Mammoet has unveiled a new jacking and cradle system for XXL offshore wind turbine foundations to minimise upgrades to grillage and sand bunds, helping customers to reduce costs.
Monopiles currently weigh in excess of 3000 tonnes and be over 120 metres long, and as developers build taller turbines, their foundations are getting larger in diameter and also longer – moving beyond the capabilities of existing handling equipment. This makes their and storage on site more challenging.
Also, when an XXL monopile is lifted, its self-weight causes big deformations. This means monopiles need to be raised higher than their supports to be loaded or unloaded.
Mammoet’s new jacking and cradle system adds 60cm of additional stroke over and above the standard SPMT systems, allowing customers to continue using existing support structures as monopiles grow.
The technology will also allow other links in the supply chain to reduce project costs said the company.
As offshore wind projects become more globalized, monopiles are travelling further distances. So, Heavy Transport Vessels need to have larger sea fastening to support monopiles during voyages.
Because of this, there is less clearance when loading and unloading large monopiles using SPMTs. Mammoet’s new jacking and cradle system can lift monopiles higher, allowing more sea transports to take place using existing support structures.
The system comprises two elements: jacking spacers that sit between SPMT modules to generate greater stroke, and hydraulic, foldable saddles that cradle the monopile so it can be supported at higher points, to prevent excessive ovalisation.
Each jacking spacer has a capacity of 430 tonnes split across two towers – with multiple units in use per transport configuration. The system slots between SPMT modules, so transport configurations maintain the same minimum ride height. This enables grillages and sand bunds to remain as low as possible, again saving on costs.
Each monopile saddle has a capacity of 1000 tonnes and can handle monopiles up to 12 metres diameter. By using the system, Mammoet customers can maintain the existing methods of supporting and moving monopiles, even as they grow from 8m to 10m diameter, and beyond the company said. This reduces project costs right through the fabrication, shipping and storage supply chains.