Xiaoying Tang

Application of Visual Beam Ultrasonic Phased Array in Inspection of Weld in Tubular Node

Responding to complexity and particularity welding on the geometry of TKY tubular node, this paper constructs mathematical model of tubular joint weld of arbitrary section by simplifying the geometry structure, and draws welded joints and ultrasonic sound beam lines based on the actual specifications in order to solve the problems of low efficiency, positioning difficulty, missing inspection and etc. The computeraided simulation technology can realize the visualization in the beam coverage model of welded joints, which can commendably guide the design of ultrasonic phased array inspection and overcome the blindness of the instrument detection parameters, thus improving the effectiveness and pertinence of the actual detection. Study shows that it is beneficial to enhance the effectiveness of the detection tubular joint weld by employment of Visual beam and ultrasonic phased array technology.Copyright

Failure Analysis of Expansion Bellows Serving in Steam Pipe Network

The failure of Type 316L stainless steel expansion bellows serving in steam pipe network has been analyzed. The expansion bellows cracked after approximately 4-year service in steam network at 230°C. The caustic stress corrosion cracking (caustic-SCC) resulting from a combined function of caustic concentrating, metal temperature and residual stress was responsible for the failure. Cracking initiated on the inside surface of the bellow at the peak where served as stress raiser by observation of sample taken from failed expansion bellows. The pattern of cracking was shown as a spider web of several small cracks in photomicrographs. The metallographic examination also indicated that cracks were predominantly transgranular. The oxides on the surface of cracks can be confirmed to be caustic NaOH through X-ray diffraction (XRD) examination.© 2013 ASME

Application of Torsional Mode of Ultrasonic Guided Wave in Pressure Pipeline

Ultrasonic guided wave technology is presented as a new non-destructive pipeline inspection method for its rapid, long distance inspection and applied to special pipelines which are inaccessible by other conventional NDT methods. It can be widely used in the field of long range pipeline inspection. Dispersion and attenuation characteristics of torsional modes of ultrasonic guided wave in pipeline are presented. Propagation characteristics of T (0, 1) mode at different frequencies are studied. T (0, 1) mode excited by utilizing the magnetostrictive ultrasonic guided wave detection system is applied to detect the defects of pipeline. It can be concluded that the surface condition of the pipeline, the T (0, 1) mode excitation of different patterns and frequency have great effects on defect detection and the distance of guided wave propagation. Multiple factors should be considered to select the optimal frequency and excitation patterns as pipeline inspection in field.Copyright

Fracture Failure Analysis of 304 Stainless Steel Bolt in Chemical Plant Onshore

This paper presented the fracture failure analysis of 304 stainless steel bolt that was in service in an onshore pipeline with medium pressure, normal temperature and non-corrosive. The fracture of the bolts was not due to obvious plastic deformation. Based on the scanning-electron microscope (SEM) findings, a lot of carbide distributed in boundary of the grains, which was primary Cr-carbide. All cracks were indicative of intercrystalline fracture. The corrosive element of chloride was above allowed standard as detected in fracture surface by energy-dispersive spectrometer (EDS). In addition, the analysis showed that some lath martensite formed since the bolt was fabricated by cold-drawing, which made it be more sensitive to SCC. Given all that, one conclusion was drawn that the failure cause of the stainless steel bolt was attributed to intergranular stress corrosion cracking (IGSCC).Copyright

Practical Application of RBI and Experiential Analysis to Sulfur Recovery Unit Inspection

According to the management and scheduled inspection of pressure vessels and piping in sulfur recovery unit, it described the evaluation of the failure probability and consequences of pressure vessels and piping by the Risk Based Inspection (RBI). This article focuses on the practical application process of RBI to the Sulfur Recovery Unit. Together with the production crafts and loop medium in pressure vessels and pipes, we could dig out high risk equipment and its’ reasons, therefore, suggest possible precautions. Further precautions will be provided for equipment manufacturers to assure production safety through personal experiential analysis and comparison with the similar product from the aspect of failure mechanism and position. It is aimed to explore the combined method of RBI and personal experiential analysis and it’s practical application.© 2011 ASME