The client required a solution for the removal of two met mast monopiles within the Robin Rigg wind farm field located in the Irish Sea. In order to complete the project Proserv designed a bespoke tool to overcome engineering challenges offshore within a tight timeframe.
Proserv provided a decommissioning solution by carrying out all dredging and cutting operations for the client which included the construction of a purpose built external guideband capable of cutting up to 4.3m. Trials were carried out at Proserv’s Birchmoss Facility which consisted of full guideband carriage installation and 360° hydraulic rotational tests on the guideband prior to mobilisation.
The work scope included internal monopile dredging operations, followed by external cutting operations using hole cutters alongside Proserv’s 10k psi abrasive slurry to enable rigging/lifting equipment to be attached. The purpose built guideband and cutting carriage was attached to the monopile subsea using a single diver operation and connected to Proserv’s 15k JetCut water abrasive equipment topside by means of a lightweight umbilical. The cutting operations were carried out in two separate stages. The first consisted of the hole cuts, this allowed for shackles to be installed, followed by external subsea cutting operations on the monopile which completed the work scope.
The quick turnaround bespoke tooling solution was executed within the short timeframe and the offshore work scope completed on schedule. The client received a fit-for-purpose solution with experienced personnel onsite, necessary to complete the decommissioning works. This is believed to be the first known monopile successfully decommissioned within the offshore renewables sector.