Extremely windy sites are, by their very nature, perfect locations for wind farms. Ironically, that’s what makes construction of their turbines challenging and potentially dangerous.
These wind farms are, however, a large part of the Victorian Government’s plan to transition the state’s power supply from reliance on coal-fired power stations to renewable energy. In June 2016, the government committed to renewable energy generation targets of 25 per cent by 2020 and 40 per cent by 2025 under The Renewable Energy (Jobs and Investment) Act 2017.
As a result, the Timboon West Wind Farm, seven kilometres southwest of Timboon Victoria, was one of nine constructed or under commission as of June 30, 2018. Completed in October 2018, it has a capacity of 7.2 MW – equivalent energy usage of about 4500 households – and connects to the existing 22 kV power line that runs adjacent to the site.
Vestas engaged Tutt Bryant to erect Timboon West Wind Farm’s two Vestas V126 turbines in August 2018. Each turbine was 150m to the tip of the blade and included an 86m hub height 128t Nacelle, three 12.5t blades and four tower sections. The first tower section was 19.7m and 69t, the second 17.3m and 45t, the third 21.6m and 41t, and the fourth 27m and 37t.
The wind farm site, on privately-owned land primarily used for grazing, was chosen because it received undisturbed wind flow with strong, consistent wind speeds, was close to the electricity grid, and enjoyed large setbacks to nearby dwellings.
The weather conditions, coupled with space constraints created by a gas line running through the property and the minimal size of the earthworks crane pads to reduce impact upon productive farmland, resulted in several unique challenges for the installation team. However, a combination of teamwork and good planning, by both Vestas and TBHL&S, saw installation completed safely in five weeks.
No crane can work when wind speed exceeds the threshold stipulated by their configuration. Tutt Bryant employed a Terex Demag CC2800-1 (600t crawler) as the main lift crane, which has a 9M/S threshold before it can no longer lift safely. The team used two Mobile All Terrain cranes (a Liebherr LTM1250-6.1 200t and Liebherr LTM1100-5.2 100t) to erect the main crane as well as unload, unpack and position the blades in a dual lift exercise.
A Hitachi Sumitomo SCX2800-2 275t crawler was also mobilised on site to get ahead of schedule and enable the main crane to be relocated to another project within the five-week timeframe. The entire main crane was disassembled, relocated and reassembled in four days to allow it to be traversed over the gas main to the next tower location.
Wind speed concerns were overcome not only through carefully planned lift studies, performed by our on-site engineer Thanes Gnaguru. The flexibility of having our engineer at hand allowed prompt changes to be made in adjusting for the changing conditions, thereby minimising delays to an already tight program. The team constantly checked outrigging heights prior to each lift and, by being flexible in our working times, managed to pre-empt good weather conditions. This allowed all lifts to be carried out safely and within OEM recommendations.
In addition, each tower had an earthworks pad constructed, not only to create a stable base for the crane, but to enable delivery and storage of components. Such pads can become extremely congested as team members work around the crane and stacked components.
Tutt Bryant National Projects Manager Anthony Prpic said a thorough forward planning process and excellent site management by the team, supported by a tight-knit and highly professional group of workers, overcame the potential for danger and scheduling disruptions.
Hook height and clearance to the beam created another challenge. A 102m main boom length was used. Lifting the Nacelle onto the top tower was the tightest lift of the project, with the clearance from the tower top to the boom very tight at one point. The team waited until there was virtually no wind before attempting that specific lift, while all lifts were assisted in their control using two teams of men, who had long taglines anchored to opposite corners of the load being lifted.
Each team, including the crane driver, had a two-way radio so they could be coordinated by the dogman controlling the lift. A ground-based rigger controlled the lift until it was within sight of the tower rigger, who was up in each tower section and then took over control of the lift. When the teams of men controlling the taglines were told to pull – they did so.
In the end, it was the combination of an experienced client in Vestas along with an extraordinarily tight-knit team that ensured all challenges were safely overcome and the project was completed on time and to budget. “We could not have asked for a better bunch of blokes,” Mr Prpic said. “Especially since all of them knew their stuff and we all looked after each other – always.”