An air-operated diaphragm pump is only as reliable as its air supply. Dirty or wet compressed air, excessive pressure or undersized lines lead to loss of performance, icing and premature wear of the air valve. This guide shows how to set up the air supply correctly and which pneumatic valves are used.
Air supply layout – from the line to the pump
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Shut-off valve (ball valve): isolates the pump from the compressed air network, e.g. for maintenance.
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Filter regulator: separates particles and condensate and sets the working pressure. A gauge shows the set pressure.
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Lubricator (optional): adds a fine dose of oil to the compressed air. Whether a lubricator is needed is stated in the pump's operating manual – many modern AODD pumps work with non-lubricated air.
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Control valve (optional): solenoid or pneumatic valve for remote switching or via a control system.
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Flexible connection hose: decouples pump vibration from the fixed pipework.
Filter-regulator-lubricator (FRL unit): The combination of filter, pressure regulator and lubricator is called an FRL or air preparation unit. For diaphragm pumps a filter regulator is usually sufficient; a lubricator is only added if the manufacturer specifies lubricated air.
Types of pneumatic valves
| Valve type |
Function |
Example on a diaphragm pump |
|
Directional control valves (2/2, 3/2, 5/2) |
Open, close or switch air paths |
3/2-way solenoid valve to switch the pump on and off |
| Non-return valves |
Allow air in one direction only (check valve) or combine signals |
Check valve in the supply line |
| Pressure valves |
Limit or regulate pressure |
Pressure regulator in the filter regulator, safety valve |
| Flow control valves |
Limit the flow |
Throttle valve to reduce the stroke rate |
| Shut-off valves |
Close the line completely |
Ball valve upstream of the FRL unit |
Pilot valves
Larger pneumatic valves are often pilot-operated: a small solenoid valve first switches a pilot air flow, which then actuates the main valve. This allows large air volumes to be switched with little electrical power. The air valve of many air-operated diaphragm pumps also works on a pilot principle.
Manual and mechanical valves
Manually and mechanically operated valves (lever, push button, roller lever, foot valve) are suitable for simple applications without electrics – for example to start and stop a mobile drum pump directly at the point of use.
Pneumatic control of diaphragm pumps
Air-operated diaphragm pumps can be automated without electronics on the pump:
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Level control: A float switch controls the air supply via a solenoid or pneumatic valve.
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Batch operation: A stroke counter or timer stops the pump after a set number of strokes.
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Speed control: An electro-pneumatic pressure regulator allows the flow rate to be set steplessly from the PLC.
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On-demand pumping: When operating against a dispensing nozzle, the pump stops and restarts by itself without any control.
Common mistakes in the air supply
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Undersized lines: The pump does not reach its performance. Size the line at least to the pump's air connection.
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No filter: Rust and particles from the network wear the air valve.
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Excessive pressure: Increases air consumption and diaphragm wear. Set the pressure only as high as necessary.
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Icing at the air exhaust: Caused by wet air expanding. The remedy is dry compressed air (refrigeration dryer).
More efficiency tips: 8 essential tips for improving AODD pump efficiency.
Frequently asked questions
Does an air-operated diaphragm pump need a lubricator?
That depends on the model – the operating manual is authoritative. Many modern AODD pumps are designed for non-lubricated air; a filter regulator, however, is always recommended.
What is the right air pressure?
As low as possible, as high as necessary. The discharge pressure of the pump roughly equals the air pressure – set it according to the required head and never exceed the pump's maximum permissible pressure.
