Dimension is given relative to the centreline of the piping.Isometrics are not drawn to scale but should be proportional to easy understanding.It shows all information necessary for fabrication and erection. An isometric drawing covers a complete line as per the line list and P&ID.Latest P&ID/PEFS (Process) (Issued signed copy) General Information about Piping Isometric drawings.and is conversant with a drafting tool can draft isometric. A draft person ( piping designer/engineer) who knows to read the piping GA.Generally, isometrics are prepared/extracted by the design group.Isometric is also used to work out the exact MTO requirement.The main purpose of an isometric is to provide all information necessary for the fabrication and erection along with the bill of material required to do so.Piping isometrics are the three-dimensional representation of the line.In this article, a few of the salient points are discussed. So Engineers and Designers must be aware of the isometric preparation steps. Piping Isometric drawing is one of the most important deliverables of the piping discipline as it provides complete information of the piping route to be erected at the construction site.