduce operational downtimes and ensure peak wind turbine power production by following wind turbine inspection protocols.
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Wind turbines are one of the primary sources of renewable energy in the world. In fact, in the United States, they are among the largest renewable energy sources and contribute around 122,000 megawatts annually of which one kilowatt-hour only costs 2 to 4 cents, making them one of the cheapest energy sources in the US.
Wind turbines convert wind energy to electricity with their large fan-like propeller blades mounted on a towering vertical structure. Rotating when high-speed winds hit them, these blades produce electricity which is then sent into the electrical grid to be managed and then distributed to consumer households.
Since wind energy is variable all throughout the year, it is critical that the time periods where wind energy is the most abundant are fully maximized. If this is not the case, a significant loss in revenue could incur, which is why it is why it is so important to conduct inspections and introduce preventive maintenance measures to ensure that the wind turbines are in good working condition.
A wind turbine checklist is a document that follows wind turbine protocols and contains all the essential tests and preventive maintenance procedures to ensure that wind turbines are operating efficiently.
As capital intensive installations, wind turbines are constructed following the IEC 61400, an international norm that details engineering requirements for wind turbines. Once erected, wind turbines should last for about 20 years, but for them to function well, they need to be inspected regularly and therefore require maintenance check-ups about two to three times per year.
Every 5 years, there will be a larger and more thorough preventive maintenance with more crews and testing procedures. Although this is the common preventive maintenance frequency, it may be increased depending on the need.
In order to ensure the longevity of a wind turbine and make sure it functions properly at all times, certified testing agencies and technicians pay attention to the following 8 areas when conducting an inspection of wind turbines:
An oil analysis refers to taking oil samples from the wind turbine components that are in a closed system and submerged in lubrication oil like the gearbox or the generator. Since the oil is in a closed system together with the mechanical parts of a wind turbine, byproducts from degradation and friction mix into the oil. The sample oil, after being carefully analyzed, is therefore an excellent indicator for early signs of failure, lubricant condition, and contamination.
A wind turbine blade inspection checks the blades for any defects. This part of the inspection is highly important since the blades are prone to damage as they take most of the load and environmental impact. In fact, blade failures are among the most common issues that can delay turbine operations.
A blade inspection involves checking the outside surfaces and the inside of the propeller blades while looking for any defects that compromise its structural integrity like thickness variation and delamination. Aside from a visual inspection, various techniques are being used such as ultrasonic testing which uses low-frequency probes to evaluate bonding, adhesion thickness, varying thickness, and wrinkles.
Since wind turbines are towering structures, they are prone to lightning strikes. That is why lightning protection systems are a very critical part of a wind turbine that should be tested reguarly. Lighting protection systems include an examination of the shielding, the air-termination systems, the down conductor, surge arrester, earth-termination systems, earth electrodes, and bondings.
A thermographic inspection is a non-destructive testing method that employs an infrared camera that can detect and capture high-resolution thermal images that show the temperatures on the surface of an object.
Thermographic inspection has been in practice especially in the electrical components of a wind turbine such as the generator and transformers. The images show “hotspots” or hot surfaces that can be caused by issues such as loose connections, insulation problems, or load imbalances.
More recently however, infrared cameras have been put to use to assess propeller blades that are taken back into a laboratory for testing. Defects will show up as thermal spots or blemishes on the images and facilitate inspections.
An imbalance of the rotor can also cause an imbalance in forces acting upon other mechanical components which is often caused by a large variation between the masses of the propeller blades and can indicate manufacturing issues that need to be addressed. This can cause long-lasting damages and greatly decrease the service life of a wind turbine.
However, an imbalance of forces can also be due to improper or misaligned pitch angles of the propeller blades. This can cause a significant reduction in the power production of wind turbines. Measurements during an inspection can be performed by using laser measuring tools and photometric devices. After analyzing the measurements, the required corrective actions can be taken.
Due to their rotating components, wind turbines experience vibration, especially on their bearing, shaft, and gearbox. Excessive vibration can cause excessive degradation and significantly reduce the service life of the mechanical components.
It is therefore required to install sensors to measure vibration and check whether it falls within acceptable values. If not, troubleshooting needs to be done to find a possible cause and make necessary repairs.
The endoscope inspection is supplementary to the vibration measurements and is performed if the suspected cause of excessive vibration is damaged gear. By inserting a small and flexible video camera that can pass through the gearbox, the device can be inspected for any damages. Some gearboxes, however, don’t have enough access for endoscopes and might need more traditional inspection methods.
Checking the foundation upon which the wind turbine is built is another important part of any wind turbine inspection protocol. The inspection procedures include checking the general condition of the foundation, concrete integrity, and corrosion. For safety purposes, a foundation inspection also includes an examination of the access equipment such as ladders, stairways, fall protection, anchors, and railings.
Regular wind turbine inspections – scheduled or spontaneous, online or offline – have never been easier than with Lumiform, a quality and safety audit software which allows you to collect data with checklists in the field via your smartphone or tablet. Reduce errors, maintain equipment and plan ahead with Lumiform so that you can perform wind turbine inspections according to protocols, ensure the longevity of your turbines and continue to source reusable energy safely and securely.