Search Results for operation failures

This chapter examines boiler tube failures attributed to operation-related causes. It discusses failures due to rapid start-ups, excessive load swing, excessive heat inputs, poor water chemistry control, and water-treatment methods.

This chapter provides an outline of the failure modes and mechanisms associated with most boiler tube failures in coal-fired power plants. Primary categories include stress rupture failures, water-side corrosion, fire-side corrosion, fire-side erosion, fatigue, operation failures, and insufficient quality control.

A system failure occurs when a system does not do what it is supposed to do when it is supposed to do it, or it does something it is not supposed to do. This chapter provides a basic understanding of how failures occur, how systems operate, and the types of failures, namely intermittent and inadvertent system failures.

Quantifying a fault-tree analysis is a useful tool for assessing the most likely causes of a system failure. This chapter addresses fault-tree analysis event probabilities and ranking of failure causes based on these probabilities. Failure rates, failure-rate sources, probability determinations, mean times between failure, and related topics are also discussed. The discussion covers the practices observed in fault-tree analysis quantification and processes involved in calculating the probability of the top undesired event.

Contaminants can be a cause of numerous types of system failures. There are numerous techniques for confirming contaminant presence. When the presence of a contaminant is suspected, the failure analysis team must find and eliminate the contaminant source, which can be obvious or quite subtle. This chapter summarizes a few commonly encountered contaminant sources to stimulate the reader's thinking about potential contaminant sources. A case study of titanium component washing at Litton Lasers is presented to illustrate how the presence of contaminants leads to a system failure.

Corrective action means the implementation or modification of things designed to eliminate or reduce failure causes. This chapter addresses developing potential solutions and selecting the best solution. It discusses the special operations that should be used only as temporary or interim corrective actions to overcome design, process, and other failure causes. The chapter concludes by describing the process of corrective action implementation.

In some cases, the failure analysis team finds that all components meet their requirements, the system was properly assembled, and it was not operated or tested in an out-of-specification manner, yet it still failed. When this occurs, the only conclusion the failure analysis team can reach is that it missed something in its analysis or that the design is defective. This chapter focuses on the latter possibility by discussing the various factors that a failure analysis team should consider to identify the causes of defects in system design. These include requirements identification and verification, circuit performance, mechanical failures, materials compatibility, and environmental factors. Examples that illustrate the value of design analysis are also presented.

This chapter reviews the knowledge of the field of gear tribology and is intended for both gear designers and gear operators. Gear tooth failure modes are discussed with emphasis on lubrication-related failures. The chapter is concerned with gear tooth failures that are influenced by friction, lubrication, and wear. Equations for calculating lubricant film thickness, which determines whether the gears operate in the boundary, elastohydrodynamic, or full-film lubrication range, are given. Also, given is an equation for Blok's flash temperature, which is used for predicting the risk of scuffing. In addition, recommendations for lubricant selection, viscosity, and method of application are discussed. The chapter discusses in greater detail the applications of oil lubricant. Finally, a case history demonstrates how the tribological principles discussed in the chapter can be applied practically to avoid gear failure.

This chapter covers the failure modes and mechanisms associated with boiler components and the tools and techniques used to assess damages and predict remaining component life. It begins with a review of the design and operation of a utility boiler and the materials used in construction. It then describes the various causes of failure in boiler tubes, headers, and steam pipes, explaining how and why they occur, how they are diagnosed, and how to mitigate their effects. The final and by far largest section in the chapter is a tutorial on damage and life assessment techniques for boiler components and assemblies. It demonstrates the use of various methods, including analytical techniques that estimate life expenditure based on operating history, component geometry, and material properties; predictive methods based on the extrapolation of failure statistics; methods that predict life based on dimensional measurements; methods based on metallographic studies; methods based on temperature estimates; and a method for estimating remaining life under creep conditions based on stress-rupture testing of service-exposed material samples. The chapter also discusses the use of fracture mechanics and presents a number of cases in which life assessments are made based on the integration of several methods.

This chapter provides a brief review of industry’s battle with fatigue and fracture and what has been learned about the underlying failure mechanisms and their effect on product lifetime and service. It recounts some of the tragic events that led to the discovery of fatigue and brittle fracture and explains how they reshaped design philosophies, procedures, and tools. It also discusses the influence of material and manufacturing defects, operating conditions, stress concentration and intensity, temperature and pressure, and cyclic loading, all of which play a role in the onset of fatigue cracking and thus should be considered when predicting useful product life.

This chapter targets areas that determine if a change occurred and if the change induced the failure: change or what's different analysis. It describes the different sources of changes that induce process deficiencies: design, process, test and inspection, environmental, supplier lot, aging, and supplier changes. The chapter presents an example of a cluster bomb failure to explain how the failure analysis team found and corrected the failure cause.

The ability to accurately assess the remaining life of components is essential to the operation of plants and equipment, particularly those in service beyond their design life. This, in turn, requires a knowledge of material failure modes and a proficiency for predicting the near and long term effects of mechanical, chemical, and thermal stressors. This chapter presents a broad overview of the types of damage to which materials are exposed at high temperatures and the approaches used to estimate remaining service life. It explains how operating conditions in power plants and oil refineries can cause material-related problems such as embrittlement, creep, thermal fatigue, hot corrosion, and oxidation. It also discusses the factors and considerations involved in determining design life, defining failure criteria, and implementing remaining-life-assessment procedures.

This chapter analyzes four gearbox failures, in each case identifying the underlying failure mechanism and recommending changes to reduce vibration. These include failure of an offset parallel gearbox due to gear tooth geometry error; high vibration on high-speed offset parallel gearbox; failure of an epicyclic gearbox; and vibration due to tooth wear.

This chapter identifies the primary causes of service failures and discusses the types of defects from which they stem. It presents more than a dozen examples of failures attributed to such causes as design defects, material defects, and manufacturing or processing defects as well as assembly errors, abnormal operating conditions, and inadequate maintenance. It also describes the precise usage of terms such as defect, flaw, imperfection, and discontinuity.

This chapter focuses on the causes of gear failure under five major headings. These include basic material, focusing on steel, engineering, focusing on the integration of design, manufacturing, heat treatment, and service application.

Many companies conduct only metallurgical evaluations in the wake of failures, discovering nothing more than the physical mechanism by which the failure occurred. The origin of failures, however, is often complex, involving not only physical mechanisms, but also human behavior and latent factors. Failures may also involve multiple parts, entire machines, or processes of any size and shape. The chapter examines the unique aspects of many failures and explains how they can sometimes be traced to systemic issues. It also covers the reasons why products fail, including improper service or operation, improper maintenance, improper testing, assembly errors, fabrication or manufacturing errors, and design errors. The case of the Tacoma Narrows Bridge collapse is presented to illustrate the consequence of overlooked factors, in this case, wind dynamics, and the importance of identifying root causes to prevent repeat failures.

The management of a failure analysis (FA) laboratory requires a broad range of activities to optimize the efficiency of the operation. The purpose of this article is to stimulate readers to consider the various aspects of FA laboratory operations and their respective business management requirements. The various aspects include: staffing, laboratory organization, lab design and operations, strategic development, financial management, and metrics and measurements. References for further reading and examples of resource materials are also included.

Semiconductor memories are superb drivers for process yield and reliability improvement because of their highly structured architecture and use of aggressive layout rules. This combination provides outstanding failure signature analysis possibilities for the entire design, manufacturing, and test process. This article discusses five key disciplines of the signature analysis process that need to be orchestrated within the organization: design for test practices, test floor data collection methodology, post-test data analysis tools, root cause theorization, and physical failure analysis strategies.

The ultimate goal of the failure analysis process is to find physical evidence that can identify the root cause of the failure. Transmission electron microscopy (TEM) has emerged as a powerful tool to characterize subtle defects. This article discusses the sample preparation procedures based on focused ion beam milling used for TEM sample preparation. It describes the principles behind commonly used imaging modes in semiconductor failure analysis and how these operation modes can be utilized to selectively maximize signal from specific beam-specimen interactions to generate useful information about the defect. Various elemental analysis techniques, namely energy dispersive spectroscopy, electron energy loss spectroscopy, and energy-filtered TEM, are described using examples encountered in failure analysis. The origin of different image contrast mechanisms, their interpretation, and analytical techniques for composition analysis are discussed. The article also provides information on the use of off-axis electron holography technique in failure analysis.

This article provides an introduction to the dynamic random access memory (DRAM) operation with a focus to localization techniques of the defects combined with some physical failure analysis examples and case studies for memory array failures. It discusses the electrical measurement techniques for array failure analysis. The article then presents know-how-based analysis techniques of array failures by bitmap classification. The limits of bitmapping that lead to well-known localization techniques like thermally induced voltage alteration and optical beam induced resistance change are also discussed. The article concludes by providing information on soft defect localization techniques.