Flaw evaluation of Japanese carbon steel piping by load curve approach

New simplified flaw evaluation method, 'load curve approach' was developed to evaluate the fracture load of circumferentially surface-cracked pipe. This approach has the same functions with the current two-criteria approach. Fracture stress and fracture criteria are easily estimated by two load curves based on elastic-plastic fracture mechanics and plastic collapse. Fracture analysis was conducted for Japanese carbon steel piping using this approach. The approach showed the dependency of flaw geometry and pipe diameter on pipe fracture. Z-factors were calculated from this approach and compared with Z-factors by ASME Boiler and Pressure Vessel Code, Section XI (ASME-XI) and Japanese Code. It is shown that Z-factors by the load curve approach can improve the conservativeness in the estimation of pipe fracture load