Even with best efforts to supply clean and dry plant air, point-of-use air preparation is still needed for safe and reliable pneumatic machine operation.
Pat Phillips, Product Manager, Fluid Power & Mechanical Products at AutomationDirect, wrote an article for the August 2018 issue of Industrial Equipment News titled Safely Provide Clean Air to Machines with Total Air Prep Units.
Phillips points out that compressed air and pneumatics are commonly used in automated machines due to simplicity, power and reliability. However, he says, plant-wide compressor and distribution systems often add unwanted water, oil and particulates that can adversely impact the pneumatics in downstream machines and processes.
Clean, dry air may enter the plant distribution system, but it still needs to be safely controlled and purified at the point of use. Total air prep units are often the best choice to provide these functions, as opposed to purchasing and assembling separate components.
Pneumatic Contaminates and Safety
Two of the main functions of a machine air preparation unit are removal of contaminates and safe control of air. Air compressors often add airborne contaminates found in the large volume of intake air. The design and operation of the compressor can also add contaminates such as lubricants and wear particles. Additional contaminates, such as rust and scale from storage tanks and distribution piping, also find their way into compressed air systems.
Phillips adds, the distribution system may cool moist compressed air, which can cause condensate to form, causing problems that can stop production. Condensate can cause wear in pneumatic cylinders, leading to air leaks. It can also plug valve ports and orifices, resulting in malfunctions and pipe corrosion. Machine air preparation units can provide both contaminate removal and required safety functions.
Machine Air Preparation Components
The devices needed to provide proper point of use air preparation are listed in the Table.
Table: Components in Air Preparation 
- Manual Shutoff Relief Valve
- Filter
- Regulator
- Pressure indicator and switch
- Lubricator (if used)
- Air distribution block
- Soft-start/dump valve
Assembly and Total Air Prep Units
An air preparation system can be assembled by combining the individual components in the Table. Combination filter-regulators units can simplify this assembly. However, combining multiple air-preparation functions into a single unit can be more convenient.
Phillips describes such a device: The AutomationDirect NITRA Total Air Prep unit includes all the components for a proper machine air preparation unit including an air filter with clogged filter indicator, relieving regulator, lockable shutoff valve, pressure gauge and electric soft-start/dump valve.
The total air prep unit typically includes a lockable shutoff valve, automatic drain air filter with clogged filter indicator, relieving regulator, pressure gauge and air dump. The air dump should include an electrically operated, adjustable, soft start shutoff valve, and an adjustable pressure switch. Combining all these pneumatic components in an all-in-one air preparation unit simplifies design, saves money and reduces installation space, while safely providing clean air supply to a machine.
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