Low Cost Automation Tutorial

#061 Countermeasures for Pneumatic Actuator Air Supplies

Category : Pneumatic Drives

December10, 2010

In this volume, troubles and countermeasures on pneumatic actuator air supply will be discussed.

Action timing and velocity of air cylinders contained in pneumatic actuators are controlled with pneumatic control system components such as electrical solenoid valves and velocity control valves. Although the pneumatic actuators are fairly easily applicable, poor design planning and inadequate maintenance practices often result in troubles of peripheral air components. Increasingly progressing miniaturization and energy efficient design of the pneumatic components are making the internal structures of the components more complex and precise, requiring more attention to such details. The trouble examples and countermeasures are explained below.

(1) Improper mounting positions and direction of pneumatic components

Trouble Detail

Explanation

Countermeasure

Electromagnetic Valve Troubles
(See [Fig.1])

Air cylinder response errors
(latencies and malfunctions)

-	Response latency caused by viscosity increase of internal slide components (prominent in reduced power operations)
-	Slide components seizure due to repeated operational cycles causing malfunctions
-	Valve air passages clogged by drain and oil causing malfunctions

1.	Mounting orientation to avoid lateral shocks and vibrations
2.	Avoid direct contact of water and oil drips, condensation, and cutting chips
3.	Provide an air
4.	Heat dissipating countermeasures for extended duration use

Velocity Control Valve Troubles

1)	Loss of air cylinder velocity control

＊	Valve movements are hindered by entrapped foreign objects (seal fragments, rust). (See [Fig.2] Seal Tape Usages)

1.	Flush the plumbing before connecting (blow clean by compressed air)
2.	Remove foreign objects from post filter plumbing (seal fragments, thread cutting chips)

2)	Air cylinder slows down intermittently

-	Temporary blockage of control valve needle by drain and oil causing increased air passage resistance

1.	Periodical removal of drain and oil
2.	Mount the control valve in high position
3.	Position the control valve close to the air cylinder

Air Filter Troubles
(See [Fig.3])

Clogged air filter causing pressure and
flow volume loss

-	Air filters can remove solid particles such as water/oil drops and rust but water vapor and oil mist will pass and become oxidized into carbon and tar
-	Excessive impurities will clog the filter and cause reduction of air supply

1.	Mount the filter close to the air cylinder and avoid exposing the post filter plumbing to temperature changes (low temp. causes condensation and water induction)
2.	Periodical maintenance such as drain removal
3.	Mount the filter in a visible location
4.	Manage flow volume using a differential pressure gage (when precision is required)

Glossary

Drain ------ Water and mixture of water and oil within pneumatic actuators, control circuits, and plumbing
Oil Mist ------ Fine oil particles in factory air environment

[Fig.1] Electromagnetic Valve (Solenoid Type) Trouble Examples

[Fig.2] Seal Tape Termination

[Fig.3] Air Filter Trouble Examples

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