In order to make it possible to perform the lifts evenly with the required lifting capacity, the hooks on both cranes were connected to a heavy-load spreader. “We placed angular position sensors on the spreader so that both crane operators would immediately be alerted if it became tilted and would be able to balance it out right away,” said Schepens.
The two CC 6800 units picked up the legs from their head end and hoisted them with the help of a crane vessel, which followed their lead as it moved the opposite end in a controlled manner while the legs were being vertically raised. Once the jackup legs had been placed in a stable upright position, the floating crane was disconnected and removed. The Terex cranes then lifted the legs approximately 312 feet (95 meters) high and swung within an approximate working radius of 69 feet (21 meters) above and beyond the vessel’s deckhouse until they reached the required position. A tugboat then towed the installation vessel to its exact required position so that the legs could be lowered down into position in the vessel and bolted there.
“The fact that the jackup legs were so heavy meant that there was always the risk that the Victoria Mathias could list and capsize due to the one-sided load,” said Schepens. In order to prevent this, the ship was balanced with water with perfect synchronicity on the opposite side while the legs were being lowered into place.
The Sarens team was able to perform each lift smoothly and on. The lifts for the second installation vessel, the “Friedrich Ernestine”, at the beginning of June were a comparatively relaxed affair for the Sarens team.