The Iso, as isometric are commonly referred, is oriented on the grid relative to the north arrow found on plan drawings. Because iso's are not drawn to scale, dimensions are required to specify exact lengths of piping runs. Pipe lengths are determined through calculations using coordinates and elevations. Vertical lengths of pipe are calculated using elevations, while horizontal lengths are caculated using north-south and east-west coordinates.
Piping isometric are generally produced from orthographic drawings and are important pieces of information to engineers. In very complex or large piping systems, piping isometrics are essential to the design and manufacturing phases of a project. Piping isometrics are often used by designers prior to a stress analysis and are also used by draftsmen to produce shop fabrication spool drawings. Isometrics are the most important drawings for installation contractors during the field portion of the project. Each pipeline in a process or power plant is detailed by at least one piping isometric drawing. These are not drawn to scale but include sufficient dimensions and a material take off list to ensure accurate procurement, fabrication, and erection of the pipeline. A pipeline isometric can show an entire piping system with a network of connected pipelines, a single pipeline, or a single spool with prefabricated assembly. At each point where a pipeline connects to equipment or to another pipeline.
Piping isometric allow the pipe to be drawn in a manner by which the length, width and depth are shown in a single view. Isometrics are usually drawn from information found on a plan and elevation views. The symbols that represent fittings, Valves and flanges are modified to adapt to the isometric grid. Usually, piping isometrics are drawn on preprinted paper, with lines of equilateral triangles form of 60°. To read a Piping Isometric is a pipe into a isometric view, is always drawn by a single line. This single line is the centerline of the pipe, and from that line, the dimensions measured. So, not from the outside of a pipe or fitting.