Eisaku Hayashi

Welding residual stresses at the intersection of a small diameter pipe penetrating a thick plate

Abstract This paper investigates welding residual stresses at the juncture of a small diameter pipe penetrating a thick plate. The pipe is welded to the plate, and TIG cladding is melted on the inner surface of the pipe to protect it from stress corrosion cracking due to environmentally-induced changes in nuclear power plant components. Welding residual stresses are calculated by heat conduction and thermal elastoplastic analyses using an assumption of “simplified pass” to save the computing time, and are also measured by the strain-relief technique. Welding residual stresses after TIG cladding are shown to have no corrosive influence on the inner pipe surface, and the residual stresses are compressive enough to protect the pipe against stress corrosion cracking on the outer surface.

Guideline of Weld Overlay Repair Method for Primary Piping of Japanese Boiling Water Reactors

A private guideline of a weld overlay (WOL) repair method for SCC cracked Boiling Water Rector (BWR) primary piping was provided by Thermal and Nuclear Power Engineering Society of Japan. In the WOL method, the overlaid structure of SCC resistant 308L weld metal substitutes for cracked existing piping weldments as pressure boundary. The guideline prescribes the applicability, welding conditions and essential variables, weld overlay structural design, evaluation of welding effects to the piping system, in-process control, post-process examination, and procedures of pre-service and in-service inspection.Copyright

Generation of welding residual stress when a pipe penetrates a thick plate

Summary This paper describes a study of the welding residual stress at the intersection of a small‐diameter pipe penetrating a thick plate. The pipe is welded to the plate, and TIG cladding is deposited on its inside surface to protect it from stress corrosion cracking due to prolonged operation in a nuclear power plant. The residual stress is calculated by a heat conduction analysis and tensile elastic‐plastic analysis and also measured by strain gauges. The welding residual stress is shown to have no corrosive effect on the pipe inside surface, and the stress is sufficiently compressive to protect the pipe from stress corrosion cracking on its outside surface. The mechanism of residual stress generation during welding is also investigated.