Pfd Process Flow Diagram

Overview

Engineering reference data for Pfd Process Flow Diagram in fluid mechanics.

Key Formulas

Reynolds Number

$Re = \frac{\rho v D}{\mu}$

Ratio of inertial to viscous forces — determines flow regime.

Bernoulli's Equation

$P + \frac{1}{2}\rho v^2 + \rho g h = \text{const}$

Conservation of energy for steady, inviscid, incompressible flow.

Continuity Equation

$A_1 v_1 = A_2 v_2$

Conservation of mass for incompressible flow.

Darcy-Weisbach

$\Delta P = f \frac{L}{D} \frac{\rho v^2}{2}$

Pressure drop due to friction in a pipe.

Variables

PFD Inclusions and Exclusions

A correctly prepared Process Flow Diagram (PFD) focuses on major system components and their operational parameters, intentionally omitting detailed installation specifications.

What a PFD Should Include

• Process piping and major equipment symbols
• Major equipment names and identification numbers
• Control valves and valves affecting system operation
• Interconnections with other systems
• Major bypass and recirculation lines
• System ratings: minimum, normal, and maximum flow, temperature, and pressure
• Fluid composition

What a PFD Should Not Include

• Pipe classes and line numbers
• Minor bypass lines
• Isolation and shutoff valves
• Maintenance vents and drains
• Relief and safety valves
• Code or class information

PFD vs. P&ID

While a PFD focuses on overall process flow and design values, a Piping & Instrumentation Diagram (P&ID) provides more detailed information for construction and operation.

• PFD: Shows major components and process design values for system understanding.
• P&ID: Shows all piping, instruments, and controls for detailed engineering, construction, and maintenance. It includes information that a PFD intentionally excludes, such as pipe line numbers, valve details, and relief device specifications.

References

• Original Source