73 M HYBRID BOOM CRANE
Happy Star was contracted by Huisman Cranes Zhangzhou, Xiamen, China, to ship their first Hybrid Boom Crane to the Hyundai yard in Ulsan, Korea. The cargo consisted of the crane and auxiliary equipment, destined for Subsea 7’s vessel Seven Arctic.
The crane was delivered horizontally with its transport saddles – up to 18 m wide – already fitted underneath. During sailing the load on the forward saddles was calculated at 600 mt and when upending the crane, the load on the aft saddle would be 730 mt. Strength calculations showed sufficient deck strength with BigLift’s smart pillar system positioned under the hatch.
A further item to include in the preparations was the limited draught of 6.3 m in Xiamen. This was overcome by Happy Star’s shallow draught and clever positioning of the vessel’s tween decks.
The crane was 73 m long and 23.5 m high but its base was only 9 m wide. This construction required lots of wires to prevent uplift or overturning. The aft support was designed for the upending action and during lifting and sailing a set of hinge points absorbed the vertical load. To erect the crane, a second set of hinge points took the load away from the forward hinge during the final stage of the lifting operation.
Huisman’s enormous 2400 mt Skycrane easily lifted the cargo from the shore on to Happy Star’s deck. The ship’s cranes could have handled this lift, but the berth alongside Happy Star was completely filled up with further J-Lay towers under construction.
After loading and extensive securing, it was time to leave. Meanwhile, a strong typhoon was on its way to Xiamen and threatened to bring 13 m waves to the planned route! With such a fragile cargo, waves like that are best avoided, so, putting the Octopus weather system to good use, Happy Star made a detour and let the typhoon pass before proceeding to Ulsan.
On arrival at Hyundai yard, sea fastenings and lashings were removed and a floating crane arrived at the vessel’s stern. The 1500 mt floating crane had to use two main hooks to perform the upending of the cargo and two smaller hooks to lift it under the angle required for installation on the Subsea 7 vessel. The distance between the hooks turned out to be just enough. The fore end was lifted from the deck and the gap seemed almost too narrow. By carefully ballasting the Happy Star and in close interaction with the floating crane, the crane was manoeuvred securely through the narrow space in the lifting gear. Finally all 990 mt was suspended in the air and the floating crane sailed to the Seven Arctic to install the crane.
On Happy Star, the remaining supports were cut loose and lifted off the vessel.