OFFSHORE WIND POWER Ӏ ENERGY
MAMMOET SAVES TIME WITH MANOEUVRABLE CRANE AND SPMT TP TRANSFER
22 kilometres off the Scottish coast, Moray West marks the third offshore wind farm in the Moray Firth region, joining Moray East and Beatrice. Global Energy Group sought Mammoet’s guidance and engineering when a planned RoRo method of offloading Transition pieces (TPs) for the farm was no longer feasible. Mammoet proposed transshipping
the TPs onto Self-Propelled Modular Transporters (SPMTs) using a crawler crane, with its ballast supported by a separate axle line combination. The method resulted in greater
manoeuvrability and less downtime between lifts. It also prevented the shifting tides at the marshalling port from impacting the operation. The TPs arrived by ship at the port of Nigg. The original plan was to drive them off the vessels using SPMT transport with a TP handler attachment. However, this plan had to be altered late in the planning stage. Oliver Smith, senior commercial manager at Mammoet, explains why: “As things developed, new information
about stowage plans, how the TPs were going to be set out on the delivery vessel, and the heights and the mooring arrangements meant this was no longer an option. “It came down to the load-out methodology and the load-in not aligning, with a big part of that being the fact that the vessel would be moored stern on to the quay. This meant there wasn’t enough space to get a TP handler onto the vessel and get the TPs off it.” Work-around solutions would have been possible, says Smith, but “ultimately to support a holistic approach to get the components from A to B we came up with a crawler crane solution”. There were two TP types: 60 units
weighing around 505t, to support offshore wind turbines, and two heavier Offshore Substation Platform transition pieces (OSP) weighing around 832t. The 60 TPs were lifted off the vessel using a LR11350 crawler crane onto a 32-line configuration of SPMT. The crane was supported by a separate 24-axle line combination, which was used to maneuver the ballast tray. Smith explains the time-saving benefits of
this method: “It is possible to move the tray by crane, but we needed a quicker, more efficient mechanism, which is why we used SPMT transport. “If you lift the tray by crane and have close to 600t worth of ballast, you must lift that block by block to relocate it. With the SPMT, once it takes the load of the ballast wagon it can move faster.” The TPs arrived at the port in varying
numbers, ranging in batch sizes from four to as many as 16. This caused challenges at times, especially if there were any delays to the vessels. The team were able to adapt, manage and prevent schedule changes from causing issues.
The crane solution also meant that the offloading stage wouldn’t be negatively impacted by the tides, as the components were lifted off the vessel instead of being rolled off. “Our working relationship with the customer is one that has been built on years of trust, having performed previous successful heavy-lift and transport projects at the same site, including for Seagreen Offshore Wind Farm. We have a good working relationship with the port and
have been able to work together in a very complimentary fashion,” closes Smith. “I think its success was a testament to
the start of the project, when we worked closely together, and offered transparent engineering feedback that enabled us to change the planning at the last minute to use the crane and complete the project to a faster schedule.”
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