P&ID shows all of piping including the physical sequence of branches, reducers, valves, equipment, instrumentation and control interlocks.
The P&ID are used to operate the process system.
A P&ID should include:
Instrumentation and designations
Mechanical equipment with names and numbers
All valves and their identifications
Process piping, sizes and identification
Miscellaneous - vents, drains, special fittings, sampling lines, reducers, increasers and swagers
Permanent start-up and flush lines
Flow directions
Interconnections references
Control inputs and outputs, interlocks
Interfaces for class changes
Seismic category
Quality level
Annunciation inputs
Computer control system input
Vendor and contractor interfaces
Identification of components and subsystems delivered by others
Intended physical sequence of the equipment
A P&ID should not include:
Equipment rating or capacity
Instrument root valves
Control relays
Manual switches and indicating lights
Primary instrument tubing and valves
Pressure temperature and flow data
Elbows and similar standard fittings
Extensive explanatory notes