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Keynvor Morlift completes challenging winter decommissioning of Moray East met mast

Wednesday, 24th March 2021

Keynvor Morlift (“KML”) has successfully completed the decommissioning of the offshore met mast as main contractor on behalf of Moray East Offshore Wind Limited.

The mast comprised an 80m high lattice, a 50 tonne platform and a 150 tonne 2.5 metre diameter monopile attached to a concrete gravity base.  It was installed in 40m water depth in summer 2014.

Urgent decommissioning had become necessary after the structural integrity of the asset was compromised.  The time-critical removal operation meant that a winter scope was required; a particular challenge given inhospitable conditions in the Moray Firth at that time.

KML ( Marine Civils & Construction Company ) developed a three-phase removal campaign using detailed metocean modelling to maximise productivity during the limited available weather windows.

The lattice was disassembled using the GMS Endeavour jack-up vessel with GWO rope access support provided to KML by PD&MS Group who worked tirelessly in frequently sub-zero conditions.  Primary processing of the lattice was carried out on the deck of the Endeavour to increase efficiency.

KML planned a break in operations to give scheduling flexibility and mitigate weather risk.  The final section of the lattice and platform were removed in two lifts by KML using the Olympic Taurus, with a short five-day campaign maximising available weather windows. 

The removal of the monopile involved a complex subsea cut and carefully engineered heavy lift.  This final phase required a 24-hour weather window and so detailed step planning was critical.
KML engineered, procured and executed a two-vessel solution involving the Olympic Zeus and Olympic Artemis: the highly capable Zeus as the lift vessel with the Artemis in a cutting and ROV support role.  KML suppliers Cutting Underwater Technologies provided the diamond wire system that was deployed on a custom frame designed in house by KML and built for KML by  FabTech Aberdeen.

The monopile was rigged on the Zeus and cut in a single pass.  The pile was then recovered to the deck of the Zeus where it was cleaned and sectioned for onward processing.

The scope concluded with installation of a subsea debris cap to fit the pile stub and protect the caisson internals and an IALA marker buoy.  The assembly was designed by in house by KML, and manufactured for KML by Tolley Fabrications and installed from the Artemis following the completion of cutting operations.  

Paul Mewse, Head of O&M at Moray East, commented: “This is our first time working with KML and I have been impressed by their flexibility and willingness to support us in delivering the project.  I’m pleased that it was completed safely and on schedule, particularly given the conditions, and would like to thank the team for their superb efforts.  I look forward to working with them again in future!”

Diccon Rogers, Managing Director of KML, added: “We’re delighted with the safe and successful completion of this challenging project.  The combination of the well-known harsh conditions in the Moray Firth and reduced daylight hours in mid-winter presented a particular challenge and we’re proud to have been able to effectively manage these risks for our customer.  We’d like to thank Moray East for their collaborative and enthusiastic approach to the project, the talented KML team and our entire supply chain for their determined efforts to make this a success.”

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