What are the key elements of a process flow diagram for FEED?

A process flow diagram (PFD) is a graphical representation of the main equipment, piping, and streams involved in a chemical or industrial process. It is an essential tool for Front End Engineering Design (FEED), which is the stage of project development where the technical and economic feasibility of a process is evaluated and optimized. In this article, you will learn about the key elements of a PFD for FEED and how they help you design a safe, efficient, and cost-effective process.

Key takeaways from this article

Label everything clearly:

Ensure every piece of equipment and stream has a unique identification number and descriptive name. This clarity helps in monitoring and maintaining the process efficiently.### *Color-code process streams:Use distinct colors for different phases and states of streams, such as blue for liquids or green for gases. This visual differentiation aids quick identification and reduces errors during operations.

This summary is powered by AI and these experts

1 Process equipment

Process equipment includes the vessels, reactors, pumps, compressors, heat exchangers, separators, and other units that perform the physical and chemical transformations of the process. Each equipment should be labeled with a unique identification number, a descriptive name, and the operating conditions such as pressure, temperature, and flow rate. The equipment should also show the main dimensions, orientation, and elevation, as well as any special features such as insulation, heating, or cooling.

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2 Process piping

Process piping connects the equipment and transports the fluids and gases between them. The piping should indicate the direction of flow, the pipe size and material, the pipe schedule and rating, and the valve types and locations. The piping should also show any fittings, flanges, branches, reducers, and expansion joints that affect the flow or pressure of the stream. The piping should be routed in a logical and efficient manner, avoiding unnecessary bends, loops, or crossings.

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Ed Simon, P.E.

Process Engineer at Wood Group USA, Inc.
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No. The topic of the article is process flow diagram. The narrative describes elements of a piping and instrument diagram. Different drawings for different purposes.

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Thomas Herrod-Taylor

Head of Digital Engineering Platforms at Carbon Clean
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Ed Simon is correct. Much of what is stated is shown on a piping and instrument diagram. The lines on the PFD show how equipment is connected and how the process works. The main mode of operation is shown in bold lines. Alternative modes of operation are shown with fine lines and covered by notes.

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3 Process streams

Process streams are the fluids and gases that enter, exit, or circulate within the process. The streams should be labeled with a unique identification number, a descriptive name, and the composition, phase, and state of the stream. The streams should also show the mass or volumetric flow rate, the pressure, temperature, and density of the stream, and any other relevant properties such as viscosity, heat capacity, or vapor pressure. The streams should be color-coded according to their phase and state, such as blue for liquid, green for gas, or red for vapor.

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Thomas Herrod-Taylor

Head of Digital Engineering Platforms at Carbon Clean
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PFDs are monochrome. The phase and fluid state is specified in the heat and material balance. This might be a table on the PFD itself or in a separate Heat and Material Balance (H&MB) document. Coloured lines get confused with the colour coding used when documents are revised and updated.

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Dave Scott

International Process Consultant
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The flows are the basis of the PFD, the mass and energy balance is derived from and defined by the PFD, This should be FIRST>

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4 Process utilities

Process utilities are the external services that support the operation of the process, such as steam, water, electricity, fuel, air, or refrigerant. The utilities should be labeled with a descriptive name and the supply and return conditions such as pressure, temperature, and flow rate. The utilities should also show the connection points and isolation valves to the process equipment or piping. The utilities should be color-coded according to their type and function, such as yellow for steam, purple for water, or black for electricity.

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Thomas Herrod-Taylor

Head of Digital Engineering Platforms at Carbon Clean
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Process utilities are shown in the same way as other process streams on a PFD. Same comments as colour coding. Electricity does not appear on a PFD.

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5 Process controls

Process controls are the instruments and devices that monitor, measure, regulate, or control the process variables such as pressure, temperature, level, flow, or composition. The controls should be labeled with a unique identification number, a descriptive name, and the set point or range of the control variable. The controls should also show the type and location of the sensor, transmitter, controller, actuator, or indicator, and the signal type and direction between them. The controls should be symbolized according to the standard notation such as ISA or P&ID.

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Thomas Herrod-Taylor

Head of Digital Engineering Platforms at Carbon Clean
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The PFD only shows the way the process is controlled. The signals and logic is shown on a P&ID. This is where the notation in ISA standards is shown

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6 Process safety

Process safety is the aspect of the process design that aims to prevent or mitigate the risks of fire, explosion, toxicity, corrosion, or environmental damage. The safety elements include the relief valves, rupture disks, safety valves, flare systems, blowdown systems, emergency shutdown systems, fire protection systems, or vent systems that protect the process equipment, piping, streams, or utilities from overpressure, overheating, or leakage. The safety elements should be labeled with a descriptive name and the design or operating conditions such as pressure, temperature, or flow rate. The safety elements should also show the connection points and isolation valves to the process equipment or piping. The safety elements should be symbolized according to the standard notation such as API or NFPA.

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What are the key elements of a process flow diagram for FEED?

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1 Process equipment

2 Process piping

3 Process streams

4 Process utilities

5 Process controls

6 Process safety

Front End Engineering Design (FEED)

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