Probable Cause Of Failure Research Articles

Graft atheroembolism as the probable cause of failure to wean from cardiopulmonary bypass

Graft atheroembolism as the probable cause of failure to wean from cardiopulmonary bypass

Development of an expert system for diagnosing component-level failures in a shuttle car

The development of a rule-based expert system (referred to as SCAR) for assisting electricians in diagnosing electrical faults in a shuttle car is discussed. Insight 2+, a microcomputer-based expert-system development tool by Level Five Research, Inc. was used in creating the system. The program requires the user to specify the initial symptoms of the failed machine; then the most probable cause of failure is traced through the knowledge base, with the software requesting additional information, such as voltage or resistance measurements, as needed. A causal-reasoning approach, which was used to develop the production rules, is described. The organization, implementation, and limitations of the knowledge base are also presented, along with a brief discussion of the ongoing development of a new system, SCAR.2. >

Analysis of rotor failures in squirrel-cage induction motors

The authors describe a procedure for analyzing rotor failures in squirrel-cage induction motors. They attempt to identify the various kinds of failure classes and patterns and relate them back to the probable cause of failure. They discuss five key areas that must be considered and related to one another in order to accurately diagnose the cause of rotor failure: failure class, failure pattern, appearance, application, and maintenance history. Finally, a summary of typical failures and tell-tale rotor appearances is presented. >

Submicron tip breakage and silanization control improve ion-selective microelectrodes.

Probable causes of failure of otherwise well-constructed liquid ion-exchanger (LIE) micro-electrodes of average tip size less than 0.15 micron were examined. The problem could be attributed to two major variables, both localized at the tip: partial tip occlusion during fabrication prevents the generation of an electromotive force (small or absent slope and/or selectivity, high resistance); or poor hydrophobicity of the tip permits water to displace the resin from the tip (small or absent slope and/or selectivity and low electrode resistance). Controlled dry tip breakage on paper coated with glassine to final tip sizes well below 0.5 micron (confirmed by scanning electron microscopy) improves the yield of usable electrodes severalfold. Adequate silanization of the tip and consequent retention of resin at the tip can be predicted from the contact angles observed at the glass-LIE-backfilling solution interface. Satisfactory silanization can be achieved despite high ambient humidity. No evidence of shunting of Na+-LIE microelectrodes by the glass wall was seen. In the isolated perfused proximal tubule of Ambystoma tigrinum, the mean intracellular Na+ activity recorded by broken-tip electrodes (13.7 +/- 1.9 meq, n = 4) was similar to that recorded by intact electrodes (15.5 +/- 1.1 meq, n = 31).

Recent materials problems relating to catastrophic balloon failures

Balloons fabricated of thin polyethylene materials have provided relatively inexpensive and reliable scientific research platforms for approximately three decades. Reliability of the modern day balloon, as launched by the U.S.A. National Scientific Balloon Facility (NSBF), has been approximately 85%. Recent balloon failures, coupled with an increased occurrence of catastrophic failures, created grave concern over the integrity of the present balloon inventory of the U.S.A National Aeronautics and Space Administration (NASA). An investigative team was established by NASA to review the circumstances surrounding the catastrophic balloon failures, determine the cause and to make recommendations to correct the problem and to prevent its reoccurrence. The most probable cause of failure as determined by the investigation was the polyethylene balloon film, although the film had passed the established standard quality control measures of the film manufacturer. The approach, findings, and conclusions of the investigation are presented along with planned procedures to assure future quality balloon film for NASA balloons.

Investigation of Thermal Effects on Weapon System Components

A three-dimensional stress analysis of a 30-mm machine gun component on the Harrier Aircraft was conducted to investigate the cause of observed fractures. The analysis was made using a general purpose finite element computer program and a laboratory environmental test chamber. Based on this study, the probable cause of failure was identified and, as a result, the component manufacturer is considering possible design changes to alleviate this problem in further production. The study clearly demonstrates that computer-based technology can be successfully used in investigating causes of failure in complex structural components.

Failure of ultrasound in the investigation of sciatica.

This paper reports a prospective study of the value of ultrasonography in detecting lesions of the lumbar spine in patients with compressive sciatica. The measurements of the diameter of the spinal canal obtained by using ultrasound were compared with the findings at operation in 17 patients in whom a total of 50 sites were examined. The ultrasound beam failed to penetrate the spinal canal at 15 sites and at only 10 of the remaining 35 sites did the ultrasound correctly detect narrowing. It is concluded that ultrasonography is unreliable in identifying the site of compression of the spinal cord and nerve roots. The technical limitations and the probable causes of failure of the technique are discussed.

Finite-element modeling of a fighter aircraft canopy acrylic panel

A detailed three-dimensional stress analysis of a canopy aircraft acrylic panel was conducted to investigate the probable cause of a recent in-flight acrylic panel failure. The analysis was made using a general-purpose finiteelement computer program. Based in part on this analysis, probable design problems associated with the canopy were identified. The study clearly demonstrates that computer-based technology can be successfully used in determining probable causes of failure in geometrically complex structures.

Anticonvulsant structure‐activity relationships: Historical development and probable causes of failure

Anticonvulsant structure‐activity relationships: Historical development and probable causes of failure

The dynamics of the hope slide

On January 9, 1965, the Hope slide occurred in the Casade Mountains of British Columbia and buried 4.5 km of B.C. highway number 3. Two minor earthquakes, with epicentres in the vicinity of the slide, are cited as the most probable cause of failure. Analysis of the pre and post slide topography defined the centres of gravity of the slide mass both before and after failure. The slope of the line joining the centres of gravity was equated to the apparent angle of friction of the slide path. This slope was found to be very similar to the value of the ultimate friction angle in shear tests on the slide debris.

Automated machinery surveillance and diagnostics

One approach toward improving the availability of nuclear power plant machinery is by continuously monitoring and analyzing the vibrational characteristics of critical machines. Through proper analysis of the vibrational characteristics, it is possible to detect impending problems before failure occurs and probable causes of failures if they do occur. This permits improved scheduling of outages, reduction of downtimes and maintenance costs. The number of critical machines, where monitoring is considered desirable, typically results in systems comprising between 100 and 200 individual sensors. The complex vibration information of each sensor must be analyzed periodically, frequencies identified, and amplitude trends recorded in order to provide the diagnostic information necessary to predict machinery health. This type of analysis requires expertise in the areas of machinery dynamics and instrumentation to provide meaningful results. Considering the number of sensors involved, coupled with the type of analyses required for each sensor, the need for a computer based automated type system becomes evident. This paper describes the development of such a system, including its capabilities and limitations. The system, funded by EPRI, is being developed for installation in the Northeast Utilities Millstone II nuclear power plant. Although not scheduled for system operation until April 1978, examples of system output run from instrument tape recording from the nuclear plant are presented.

Workover and Completion Technology - A Survey

There's gold in them thar workovers, pardner-so let's see how to get it out. By participating in a survey, a representative group of engineers has brought us up to date on the subject and has done some "If only we could..... or had..... or knew how to ". . . to push us into the future. Introduction When costs represented by the annual workover forecast become comparable with the drilling budget, and when a rig-time analysis discloses that completion operations are costing as much as drilling operations, economics, as always, rears its head. In company after company, more manpower is being diverted toward workovers, with the result varying from a few transferred people to major company reorganization. Some companies are reporting 30 percent or higher increases in workover activity, sometimes in a single year. Workover and completion operations more and more are being accomplished by a separate so of "experts" rather than being tacked on to the responsibilities of a drilling or production group. Service companies, expecting a lull in their activity as a result of the declining volume of drilling, are pleasantly surprised to find their business volume pleasantly surprised to find their business volume stable, and sometimes rising, because of the increasing number of workovers. Many of these workovers are appearing in the normal course of events with time and production, just as workovers always have. Many more result from the increasing age of wells and, more important, from higher demand that makes profitable many jobs that were marginal 5 to 10 years ago. With these facts of life and economics goes the hustle that has been added to this phase of our operations. Declining production and lack of drilling opportunities make managers look harder for prospective workover ventures. The increase is offshore as well as onshore, in upper zones as well as lower, and in good wells as well as poor. The subtler "pimples" on logs are being investigated, more stimulation attempts are being made, and more expensive and high-risk workovers are being attempted. Where, then, is workover and completion technology at this time of changing emphasis? It is very much in a state of flux, and few specific ideas are accepted and practiced universally. The technology being used is not practiced universally. The technology being used is not fully documented and reported. The activity is growing at a rate that places technical staffs almost continuously in the role of fire-fighters, without the time and manpower for deliberate study. Far too often it does not permit even a cursory follow-up on results and probable permit even a cursory follow-up on results and probable causes of failure or overexpenditure. For an engineer to take the time to write a technical paper under such circumstances has been out of the question. With this in mind, I have tried to get art idea of what is current in this area of technology. To reach a cross-section of big producers, independents, consultants, contractors, and service companies, I have interviewed about 20 individuals in key spots of workover and completion responsibility and sent out about 80 questionnaires. The questions asked were: What are you doing now? What are you trying that's new? What do you need the most? What are the trends for the next 5 years? JPT P. 1375