December 2010 Archives

Compressed air as the energy source for factory pneumatic actuators are produced by oil lubricated air compressors. The air as produced contains oil, water, and machine dusts, thus is not suitable to be used as is for the energy source for the equipment.
Additionally, there is a significant distance of various plumbing connecting the air compressor and the LCA actuators. Various other machines also share this compressed air over this distance and they mutually affect the air quality.
The drive components for LCA and pneumatic components are becoming more complex and elaborate due to demands for miniaturization and cost reduction, often resulting in troubles caused by inadequate maintenance activities.

The Clean Air System basics that generate appropriate quality air to avoid pneumatic system troubles will be explained.

（1）Classification of Factory Air Plumbing

The plumbing from the air compressor to the actuator end is classified into the following four sections.
　1. Air Source Line
　2. Main Line
　3. Sub Line
　4. Terminal Line

(2) Classification of Air Quality

The air quality is classified based on the production line and products which the sir is used for.
　a）General Industrial Air　d）Precision Clean Air
　b）Precision Industrial Air　e）Ultra Precision Clean Air
　c）Clean Air　f）Medical Clean Air

（3）About Air Quality

Air quality is classified by the following parameters.
　1. Quality of air (Foreign material types in compressed air)
　2. Water and oil contents
　3. Size of solid particles and removal rate
　4. Odor

（4）Air Quality Classifications and Clean Air System

For types of air quality strongly related to LCA are explained here.

Glossary

Condensation Point ---Temperature point where water vapor containing air at a certain pressure becomes saturated and dew forms when cooled. Air dryness is evaluated with this index.

(5) Example of a Clean Air System

Various filters shown below are placed at the four classified air supply line, and air quality corresponding to each LCA are generated.

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

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

For single axis slide based LCAs, pneumatic cylinders are often used for its ease of maintenance as shown in [Table 1] from the previous discussion. On the other hand, the easy to maintain characteristic seems to cause lack of completeness in preventative maintenance design concepts that should be considered in the first place.
Here, trouble examples of pneumatic actuator applications and countermeasure designs are explained.

(1) Pneumatic Actuator Troubles and Causes

Pneumatic actuator trouble causes and origins (where countermeasures should be addressed) are shown below.

(2) Trouble Examples and Countermeasures

The trouble details of 1.~3. above and countermeasures are explained below.

(1) Inappropriate Mounting to Mechanisms

[Table 1] Mounting Methods of Pneumatic Cylinders (partly excerpted)