Construction of Heerema Marine Contractors’ new H-731 float-over barge has reached the keel-laying stage, around eleven months after the first steel was cut for the vessel at the CIMC Sinopacific Offshore & Engineering (CIMC SOE) yard in Daishan, China.
Heerema announced the milestone on social media, saying the keel was laid this week at the Chinese shipyard. The company started construction of the 222.5-metre-long barge in December 2025.
H-731 is being built specifically to support the installation of offshore converter station topsides under TenneT’s 2 GW offshore grid programme, for which the companies signed a contract in January 2025.
TenneT’s programme involves the installation of 14 high-voltage direct current (HVDC) offshore grid connection systems in the North Sea, in both Germany and the Netherlands, each with a capacity of 2 GW.
The H-731 barge is scheduled for delivery in the second quarter of 2027 and will support the installation of TenneT’s 2 GW offshore substations from 2028, according to Heerema.
According to the vessel owner, the barge will have a float-over capacity of up to 40,000 tonnes and will be used to install topsides weighing more than 30,000 tonnes.