The UK division of Certex – a supplier of steel wire ropes, lifting products, and services for the oil, gas, industrial and renewable markets – was commissioned to lift two nonidentical halves of a helipad off a gas rig and onto a supply vessel in the Dutch Sector of the North Sea, 70 miles off the Danish coast, recently.
To do the job Certex utilised a 300t capacity crane aboard a barge in conjunction with two modified spreader beams from UK lifting beam solutions provider Modulift. Certex lifted each half of the helipad separately using corresponding spreader beam and rigging setups. The heavier pad weighed 89t and Certex used Modulift’s MOD 110H at a height of 6m (19 ft.) to help lift it. The smaller pad weighed 35t and for this Certex used Modulift’s MOD 110 at a height of 6.5m (21 ft.).
According to Modulift, the MOD 110H can lift up to 170t at 11.5m (37 ft.) and lower capacities up to 18m (59 ft.), while the MOD 110 provides 110t capacity at 14m (46 ft.) and lower capacities up to 18m (59 ft.).
The beams were modified by Modulift at Certex’s request in order to eliminate the use of guide ropes and so that personnel did not need to work in close proximity to the loads as they were landed on the supply vessel. “Pad-eyes were required on the side of the end units so they could be connected to winches on the barge crane to control manoeuvring of the helideck during positioning into place,” explained Jason Griffen, a sales engineer at Certex UK. “We provided calculations in advance of the project so Modulift could weld the modifications accordingly.” Further, there was not a lot of margin for error and the modified beams simplified the process. Certex was also able to utilise permanent lifting fixtures on both halves of the helipad.
Different rigging equipment, supplied by Certex, was used with each spreader beam. Above the MOD 110H was a two-leg, 7m-long sling made from 90mm diameter wire rope, while beneath the beam were two two-leg, 16m-long slings made from 64mm diameter wire rope. Above the MOD 110, a two-leg, 8m-long, 64mm sling was combined with a pair of two-leg, 16m-long, 56mm slings. All were utilised at 30 degrees. “We worked closely with the client’s engineering department to calculate the capacity, type and length of slings required, to complement the spreader beams,” added Griffen. “We also extracted additional information from the design plans for the helipad, such as centre of gravity.”
With no helipad, the rig can now only be accessed by marine transport.