Primary failures

KDC has a cause and effect relationship between as the primary cause leading to secondary failures. Besides its drastic operational effects on redundant systems, the numerical etlects that reduce sy.stem reliability are pronounced Equation 2.4-5 shows that the probability ut failing a redundant. system composed of n components is the component probability raised to the n-th power. If a common clement couples the subsystems. Equation 2.4-5 is not correct and the failure rate is the failure rate of the common element. KDC is very serious because the time from primary failure to secondary failures may be too short to mitigate. The PSA Procedures Guide (NUREG,/CR-2.3(X)) cl.issities this type as "Type 2."... 

The primary failure mechanisms encountered in reinforced concrete buildings arc flexure, diagonal tension, and direct shear. Of these three mechanisms,. flexure is preferred under blast loading because an extended plastic response is provider prior to failure. To assure a ductile response, sections are designed so that the flexural capacity is less than the capacity of non-ductile mechanisms. 

The primary failure modality identified clinically for restorations in posterior teeth is loss of material through abrasion. The complex nature of this failure mode in composite materials makes it difficult to correlate this phenomenon with any one mechanical property. A number of studies have suggested improvements in the system by using various mechanical properties as evidence. These studies have identified major factors such as ceramic filler loading and type of filler [186-191]. Some effects have been identified related to the... 

Estrogens have been used extensively for replacement therapy in estrogen-deficient patients. The estrogen deficiency may be due to primary failure of development of the ovaries, premature menopause, castration, or menopause. 

Parathyroid Hormone Receptor, Skeletal Dysplasias, and Primary Failure of Tooth Eruption... 

Exome resequencing combined with linkage analysis identifies novel PTHR1 variants in primary failure of tooth eruption in Japanese. J Bone Miner Res 26 1655-1661... 

Roth H, Fritsche LG, Meier C et al (2014) Expanding the spectrum of PTHR1 mutations in patients with primary failure of tooth eruption. Clin Oral Investig 18(2/377-384... 

Primary failure of respiration after exposure to toxicants other than nerve agents suggests a severity of exposure that requires intensive medical support at this point, a triage decision may be needed. The presence of wheezing indicates severe bronchospasm, which requires immediate therapy. The presence of dyspnea necessitates careful observation of the patient for at least 4 to 6 hours, until severe, potentially lethal respiratory damage can be reasonably excluded. 

Primary failure of cardiac function, like respiration, is a grave sign after exposure to toxicants other... 

Airworthiness of civil aircraft depends upon a process by which a team composed of aircraft manufacturers, regulators, and one or more airlines predicts possible system failures. This process. Maintenance Steering Group 3 (MSG-3), considers possible failure pathways (e.g., in structures, controls, avionics) and for each pathway determines a recovery strategy. For structural failure, this may be replacement after a fixed service life, regular inspection to ensure detection, or an indication to crew of the malfunction. The concern here is with the reliability of the primary failure recovery system for aircraft structural inspection regular inspection to ensure detection. 

At each visit the HTA model of FPl was further developed and both good and poor human factors practices were noted. The HTA had seven major tasks, most of which would be classified under Setup in our five-function model. The tasks are shown in a HTA format in Figure 4. Note that Load/ transport part in FPl would be equivalent to the Present function, and Read part for defects to Search, Decision, and Respond. For each of these seven tasks, two levels of subtasks were developed and potential errors listed. A fault tree for the primary failure, defect not reported, was developed and used to help generate a set of human factors good practices. Table 5 shows an example of the most detailed level for function 3, Apply penetrant, with the listing of human factors issues and process variances. 

Fracture toughness tests for isotropic materials normally use edge-notched flexure beams and compact tension specimens. These methods are. as for the impact tests, only suitable for the injected or compression molded materials, which do not have a strongly laminated structure. Laminated composite materials have their primary failure path between the layers, and a new set of test geometries has been developed. 

For aluminum and magnesium, FFC and blistering are the predominant coating failure mechanisms. For iron, FFC is observed only under special conditions and cathodic delamination is the primary failure mechanism see Ref. [168] and references therein. 

Figure 13.7 Predictions of the energy dissipated in the four primary failure modes observed in four-ply AS4/PEEK laminates based on different stacking sequences.

Equipment failures can be primary, secondary, or command. A primary failure is one that occurs under normal operating conditions and for which the component itself is responsible. A secondary failure is one that is caused by external conditions or factors and for which the equipment item itself cannot be held responsible. For example, if a corrosive liquid is inadvertently fed to a pump, then the subsequent failure of the pump is secondary. A command failure is one that is caused by... 

Primary failure mode Flank wear Flank wear... 

In [3] the word primary failure is used. However, since one does not always refer to a failure, the more general term primary event is used here. Often the term component failure Is applied. 

In several studies, attempts have been made to explain the high primary failure rate. The use of coils as the only embolic agents was found to be associated with rebleeding [7]. Other investigators did not confirm an association with procedural parameters. Coagulopathy [7, 8, 102], multi-organ failure or shock [6,8] and corticosteroid use [6] are... 

The Primary Secondary-Command (P-S-C) concept is to concentrate the analyst on specific causal factors. This concept is based on components having three ways of failing, the primary failure mode (inherent failure), secondary failure mode (external influence) or a command path fault (function provided when not required). All of these failure modes should he considered to ensure nothing is overlooked. 

The second term in the sum above represents two consequent hinnan failures 1) primary failure of process control 2) secondary failure of taking adequate measure to eliminate the consequences of primary failure. As it has been pointed out in many human reliability analysis methodologies and studies, there is no discussion regarding independency - such actions are dependent to some extent by substance. 

Rooijens PP, Tordoir JH, Stijnen T, Burgmans JP, Smet de AA, Yo TI. Radiocephalic wrist arteriovenous fistula for hemodialysis meta-analysis indicates a high primary failure rate. Eur J Vase Endovasc Surg 2004 28(6) 583-9. 

Once the particular type of failure is placed in that top block, then deductive logic and an in-depth knowledge of the system are used to determine the different ways in which that failure could occur. At each level, three particular types of component failures are examined. These are primary failures, secondary failures, and command failures. 

Examples of a primary failure (failure within design criteria) ... 

One type is the primary failure, that is, the failure of that particular item, component, or piece of hardware within its design criteria. The second type of failure to be examined is secondary failure, which is caused by something external to the system. The third type of failure is command failure, which involves something internal to the system other than the failed component causing or being responsible for the failure. 

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