Test method safety factor

Most of the methodologies rely on a generic safety factor of 2 applied to pressure stress, with the safety factor on thermal stress set at unity. For leak and hydrostatic tests, the safety factor on pressure generally is reduced to 1.5. The Russian approach and the French Method 2 use a safety factor of unity for pressure stress, but the fracture toughness curve either has a safety factor included (Russian approach) or additional safety factors are applied to the fracture toughness curves (French Method 2). As indicated earlier, the new risk-informed approach which will appear in the 2011 edition of the ASME Code uses a safety factor of 1 on pressure stress. 

Analytical and Test Methods, Specification, and Safety Factors... 

The acceptable operator exposure level (AOEL) for each route of exposure is assigned from the no effect level (NOEL) in a specific toxicity test multiplied by a safety factor. The value for samples containing no detectable residues is assumed to be one half the limit of detection. For cyromazine, the seasonal use pattern indicates that the exposure is most comparable to the 21-day dermal exposure interval, and a value of 2000 mg/kg bw/day was taken as the dermal AOEL. The inhalation AOEL was obtained from a 28-day inhalation study with rats. As cyromazine is not a carcinogen, the safety margin used for calculation of the of the results using the EEC method... 

Defoamers, 3 236-254 9 23 applications, 3 245-249 commercial sources, 3 240, 241t components, 3 237-240 defoaming theory, 3 241-245 economic aspects, 3 249-250 health and safety factors, 3 251-252 in paper manufacture, 13 118 in polymer colloids, 20 386 silica in, 22 376 surface tension, 8 244t test methods, 3 250-251 Defoaming, 3 240-242 Defoaming (antifoaming) agents, 25 in diesel fuel, 12 428 in food, 12 63-64... 

Document of material specifications and test methods. Verification of the specifications must be done to satisfy the design, and the test method must be validated where needed. Because the material is a critical safety factor, the selection of material for IOL should meet both the physicochemical and compatibility specifications described in ISO 11979-2 and 11797-3. The in-house (receiving) specifications of material should thus be documented. Where a test method is developed, the method must be validated. The equipment used for the test must be calibrated. 

The Draize method has generally erred on the side of safety in that it over predicts the severity of skin damage produced by chemicals, thus producing a safety factor for those exposed. Some investigators report repeatedly that the test is not sensitive enough to separate mild from moderate irritants. Although Draize-type tests will be replaced by in vitro assays some time in the future, we have no validated in vitro substitute at present. 

Another typical source of uncertainty in mixture assessment is the potential interaction between substances. Interactions may occur in the environment (e.g., precipitation after emission in water), during absorption, transportation, and transformation in the organism, or at the site of toxic action. Interactions can be either direct, for example, a chemical reaction between 2 or more mixture components, or indirect, for example, if 1 mixture component blocks an enzyme that metabolizes another mixture component (see Chapters 1 and 2). Direct interactions between mixture components are relatively easy to predict based on physical-chemical data, but prediction of indirect interactions is much more difficult because it requires detailed information about the processes involved in the toxic mechanisms of action. One of the main challenges in mixture risk assessment is the development of a method to predict mixture interactions. A first step toward such a method could be the setup of a database, which contains the results of mixture toxicity tests. Provided such a database would contain sufficient data, it could be used to predict the likelihood and magnitude of potential interaction effects, that is, deviations for CA and RA. This information could subsequently be used to decide whether application of an extra safety factor for potential interaction effects is warranted, and to determine the size of such a factor. The mixture toxicity database could also support the search for predictive parameters of interaction effects, for example, determine which modes of action are involved in typical interactions. 

The design of thickwalled components for pulsating pressure is based on the stress calculation with analytical or numerical methods and the determination of the maximum equivalent stress in relation to the admissible stresses at uniaxial conditions. The latter have to be extracted from Woehler-tests with specimen. If the stresses yield too large at load conditions including a safety factor, the design must be optimized by avoiding the major stress concentrations at bore intersections. The avoidance of T-intersections is reducing stresses by factor 2-3 (Fig. Id). 

When using the spark test apparatus, the safety factor of 1.5 (if required) shall be obtained by one of the following methods ... 

This is determined by applying a suitable safety factor to the maximum stress that the material could be expected to withstand without failure under standard test conditions. The safety factor allows for any uncertainty in the design methods, the loading, the quality of the materials, and the workmanship. 

The traditional method, used widely in nutrition, pharmacology, and toxicology, is to assume the equivalence between species of doses expressed as milligrams of test substance per kilogram of body weight. This method was adhered to by the Scientific Committee of the Food Safety Council and is implicit also in the traditional safety factor approach. 

C. Joint position coefficient B B value is determined by the relative azimuth angle of control joint surface and working face roof Based on classification method, joint fissure survey results in field and coal and rock physical and mechanical parameters test results. The dip angle of controlled joint surface is steep dip in working face roof Working face roof is normally horizontal. The joint position coefficient B of surrounding rock is 0.85 when it is classified by the unfavorable principle. This value is used to improve safety factor. 

Some assessors also do a useful life analysis to provide the safety instrumentation engineer with knowledge of any wear out mechanisms and the time periods imtil wear out. Preventative maintenance programs can be established to replace instruments at the end of their useful life knowing this information. Some FMEDA analyses are also extended to evaluate the effectiveness of proposed proof test methods. This provides the safety instrument engineer with proof test coverage factors used for more realistic PFH/PFD/PFDavg calculations. 

It should be noted, however, that tabulations of properties of flammable substances are based on standard test methods, which may have very different conditions from those encountered in practical laboratory use. Large safety factors should be applied. For example, the published flammability limits of vapors are for uniform mixtures with air. In a real situation, local concentrations that are much higher than the average may exist. Thus, it is good practice to set the maximum allowable concentration for safe working conditions at some fraction of the tabulated LEL 20% is a commonly accepted value. 

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