Consequence of failure

Breakdown maintenance is suitable for equipment whose failure does not threaten production, safety or the environment, and where the cost of preventing failure would be greater than the consequence of failure. In this case, the equipment would be repaired either on location or in a workshop. Even with this policy, it is assumed that the recommended lubrication and minor servicing is performed, just as with a motor car. 

Measures to minimize safety problems must be initiated at the start of the life cycle of any product, but too often determinations of criticality are left to production or quality control personnel who may have an incomplete knowledge of which items are safety critical (Hammer, 1980). Any potential non-conformity that occurs with a severity sufficient to cause a product or service not to satisfy intended normal or reasonably foreseeable usage requirements is termed a defect (Kutz, 1986). The optimum defect level will vary according to the application, where the more severe the consequences of failure the higher the quality of conformance needs to be. 

Severity Class. Severity of the consequences of failure are expressed qualitatively as pr ted in Table 3.3.5-1... 

Quality control is often regarded as a post-event activity i.e. a means of detecting whether quality has been achieved and taking action to correct any deficiencies. However, one can control results by installing sensors before, during, or after the results are created. It all depends on where you install the sensor, what you measure, and the consequences of failure. 

All data should be examined before use, otherwise you may inadvertently introduce errors into your work. The standard does not require that data controls be the same as document controls so you are at liberty to pitch the degree of control appropriate to the consequences of failure. 

S = Safety what are the consequences of failure If they are serious, a more resistant material than usual may be justified. For example, on a plant where leaking v. ater would react violently with process materials, the water lines were made from a grade of steel resistant to stress corrosion cracking (from the chloride in the cooling water) as well as rust. 

Only task elements which are particularly critical (from the point of view of the consequences of failure) or where errors are particularly likely, are included in the job aid. The development of procedures obviously has to be closely integrated with the content of training, since the design of procedures has to assume that the individual has received appropriate training for certain aspects of the task. 

Given these uncertainties, it becomes even more important that a systematic and comprehensive qualitative method is adopted for identifying the sources of risk and the consequences of failures. Such a procedure must ensure... 

Close tanker valve Independent check on action. Use checklist Ensure operator is aware of consequences of failure Valve position indicator would reduce probability of error... 

Modification of alkyd resins with high proportions of silicones considerably reduces rates of attack, but the most spectacular extension of life is shown by fluorinated polymers such as polyvinylidene fluoride where erosion rates can be reduced to 0 -1 /tm/year. If this level of durability can be achieved an initial coating, if firmly adherent and free from any breaks, may often be expected to maintain protection over a metal substrate for the likely life of the structure. The considerably increased first cost, as compared with more conventional coatings, has to be balanced against the probable saving in maintenance costs or consequences of failure. 

Develop final Perform structural design of analysis of component acceptable accuracy Determine structural response—stresses, support reactions, deflections, and stability—based on a structural analysis of acceptable accuracy. Determine acceptable accuracy based on economic value of component, consequences of failure, state-of-the-art capability in stress and stability analysis, margin of safety, knowledge about loads and materials properties, conservatism of loads, provisions for further evaluation by prototype testing... 

Develop practical test program to demonstrate components ability to meet structural and performance criteria. Extent of such test program, if any, depends on economic value of component, number of units to be produced, consequences of failure, accuracy of structural analysis and design, margins of safety used in design, knowledge about service loads and environments, and difficulty of duplicating service loads and conditions in test... 

There are no hard-and-fast rules to follow in setting safety factors for any given material unless experience exists. The most important consideration is of course the probable consequences of failure. For example, a little extra deflection in an outside wall or a hairline crack in one of six internal screw bosses might not cause concern, but the failure of a pressure vessel or aircraft wing might have serious safety or product-liability implications. 

New systems or processes may also need to be qualified from an operational safety perspective. This is particularly relevant in the case of chemical synthesis involving exothermic reactions. Critical safety aspects are usually identified using hazard operability or HAZOP assessments and studies. For example, a HAZOP analysis of an exothermic reaction vessel would involve consideration of the consequence of failure of the motors for mixers or circulation pumps for cooling water. Thus, the qualification of such a system would involve checks and assessment to ensure that the system/process can be operated safely and that pressure relief valves or other emergency measures are adequate and functional. 

The pathogenesis of bacterial overgrowth is reviewed by considering separately the consequences of failure of the two main defense mechanisms in the upper gut responsible for the two types of bacterial overgrowth (table 1) the gastric acid barrier and intestinal clearance. 

In the frames of the basic goal to protect the population from the harmful effects of failures, there are a number of measures to be implemented for the protection of and for the diminishing the consequences of failure on personnel and local inhabitants in areas with dangerous chemical production industry. More than 3,930 thousands of tons of hazardous chemical substances are stored or used in production activities of the 78 industrial plants that operate in the Zaporozhia region. These substances include over 0,9 thousands of tons of chlorine, over 1,831 thousands of tons of ammonia and about 1,101 thousands of tons of other hazardous chemicals. 

The criterion for end-of-life may include a safety factor depending on the consequences of failure, which include replacement of the whole assembly, safety of personnel, costly repair and outage costs. 

For complex and safety-critical devices where the consequences of failure are high, accelerated simulation of the entire service life can be performed. 

Assessment of polymer lifetime is of importance in electrical generating and distribution equipment where the consequences of failure may be significant and costly, particularly... 

MMBS modifiers a have poor resistance to thermal oxidative degradation. This poor resistance may manifest itself most strongly during such procedures as isolation and oven drying. The least severe manifestation is slight discoloration, while dryer fires are an extreme, though not uncommon, consequence of failure to stabilize MMBS modifiers (12). 

Note that with highly complex networked systems (i) there are likely to be uncertainties and arguments about system boundaries, (ii) the very complexity of the system (and its specification, if it has one) can be a major problem, (iii) judgments as to possible causes or consequences of failure can be subtle and disputable and (iv) any provisions for preventing faults from causing failures are themselves almost certainly fallible. 

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