Transport engineering and heavy lift specialist Mammoet has supported the load-out of a topside and jacket for the N05-A platform, the first offshore gas platform in the Dutch North Sea to be powered solely by wind power.
The platform, which is owned by ONE-Dyas, uses electricity via cable from the nearby 113.4 MW Riffgat offshore wind farm and is part of the Gateway to the Ems (GEMS) project. The electrification of the N05-A platform is projected to reduce carbon emissions by over 85 percent throughout the project’s duration.
Weighing 3,150 tonnes, the jacket was fabricated and assembled in two parts and its rows were upended by four mobile cranes – two LTM-1650 (650-tonne) and two LTM-1450 (450-tonne) cranes from Liebherr. A 750-tonne mobile crane installed the jacket’s pile sleeves.
Once in the correct spot, the top section of the jacket was moved to the quayside where heavy lifting was executed using two sheerlegs, creating the space for the bottom section to be placed underneath so the two parts could be joined. SPMTs were driven underneath the topside and then drove it outside the fabrication facility – in Schiedam, Rotterdam – and onto the quay. Conventional trailers and mobile cranes then installed a pedestal crane onto the topside.
Both the jacket and the topside were picked up by SPMTs and, following final weights being recorded using Mammoet load cells, the load-out operation began. This was made difficult as both structures had to be loaded out onto the same vessel, to shorten the operations schedule. Because of this, pumps and winches had to be installed onto the transport vessel.
“Normally, we would use a configuration of winches to moor and stabilise the vessel, but that wasn’t possible because of the force of the considerable loads,” said Sven Segeren, project manager at Mammoet. “The loads on the winches were too high and the bollards not strong enough, so a small spud leg barge was used to secure the vessel and keep it in position prior to, during and after load out.”
Five days were needed to prepare the main barge, which included installing the ballast equipment, performing the pre-ballasting, and checking the sailing conditions to the destination. With four trains of 32 axle line SPMT trailer used, the load-out operation of the jacket foundation and topside was completed in two days.
In December 2024, Mammoet commenced work on a major bridge replacement project in Amsterdam.
