Tony Walker – technical support group
To keep offshore wind power installations in good working order, it is usual to routinely inspect the blades of around 10% of the turbines each year. Carrying out this work is a far from trivial operation that requires careful planning and workers with an exceptionally good head for heights.
Normal practice is to hire a vessel and specialist crew, typically comprising a captain, a ship’s mate, a technician and two abseilers. The first stage is a visual inspection carried out from the boat using a high-resolution camera with a long lens. If this shows that a more detailed inspection is needed, the two abseilers ascend to the top of the turbine and the technician climbs to the position from which the blades can be turned. The blades are then put into the “bunny ear” position – two blades upright at 60º to the vertical, and the third blade aligned with the vertical main shaft.
One of the abseilers climbs down the blade aligned with the column, inspecting during his descent. When he reaches the platform level, he ascends again using the lift in the main shaft, and the technician rotates the blades through 120º so that the next one is vertical. This is then inspected in the same way as the first and the process is finally repeated for the third blade.
Weather is a key factor in these operations, since safety requirements dictate that abseilers cannot work if the wind speed exceeds 10 m/s. This means that weather forecasts are very carefully scrutinised before the abseilers are booked, as their services usually have to be paid for even if bad weather prevents them from completing their work.
Next time you are performing some routine inspection on a dull day near your home, think about the challenges facing your colleagues working on offshore wind turbines!