Sarens, Allseas and Aker BP Change Plans for Heavier Than Expected Valhall DP Topside Delivery

Early in 2022, Sarens equipment stood at the ready, awaiting a massive topside that would be loaded in at the Aker Solutions decommissioning yard in Stord, Norway. But when the topside turned out to be heavier than expected, Sarens and clients Allseas and Aker BP had to think fast and work together to make the load-in a success.

For this operation, Sarens had deployed the following equipment:

• 136 axle lines Kamag K2400-ST SPMTs
• 70 axle lines Scheuerle M78 SPMTs
• Sarens barge LOUIS, with steel grillages
• Steel transport structure on SPMTs
• 14 ballast pumps rated at 400t/h
• 6 ballast pumps rated at 600t/h

The Sarens barge, LOUIS, had been prepared for the operation in Ghent, Belgium, and towed to Norway. The remaining equipment, including SPMTs, pumps, ramps, and steel supports, had been transported via several trucks. The crew had been prepared to load in and once on site, equipment assembly took approximately one week.

The 5.205t Valhall DP topside measured:

• length    63m
• width     46m
• height    35m

Operations began, with the Allseas vessel, Pioneering Spirit, unloading the topside onto the Sarens barge, LOUIS. From there, the plan was to moor the barge at the Aker Solution yard, use SPMTs to pick up the topside, and then load it onto the quay while ballasting the barge.

However, during the lift by the Pioneering Spirit, the decommissioned topside weighed in significantly heavier than foreseen, meaning that the stability of the barge LOUIS would be too low for the operation to proceed as planned.

In close collaboration with Allseas and Aker BP, the operation was re-engineered, and it was arranged to mobilize a second, larger barge to assist with the operation. The two barges were then moored aft-to-aft, parallel to the quayside, as the topside was driven from the LOUIS to the second barge. After this roll-over, the second barge was moored perpendicular to the quay for the Load In operation. The topside was then driven off and set down on its decommissioning supports.

“Congratulations on this major milestone, where we turned this overweight challenge into a successful completion of the load-in of the topside,” said Allseas project manager Eric van der Plas. “This was a great achievement within a very short timeframe, safely executed. Thank you for all the hard work!”

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