Failure state profile

FIGURE 2.10 TRIPOD Failure-State Profiles of Two Production Platforms (Wagenaar, 1992). 

The absence or presence of each of the eleven general failure types is determined through the employment of indicator questions, which are administered through a questionnaire to the workforce. There are about 2200 such questions. Each time a questionnaire is distributed at a plant, a random selection of 10 per cent of the questions covering all general failure types are selected and adapted to the conditions at the plant. The results are used to compute a so-called failure-state profile. Eigure 19.1 shows an example. 

The combinations of failures and non-failed conditions define the state of the pJani at the right branches. The damage associated with these plant damage states are calculated using thermal-hydraulic analyses to determine temperature profiles that are related to critical chemical reactions, explosions and high pressure. These end-states serve as initiators fot breaking confinement that leads to release in the plant and aquatic and atmospheric release outside ol the plant,... 

Ion selective membranes are the active, chemically selective component of many potentiometric ion sensors (7). They have been most successfully used with solution contacts on both sides of the membrane, and have been found to perform less satisfactorily when a solid state contact is made to one face. One approach that has been used to improve the lifetime of solid state devices coated with membranes has been to improve the adhesion of the film on the solid substrate (2-5). However, our results with this approach for plasticized polyvinylchloride (PVC) based membranes suggested it is important to understand the basic phenomena occurring inside these membranes in terms of solvent uptake, ion transport and membrane stress (4,6). We have previously reported on the design of an optical instrument that allows the concentration profiles inside PVC based ion sensitive membranes to be determined (7). In that study it was shown that water uptake occurs in two steps. A more detailed study of water transport has been undertaken since water is believed to play an important role in such membranes, but its exact function is poorly understood, and the quantitative data available on water in PVC membranes is not in good agreement (8-10). One key problem is to develop an understanding of the role of water uptake in polymer swelling and internal stress, since these factors appear to be related to the rapid failure of membranes on solid substrates. 

Food-effect studies are necessary for all multisource modified-release formulations to ensure the absence of dose dumping . The latter signals a formulation failure such that the dose is released all at once rather than over an extended period of time. This results in a premature and abrupt rise in the plasma concentration time profile. A high-fat meal often provides a maximal challenge to the robustness of release from the formulation with respect to prandial state. The composition of the meal should also take local diet and custom into consideration (see also section 6.2.4). 

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