A ring-type joint in a reactor pipeline for a hydrocracker unit had failed. Cracks were observed on the flange and the associated ring gasket during an inspection following a periodic shutdown of the unit. The components were manufactured from stabilized grades of austenitic stainless steel; the flange from type 321, and the ring gasket from 347. Examination revealed that the failure occurred by transgranular stress-corrosion cracking, initiated by the presence of polythionic acid. Detailed metallurgical investigation was subsequently conducted to identify what may have caused the formation of polythionic acid in the process gas.

A case of continual product refinement stimulated by product failures was described. Brittle fracture of gas transmission line pipe steels occurred demonstrating a poor combination of materials, environment, manufacturing and installation problems, and loads. Initial efforts were concentrated towards decreasing the Charpy ductile-to-brittle transition temperature to avoid brittle fracture. It was subsequently revealed that the absorbed energy on the upper shelf of the Charpy energy-temperature curve was critical for arresting a moving crack. Both fracture initiation and fracture propagation were needed be controlled. It was concluded that improved steel processing procedures, chiefly hot-working temperature and deformation control, were also required to optimize microstructure and properties.

Stainless steel bolts broke after short-term exposure in boiler feed-pump applications. Specifications required that the bolts be made of a 12% Cr high-strength steel with a composition conforming to that of AISI type 410 stainless steel. Several bolts from three different installations were examined. It was found that fracture of the bolts was by intergranular stress corrosion. A metallic copper-containing antiseizure compound on the bolts in a corrosive medium set up an electro-chemical cell that produced trenchlike fissures or pits for fracture initiation. Because the bolts were not subjected to cyclic loading, fatigue or corrosion fatigue was not possible. To prevent reoccurrence, bolts were required to conform to the specified chemical composition. The hardness range for the bolts was changed from 35 to 45 HRC to 18 to 24 HRC. Petroleum jelly was used as an antiseizure lubricant in place of the copper-containing compound. As a result of these changes, bolt life was increased to more than three years.

Several tin plated, low-alloy steel couplings designed to connect sections of 180 mm (7 in.) diam casing for application in a gas well fractured under normal operating conditions. The couplings were purchased to American Petroleum Institute (API) specifications for P-110 material. Chemical analysis and mechanical testing of the failed couplings showed that they had been manufactured to the API specification for Q-125, more stringent specification than P-110, and met all requirements of the application. Fractographic examination showed that the point of initiation was an embrittled region approximately 25 mm (1 in.) from the end of the coupling. The source of the embrittlement was determined to be hydrogen charging during tin plating. Changes in the plating process were recommended.

This article discusses the failure analysis of several steel transmission pipeline failures, describes the causes and characteristics of specific pipeline failure modes, and introduces pipeline failure prevention and integrity management practices and methodologies. In addition, it covers the use of transmission pipeline in North America, discusses the procedures in pipeline failure analysis investigation, and provides a brief background on the most commonly observed pipeline flaws and degradation mechanisms. A case study related to hydrogen cracking and a hard spot is also presented.

This article focuses on the mechanisms of microbiologically influenced corrosion as a basis for discussion on the diagnosis, management, and prevention of biological corrosion failures in piping, tanks, heat exchangers, and cooling towers. It begins with an overview of the scope of microbial activity and the corrosion process. Then, various mechanisms that influence corrosion in microorganisms are discussed. The focus is on the incremental activities needed to assess the role played by microorganisms, if any, in the overall scenario. The article presents a case study that illustrates opportunities to improve operating processes and procedures related to the management of system integrity. Industry experience with corrosion-resistant alloys of steel, copper, and aluminum is reviewed. The article ends with a discussion on monitoring and preventing microbiologically influenced corrosion failures.

A newly installed pipeline leaked during cleaning prior to hydrotest at a pressure of approximately 400 psig. The intended hydrotest pressure was 750 psig. The pipeline was constructed from spiral-welded API 5L-X65 HSLA steel and was intended for seawater injection. Analysis included nondestructive testing, metallography, and scanning electron microscopy. Based on the results, the failure was attributed to transit fatigue, caused during highway transportation. Cracks along the toes of the weld from both the outside and inside surfaces, the transgranular nature of cracking, and the presence of fatigue striations all supported transit fatigue as the damage mechanism.

Sucker-rod pumps are operating in very aggressive environments in oil well production. The combined effect of a corrosive environment and significant mechanical loads contribute to frequent cases of failure of the rod string during operation. Standards and recommendations have been developed to control and avoid those failures. This study presents various failure cases of sucker rods in different applications. The heat treatment of the steel material and the resulting microstructure are an important factor in the behavior of the sucker rod. A spheroidized microstructure presents a weaker resistance to corrosion affecting the rod life. Non-metallic inclusions are a pitting preferential site leading to fatigue crack initiation. Heterogeneous microstructure as banded martensite and ferrite/pearlite decreases the ductility of the material affecting the fatigue propagation resistance.

Nineteen out of 26 bolts in a multistage water pump corroded and cracked after a short time in a severe working environment containing saline water, CO 2 , and H 2 S. The failed bolts and intact nuts were to be made from a special type of stainless steel as per ASTM A 193 B8S and A 194. However, the investigation (which included visual, macroscopic, metallographic, SEM, and chemical analysis) showed that austenitic stainless steel and a nickel-base alloy were used instead. The unspecified materials are more prone to corrosion, particularly galvanic corrosion, which proved to be the primary failure mechanism in the areas of the bolts directly exposed to the working environment. Corrosion damage on surfaces facing away from the work environment was caused primarily by chloride stress-corrosion cracking, aided by loose fitting threads. Thread gaps constitute a crevice where an aggressive chemistry is allowed to develop and attack local surfaces.

An HK-40 alloy tubing weld in a reformer furnace of a petrochemical plant failed by leaking after a shorter time than that predicted by design specifications. Leaking occurred because of cracks that passed through the thickness of the weldment. Analysis of the cracked tubing indicated that the sulfur and phosphorus contents of the weld metal were higher than specified, the thickness was narrower at the weld, and the mechanical resistance of the weld metal was lower than specified. Cracking initiated at the weld root by coalescence of creep cavities. Propagation and expansion was aided by internal carburization. Quality control of welding procedures and filler metal was recommended.

The outer tube, or stem, on a bicycle frame fractured after two years of use. Detailed investigation revealed that the lower stem bearing had been loose for some time and the bottom bearing cup contained many cracks. Metallographic examination of the chromium-plated cup confirmed the brittle nature of the cracks, located along prior austenite boundaries. The failure was attributed to hydrogen embrittlement due to improper manufacturing procedures following chromium plating. The cracking led to looseness in the bearing and consequent scoring, cracking, and overloading of the stem.

This article describes the failure characteristics of high-pressure long-distance pipelines. It discusses the causes of pipeline failures and the procedures used to investigate them. The use of fracture mechanics in failure investigations and in developing remedial measures is also reviewed.

This article provides some new developments in elevated-temperature and life assessments. It is aimed at providing an overview of the damage mechanisms of concern, with a focus on creep, and the methodologies for design and in-service assessment of components operating at elevated temperatures. The article describes the stages of the creep curve, discusses processes involved in the extrapolation of creep data, and summarizes notable creep constitutive models and continuum damage mechanics models. It demonstrates the effects of stress relaxation and redistribution on the remaining life and discusses the Monkman-Grant relationship and multiaxiality. The article further provides information on high-temperature metallurgical changes and high-temperature hydrogen attack and the steps involved in the remaining-life prediction of high-temperature components. It presents case studies on heater tube creep testing and remaining-life assessment, and pressure vessel time-dependent stress analysis showing the effect of stress relaxation at hot spots.

A wire hoisting rope on a drilling rig failed during a lift, after a few cycles of operation, causing extensive damage to support structures. The failure investigation that followed included mechanical property testing and chemical, metallurgical, and finite element analysis. The rope was made from multiple strands of 1095 steel wire. Its chemical composition, ferrite-pearlite structure, and high hardness indicate that the wire is a type of extra improved plow steel (EEIPS grade). The morphologies of the fracture surfaces suggest that the wires were subjected to tensile overloading. This was confirmed by finite element analysis, which also revealed compressive contact stresses between the wires and between the rope and sheave surface. Based on the results, it was concluded that a tensile overload, due to the combined effect of a sudden load and undersized sheave, is what ultimately caused the rope to fail.

Microbial degradation in the environment is initiated by abiotic (nonliving physical or chemical) processes. Mechanical weathering and other mechanical processes are the main drivers of the initial degradation. This article presents an overview of weathering and biodegradation. It summarizes the main synthetic polymers that are released and available for bacterial and fungal decomposition. The article also presents a detailed discussion on the enzymes that are involved in plastic degradation, and the measurement of polymer degradation.

This article provides assistance to a failure analyst in broadening the initial scope of the investigation of a physical engineering failure in order to identify the root cause of a problem. The engineering design process, including task clarification, conceptual design, embodiment design, and detail design, is reviewed. The article discusses the design process at the personal and project levels but takes into consideration the effects of some higher level influences and interfaces often found to contribute to engineering failures.

A four-million gallon capacity (15,142 cu m) oil storage tank ruptured upon filling after re-erection near West Elizabeth, PA on 2 Jan 1988. The tank shell split vertically with failure originating at a flaw existing prior to the reconstruction. Brittle fracture occurred both up and down from the defect when the stress induced by filling reached a critical value for the steel, which had poor toughness properties. This steel had been used in the original construction of a tank in Ohio more than 40 years previously. The defect at which brittle fracture originated in the tank shell showed evidence of burning from a torch. This tank failure was the catalyst for the introduction of new rules concerning the inspection and assessment of older storage tanks.

Hydrogen damage is a term used to designate a number of processes in metals by which the load-carrying capacity of the metal is reduced due to the presence of hydrogen. This article introduces the general forms of hydrogen damage and provides an overview of the different types of hydrogen damage in all the major commercial alloy systems. It covers the broader topic of hydrogen damage, which can be quite complex and technical in nature. The article focuses on failure analysis where hydrogen embrittlement of a steel component is suspected. It provides practical advice for the failure analysis practitioner or for someone who is contemplating procurement of a cost-effective failure analysis of commodity-grade components suspected of hydrogen embrittlement. Some prevention strategies for design and manufacturing problem-induced hydrogen embrittlement are also provided.