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Process flow diagrams 0 8

A process flow diagram(PFD) is a diagram commonly used by chemical engineersin the process design of petroleum refineries, natural gas

processing plants, petrochemicaland chemical plants, and other industrial facilities to indicate the general flow of plant process streams and

equipment.

The PFD displays the relationship between the major equipment items of a plant facility. It does not include minor equipment items, piping

materials of construction and piping sizes. Another commonly-used term for a PFD is aprocess flowsheet.

Typical content of a process flow diagram

Process flow diagrams of a single process unit will typically include the following:

Process piping

Major bypass and recirculation lines

Major equipment symbols, names and identification (either by name, number or both)

Flow directions (indicated by arrows on the process streams)

Pressuresand temperatures, as well as other control valves and systems that monitor and

control the operation of the process (shown schematically, rather than in complete detail)

Interconnecting lines with other systems (if any)

Pressures, temperatures, flow rates and other pertinent operational values for each of the

equipment items such as pumps, gas compressors, distillation columns and other vessels

In some cases, the process flow diagram includes a material balance that lists the normaltemperature, pressure, amount and composition of all the major process streams. Also

included, in some cases, are the amount of heat provided by any process furnaces and the

amount of heat exchanged by any process heat exchangers.

The adjacent drawing depicts some of the typical symbols used in a process flow diagram to

indicate the major equipment items.

Process flow diagrams generally do not include:

Pipe classes or piping line numbers

Pipe sizes

Process control instrumentation (sensors and final elements) in detail

Minor bypass lines

Isolation and shutoff valves

Maintenance vents and drainsRelief and safety valves

Flanges (if any)

The adjacent image provides some examples of the typical symbols used in PFDs to represent various major equipment items, piping and valves.

It is by no means completely inclusive, but it is representative of the great many such symbols commonly used in drawing PFDs.

Process flow diagrams of multiple process units within a large industrial plant will usually contain less detail and may be called ''block flow

diagrams'' or ''schematic flow diagrams''.

Process flow diagram examples

Single process unit

The process flow diagram below depicts a single chemical engineering unit process known as a catalytic reforming unit which is widely used in

most, if not all, petroleum refineries. It does not include all of the above listed process flow diagram components to avoid disclosure of proprietaryinformation and, although not usually done in practice, some color has been added.

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Multiple process units within an industrial plant

The process flow diagram below is an example of a schematic or block flow diagram and depicts the various unit processes within a typical oil

refinery:

Simple block flow diagrams

Below are two examples of very simple process block flow diagrams. One is a diagram of the processes used to produce ammoniaand the other

is a diagram of a process for producing petroleum asphalt:

Other items of interest

A PFD can be computer generated from chemical process simulators, computer-aided design (CAD) packages, or flow chart software using a

library of chemical engineering symbols. Rules and symbols are also available from standardization organizations such as:

ISO DIS 10628-2: Diagrams for the Chemical and Petrochemical Industry - Part 2: Graphical Symbols [6]

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Contributions to http://chemengineering.wikispaces.com/ are licensed under a Creative Commons Attribution No-Derivative-Works Non-Commercial 3.0 License.

Portions not contributed by visitors are Copyright 2014 Tangient LLC

Many large industrial companies in the process industries, and the engineering companies that serve them, have their own extensive proprietary

sets of PFD symbols.

PFDs of many commercial processes can be found in the literature, although some might be outdated. To find recent ones, patent databases

such as those available from the United States Patent and Trademark Office can be useful.

References

1. Martyn S. Ray and Martin G. Sneesby (1998), Chemical Engineering Design Project: A Case Study Approach, 2nd Edition, Gordan and

Breach Science Publishers, ISBN 90-5699-136-1.

2. Richard Turton, Richard C. Bailie, Wallace B. Whiting and Joseph A. Shaeiwitz (2002), Analysis, Synthesis, and Design of Chemical

Processes, 2nd Edition, Prentice Hall, ISBN 0-13-064792-6.

3. James R. Couper, W. Roy Penny, James R. Fair and Stan Walas (2005), Chemical Process Equipment: Selection and Design, 2nd

Edition, Gulf Professional Publishing, ISBN 0-7506-7510-1.

4. Charles E. Thomas (2007), Process Technology Equipment and Systems, 2nd Edition, Delmar Cengage Learning, ISBN 1-4180-3067-8.

Chapter 12 includes comprehensive, detailed displays of all the typical symbols for the process flow diagrams used in the petroleum,

natural gas, chemical and petrochemical industries. A copy of Chapter 12 is available here online.

5. Same as Reference 4.

6. IHS Standards Store

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