Papers by Keyword: Failure Analysis

Abstract: In this paper, the physical and chemical analysis method was used to analyze the leakage of a regeneration gas heater device accident. The result shows that this device was heated seriously at local area, and oxidized severely. The carbon content around the leakage is obviously lower than the limit of standard, and the grain deformation at crack tip of the leakage is obvious.It shows that reason of device failure is caused by typical plastic Instability, and low carbon content leads to insufficient mechanical properties at high temperature. According to data from manufacturer, the unreasonable arrangement of thermo-couples may be the root cause of this leakage.It can be considered that replace the higher grade materials conservatively, while optimizing the arrangement of thermo-couples.

Abstract: A spring is a component which is designed to have relatively low stiffness compared to normal rigid rods, thereby making it possible to accept certain forces that are charged. A leaf spring is an important suspension component for heavy vehicles, as a failure of the leaf spring can cause severe if not fatal accidents. This study aims to investigate the factors that cause leaf spring failure in the form of a 125 PS dump truck vehicle suspension system. The method employed incorporated experimental and finite element analyses. The experimental work included visual observations, observation using a scanning electron microscope (SEM), hardness testing, and microstructure testing. Leaf spring modelling was conducted using Autodesk Inventor 2017 software, and the finite element analysis (FEA) was performed using Siemens ™ FEMAP V12.0.1 application software to calculate the maximum stress and strain that occurred near the crack tip of the leaf spring. The results from the analysis indicated that the cause of the fracture that occurred in leaf spring No. 3 was due to a defect discovered on the surface of the leaf spring. Based on the observations of the fracture surface, it is revealed that the cause of failure was due to the cyclic load experienced by the components during operation which caused crack propagation beginning from micro-cracks until reaching a significant dimension to cause a final fracture. In addition, the overload imposed on the leaf springs also caused maximum stress on the springs to increase, thus accelerating the failure of the leaf springs. Further results also showed that the value of the stress intensity factor, K_I = 29.15 MPa.m^1/2 was greater than the value of fracture toughness, K_IC = 23 MPa.m^1/2 of the spring material.

Abstract: The screw press is a type of machine press used for extracting crude palm oil from the oil palm’s mesocarp, where its short driveshaft, a mechanical component for transmitting torque and rotation, is often found to be susceptible to failure. Since the initial damage to the short driveshafts in the shaft keyway area is associated with the frequent incidence of shaft failure, this research aimed to discover the root cause of this failure and how to prevent it using visual inspection and stress analysis methods as well as those of the fractography, metallography, chemical composition, and hardness tests. Using the descriptive method to analyse the collected data, the visual inspection and the fractography results of the research indicated that the fatigue crack failure of the short drive shaft in the palm oil screw press machine was caused by the fatigue crack initiation that was safe from stress concentration in its keyway areas. This crack initiation was followed by crack propagation as indicated in beach mark forms. Finally, the ductile fracture observed on the shaft surface was found to have resulted from the continuous rotational motion and the loading and unloading effect of the central shaft driving system.

Abstract: In the process of layer inspection and hole mending, it was found that the corrosion of tubing in a well was serious, and perforation and fracture occurred. Part of the tubing was found to be cracked from the failed pipe samples, and relatively serious pitting corrosion pits were found on the surface of the outer wall. The fracture morphology and corrosion products were analyzed by means of macroscopic analysis and metallographic microscope, SEM and EDS. The result show that the mechanical damage of the outer wall of the tubing was the primary condition for accelerating corrosion, and the severe corrosion thinning of the inner and outer walls of the tubing was the main reason for the failure of the tubing string. The corrosion perforation of tubing was mainly caused by internal corrosion.

Abstract: The leakage accident of corrosion perforation occurred in the L245 oil pipeline. After pipe replacement,the defects were analyzed by means of macro analysis, corrosion product analysis, medium composition analysis, chemical composition analysis, mechanical property test and SEM. The results showed that the corrosion perforation was caused by local corrosion, and the synergistic effect of HCO₃^- and Cl^- in transportation medium was the main cause of local corrosion.

Abstract: This paper gives a thorough investigation on the fracture failure of the blowout preventer (BOP) ram. Through appearance inspection, magnetic powder inspection, physicochemical inspection, metallographic inspection and scanning electron microscope (SEM), the main fracture reason of the BOP ram is that there was some original cracks in the BOP ram before fracture, during the service process the bop ram is subjected to impact load, therefore brittle fracture occurs due to the high brittleness of the gate material (which is caused by large internal structure) and low anti-crack propagation ability. Key words: Blowout preventer (BOP) ram; Fatigue break; Brittle fracture; Failure analysis

Abstract: The material of the tubes has suffered localized overheating and corrosion, probably as a result of local heat flux impingement phenomenon, combined with high temperature corrosion. Boiler tubes that experienced failure indications were tubes material SA 213 T22 with the dominant alloy elements is Cr. Materials with these specifications are which should be resistant to corrosion, so it is necessary to carry out laboratory testing to answer suspected indications of failure. The methodology of analysis and identification carried out is by observing the microstructure in 3 dimensions supported by other mechanical tests, namely visual observation, hardness testing, chemical composition testing using SEM and EDAX and testing the chemical composition of the material using a spectrum analyzer. Observation using an optical microscope shows that the microstructure condition of the tube is ferritic and the results of 3D metallography observations show that the tube has undergone micro crack with a measured depth of 1853,28 μm. After the metallography testing is carried out, the hardness test is carried out with the hardness vickers (HV) unit and the minimum hardness is 149 HV and the maximum hardness is 177 HV. Testing of the chemical composition of the deposit showed that there were chemical elements found in seawater that trigger corrosion such as sodium and chlorine which enter the water vapor system. The results showed that the tube had pitting corrosion, which was indicated by the presence of microcrack at the grain boundaries and an oxide deposit had been formed which would cause an overheating phenomenon and deterioration.

Abstract: Owing to low cost, excellent pressure and corrosion resistance, bimetallic lined pipes were regarded as one of the most important methods to resolve corrosion of traditional steel pipes used for oilfield. Nowadays, the pipes are widely used in the projects of oil and gas gathering and transportation. However, there were some failure cases in succession in recent years. In this paper, the failure causes were excavated from multiple perspectives, and on this basis further countermeasures were put forward. Firstly, three typical failure accidents, including CRA layer collapse, CRA layer corrosion and weld joint failure, were listed throughout the whole life cycle from product ordering, construction technology to later operation. Secondly, failure analysis was carried out from five aspects: product quality, test technology, welding process, standard specification and application threshold, and a serial of comprehensive views were proposed. 1) Manufacturing period: Water seepage and tightness between CRA layer and backing pipe could not be effectively monitored. The ratio of collapse test was low so that proposed relevant risk could not be eliminated; 2) Welding period: the process has high risk failure in theory and lack of process assessment and construction acceptance standards. Potential danger could not be effectively assessed, and weld quality could not be guaranteed; 3) Application period: The CRA application range remained unclear, and bimetallic lined pipes were used in the environment beyond the threshold sometimes. The paper also summarized further improvement measures and research directions about these five aspects, including process quality, inspect technique, welding process, standard specification and application range. Finally, solution suggestions were proposed for the whole chain from manufacturers, testing institutions, construction units to oilfield users.

Abstract: This paper provides a thorough investigation on the leakage reason of the ERW steel pipeline in an oil field. Through appearance inspection, physicochemical inspection, metallographic inspection and scanning electron microscope (SEM), it was found that the main reason of corrosions was caused by residual liquid at the bottom of the pipeline and O₂ and CO₂ in the air pressure test. The corrosion medium was large volume of O₂ and CO₂ forming continuously saturated corrosive aqueous solution in small volume of residual liquid, and the corrosion type was the under-deposit corrosion. It is recommended to conduct hot air purging on the pipelined before pressure test for building pipelines in the future, and if the pipeline is not put into use in time, it is recommended to use nitrogen to maintain pressure.

Abstract: The reason for perforation leakage of gathering pipeline in an oilfield was investigated by size measurement, mechanical properties, metallographic structure, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrum (EDS). The results showed that the failure form of the spirally submerged arc welded pipe (SAW) was the corrosion perforation caused by local corrosion. The main cause of corrosion perforation was due to the existence of chlorine ion, H₂O and O₂ in the pipeline transportation medium. A large cathode and small anode electrode corrosion formed in the pipe marking area and the base metal, which eventually led to the perforation of the steel pipe.