ESAB GROUP CHOSEN BY CONSAFE FOR SUCTION ANCHOR FABRICATION
The Burntisland, Fife based company has recently completed a major contract for Burlington Resources (Irish Sea) Limited to supply an unmanned gas platform for the Millom West Field, which required the platform to be fitted with large diameter suction anchors.
The suction anchors are attached to the legs of the platform and consist of 7 metre diameter tubes, 14 metres long, that are driven into the sea bed. Through the action of suction, the sea bed is effectively pulled into the anchor thereby securing the platform.
Being the largest tubes ever fabricated by Consafe, each anchor was constructed from three 7 metre diameter sections using 35mm thick structural steel Grade 355EM and welded using the GSFCAW process. These three cans were then joined together form the completed anchor using the submerged arc process.
ESAB supplied welding consumables for the project that involved the high productivity processes of submerged-arc, and gas shielded flux cored arc welding, as well as manual metal arc welding. OK Autrod 13.24 and OK Flux 10.62 were used for the submerged arc welding process. These two products are particularly suitable for off-shore applications where good impact properties are required at sub-zero temperatures.
With the added pressure of a six week deadline, it was essential that the GSFCAW wire selected had a good track record in the offshore industry. Murex Corofil R59 Ni was selected on the basis, coupled with its consistent performance, welder appeal and excellent mechanical properties. For the SMAW process, Consafe chose Filarc 76S and to ensure the lowest hydrogen levels, the product was supplied in Vac-Pac.
Steel sections up to 95mm thick were used in the construction of the anchors, with both 355 and 450 grade structural steels being utilised. Stringent CTOD (Crack Tip Opening Displacement) testing was a requirement for the heavy section flux cored wire.
A quick turnaround was required for the suction anchor fabrication. The company worked 24 hours a day, 7 days a week, to complete the order, so it was important that the right welding consumables were selected, stated Mr Allan MacFarlane, Welding Engineer at Consafe. "Using the ESAB consumables meant we were basically using familiar products that we knew we could rely on, and would give us the results we were looking for. We always get good service from ESAB, and because of the large volume of consumables required (16 tonnes of cored wire alone) reliable products and supply routes were paramount. They give sound technical back-up and they are always available to discuss and resolve any issues that arise."