ISO 1219-1:2012 is a sub-division of the ISO 14617 series, which lays down the basic elements required to produce universally recognised standard symbols. In ISO 1219-1, rules are established for devising symbols specifically related to fluid power systems.
Pneumatic Air Supply and Distribution Symbols
Symbols are used in pneumatic air supply and distribution to illustrate the function of valves and other necessary devices in the system. They are used on the components themselves as well as in the circuit design diagrams. The fixed dimension ratios may vary, as they are intended for direct use in data processing.
The symbol is the same as the Main Air symbol, as this is normally supplied by a compressor. High pressure air can be produced using piston, screw or vane compressors.
Main Air is stored in a receiver or reservoir for future use, to smooth uneven pressure and separate out water for drainage.
Compressed air filters move moisture and contamination particles from the compressed air systems. Particles are retained or collected by a sintered filter, depending upon the grade of filtration particles between 40…5 μm can be removed. Liquids and moisture are separated using centrifugal force, the condensate that accumulates in the filter bowl must then be emptied or else the moisture will be pulled through by the drawn in air flow.
With manual drain
With automatic drain
With manual drain
With automatic drain
Main air is usually at a higher pressure than is required for the distribution system, so a regulator is used to reduce it.
Pressure Regulator With Pressure Gauge
Differential Pressure Regulator
Lubricate the compressed air after it has been filtered and regulated.
Soft Start Valve
Soft start valves emulate a 3/2 manual valve function, that limits the amount of air input directly to the valve, allowing pressure to build up gradually and venting excess air from the exhaust port.
Lockable Isolation Valves
An isolation lock that will block the input air flow to the valve for greater safety when servicing pneumatic equipment. With the valve locked, all the downstream pressure will be vented, and no output device can function. These valves are often positioned before the FRL unit.
Allows connection and switching of several components in a circuit.
Air Pipes Connected/Not Connected
The compressed air distribution system via connected lines or pipes to operating equipment, or not connected and crossing over. Pneumatic pipes running in a factory are installed running downhill in a further attempt for excess water to run off.
Pneumatic Valve Symbols
Most valve symbols are drawn in three parts, number of ports, number of positions and type of actuation. Pneumatic valve symbols are always drawn in their unactuated state. The arrows on the valve indicate the direction flow of the air.
Each box gives an indication of how many ports the valve has, so if each box shows two ports (top and bottom centre) then it is a 2-port valve. If there are only two boxes in the symbol this indicates a valve with only two positions, called a 2-stage valve. So a valve with two ports in each of two boxes is a 2-port, 2-stage valve (2/2 Valve).This indicates its two positions or operating states (Input and Output : Open or Closed).
In the box on the left, the directional arrow indicates that each of the two ports is open, so that air may flow through the valve. In the box on the right, those two ports are both depicted as blocked, so that no air may pass through.
Ports are the valve openings where pipes or hoses can be connected. They are usually numbered. In the case of a valve conforming to ISO 5599 they have up to five ports:
Port 1: Main Air
Main Air is the input air supplied from a compressor or other similar device.
Port 2: Output Connection
The output is where other components are connected, usually cylinders. On a 5-port valve, commonly used with a Double-Acting Cylinder, the output is usually connected to the in-stroke, with Port 4 usually connected to the out-stroke.
Port 3: Exhaust
Exhaust is the waste or trapped compressed air that is vented into the atmosphere after the actuation of the valve. On the 5-port valves used for Double-Acting Cylinders, there is a second Exhaust outlet, at Port 5.
Pneumatic Actuator Symbols
Control valves can be actuated in several ways, including Diaphragm, Pilot, Solenoid or Mechanical.
A Pilot can operate a switch or send signals to an actuator which will set its working pressure.
Solenoids change a valve's state with an electrical pulse. Solenoid control combines pneumatics with electrical or, more recently, electronic governance systems, using a computer or PLC (progammable logic control).
Pneumatic Cylinder Symbols
Pneumatic cylinders can use piston rod or rodless actuation. Double-acting cylinders drive the rod back and forth, allowing a push-pull load motion, while single-acting cylinders use a return spring with only the outstroke moving the load.
Single-Acting Cylinder (front spring)
In a single-acting cylinder, compressed air is used to push the piston rod out and a spring to return it (instroke).
Double-acting cylinders use compressed air for the out-stroke and also for the in-stroke by reversing the air flow direction.
Pneumatic Cylinder Cushioning Diagrams
Cushions can be applied to the cylinder in a variety of configurations, to absorb impact and prevent unnecessary wear.
Double-Acting Cylinders, Fixed Cushions
Double-Acting Cylinders, Cushioned Magnet
Double-Acting Cylinders, Through Rod, Fixed
Double-Acting Cylinders – Magnetic, Through Rod Fixed Cushions
Double-Acting Cylinders – Magnetic, Adjustable Cushions in both directions
Double-Acting Cylinders – Magnetic, Through Rod, Adjustable Cushions in both directions
A self-adjusting cushioning for optimal cushioning even with varying loads and speeds
Other types of pneumatic cylinders
Single-Acting Rotary Cylinder
Double-Acting Rotary Cylinder
Rotary Indexing Table
A 3/2 valve is commonly used for Single-Acting Cylinders. It has three ports and two states or positions. 3/2 Valves can be normally open or normally closed allowing air to either flow or stop the flow of air when actuated. In the case of a NO (normally open valve):
State 1 – Off (unactuated state)
The main air input to the valve is blocked, so the air in the valve is unable to reach the output connection. Any air remaining in the cylinder can be dispelled through the Exhaust, allowing the cylinder to revert to its original position.
State 2 – On (actuated state)
The main air input flows freely through the valve, supplying output connections. A 3-port valve symbol depicts both states or positions side by side, generally in the Off (unactuated) state.
This valve has five ports depicted in each of two boxes, indicating that it has two stages of operation. 5-port valves have one Main Air, two Output Connection and two Exhaust ports, and are commonly used for Double-Acting Cylinders. The 5-port valve is then operated by signals from an actuator.
This valve has five ports in three boxes, indicating that it has three stages of operation. 5-port valves have one Main Air, two Output Connection and two Exhaust ports, and are commonly used for Double-Acting Cylinders. The 5-port valve is then operated by signals from an actuator. 5/3 Valves can have the centre position either blocked, open to exhaust or pressurised.
Flow Control Valves
Unidirectional Flow Control
Unidirectional flow control valves are used to limit the speed of the cylinder's operation by controlling the flow direction of compressed air. The symbol depicts a non-return or check valve, which restricts the air supply so that it air is restricted in one direction and free flowing in the other direction.
Bidirectional Flow Control
Bidirectional control valve symbols are the same as unidirectional, but without the check valve, indicating that the air is restricted in either direction.
Non Return Valve
Non-return valves allow compressed air flow in one direction only, flow in the other direction is blocked.
The logic symbols for some valve types are more complex than the valves themselves, such as these:
Shuttle Valve (‘OR’ valve)
A shuttle valve allows air flow to pass through it from either or both of two input sources. The higher of the two inlet pressures forces a small ball or blocking element inside the valve from that end to the other, blocking it off, but leaving a central port open for the air to flow through.
An AND valve has two input signals which it must receive simultaneously in order to permit an output signal. AND valves can be connected together in a series, with the output of the first unit forming one of the inputs on a second AND valve.
Vacuum Pneumatic Symbols
These symbols pertain to any items used in a pneumatically driven vacuum system.
Suction Cup Filter
Silencer Pneumatic Symbols
Compression systems can be loud, particularly when the exhaust air is vented, so a silencer is often fitted to reduced operational noise.
Silencer with Exhaust Control