Typically, process flow diagrams of a single unit process include the following:
* Process piping
* Major equipment items
*Connections with other systems
* Major bypass and recirculation (recycle) streams
* Operational data (temperature, pressure, mass flow rate, density, etc.), often by stream references to a mass balance
* Process stream names
Process flow diagrams generally do not include:
* Pipe classes or piping line numbers
* Instrumentation details
* Minor bypass lines
* Instrumentation
* Controllers like Level Control or Flow Control
* Isolation and shutoff valves
* Maintenance vents and drains
* Relief and safety valves
* Flanges
Process flow diagrams of multiple process units within a large industrial plant will usually contain less detail and may be called block flow diagrams or schematic flow diagrams.