Abrasive Cutting of Mooring Piles

During the summer of 2007, Proserv Offshore Scandinavia performed the removal of FPSO mooring piles on the Volve field in the North Sea. End client was Statoil and Subsea contractor was Deep Ocean.

Data

• Water depth: approx. 100m
• Number of piles to be cut: 9
• Pile size: 72"
• Wall thickness: 80 mm
• Cutting length: approx. 3,000 mm
• All piles were cut from the inside of the pile at 1 m below seabed.
• Weight of each piece after cut: 10 tons

Proserv Offshore designed and engineered a specially combined tool to both cut and lift the piles. The tool was manufactured locally and assembled at Proserv Offshore's yard in Risavika. All testing was also performed in-house.

The tool built had the following data

• Type of cutting method: Abrasive water jet cutting
• Pressure: 2,000 bar
• Flow: 35 l/min
• Cutting speed: 30 mm/min
• Lifting capacity: 50 tons
• Safety mechanisms: To release the tool in case of stuck or incomplete cut
• The operation could be monitored by camera and acoustic signals and a software package was developed.

The job was a success and all 9 piles were recovered.

 Onshore Test

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