Reliability process evolution

Pressure-relieving systems are unique compared with other systems within a chemical plant hopefully they will never need to operate, but when they do, they must do so flawlessly. Other systems, such as extraction and distillation systems, usually evolve to their optimum performance and reliability. This evolution requires creativity, practical knowledge, hard work, time, and the cooperative efforts of the plant, design, and process engineers. This same effort and creativity is essential when developing relief systems however, in this case the relief system development must be optimally designed and demonstrated within a research environment before the plant start-up. 

Reaction characterisation by calorimetry generally involves construction of a model complete with kinetic and thermodynamic parameters (e.g. rate constants and reaction enthalpies) for the steps which together comprise the overall process. Experimental calorimetric measurements are then compared with those simulated on the basis of the reaction model and particular values for the various parameters. The measurements could be of heat evolution measured as a function of time for the reaction carried out isothermally under specified conditions. Congruence between the experimental measurements and simulated values is taken as the support for the model and the reliability of the parameters, which may then be used for the design of a manufacturing process, for example. A reaction modelin this sense should not be confused with a mechanism in the sense used by most organic chemists-they are different but equally valid descriptions of the reaction. The model is empirical and comprises a set of chemical equations and associated kinetic and thermodynamic parameters. The mechanism comprises a description of how at the molecular level reactants become products. Whilst there is no necessary connection between a useful model and the mechanism (known or otherwise), the application of sound mechanistic principles is likely to provide the most effective route to a good model. 

Based on the use of the NARCM regional model of climate and formation of the field of concentration and size distribution of aerosol, Munoz-Alpizar et al. (2003) calculated the transport, diffusion, and deposition of sulfate aerosol using an approximate model of the processes of sulfur oxidation that does not take the chemical processes in urban air into account. However, the 3-D evolution of microphysical and optical characteristics of aerosol was discussed in detail. The results of numerical modeling were compared with observational data near the surface and in the free troposphere carried out on March 2, 4, and 14, 1997. Analysis of the time series of observations at the airport in Mexico City revealed low values of visibility in the morning due to the small thickness of the ABL, and the subsequent improvement of visibility as ABL thickness increased. Estimates of visibility revealed its strong dependence on wind direction and aerosol size distribution. Calculations have shown that increased detail in size distribution presentation promotes a more reliable simulation of the coagulation processes and a more realistic size distribution characterized by the presence of the accumulation mode of aerosol with the size of particles 0.3 pm. In this case, the results of visibility calculations become more reliable, too. 

The impact of these developments on the instrument manufacturers has been twofold firstly, by incorporating these advances as they occurred into successive generations of instruments, manufacturers have been able to lower production costs and increase the accuracy and reliability of their instruments, thus making them available to a wider market. Secondly, it has led to the development of increasingly sophisticated instrumental techniques which were not previously feasible for either economic or technical reasons. In order to view this process of evolution in perspective, it is wortwhile to consider briefly some of the developments in electronics which have helped it to occur. 

The evolution of structural adhesives will certainly continue. Each increment in strength, durability, processing speed and ease, safety, reliability and reproducibility opens new commercial markets, not only to displace older joining methods but also to allow for the manufacture of new structures not possible without adhesives. 

The complexity of environmental matrices and the problems due to the spatial-temporal evolution of pollutants and their involvement in biogeochemical cycles calls for the utmost accuracy in data collection, data analysis and environmental control. The first and fundamental requisite to be satisfied in order to give definitive answers to existing environmental problems is the capacity to produce absolutely reliable data, particularly where trace toxic chemical substances are concerned. It is imperative that measured concentrations correspond strictly to the truth. This reminder might appear superfluous, but unfortunately the technical-scientific difficulties involved in the analytical process are often underestimated, as the scientific literature has already amply demonstrated (see for instance refs. 7 through 13). 

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