What is a P&ID?

 P&ID is a series of letters that mean: Piping and instrumentation diagram – This is a schematic diagram showing piping, equipment and instrumentation connections within process units in oil refineries, petrochemical and chemical plants, natural gas processing plants, power plants, water treatment and other similar process plants.

The typical P & ID is a full diagrammatic representation of a process plant. Each piece of equipment is shown along with its connecting pipe lines to other equipment. It may be regarded as an enhanced process flow diagram (PFD) which shows, in addition to the process itself, details such as control and instrumentation equipment, pump and pipe sizes etc. Each instrument / piece of equipment is shown by a symbol denoting its type (pump, sensor, valve etc.) and a unique identification number or tag for differentiation from others. On the typical P&ID the pipe lines are detailed to the extent that all valves are shown along with other significant in-line and on-line mechanical or instrument item.