Pipeline above-ground installation

In the early years of industrial development in the United States, many plants buried their outside pipelines. The initial cost for this type of installation is low because no supports are required and the earth provides insulation. However, location and repair of leaks are difficult, and other pipes buried in the same trench may make repairs impossible. Above-ground piping systems in industrial plants have proven to be more economical than buried systems, and, except for major water and gas lines, most in-plant piping systems in new plants are now located above ground or in crawl-space tunnels. 

For evaluation of the potential hazard to the technical installation or to the staff, it will be necessary to conduct a comprehensive site analysis. This should include the listing of all potential sources of danger within the installation itself, on the plant premises as well as in the installation s immediate environment. Sources of danger in the vicinity may include depots for flammable liquids, depots for chemicals, pipelines above or below ground level carrying explosive or harmful substances, and busy air lanes (e.g., lanes of approach to an airport). 

This chapter has provided solid, basic information about the installation of above-ground piping systems. There are, of course, numerous options in the design and construction of above-ground pipelines. 

The first term in Eq. (3-27) represents the voltage drop between the reference electrode over the pipeline and the pipe surface. The second term represents the potential difference AU measured at the soil surface (ground level) perpendicular (directly above) to the pipeline. Average values of the values measured to the left and right of the pipeline are to be used (see Fig. 3-24) [2]. In this way stray IR components can be eliminated. The third term comprises the current densities where, in the switched-off state of the protection installation, there is a cell current J. In the normal case J = 0 and also correspondingly AU f = 0 as well as = t/ ff On... 

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