Process Flow Diagram (PFD) — definition
Process Flow Diagram (PFD) is a schematic representation of the major process steps, equipment items and material flows in a production system, without piping or instrumentation detail.
A PFD is typically produced early in basic engineering to establish the overall process logic, mass and energy balances, and equipment list before detailed piping and instrumentation diagrams are developed. It serves as a common reference between process engineers, equipment suppliers and the buyer's operations team.
Why it matters to industrial buyers
A clear PFD lets buyers validate that the proposed process sequence matches their intended product and capacity before detailed engineering commitments are made.
Key reference points
Level of detail
PFDs typically show major unit operations and flow direction rather than individual valves or instruments.
Sequence
PFDs usually precede piping and instrumentation diagrams (P&IDs) in the engineering sequence.
Commonly confused with
P&ID
A PFD shows overall process logic and major streams; a P&ID adds piping, instrumentation and control detail for construction.
How it is used in practice
The PFD for a dairy processing line shows the sequence from raw milk reception through pasteurisation to packaging.
Frequently asked questions
Who prepares a PFD?
Typically a process or systems engineer, often the equipment supplier or an independent engineering consultant during basic design.
Is a PFD contractual?
It is commonly referenced in the technical specification and contract as the agreed process basis.
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Related terms
Basic Engineering Design
Basic engineering design is the early project phase that establishes process flow, major equipment sizing, layout and technical specifications sufficient to define scope and budget.
General Arrangement Drawing (GA Drawing)
General Arrangement Drawing (GA drawing) is a scaled drawing showing the overall dimensions, footprint and spatial layout of a machine or production line within a facility.
Technical Specification
Structured document describing the functional, performance, materials, and interface requirements an item of equipment or system must meet.
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Reference content only. Global B2B Group is independent of equipment manufacturers and financing institutions; definitions are provided for education and do not constitute engineering, financial or legal advice.