Innovative Yoke for Safe Wind Turbine Blade Lifting
Most mechanical constructions that are 14 meters long, 8 meters tall and weigh 78 metric tons are not described as fast or flexible. Especially when the thing it lifts is 75 meters long and weighs 25 metric tons.
Then again, the new B75 lifting yoke from the Siemens Wind Power Division is no average construction. And Siemens is taking out the patents to prove it.
As wind turbines develop – and especially grow in size – new equipment related to all aspects of them also need to be developed. Whether in design, manufacturing, transportation or installation, safety must come first, with quality and cost-efficiency following. Meeting these requirements when related to installing 75 meter rotor blades when out to sea at the same time clearly required a new solution.
For large-scale installations of these enormous wind turbine blades, the R&D team at the Wind Power Division identified this need years ago.
“Rotor blades are installed on what are known as hubs to form a rotor. The rotor is itself attached to the nacelle, the large section of the turbine at the top of the tower. This takes place at heights often between 60 – 90 meters, depending on the prevalent wind resources. There are two ways to install them: in a single-blade lift, meaning one at a time onto the hub which has already been installed on the nacelle, or in a full rotor lift, where the three blades and hub have been preassembled on the ground,” informs Kenneth Helligsø Svinth, who headed the project. He continues:
“Each method has its pros and cons. For the large-scale installations of our 75-meter blades, it was decided to develop a new single-blade installation tool. The size of the blade, along with the challenges of aligning the hub of the SWT-6.0 nacelle, made this the better solution.”
It will be the world’s largest lifting yoke for offshore installation of a series-produced wind turbine. It can install blades in winds of up to 14 meters per second, and is fully automatic. Three patent applications have been submitted.
Recently the Siemens Wind Power project team for the Westermost Rough offshore wind power project, customer DONG Energy and installation vessel crew from partner A2SEA received an introduction to the lifting yoke. Mounted on a crane in Østerild, Denmark, functions were demonstrated and lifts were performed.
Automatic sling connection
In traditional single-blade lifts, a crane lifts the blade hanging from secured slings. A great deal of manual work is required to attach and release the slings, some of it needing to take place at heights far above the ground or surface of the water.
A key function of the B75 lifting yoke is the automatic sling connection. This ensures that no technician is working at heights doing the rigging or operation of the yoke. Remotely controlled, a highly-trained Siemens yoke operator does so from the safety of the deck of the installation vessel. Furthermore, a reduction of shackles where possible was also implemented to avoid manual handling.
Flexibility in focus
The active yaw function allows adjustments at height that are not possible with existing single-blade lifting solutions. Flexibility is indeed in focus in the B75 lifting yoke. Numerous adjustment functions have been integrated, according to Moeller.
“We are able to actively tilt and pitch the blade several degrees, as well as turn, or yaw it, as we say, allowing us to make adjustments at height that simply are not possible with existing single-blade lifting solutions. This new yaw feature will allow us to keep full tension in the taglines connected to the crane boom while we simultaneously instruct the crane operator to yaw the crane for positioning the blade. We can easily adjust the alignment between the hub and blade without needing to adjust tagline tension. This allows us to install blades more safely and efficiently, the latter which helps us reach our goal of lowering the cost of wind energy,” he states.
The B75 lifting yoke will be employed during the installation of the 210 MW Westermost Rough offshore wind power plant in the UK beginning in summer 2014. A total of 35 Siemens SWT-6.0-154 wind turbines with 105 B75 rotor blades will be installed. This is the first offshore installation of the 75-meter blades on the Siemens 6 MW machine.
“It has been very important for me during the development of this yoke that we have taken all the lessons learned from the previous yoke into consideration. Also, a key stakeholder during development was a ‘super user operator’ from the existing yoke solution. In that way, we ensured that the technicians receive a tool that they can operate safely and effectively in the field from Day One,” Svinth concludes.