ASSESMENT OF INTEGRITY OF THE WELDED PIPES

Abstract

The subject of work includes an analysis of integrity of the welded pipes made of steel API J55 of the high frequency contact welding (HF). Experimental testings of the mechanical properties of the based materials are performed on tubes removed from exploitation after 70 000 hours of work. The impact of damage type of the surface of crack on the integrity of pipe is tested by hydrostatically pressure of tube with an axial surface crack in the base material. The behaviour of fracture was tested using a modified compact testing tubes on tightening (CT), with an initial crack in the base material, welded joint and heat affected zone (HAZ). The critical value of the stress intensity factor CIc is determined on the basis of the critical value of J integral of the JIc. In addition to the experimental research, based on the obtained values for Cr and Sr using the fracture analysis diagram (FAD) is carried out an assessment of the integrity of welded pipes with an axial surface crack on the outer surface.

Keywords

• axialsurfacecrack
• highfrequencycontactwelding
• fractureanalysisdiagram(FAD).