What is a Pneumatic Symbol?

What is a Pneumatic Symbol?

Symbols provide an effective way of describing the functionality and operation of often complex systems, providing they are consistent across all providers of the systems.

For pneumatic components, ISO 1219-1 is a recognised standard ensuring this consistency; there is also the Japanese Industrial Standard (JIS) but, fortunately, in most cases the symbols are identical between the two standards.


How do pneumatic symbols work?


The Standard lays out several elements that must be represented by each symbol, where applicable: The function of the component; actuation and return mechanisms; the number of switching positions; the number of connections; an indication of the flow path and the operating principle. The chart above shows a good representation of common symbols and more is outlined below.


How do I select a pneumatic symbol?

  • general actuation and return symbols - there are common actuation and return mechanisms between components and these have standardised symbols. A common mechanism is the spring, but others are solenoid, (air) pilot, pilot assisted solenoid and air spring. Manual and mechanical valves have a variety of operators and some are shown in the chart above; for example, toggle lever and push button. Often single components can utilise more than one operator, for example a solenoid valve with spring return but, because of the standardisation, it is always clear which operator is fulfilling which function.
  • valve symbols - control valves are defined by two numbers, for example 3/2; the first number gives the number of ports in the valve body and the second, the number of positions. In the symbol, each position is identified by a box, so a 3/2 valve would have two boxes. Each port is labelled; for example for a 5/2 valve, port 1 is supply; 2 and 4 are outlets and 3 and 5 are exhausts, for ports 2 and 4 respectively. Each operator is labelled (for example 12 or 14) to show the connection made between ports.
  • cylinder symbols - the basic symbol for a piston actuator is like a section of the component itself, with the piston shown sliding inside the cylinder body and two air connections; one connection will be blocked for single acting cylinders. Cushioning is denoted by a smaller rectangle placed to one side of the piston section; one on both sides of the piston shows cushioning at both ends of the stroke. Adjustable cushioning is indicated by a diagonal arrow passing through the cushion symbols. Magnetic actuators are denoted by a solid black band inside the piston section. Please refer to the chart to see this pictorially.


Typical applications for pneumatic symbols?

Pneumatic symbols will not normally be used in isolation; they will be combined to represent the pneumatic system being designed or ‘mapped’. So, for example, air supply may pass through a filter regulator lubricator with automatic drain and 3/2 shut-off valve, to a 5/2 solenoid/solenoid in-line valve driving a double acting magnetic actuator with adjustable cushioning at either end. The appropriate symbols will be joined together to show the ‘circuit diagram’. Because ISO 1219-1 makes interpretation of the symbols universal, any builder will always use the correct type of component.


More information

Click below for a full list of pneumatic symbols