Failure components

In a complex datacentre component failure is a regular occurrence simply due to the sheer number of components involved and the fact that almost aU components of a system are prone to one or more failure modes over their lifetime. 

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These systems have been operated in extremely low quality (and radioactivity contaminated) industrial environments for the past several years without any major equipment or component failures. Utilizing specialized operating/warm-up procedures, they have operated in low grade, out-of-doors, dust ridden, rain-soaked, industrial environments at temperature ranges which greatly exceed the original equipment manufacturers (OEM) specified limits. The systems have been successfully operated at ambient temperatures of minus 10 to plus 103 degrees Fahrenheit without any pre-mature or un-anticipated equipment failures. 

NDT has a very important formal status. Requirements for performanee of NDT, acceptance criteria and requirements for personnel qualification are implemented in codes and standards. The NDT procedure is part of the contract. During the many years that NDT methods have been used in industry a well-established situation has evolved, enabling the use of NDT for the evaluation of welds against Good Workmanship Criteria on a routine basis, thus maintaining workmanship standards and minimising the risks of component failure. 

Fig. 10. Components of GM RTS methanol-powered coach replaced, 0> replaced because of component failure, , as a function of distance...

The resulting fault tree is shown in Figure 6, in which the top event is defined in terms of two intermediate events failure of the tank system or failure of the pumping system. Failure in either system would contribute to the overall system failure. The intermediate events are then further defined in terms of basic events. All of the basic events are related by AND gates because the overall system failure requires the failure of all of the individual components. Failures of the tanks and pumps are basic events because, without additional information, these events cannot be resolved any further. 

Component Failure rate, p.,faults/yr Rehabihty,- = e F ailureprob abiflty, P = - R... 

The hardware and software used to implement LIMS systems must be vahdated. Computers and networks need to be examined for potential impact of component failure on LIMS data. Security concerns regarding control of access to LIMS information must be addressed. Software, operating systems, and database management systems used in the implementation of LIMS systems must be vahdated to protect against data cormption and loss. Mechanisms for fault-tolerant operation and LIMS data backup and restoration should be documented and tested. One approach to vahdation of LIMS hardware and software is to choose vendors whose products are precertified however, the ultimate responsibihty for vahdation remains with the user. Vahdating the LIMS system s operation involves a substantial amount of work, and an adequate vahdation infrastmcture is a prerequisite for the constmction of a dependable and flexible LIMS system. 

A reliability block diagram can be developed for the system from the definition of adequate performance. The block diagram represents the effect of subsystem or component failure on system performance. In this preliminary analysis, each subsystem is assumed to be either a success or failure. A rehabihty value is assigned to each subsystem where the appHcation and a specified time period are given. The reUabiUty values for each subsystem and the functional block diagram are the basis for the analysis. 

What-if At each process step, what-if questions are formulated and answered to evaluate the effects of component failures or procedural errors. This technique relies on the experience level of the questioner. 

In some instances, plant-specific information relating to frequencies of subevents (e.g., a release from a relief device) can be compared against results derived from the quantitative fault tree analysis, starting with basic component failure rate data. 

The true influence of flaws and defects on component failure is commonly misunderstood. This misunderstanding often arises from one of two misconceptions. The first misconception can be clarified by simple definitions of a flaw and a defect. 

QRA practitioners can use to satisfy some QRA objectives. Also, the American Institute of Chemical Engineers (AIChE) has sponsored a project to expand and improve the quality of component failure data for chemical industry use. And many process facilities have considerable equipment operating experience in maintenance files, operating logs, and the minds of operators and maintenance personnel. These data can be collected and combined with industrywide data to help achieve reasonable QRA objectives. However, care must be exercised to select data most representative of your specific system from the wide range available from various sources. Even data from your own plant may have to be modified (sometimes by a factor of 10 or more) to reflect your plant s current operating environment and maintenance practices. 

AccuracyAJncertainty The lack of specific data on component failure characteristics, chemical and physical properties, and phenomena severely limit accuracy and can produce large uncertainties. 

It is often found that wet corrosion attacks metals selectively as well as, or instead of, uniformly, and this can lead to component failure much more rapidly and insidiously than one might infer from average corrosion rates (Fig. 23.7). Stress and corrosion... 

The basic code, local regulations and this specification carmot be referred to in case of a component failure. 

Boolean equations show how component failures can fail a system. A minimal cut. he smallest combination of component failures that can fail a system. It is the set of non-sup us components, such as in the previous example, with the superfluous combination Y Z(X Y,. Z) e uded. If they all occurred they would cause the top event to occur. One-component minimtil cut s( if there are any, are single failures that cause system failure. Two-component minimal cutsets ai tairs of components, if they occur together cause system failure. Triple-components minimal Cl sts are sets of three components that, if they fail together cause system failure, and so on to hi er cutsets... 

While Bimbaum Importance identifies systems important to safety, it does not consider the likelihood of component failure. 

Possible large pipe and pipe component failures due to corrosion. 3 b ... 

Cutset means one combination of component failures that fail the system It 3d to have originated as cuts across the flow in reliability block diagrams . In Figure 3,4 3-1, Dugh... 

Under the primary event symbols, the circle represents a component failure for which a description and failure-on-demand or failure frequency data is provided. 

This is the mincut (minimal cutset) representation (Section 2.2) - the smallest combination of component failures that will result in the top event. 

Thus, the fault tree of Figure 3.4.4-4 is represented in mincut form as T =C+A B and by fault tree as Figure 3.4.4-5 which shows the remarkable simplification and reduction provided by the mincut form. This shows that the top event, T, consists of a single component failure, C, and a doubly-redundant failure. 

The fault tree identifies component failures that cause the top event. Systems ma be required to respond in different ways to different accidents, suggesting a general top event )r a general purpose fault tree that adapts to specific system configurations. This may result in ambi jity in the top event definition and difficulty in construction. It is better and easier to prec fy... 

A failure modes and effects analysis delineates components, their interaction.s ith each other, and the effects of their failures on their system. A key element of fault tree analysis is the identification of related fault events that can contribute to the top event. For a quantitative evaluation, the failure modes must be clearly defined and related to a numerical database. Component failure modes should be realistically and consistently postulated within the context of system operational requirements and environmental factors. 

Human factors, discussed in Section 4.2, enter a fault tree in the same manner as a component failure. The failure of manual actions, that prevent or mitigate an accident, are treated the same as hardware failures. The human error failure probability is conditioned by performance sluiping factors imposed by stress, training and the environment. 

USC may be modeled as a power-series expansion of non-CCF component failure nates. No a priori physical information is introduced, so the methods are ultimately dependent on the accuracy of data to support such an expansion. A fundamental problem with this method is that if the system failure rate were known such as is required for the fitting process then it would not be neces.sary to construct a model. In practice information on common cause coupling in systems cannot be determined directly. NUREG/CR-2300 calls this "Type 3" CCF. 

SPASM Fault tree or reduce tern equation, component failure data Combination (similar to BOUNDS) Lxignormal Works in conjunction with WAMCUT ... 

Two IBM-PC interactive codes calculate importances and risk and allow the operator to investigate the effects of system and component failures on the risk and importance. The BNL code NSPKTR models the Indian Point Plants 2 and 3 using information in their PSAs. NSPKTR uses... 

Component Failure Mode Error Rale Upper Bound Number of Record-. 

Unfortunately, maintenance reports do not always present all the information indicated in Table 4,3-2. Descriptions of component unavailability or work performed may be unclear, requiring engineering judgment regarding whether a component was made unavailable by maintenance or maintenance was required because of component failure. 

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