Abstracts:This paper presents the failure analysis of carbon steel roller shaft of continuous pad steam machine used in textile industry. The fracture position was located at a stepped diameter. The failed component was the shaft made of carbon steel AISI 1040. Standard procedure for failure analysis was employed in this investigation. Visual examination, chemical analysis, hardness and tensile strength measurements, microstructural characterization, fractography analysis by Scanning Electron Microscopy (SEM) and Finite Element Analysis (FEA) were used for the failure analysis. Using this failure analysis approach, we pinpointed the root cause of failure and developed a means of solving this type of failure in the future. Firstly, the chemical composition of the shaft is done by an Optical Emission Spectroscopy (OES) method, the found chemical composition was matching with required standard value. Mechanical testing consists of two test i.e. tensile test and hardness test and it was found out that the strength and hardness of specimens were within the required capacity. For metallurgical analysis, the microstructure of the shaft was developed by using an optical microstructure. Equal distribution of ferrite perlite shows that heat treatment was performed well and carbon percentage in a material is satisfying the standard values. Thus, it proves that the material used was of good quality and indicates that failure is not due to material property. Further for the fractography, the fractured surface was examined by SEM. The cross-section was taken in a quarter segments and divided into four regions i.e. A, B, C, and D. Fractography morphology mainly showed that the failure of roller shaft was caused due to fatigue. To examine the stress distribution at the fractured surface the Finite Element Method (FEM) was also carried out. Based on the shaft size, a precise ANSYS model was developed. The result of FEM shows that stress concentration was significant at roller shaft step which could reduce the material reliability to some extent. Based on the failure analysis it could be concluded that due to stress concentration a micro crack is initiated along the weak interface and further it converted into the major fatigue failure. Fractography morphology of failed roller shaft also confirms the fatigue failure.

Abstracts:This paper relates to an upgraded Industrial tracked vehicle which was found with a failed Balance arm during disassembly. The failure analysis of an actual Balance Arms surface was carried out using Fractography and Non Destructive testing techniques to dig out the root cause. The analysis revealed microscopic signatures categorically pointing towards post failure surface mechanical damage. The factor causing to promote failure was improper manufacturing i.e. casting which was further attributed to MnS inclusions.

Abstracts:Rolling bearing is an important and fragile component in the wind turbine transmission system. The failure of rolling bearing is one of the highest risk events which may result in unexpected economic loss. To give a proper condition assessment of rolling bearing, especially for early fault detection, is of great importance and become an urgent issue to the wind energy industry. In this paper, sample entropy is studied through the field data of wind turbine transmission system measured from Lu Nan Wind Farm in China. Compared with several frequently used statistical indicators, sample entropy features advantages in detecting and evaluating the progress of the early faults of the rolling bearing. The studies show that the sample entropy is an effective and practical tool for condition monitoring of rolling bearing for a wind turbine transmission system.

Abstracts:Amine exchangers are widely used in gas sweetening plants for amine solution regeneration process. This study is investigates cracking and leakage of a 304 type stainless steel plate in an amine exchanger unit, used between absorption and stripper towers. In this regard, micro and macro examinations were performed on the plate, and solution was analyzed. Micro cracks were observed on both sides of the plate, especially under the gasket region of the plate. Results showed that the main reason of cracking was intergranular corrosion accompanied by stress. High concentration of Formate in amine solution, and also high level of stress under gasket region, had initiated the intergranular corrosion and cracking.

Abstracts:In recent years, there has been a rise in the number of product liability cases involving the failure of toilet water supply line acetal plastic nuts. These nuts can fail in service, causing water leaks that result in significant property and financial losses. This study examines three possible failure modes of acetal plastic toilet water supply nuts. The three failure modes tested were all due to over load failure of the acetal nut and are as follows: (1) Overtightening of the supply line acetal nut, (2) Supply line lateral pull and, (3) Embrittled supply line lateral pull. Additionally, a “hand-tight” torque survey was conducted. The fracture surfaces and characteristics of these failure tests were examined with Stereo Microscopy and Scanning Electron Microscopy (SEM). The failure modes were compared and contrasted to provide guidance in determination of cause in these investigations.

Abstracts:Failure of a pipe elbow used in geothermal production facility was reported to occur after 2 months in service. A leak was found to form at the bottom of elbow of horizontal pipe. The main cause of failure was investigated through conducting standard failure analysis including visual examination, chemical analysis, mechanical characterization, metallurgical examinations using optical microscopy in combination with scanning electron microscopy (SEM) equipped with energy dispersive X-ray (EDX) analysis and corrosion test using a three-electrode potential technique. Results of this investigation indicated that the failure of elbow was caused by an erosion-corrosion with the presence of wall thinning in leak area. The failure mechanism was discussed in this paper.

Abstracts:Gas turbines casings are susceptible to cracking at the edge of eccentric pin hole, which is the most likely position for crack initiation and propagation. This paper describes the improvement of transient thermal fatigue crack propagation life of gas turbines casings through the application of additional holes. The crack position and direction was determined using non-destructive tests. A series of finite element patterns were developed and tested in ASTM-A395 elastic perfectly-plastic ductile cast iron. The effect of arrangement of additional holes on transient thermal fatigue behavior of gas turbines casings containing hole edge cracks was investigated. ABAQUS finite element package and Zencrack fracture mechanics code were used for modeling. The effect of the reduction of transient thermal stress distribution around the eccentric pin hole on the transient thermal fatigue crack propagation life of the gas turbines casings was discussed. The result shows that transient thermal fatigue crack propagation life could be extended by applying additional holes of larger diameter and decreased by increasing the vertical distance, angle, and distance between the eccentric pin hole and the additional holes. The results from the numerical predictions were compared with experimental data.

Abstracts:In this study failure of AISI 347 stabilized stainless steel pipe after 60,000 of working in a petrochemical plant was investigated. Result showed that the main cause of failure was thermal stress fatigue. Fatigue cracks were formed at the outer surface of the investigated pipe, and were grown towards the inner surface at the fusion line of welded area. The formation of chromium-rich phases together with thermal fatigue stresses were found to be main causes of failure.

Abstracts:The reasons for the failure of a buried pipeline perforated during construction were investigated by a chemical composition analysis; a metallographic test; macromorphology observation; characterization of the corrosion products by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction; field medium characterization; and an analysis of the working conditions. The results revealed that the material composition and organization of the steel pipe conformed to API Specification 5CT. However, the reason for the perforation of the L415 steel pipe was an ultrahigh growth rate of pitting corrosion, as high as 14mm per year. We confirmed that the synergistic effect of a high partial pressure of oxygen introduced by an improper packing process and concentrated Cl⁻ in the corrosion product layer, which originated from groundwater with a high salt concentration that was used for the water pressure test, were responsible for the failure process.

Abstracts:In mineral processing industries vibrating screens operate under high structural loading and continuous vibrations. In this regard, this may result in high strain rates, which may often lead to structural failure or damage to the screen. In order to lessen the possibility of failure occurring, theories and techniques for analyzing machine structures are investigated and applied to perform a sensitivity study of a newly developed vibrating screen. Structural strength and stability of a vibrating screen is essential to insure that failure doesn’t occur during production. In this paper a finite element analysis (FEA) on a reconfigurable vibrating screen (RVS) is carried out to determine whether the structure will perform as desired under extreme working conditions at the different configurations of 305mm×610mm, 305mm×1220mm and 610mm×1220mm. This process is aimed at eliminating unplanned shutdowns and minimizes maintenance cost of the equipment. Each component of a screen structure is analyzed separately, stress and displacement parameters are determined based on dynamic analysis. In addition, a modal analysis was carried out for the first three (3) modes at frequency f of 18.756Hz, 32.676Hz and 39.619Hz respectively. The results from the analysis showed weak points on the side plates of screen structure. Further improvements were incorporated to effectively optimize the RVS structure after undergoing an industrial investigation of similar machines.