Steel reuse for offshore wind farm
Project summary: Subsea cable ducts for offshore windfarm
Location: Wick, Scotland
Key information
Project type: Industrial
Size: 136 tonnes
Completion: June 2021
Stakeholders involved:
- LMR Drilling (client)
- Cleveland Steel and Tubes (steel stockholder and reclaimed steel supplier)
Project description
- Offshore wind farm required 3 cable ducts to be drilled under the seafloor, and then cables inserted to bring power back to land. Tubes required a spigot style joint to allow 12m lengths to be pushed together and then welded before being fed down the hole behind the drill.
Key drivers for steel reuse
Price and availability.
Amount of steel reused
136 tonnes
Embodied carbon savings
274 tonnes
Business considerations
Reclaimed steel procurement route: Steel was bought as waste/surplus from a mill and also from a stockist left with a project surplus. No other players were interested in this inventory due to plastic and paint coatings.
The information available on reclaimed steel: Material was new quality but was overrun and short lengths from a production run. All major gas projects over-order material and this surplus is usually scrapped as there is no specific demand for these materials within a commercial timeframe for onward new use.
Quality of reclaimed steel, testing and certification: The material was independently tested in batches as it had no original test certificates.
Warranty issues:No warranty issues have occurred.
Cost of reclaimed steel versus new steel: Reused steel represented approximately a 20% discount versus new steel.
Economical implications of steel reuse: Money saved from new procurement route.
Implication of steel reuse on project timelines: Reused material was available from stock so the work could begin immediately. The mill lead times were 12-20 weeks at the time due to COVID impacts.
Lessons learned, challenges and critical success factors
- The project was very successful and did not encounter any significant obstacles. However, further projects may be challenged by the availability of sufficient pipes of the same diameter and thickness for considerable lengths of duct runs.
- If ducts could be made from multiple thicknesses, then more could be achieved. The current design is inflexible, and carbon emissions are not taken into account during procurement.
- Accounting for carbon emissions could potentially enhance the success of this work.
This case was compiled based on an interview with Cleveland Steel and Tubes, as part of the DISRUPT project (Delivering Innovative Steel ReUse ProjecT).