Integrity of welded joints

The integrity of welded joints is of prime importance from many viewpoints, not least of which are the safety and economy of plant operation. A previous IMechE seminar discussing high temperature welds indicated that welded joints in pressure vessels are the least tractable in terms of design. Progress since then has been minimal. This is particularly true for power generating and petrochemical industries in which welded vessels are subjected to aggressive environments and loading whilst being expected to sustain economic lifetimes beyond 30 or more years. In these cases the vessels are often subjected to temperatures within the creep range causing internal cavities to be generated which can be life limiting at fractions of the design lives. The welded joints at nozzle intersections in these cases are clearly limiting factors in the overall success – both legal and economical – of the industries concerned.