Process flowchart or PFD is also known as the system flow diagram or SFD. The main reason of using process flowchart is to show the relation between major parts of the system. Process flowchart or PFD does not include minor parts or components of the system like piping ratings or piping systems. In many organizations, users term process flow diagrams as flow sheet.
Process flowchart are used primarily in process engineering and chemical industry where there is a requirement of depicting the relationship between major components only. These process engineering and chemical industry are least concerned about the minor components involved in the system. Process flow diagrams for single unit or multiple units differ in their structure and implementation. Process flow diagrams for multiple units do not include detailed information and are known as the schematic flow diagrams or block flow diagrams.