Simplified Pneumatic Symbols

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The components needed to manufacture and听construct pneumatic logic control circuits are听readily available, reliable and have been proven in听countless applications.听The symbols needed to design a pneumatic circuit听are few, yet until now no practical rapid symbology听for the control designer existed. Most of the听symbols available to the designer are too complex听to facilitate clear, creative thinking, take too long听to record, leave room for significant errors, and听generally slow down the design process.听In an effort to improve both the speed and accuracy听of creative design, we offer for your consideration听and use this simplified system of symbols for听designing pneumatic control circuitry.

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Basic Requirements

Before a circuit can be designed, one needs a听basic understanding of the various components听available and how they function. This understanding听is a requirement for the successful use of any听symbol. To 听depict these functional concepts,听graphic symbols are used.

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Historically, pneumatic symbols have been overly听detailed and cumbersome. Symbols (such as ANSI)听are often used to tell a complete narrative story.听The symbols of this type are difficult to use听because of their complexity. The writing and the听reading of them is always lengthy, robbing time听from creative efforts. As a finished product they are听useful, and tell a great deal about the component,听pertinent or otherwise, but they were never intended听for air logic control designs. To a circuit designer听such symbols are a burden that can slow or derail听the thought process.

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Time-saving

What is needed is a group of pneumatic component symbols that will provide the circuit designer,听both novice and professional, with a viable shorthand that will save time, yet clearly record and听communicate ideas. They should be open-ended听and expandable to truly represent the variety of听pneumatic controls available to the designer now,听as well as in the future.

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Fast and Functional

They must be fast and easy to draw. They should听be both pictorial and functional in nature to help听the designer visualize the circuit, and to provide听the necessary pertinent information about how听components work (inputs, output, actuators, etc.).听What follows is a basic set of symbols designed to听meet these criteria. They have proven to be fast听and informative in years of daily use. These听symbols are recommended for anyone with a听basic understanding of pneumatic control听components鈥� functions, and who seeks to design听in a useful and productive manner.

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Simplified symbols for faster, easier and听
听听听听听听听听听听听听more creative pneumatic circuit design.

Directional valves comprise the largest portion of any air logic circuit.听Complete directional valve symbols are created by combining the听appropriate actuator and valve symbols found along the horizontal and听vertical edges of the chart.

Seven of the most commonly used actuators are shown in the top bar. The听designer is free to extend this list as may be required to suit a particular听need.

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A close study of most air logic control circuits will reveal that there are听only six basic valve functions commonly used. The symbols for these听valve functions are shown in left graphic. These six basic valve symbols,听when combined with the basic actuator symbols, comprise virtually all听the directional valve symbols needed for air logic control.

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Accessory components are designed for a specific purpose. The valves听included in accessory components are basically flow devices that alter听flow paths or signals, but do not generate signals by themselves.

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Simplified symbols for accessory components are, for the most part, self听explanatory and are shown at the bottom of page.

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A brief review of the valves, their actuators, and how they combine into听useful symbols, together with the examples contained in the following听pages, will give the reader a valuable, time-saving method for drawing听air logic control circuits.

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Symbols created by combining valves and actuator

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Derivation of Simplified Symbol from ANSI

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Rules to help guide application:听
8 simple rules in applying these air logic听control symbols are as follows:

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1. 听Symbols are always drawn in the valve鈥檚 normal听unactuated position听- not as held at the start of a cycle or听as actuated. The flow direction or condition of the valve鈥檚听inlet is in its normal position. The symbol does not听change, even if the valve is shown as actuated. To听change the symbol would change the type of valve听shown in the circuit.

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2. Symbols do not show exhaust flow paths.听Nearly all air logic circuit components exhaust to听atmosphere, and exhaust flow paths are of little or no听importance in understanding a pneumatic control circuit听It is implied that all directional valves have their output听either connected to their input or to atmosphere.

3.听In all symbols the valve is assumed to have a spring听returning it to its normal condition听unless otherwise听shown. Remember, more than one type of actuator can听be shown on opposite ends of the valve.

4.听Actuators are understood to push the flow path听indicator when actuated, pushed or energized.听Since the听methods of actuating air logic valves are nearly limitless,听the circuit designer may create additional actuator听symbols to represent a special requirement.

5.听Circuits should not be burdened with excessive听supply lines.听Supplies are shown at each component听requiring one. Subscripts are used to identify different听supplies, such as different pressures or medias. 听

6.听Special valve symbols may be constructed by the user听or multiple symbols may be tied together and indicated听as one component.	7.听In some specialized components more than one actuator听(usually the same type)听can be put on a valve.听听

8.听2-way valves听are seldom used in air logic circuits but听on those occasions where a 2-way valve is needed the听3-way valve symbol can be used, with an appropriate听notation as to its function in the circuit such as shown.
	The 3-way N.O. valve 听is the same听regardless of how it is听oriented听or whether the听outlet is to the right or left. Free orientation of听symbols allows clarity in drawing circuits,听minimizing design time spent on layout and in听drawing.

Versatile:听It should be emphasized that the simplified symbols听provided here are intended as a design aid, and may or听may not be used to replace other formal symbologies for听finished drawings. They are applicable to components of听any manufacture as long as the component gives the听same function.

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Comparisons to Existing Symbols:听It may be helpful to understand the useful simplicity of these new symbols by comparing them to existing symbology听now in use.听

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Shown below are air circuits using existing symbols for various types of valves, and the same circuits using the simplified听symbols provided in this new method. The more complex symbols involve considerable time in drawing them. Many听of the symbols are so closely alike as to cause confusion in understanding what is meant. 听Simplified symbols help听eliminate this confusion.

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A few moments review of the comparisons will quickly reveal that the new simplified symbols provide an important aid听for speed in designing new circuits. In air logic design where drawing time needs to be kept to a minimum, the new听simplified symbols offer the designer new freedom to spend his time in the creative aspects of the task, rather than in听the time-consuming details of excessive drawing.

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Here is a complete chart of the basic valves, actuators, combinations and the auxiliary components听used in pneumatic logic control circuitry.