Failures analyzing

Are all failures analyzed Are correction actions promptly taken ... 

Oil in machines carries the products of deterioration resulting from wear and mechanical failure. Analyzing the oil resident in a machine or the debris the oil carries allows predictions to be made about the state of health of the machine. The critical measurement reflecting the condition of machine wear is the number of microscopic metal wear particles that are suspended in the oil system of the machine. The spectrometric oil analysis process is a laboratory technique that uses various instruments to analyze a used oil sample from a machine. The spectrometric result is compared to a baseline level of metal found to be typically suspended in the oil under normal operating conditions. When the wear is meaningful, the sample will show high levels (in parts per million) of wear metals compared to the baseline oil sample. 

FAILURE[7] is the failure recovery module. Sometimes Ml fails to meet all specifications and constraints. FAILURE analyzes the cause of these failures, and allows the user to interactively fix it. Fixes typically consist of either choosing a different part, or relaxing the violated constraint. FAILURE uses a dependency network [17] to automatically determine the affected portions in the design. FAILURE then directs Ml to redesign them. 

Execution of each test must be documented, showing when it was done, by whom, and the results. Failures must be analyzed for possible changes in the design or implementation of the interlock. 

Discontinuous operation (idle periods) of instruments such as flow meters, pH meters, analyzers, etc., could lead to failure as a result of plugging, drying out, etc. 

The accuracy of absolute risk results depends on (1) whether all the significant contributors to risk have been analyzed, (2) the realism of the mathematical models used to predict failure characteristics and accident phenomena, and (3) the statistical uncertainty associated with the various input data. The achievable accuracy of absolute risk results is very dependent on the type of hazard being analyzed. In studies where the dominant risk contributors can be calibrated with ample historical data (e.g., the risk of an engine failure causing an airplane crash), the uncertainty can be reduced to a few percent. However, many authors of published studies and other expert practitioners have recognized that uncertainties can be greater than 1 to 2 orders of magnitude in studies whose major contributors are rare, catastrophic events. 

In the event of failures due to lubrication problems, the failures should be thoroughly analyzed to determine if they were indeed caused by lubricant failure or incorrect maintenance procedures. Once the problem has been isolated, corrective action can be initiated to prevent subsequent similar failures—whether it requires changing lubricants or procedures. 

For many reasons, it may be ineonvenient to take the speetrum analyzer to the field eaeh time an analysis is to be made. Often, several maehines are to be analyzed at various loeations. Also, a hostile environment may exist at the test site, whieh might result in damage to the analyzer. A way of over-eoming these problems is offered by data taping. With a tape, a permanent reeord is made. Sinee eaeh ehannel of the tape offers a plaee for data to be stored, this reeord may be a eondensation of several inputs either from different transdueers or from the same transdueer at various loeations. A eontinuous tape monitor is very benefieial. In the event of maehine failure, an analysis of the playbaek will help diagnose the problem. 

Laser ionization mass spectrometry or laser microprobing (LIMS) is a microanalyt-ical technique used to rapidly characterize the elemental and, sometimes, molecular composition of materials. It is based on the ability of short high-power laser pulses (-10 ns) to produce ions from solids. The ions formed in these brief pulses are analyzed using a time-of-flight mass spectrometer. The quasi-simultaneous collection of all ion masses allows the survey analysis of unknown materials. The main applications of LIMS are in failure analysis, where chemical differences between a contaminated sample and a control need to be rapidly assessed. The ability to focus the laser beam to a diameter of approximately 1 mm permits the application of this technique to the characterization of small features, for example, in integrated circuits. The LIMS detection limits for many elements are close to 10 at/cm, which makes this technique considerably more sensitive than other survey microan-alytical techniques, such as Auger Electron Spectroscopy (AES) or Electron Probe Microanalysis (EPMA). Additionally, LIMS can be used to analyze insulating sam-... 

The path of failure of an adhesive joint can give information about the mechanism of failure if analysis of the elemental and chemical composition can be conducted along the path. Several authors have performed such analyses by loading the adhesive joint until it fractures and then using XPS to analyze each side of the fracture. 

When analyzing such individual control valve failures, one should consider the action of other control valves in the system. In the first two cases above, credit may be taken, where applicable for the reduction in pressure of a high-pressure source due to net inventory depletion during the period that the downstream equipment pressure is rising to relieving pressure. However, the pressure relieving facilities must be sized to handle the calculated peak flow conditions. 

Absorbent Flow Failure - For lean oil absorption generally, no relief requirement results from lean oil failure. However, in a unit where large quantities of inlet vapor may be removed in the absorber, loss of absorbent could cause a pressure rise to relief pressure, since the downstream system may not be adequate to handle the increased flow. In such cases, the effect of this additional vapor flow into downstream equipment must be analyzed. 

The FMEA is a methodieal study of eomponent failures. This review starts with a diagram of the operations, and ineludes all eomponents that eould fail and eoneeivably affeet the safety of the operation. Typieal examples of eomponents that fail are instrument transmitters, eon-trollers, valves, pumps, and rotometers. These eomponents are listed on a data tabulation sheet and individually analyzed for the following ... 

Multiple eoneurrent failures are also ineluded in the analysis. The last step in the analysis is to analyze the data for eaeh eomponent or multiple eomponent failure and develop a series of reeommendations appropriate to risk management. 

Two types of initiators are internal and external. Internal initiators result from failures within a plant or the plant s support utilities. Thus, vessel rupture, human error, cooling failure, and loss of offsite power are internal events. All others are external events earthquakes, tornados, fires (external or internal), and floods (external or internal). Event trees can be used to analyze either type of initiator. 

RMDB is supplemented by microfilmed reports containing failure rates/modes and analyzed data. Reports relating to the theory and procedural techniques to obtain and analyze reliability-maintainability data are cataloged, abstracted, microfilmed and computer listed in the R-M Data Summaries. 

System failure probability for each system analyzed, and the specific conditional failure probabililic > for each component in the system. ... 

Failure of power or controls to the valve (generally related to the seismic capacity of the cable trays, control room, and emergency power). These failure modes are analyzed as failures of separate systems linked to the equipment since they are not related to the specific piece of equipment (i.e., a motor-operated valve) and are common to all active equipment. 

Analysis may show one mode of failure to be most likely in which case further analysis conteiunilcs on ihat mode thereby considerably reducing the scope of the analysis. If there are several etiiiallv likely modes, they must all be analyzed. 

This chapter overviews the techniques for incorporating external events into a PSA. The discussion was primarily aimed at nuclear power plants but is equally applicable to chemical process plants. The types of external events discussed were earthquakes, fires and floods. Notably absent were severe winds and tornados. Tornados are analyzed as missiles impacting the structures and causing common-cause failures of systems (EPRINP-768). Missile propagation and the resulting damage is a specialized subject usually solved with computer codes. 

Accident progression scenarios are developed and modeled as event trees for each of these accident classes. System fault trees are developed to the component level for each branch point, and the plant response to the failure is identified. Generic subtrees are linked to the system fault trees. An example is "loss of clcciric power" which is analyzed in a Markov model that considers the frequencies of lo,sing normal power, the probabilities of failure of emergency power, and the mean times to repair parts of the electric power supply. 

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