List of pneumatic symbols
Pneumatic symbols are like electronic component symbols, in that they are used on schematics and are used to indicate what type of device is being used in a circuit or in a line. Pneumatic and hydraulic systems use the same symbols.
Knowing these symbols will be of benefit if you plan on being a heavy machinery mechanic or work around pneumatics or hydraulics a lot.
There are 3 different types of lines for pneumatics. A continuous line is used to indicate a flow line. A dashed line is used to indicate a pilot or a drain. A line comprised of long and short dashes around two or more component symbols, indicates an envelope.
A large circle is an indicator of a pump, a motor, or a compressor. Smaller circles are indicators of measuring devices. A half circle indicates a rotary actuator.
A single square indicates a pressure control function. Multiple squares that are adjacent to one another represent a directional control.
Diamond shapes represent fluid conditioners, such as filter, a lubricator, a separator or a heat exchanger.
Triangles signify flow direction, and whether you are dealing with pneumatics or hydraulics. A solid triangle indicates the direction of hydraulic flow, while an open triangle indicates the direction of pneumatic flow.
Other basic symbols
Two other common symbols are a zigzag and what looks like two parenthesis with the curved sides facing each other. The zigzag indicates a spring is in use. The parenthesis represent flow restriction.
These basic symbols make up the majority of the symbols in a hydraulic or pneumatic schematic. You can place multiple symbols together and create "compound" symbols. For instance, the large circle symbol, If it has a solid triangle pointing out inside of it, it means it is a unidirectional hydraulic pump. Two solid triangles facing outward and opposite each other inside a large circle, means it is a bidirectional hydraulic pump. Change the arrows to facing in, and it becomes a hydraulic motor. The triangles work the same for rotary actuators. If a half circle has a solid triangle inside, it is a hydraulic rotary activator.
Squares work similarly. When more than one square is in a circuit or line and they are adjacent, they are control valves. Stretch them to be rectangles, and you have cylinders. If a square has an arrow inside of it, it indicates being a normally closed switch, while an arrow whose tail sticks out of the square a bit, indicates a normally open switch. Any symbols with an arrow completely through them at a 45 degree angle from the line, indicates variable or adjustable flow or control.