PID diagram is the flow chart of pipeline instrument, that is, process-flow chart; Instrument diagram, abbreviated as PID. It includes all equipment, pipelines, valves, instruments and so on. The pipeline has detailed data such as pipeline number, pipe diameter, material and grade, among which the data in the equipment is design data.

PID diagram shows the whole process of the device from raw materials to product realization, which is the basis of learning and training for device personnel.