The lifting skills of Johnson Crane Hire were successfully put to the test on a challenging heavy lift contract for a large marine diamond miner.
As part of routine quarterly maintenance, dredging vessels are brought into Cape Town harbour where the necessary servicing and repair work is undertaken in the dry dock. In this particular instance, Johnson Crane Hire was called upon to remove three large components from the vessel, being the vessel’s 52 t gimbal head, the 42t derrick and the 20t crown.
Engineering News, removal of these large components facilitated important repairs to both these critical items and the dredging vessel while it was in the dry dock. A set number of days had been allocated to the maintenance program and this meant that all contractors needed to adhere to the work schedule.
Richard Simmons, heavy lift hydraulic cranes manager at Johnson Crane Hire, say that careful planning prior to the lifts being undertaken played an important role in ensuring the success of the lifts.
Close interface between the crane specialist and the mining house’s own maintenance teams was critical. “The mining house had allocated exactly 35 days to the maintenance program and we therefore had to ensure that we were able to make their lifting deadlines,” he says.
Among the challenges that Johnson Crane Hire had to content with on this specialized lift was the high wind speeds that occur in the area, which at times can reach 108 km per hour. This caused lifting operations to be stopped during these periods. Conditions were monitored and close communication between the operator and the team on the ground was essential as the lifts could only be done when the wind was below 38 km per hour.
Another complexity was the extremely congested working environment on the quay side, where there was just enough space in the laydown area to place equipment and lower the boom and luffing section of the crane.
Johnson Crane Hire made use of its 750 t mobile crane to undertake all three lifts. The crane was equipped with 204 t of counterweight and a 31,5 m luffing jib. The first component to be lifted was the gimbal head as this was on the critical path of the project.
The gimbal is a pivoted support that allows the rotation of equipment on a single axis and more importantly keep them upright with respect to the horizon despite the rolling or pitching of the vessel when at sea.
“This gimbal with its 35 meter lifting radius was the most complicated component to lift, and required accurate movements to extract it from the vessel in the dry dock and raise it safely out of the ship,” Simmons says.
The crane’s sophisticated guide system aided the seasoned Johnson Crane Hire operator to accurately control the deflections on the boom during all the lifts. This was particularly important during the lifting of the gimbal head.
While state-of-the-art equipment is essential in ensuring successful lifts, Simmons is quick to point out that the company has a large pool of skilled operators. “Our operators have extensive heavy lift experience, and undergo regular training both in-house and at crane OEMs.”
This is exactly what continues to give Johnson Crane Hire its competitive edge in the heavy lifting market.
