Laser orbital welding applied to offshore pipe line construction

摘要

The capabilities of CO2 laser beam welding (LBW) are established and recognised in applications where small thicknesses have to be high speed welded. The recent availability of compact CO2 laser with power up to 20 kW permits nowadays to take advantage of LBW (high production rate, full automation) in other fields of application where higher wall thickness are required. The application developped by BOUYGUES OFFSHORE is related to offshore welding of pipeline where it is demonstrated that LBW is applicable in orbital 5G welding position and may be integrated in the difficult environment of a lay barge. This article describe the experimental program implemented by BOUYGUES OFFSHORE to develop the CO2 laser beam welding process and to dispose of an equipment applicable on barge for pipeline orbital welding. The welding process development was conducted on pipe diameter 10" to 24" and thickness 10mm to 15mm. The metallurgicla weldability was studied and characterised through an R&D project sponsored by E.C (THERMIE OG 153.97) carried out with two major line pipe suppliers (EUROPIPE and VALLOUREC-MANNESMANN). The experimentations were successfully conducted on various steel grades covering X52 to X65 grade for sour and sweet service applications from TMCP steel pipes and quenched and tempered seamless pipe. A prototype of orbital LBW machine applicable for S-lay was constructed and integrated in a lay barge and tested offshore.