Mobile crane hire company Johnson Crane Hire (JCH) completed several complex lifts of wind turbine components during two visits to the Port of Ngqura, near Port Elizabeth, in April and June last year.

The components that were lifted and offloaded included 18 freestanding nacelles, each weighing 86 t, and twenty-eight 22-m-long tower sections, each weighing 62 t. These were handled with a mobile 550 t Liebherr crane.

The cargo lifted by JCH was delivered to the Cookhouse wind farm, situated on 9 000 ha of land about 150 km north-east of Port Elizabeth. This wind farm is the largest in Africa and construction is being undertaken by Indian wind turbine manufacturer Suzlon Energy and its South African partner, African Clean Energy Developments. A total of 66 turbines, with a combined installed capacity of 138.6 MW, will be required.

branch manager Richard Simmons explains that the lift was challenging owing to the company having to lift components from both the hold and the deck of a 100-m-long ship. “This meant that the crane should have been strategically placed in the centre of the ship. “However, this positioning would mean that the crane would not have sufficient reach to the fore and aft sections of the ship,” he says. “The docking fees are high, which means that we were forced to mobilise our team quickly to reduce the ship’s time in port,” adds Simmons.

To overcome this challenge, JCH repeatedly moved a fully configured crane, with a 165 t counterweight and fly jib, to facilitate the lifting and offloading of the components. Once one-half of the ship was offloaded, the ship was turned around and JCH repeated the process of moving up and down the quayside to lift and offload the remainder of the components. Simmons says that during JCH’s lifting exercise, a third party offloaded the large turbine blades from the ship, adding extra congestion to the busy work area.

Prior to the lifts, JCH engineers planned the exact positioning of the crane to ensure that the loading on the quayside was within acceptable limits. “The total loading on the quay comprised 165 t of counterweight, 96 t of crane and up to 86 t of cargo,” says Simmons, adding that the edge of the quayside is concrete, with an inner gravel portion, which the crane traversed on each horizontal movement along the length of the ship. “Once the crane was again in position for a lift, we strategically placed the outriggers on the quay’s concrete load bearing beam, which was a mere 300 mm wide,” he says.

Owing to high winds, common in the area, JCH had to schedule lifting times for periods when it was ascertained that wind speeds would be lower. Using long-range forecasts through wind forecaster Windguru, together with handheld windspeed devices and a crane-mounted windspeed meter, JCH established that the ideal time would be between 18:00 and 21:00. “We were fortunately granted permission by the port authorities to operate a 12-hour shift to mitigate against the inclement weather, and we used the ship’s bulk to partially shelter us from the wind,” Simmons says.

Adding to the aggravating factors included movement of the ship owing to tidal activity, and the shifting of the ship as weight transfer occurred. “We took great care to ensure that the outer fibreglass shell on the components was retained in pristine condition,” Simmons says.

He adds that the lifts were precedent setting in terms of the challenges faced, how JCH overcame them and the weight of the lifts. “The fact that we were able to accomplish these lifts in such a short space of time and coordinate our movement with the other quayside activities, underlines our commit-ment to customercentric, quality service,” Simmons says.

“As testament to JCH’s experienced and skilled teams, we used a different crane and crew on each of the April and June lifts,” Simmons says. He adds that extensive training undertaken by JCH operators and rigging crew ensures that they are able to leverage their knowledge acquired through other heavy lifts to provide customers with a quick, yet safe, lifting experience.