PFD
Process Flow Diagram
A Process Flow Diagram (PFD) is the high-level engineering schematic showing major process equipment, primary process streams, and heat-and-material balance data for a process plant. PFDs sit upstream of P&IDs in the engineering deliverable lifecycle and form the foundation of process design, equipment sizing, utility load calculation, and operating philosophy. Every process unit in an EPC project produces at least one PFD.
Full Definition
A Process Flow Diagram (PFD) is the schematic engineering drawing showing the high-level process flow through a unit or plant. PFDs include major process equipment (vessels, exchangers, pumps, compressors, columns), primary process streams (with flow rate, composition, temperature, pressure at each significant point), key process data tables (stream summary, equipment summary), utility connections (steam, cooling water, electricity, fuel gas), and process control philosophy. PFDs come first in the process design cycle and are released for client approval before P&ID development begins. See the P&ID standard reference for the downstream detailed deliverable.
Context & Detail
PFD vs P&ID
PFD is the high-level process schematic showing primary equipment and streams. P&ID is the detailed engineering drawing showing every piping line, every instrument, every valve, and the control philosophy. PFD comes first in the design cycle; P&IDs are developed from approved PFDs and become the primary detailed engineering deliverable. PFD typically covers an entire process unit in one or two drawings; the same unit is then expanded into 20-200 P&IDs depending on complexity.
PFD content
A typical PFD contains: major equipment with equipment numbers (V-100 vessels, E-100 exchangers, P-100 pumps, C-100 compressors, T-100 columns), primary process streams with stream numbers and arrows indicating direction, stream summary table (mass flow, composition, temperature, pressure, phase at each numbered stream), equipment summary table (design conditions, capacity, materials), utility connections (steam, cooling water, electricity, fuel gas), and high-level control philosophy.
PFD lifecycle
PFDs go through revisions similar to P&IDs: IFR (Issued For Review by other disciplines), IFA (Issued For Approval by client), and IFC (Issued For Construction at mechanical completion). PFD approval is a major project milestone because P&ID development cannot begin in earnest until PFD is approved. PFD revisions during P&ID development trigger downstream impact on P&IDs, line lists, equipment lists, and instrument schedules.
PFD in process design
PFD is the basis for process design calculations: heat-and-material balance, equipment sizing, utility load calculation, vent system sizing, flare load calculation, and pressure relief sizing. The PFD stream summary table provides the design basis for downstream calculations. Process engineering software (Aspen HYSYS, Aspen Plus, PRO/II, ChemCAD) outputs streams and equipment sizing that populate the PFD.
EPC Usage
- 01
Every greenfield refinery, petrochemical plant, fertiliser plant, and gas processing facility produces 20-100 PFDs covering process units, utility units, and offsites.
- 02
Indian PSU refineries (IOCL, BPCL, HPCL, ONGC, Reliance, Nayara) maintain PFDs across 8-20 process units per complex. Brownfield revamp PFDs reference existing PFDs as the design basis.
- 03
Petrochemical plants with complex process chemistry (ethylene cracker, urea synthesis, methanol synthesis, propylene oxide) produce highly detailed PFDs with stream-level material balance covering reaction kinetics, separation thermodynamics, and recycle loop balance.
- 04
PFD approval is a major project milestone. EPC contractors target PFD approval at 25-35% of detailed engineering progress so P&ID development can begin in earnest.
- 05
Brownfield revamp PFDs require reconciliation between existing plant baseline and new modification scope. The PFD revision drives downstream P&ID and equipment sizing impact analysis.
- 06
Indian PSU brownfield projects often use legacy PFDs from the original commissioning era (1970s-1990s) plus all subsequent revisions. Digitisation of legacy PFDs into modern process simulation tools (Aspen HYSYS) is a common requirement.
How Pathnovo Handles It
Pathnovo's P&ID extraction product supports PFD extraction alongside P&ID extraction. The product extracts major equipment, primary streams, stream summary data, and utility connections from PFD PDFs and scanned drawings. Combined with P&ID extraction downstream, the workflow produces a complete process unit data set ready for digital twin platforms (AVEVA AIM, Bentley iTwin, Hexagon SDx2, Cognite Data Fusion) or process simulation tools (Aspen HYSYS, Aspen Plus). Used by Indian EPC contractors and PSU refineries for brownfield digitisation, legacy PFD reconstruction, and digital twin programmes.
Frequently Asked Questions
What does PFD stand for?
PFD stands for Process Flow Diagram. A PFD is the high-level engineering schematic showing major process equipment, primary process streams, and heat-and-material balance data for a process plant. PFDs sit upstream of P&IDs in the engineering deliverable lifecycle.
What is the difference between PFD and P&ID?
PFD is the high-level process schematic showing major equipment and streams. P&ID is the detailed engineering drawing showing every piping line, every instrument, every valve, and the control philosophy. PFD comes first in the design cycle; P&IDs are developed from approved PFDs and become the primary detailed engineering deliverable.
What does a PFD contain?
A PFD contains major equipment with equipment numbers, primary process streams with stream numbers, stream summary table (mass flow, composition, temperature, pressure, phase), equipment summary table (design conditions, capacity, materials), utility connections (steam, cooling water, electricity), and high-level control philosophy.
How many PFDs does an EPC project produce?
A typical greenfield refinery produces 20-100 PFDs covering process units, utility units, and offsites. Petrochemical and fertiliser plants run 15-60 PFDs. Mid-EPC projects ($50M-$500M scope) run 5-30 PFDs. PFD count is roughly 10% of the eventual P&ID count for the same scope.
Why is PFD approval a major project milestone?
PFD approval establishes the process design basis. P&ID development cannot begin in earnest until PFD is approved because P&IDs derive from PFDs. EPC contractors target PFD approval at 25-35% of detailed engineering progress so P&ID development can ramp up. PFD revisions after P&ID development triggers significant downstream impact.
Can Pathnovo extract PFD data?
Yes. Pathnovo's P&ID extraction product supports PFD extraction alongside P&ID extraction. The product extracts major equipment, primary streams, stream summary data, and utility connections from PFD PDFs and scanned drawings. Combined with P&ID extraction, the workflow produces a complete process unit data set for digital twin and process simulation platforms.
What software produces PFDs?
Process engineering software including Aspen HYSYS, Aspen Plus, PRO/II, and ChemCAD outputs streams and equipment sizing that populate the PFD. CAD tools (AutoCAD, MicroStation) and authoring suites (AVEVA Engineering, Hexagon SmartPlant P&ID) draw the formal PFD deliverable. Brownfield digitisation projects extract structured data from legacy PFDs to populate modern simulation tools.
Related Pages
P&ID Data Extraction
Extract PFD and P&ID structured data with 99.5% accuracy.
P&ID Standard Reference
Detailed downstream deliverable derived from approved PFDs.
Digital Twin Data Integration
AVEVA AIM, Bentley iTwin, Hexagon SDx2 feeds from PFD and P&ID data.
Engineering Document Intelligence
Full document intelligence platform across PFD, P&ID, datasheets.
Asset Information Management
CFIHOS / ISO 15926 asset register from PFD and P&ID data.
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