This paper presents a new approach based on the method of magnetic flux leakage (MFL) for the double-sided butt weld (DSBW) of the welding equipment such as the pressure vessel in order to detect and identify the weld defect. In this approach, a new magnetization structure is adopted whose magnetization direction is perpendicular to weld line, also, a new continuous non-contact scanning method is used, what aims to solve the problems about complex leakage magnetic field (LMF) space distribution. Then, the LMF distribution laws with non-defect (ND) and laws with precrack from heat affected zone (PFHAZ) are obtained through using these methods such as theoretical analysis, numerical simulation, and experimental study. Afterwards, this paper reviews the recognition analysis of the above-mentioned two kinds of state (ND and PFHAZ) by binding the contrastive curves. The outcomes indicate that the suggested method of MFL has realized the recognition of ND and PFHAZ; The numerical simulation results and experimental results match each other well and their correlation coefficient R is 0.9729. Furthermore, the results verify the feasibility and the validity for the suggested method. This is a new way for exploration detection of the double-sided butt weld.

In order to quantitatively identify critical hidden damage for weld joints by using the metal magnetic memory technology (MMM), the modified maximum likelihood estimation MMM model is first proposed. The experimental materials are Q235B welded plate specimens. Fatigue tension experiments were operated to find the MMM feature laws of critical hidden damage by comparing with synchronous X-ray detection results. Four MMM characteristic parameters, that is, ΔHp(y) , Kymax , mmax and S(K), are extracted corresponding to the normal state and the hidden damage state, respectively. The probability density values of ΔHp(y) , Kymax , mmax and S(K)are calculated by the optimized bandwidth kernel density estimation. The quantitative maximum likelihood estimation MMM model is established based on optimized bandwidth kernel density. The verification result shows the maximum likelihood value of hidden damage state is twice as much as that of the normal state, which is consistent with the practical results. This provides a new method for quantitative MMM identification of weld critical hidden damages.

In this paper, The tesile damage process of the blowout preventor shell material ZG25GrNiMo was researched using acoustic emission technique. Analyzed the acoustic emission characteristics in different damage phases of this material using parameter analysis and waveform analysis. The result indicated that the acoustic emission characteristics are different in yielding, plastic deformation and rupture process. The differences of frequency spectrums of different damage modes are evident.

Using acoustic emission (AE) technique, test the blowout preventer (BOP) shell with a crack in the pressing process. Firstly, cut a notch of 100mm long and 5mm wide on a BOP shell and weld partly, then pressurized by pneumatic pumps. Test the BOP shell during the crack propagation by AE. The result showed that the AE technique can reflect the activities of the defects timely and effectively, and the destroy situation of the blowout preventer shell in the process of pressured and the location was accurate.

EST use the uniform weights to evaluate the pipeline, making the evaluation results do not truly reflect the risk profile of pipeline, so base on the EST , introduce the entropy theory to improve it. Determine the weight factors of every risk factor by calculating the entropy value of every accident factor, clear out the influence of various factors on the pipeline, make risk scoring methods can be more reasonable, accurately reflect the risk of pipeline case. At last, north line pipeline are evaluated by applying the improving method.