June 5 - South Africa's Johnson Crane Hire has safely removed and replaced a number of heavy components on board Debmarine Namibia's offshore diamond mining vessel, !Gariep.

Johnson Crane Hire says it has supplied a number of small cranes to various De Beers Marine projects in the past, but this was the first time it has performed a heavy lift for the diamond miner.

Johnson Crane Hire removed and installed, in this order: the 24-tonne crown, the 45-tonne lifting guide beam complete assembly, the 42-tonne compensating guide beam complete assembly, including spout and upper universal; a 42-tonne stabiliser guide beam; the 22-tonne gimbal; two 50-tonne drill bits; and various other pieces of system equipment.

"Working conditions on a marine vessel heavy lift could be compared to the congested conditions and space constraints experienced on petrochemical contracts," said Cornelis Grotius, general manager of the Johnson Crane Hire's heavy lift division.

"The emphasis on safe operating conditions, while always a priority for Johnson Crane Hire, is magnified in such environments. Careful planning, reliable equipment and a well trained and experienced operational team are critical factors in the success of these projects," Grotius observed. 

Eugene Lamont, De Beers Marine senior mechanical engineering officer, said the plant and equipment upgrades will improve the performance of the vessel, and such an overhaul requires extensive forward planning. "Once the !Gariep is placed in the dry dock, it is critical that all repairs and upgrades are expedited quickly, to allow the vessel to return to base as rapidly as possible. We have already started planning the next round of upgrades for 2018."

Johnson Crane Hire mobilised its 750-tonne capacity Liebherr all-terrain hydraulic crane for the !Gariep contract, due to the sheer size and weight of the components to be lifted. The crane was deployed from Johannesburg under its own power; while the counterweight and 28 m luffing jib were transported separately on low bed trucks. Travelling time was two days and set up on the quayside at the Sturrock Dry Dock in Cape Town harbour took three days. 

Grotius added: "The sometimes excessive winds in the harbour area were an aggravating factor but, due to careful planning and our ability to work in challenging environmental conditions, we were able to abide by the project schedule without incident. Working between 10 and 12 hours each day, the team successfully completed the project within the revised forecasted period of 55 days."