Piping isometrics are drawn for every piece of pipe required in the plant. These drawings are 3-D
sketches of the pipe run, indicating the elevations and orientation of each section of pipe. In the past, it
was also common for comprehensive plants to build a scale model so the system could be viewed in
three dimensions and modified to remove any potential problems. Over the past twenty years, scale
models have been replaced by three-dimensional computer aided design (CAD) programs that are
capable of representing the plant as-built in three dimensions. They provide an opportunity to view the
local equipment topology from any angle at any location inside the plant. One can actually “walk through”
the plant and preview what will be seen when the plant is built. The ability to “view” the plant before
construction will be made even more realistic with the help of virtual reality software. With this new
tool, it is possible not only to walk through the plant but also to “touch” the equipment, turn valves, climb
to the top of distillation columns, and so on. In the next section, the information needed to complete a
preliminary plant layout design is reviewed, and the logic used to locate the process units in the plant and
how the elevations of different equipment are determined are briefly explained.