Application of 40-year Coatings for Wind Turbine Structures

Background

Conventional organic coating systems are highly susceptible to mechanical damage in the splash and tidal zone of offshore structures. Maintenance of these coatings is prohibitively expensive (up to x10 original application costs) but is essential if the structure is to meet design life requirements. A recent project managed by TWI demonstrated the superior performance of thermal spray aluminium (TSA) coatings for splash and tidal zone locations. However, surface preparation and coating application remain labour intensive and the project aim is to provide partners with the knowhow required to set up a mechanised coating system for simple tubular structures such as monopiles and the sub-elements of a jacket structure.

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Project Deliverables

Individual work package reports detailing the effect of surface preparation and TSA coating parameters on productivity, efficiency, coating adhesion and cost for tubular structures.
Best practice guide for implementation of mechanised surface preparation and TSA coating for tubular structures.

Project Summary

The programme of work is relevant to tubular structures ranging from pipelines to jacket structures and monopiles. The final work plan will be completed during the first 3 months of the project but is it is proposed that parametric studies will determine the effects of surface preparation and TSA coating parameters on process productivity, efficiency and coating adhesion. Data generated will be used to develop cost analysis studies. Key data and conclusions will be used to produce a best practice guide covering implementation of mechanised surface preparation and TSA coating plus advice relating to health, safety and environmental issues and QA/QC during application.

Additional Project Information

Preliminary work

Capture end user coating requirements for jacket and pipeline fabrications.
Capture design requirements and implications for mechanised surface preparation and spraying.
Confirm surface preparation (grit blasting) and metal spraying equipment requirements.
Confirm manual metal spraying equipment requirements for field joint coating.

Effect of blasting parameters, productivity, process efficiency and surface profile

Inputs: abrasive type, size range and morphology; blast air pressure and flow rate; and blast nozzle design (size).
Responses: productivity (blast area rate), media consumption rate including recycling and surface profile.
Validation by mechanised blasting of trial components and benchmarking with manual blasting.

Effect of surface condition on coating adhesion

Effect of surface profile and chloride contamination on coating adhesion.
Effect of surface profile of weld joints on coating adhesion.
Manual arc spraying benchmarked with mechanised arc spraying.
The need for surface preparation for TSA to conform to Sa2.5 or Sa3.

Effect of spraying parameters on productivity, deposit efficiency and coating adhesion

Inputs: energy, stand-off distance, compressed air pressure, gun nozzle design, coating composition.
Responses: productivity, deposit efficiency and coating adhesion.
Effect of increasing spray gun throughput on responses.

Estimation of mechanised TSA costs benchmarked against manual TSA and organic paint systems

Cost analysis studies for tubular structures and jacket elements.
Benchmarking of mechanised and manual TSA against organic paint systems.

Best practice guide

Implementation of mechanised surface preparation and TSA coating.
Implications for surface preparation and coating application QA/QC.
TSA coating specification based on published offshore TSA performance and TWI project data.
Outcome of consultation on corrosion allowance with engineering design authorities or regulators.

For more information, please email contactus@twi.co.uk.

For more information please email:

contactus@twi.co.uk