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As people and businesses become more environmentally aware and want to reduce their carbon footprint, the switch to renewable energy grows apace. To meet this demand the number and scale of wind farms are increasing, and so too is the requirement to ensure they are operating effectively.
Operating over 35 metres (114 feet) from the ground and with three blades each measuring over 20 metres (65 feet), a wind turbine inspection is not the easiest project.
Why is inspection necessary?
For obvious reasons a wind turbine is situated on a hillside in a fairly harsh environment, which means it is continually exposed to the elements. Couple this with the sheer scale of the technology involved, and the reasons for ensuring that all the components are operating the way they should and are structurally sound is clear.
After all, you MOT your car each year to make sure it’s working as it should.
How do you inspect something of this scale?
With three decades experience of inspecting things this is a question which we are often posed. But, we are no strangers to answering such questions.
Technology has advanced greatly in recent years, and in some instances it has been manipulated and developed to allow man to go places that he physically can’t. This has led to us using it in some innovative ways.
Using different technologies and techniques, including video probes and Non-Destructive Testing, we can survey every part of a wind turbine; from the concrete base on which it stands, to the very tip of its blades and all the mechanics in between. Each survey which we undertake is carried out in a way which minimises the risk to the inspector and the time involved in the turbine being out of operation.
Continually exposed to the elements, with gale force winds battering it, the tower can bear the brunt of the weather. Constructed out of welded steel, each section of the tower is bolted together on the inside.
An inspection of the outside of the tower examines the integrity of the welds and also details any possible damage. A remote access crawler attaches to the tower with the use of magnets, which allows it to travel vertically and horizontally on the structure to carry out an inspection and feed information back to the inspector on the ground. This eliminates the need for costly scaffolding or rope access.
Internally, visual inspections are carried out to identify any damage to the bolts or flanges. Damage to these can impact on the safety of the turbine.
One of the most important parts, the nacelle houses much of the mechanics of the turbine, including the gearbox, generator, brake, controller and yaw mechanism. If each of these items did not operate correctly then the turbine could fail to generate electricity.
Inspections are carried out with video probes to ensure that there is no damage, and no debris has built up around the moving parts. If the yaw mechanism is damaged then the turbine may not be able to turn its blades against the wind, which could result in greater damage.
As a turbine rotates, heat is generated in the nacelle. If there was debris in the nacelle, this in the worst case could ignite. Video probes allow the inspector to see parts of the mechanism which he can’t by sight. Using retrieval tools debris can be removed.
Exposed to whatever the weather throws at them, rotating at 10 – 22 rotations per minute and designed to endure more than 120,000 operating hours, the blades are some of the hardest working parts of a wind turbine. Made of fibreglass and weighing around 12 tonnes each, there is a need to ensure they are structurally safe.
Thermographic cameras can be used to identify areas of the blade which are delaminating, as it detects variances in the heat of the blade structure. Inspection of the blades can also be carried out using a telescopic mast and a zoom camera which can examine the blade in detail.
The growing demand for clean, green energy will put greater demands on wind turbines, so ensuring they are operating safely and effectively will become more important.