Narrow gap welding of heavy gauge steel nuclear components

Abstract

Heavy gauge steels can be welded by conventional methods or by special ‘narrow gap’ welding techniques, used particularly in the primary circuits of PWR nuclear power stations.

The advantages of narrow gap welding lie not only in terms of cost, but also in considerations of a metallurgical and mechanical nature, while the drawbacks are all related to the operational difficulties of obtaining good fusion on the sides of the groove.

After looking at the characteristics of various welding processes and techniques, a description is given of a new submerged-arc narrow gap welding system, having a fixed head with two tandem wires. The simple design of the head ensures excellent operating reliability, while the tandem technique improves both the productivity of the system and the metallurgical quality of the joints.

Finally, an orbital TIG narrow gap welding process is illustrated, designed for the site welding of heavy gauge pipes in nuclear power stations.