The Study Of Safety Assessment Engineering Method Of The Pressure Piping Containing LOP Defect

Lack of penetration (LOP) is one of the main defects in piping. It is necessary to study the safety assessment engineering method of LOP not only in academic research but also in practice engineering. Aiming at the LOP, which has often occurred in in-service industrial piping, all kinds of safety assessment engineering methods have been studied according to the request of the research project which sponsored by the Natural Science Foundation of Jiangxi province. On the basis of the study, the some new method of safety assessment for piping containing LOP defects, in which the geometric and material property of defects were included, were established through analyzing, calculating and comparing methods in this dissertation. The main achievements are as follows:1. Some safety assessment methods, which can be used in safety assessment in piping containing LOP defect in world, were summarized and the failure assessment diagram (FAD) method and engineering simplified gene method were suggested to be use in the safety assessment of the piping containing LOP defect through some analysis and comparing.2. It is well known that R6-Rev.3 op.1 all-purpose failure assessment curve (FAC) is more safety than R6-Rev.4 op.l all-purpose FAC, so it is suggested that, using R6-Rev.4 op.1 all-purpose FAC to assess the piping containing LOP defect when there have no special SINTAP leve 1 or level 2 FAC which aim at material (base material & weld material), otherwise using special SINTAP leve 1 or level 2 FAC to assess the piping containing LOP defect. It can reduce the conservation and ensure safety in assessment.3. The calculation method of the parameter K_r and L_r, which are needed in assessing the pressure piping containing LOP defect by the FAD, were established on the basis of present research achievements. It provided necessary conditions for assessing pressure piping containing LOP defect by using FAC.4. The all-purpose FAC series considering the dimension A(θ/π,a/t) of the LOP defect were established on the basis of the R6-Rev.4 op.l all-purpose FAC and op.2 FAC. Because they have included the dimension(θ/π,a/t) of the LOP defects, so they are more resonable and safer than R6-Rev.4 op.l all-purpose FAC, since the all-purpose FAC series established in this paper were based on R6-Rev.4 op.l all-purpose and op.2 FAC, and the original all-purpose FAC series were based on the R6-Rev.3 op.1 all-purpose and op.2 FAC.5. On the basis of the all-purpose FAC series establised in this paper, new U factor for engineering assessment method, which can be used in both the fracture assessment and plastic collapse assessment for piping containing circumferential lack of penetration, was developed. The reliability of the method was verified by the experiment data reported in famous short circumferential surface-crack pipe research project in USA. Comparing with the original U forctor method, it is indicated that the new U factor is reliable, and it is safer than the original U factor.6. In the process of study, it is found that there is a big neglect affecting the accuracy of...