This article describes 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 inch to 24inch and thickness10 mm to 15 mm. The metallurgical 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 succesfully 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. From the results of this development, one can conclude that in the area of process and operations, the laser beam welding process can produce satisfactory orbital single run welds in line pipe steel of mid thickness range 10 - 15 min; the welding process associated with sensors to enlarge the acceptable tolerance can be operated in a full automated welding cycle on industrial line pipes; with the use of classic industrial features for the integration, the system is not so sensitive. It can be operated in difficult situation and surroundings such as an offshore lay barge, and become a reliable tool for all position 5G welding encountered in S-lay operation; the compliance of welded joints with standard requirements of pipeline construction is achieved on industrial line pipe provided that the line pipe type and quality are coherent with the targeted applications.