Cooling
Aftercooler
Cools hot discharge air so a large portion of water vapor condenses into liquid before the air reaches the treatment equipment.
Compressed Air Treatment Planning Guide
Air Treatment System Design
A reliable compressed air treatment system removes bulk water, water vapor, oil aerosols, solid particles and oily condensate in the correct sequence.
Use this guide to design the treatment train around your compressor, application, pressure dew point and air-quality requirements.
Quick Answer: What Is the Correct Air Treatment Order?
A common industrial air treatment sequence is: compressor → aftercooler → receiver and drain → water separator → prefilter → air dryer → final filter → distribution system or point of use.
Oil-lubricated systems also need condensate treatment for liquid collected from the aftercooler, receiver, filters and dryer.
The exact order changes with dryer type, compressor configuration, air-quality requirement and whether the application needs centralized or point-of-use treatment.
Typical Compressed Air Treatment Train
Air Compressor
Aftercooler
Receiver & Drain
Water Separator
Prefilter
Air Dryer
Final Filter
Point of Use
System order matters. A desiccant dryer exposed to liquid water or oil can lose performance and desiccant life. A refrigerated dryer without proper bulk-water removal may be overloaded. Always follow the exact equipment manufacturer's installation requirements.
What Each Air Treatment Component Does
Storage
Air Receiver
Provides storage, helps stabilize demand and creates another location where moisture can cool, collect and drain.
Bulk Water
Water Separator
Removes entrained liquid water before it reaches filters and dryers.
Particles & Oil
Compressed Air Filters
Remove particulate, oil aerosol and other contaminants according to filter grade.
General Drying
Refrigerated Dryer
Provides economical moisture control for most indoor plant air systems.
Low Dew Point
Desiccant Dryer
Provides much drier air for freezing conditions, instrument air and sensitive processes.
Condensate
Oil-Water Separator
Treats oily compressor condensate before discharge where required.
Local Protection
Point-of-Use Treatment
Adds final filtration, regulation or drying close to the process that needs the highest air quality.
Interactive Air Treatment System Builder
Select your application and operating conditions for a preliminary treatment-train recommendation.
Recommended Treatment Train
Dryer type—
Filtration level—
Condensate treatment—
Important: This builder is a planning aid. Final design must confirm airflow, pressure, inlet temperature, pressure drop, filter grades, applicable standards, redundancy and manufacturer installation requirements.
Air Treatment Design by Application
Application-Based Treatment Recommendations
| Application | Common Treatment Train | Primary Risk | Key Design Note |
|---|---|---|---|
| General Manufacturing | Separator → prefilter → refrigerated dryer → final filter | Liquid water, rust and tool wear | Size for peak corrected CFM and pressure drop. |
| Pneumatic Tools | Separator → refrigerated dryer → particulate/coalescing filtration | Corrosion and tool damage | Use point-of-use regulators and lubricators only where appropriate. |
| Paint Booth | Separator → dryer → coalescing filter → point-of-use final filter | Water and oil causing finish defects | Confirm booth and coating requirements before selecting dew point. |
| Instrumentation | Separator → high-efficiency prefilter → desiccant dryer → after-filter | Freeze-up and blocked controls | Commonly designed around a -40°F pressure dew point. |
| Food Packaging | Engineered dryer and filtration train | Product or packaging contamination | Design to applicable air-quality standards and contact risk. |
| Medical / Pharmaceutical | Validated engineered purification system | Patient, product and compliance risk | Dew point is only one part of the required purity system. |
| Outdoor Air Lines | Separator → prefilter → desiccant dryer → after-filter | Condensation and freezing | Select a pressure dew point below the coldest pipe temperature. |
Where Should Filters, Dryers and Separators Be Installed?
Before the Dryer
Protect the Dryer
Bulk-water separation and appropriate prefiltration reduce liquid water, oil and particulate loading on the dryer.
After the Dryer
Protect the Air Network
Final filters capture remaining aerosols, fine particles or desiccant dust before the air enters distribution piping.
At the Point of Use
Meet Local Process Needs
Add final polishing filtration, regulation or specialty treatment near the process with the strictest requirement.
Design for Low Pressure Drop
Every separator, filter, dryer, valve and pipe fitting adds resistance. Excessive pressure drop may force the compressor to operate at a higher discharge pressure, increasing energy use.
Size Correctly
Use Corrected Peak CFM
Do not size treatment equipment to average demand. Peak flow determines pressure drop and treatment performance.
Maintain Filters
Replace Loaded Elements
Dirty filters and saturated media increase differential pressure and operating cost.
Plan Bypass Carefully
Support Service Without Contamination
Bypass piping can support maintenance, but uncontrolled bypass may send untreated air into the plant.
Condensate Management Is Part of System Design
Aftercoolers, receivers, separators, filters and refrigerated dryers all create condensate. In oil-lubricated systems, that condensate may contain compressor oil and require treatment before discharge.
Collection
Automatic Drains
Remove collected liquid from low points and treatment components without wasting excessive compressed air.
Treatment
Oil-Water Separators
Use appropriate condensate treatment for oil-lubricated compressors.
Verification
Inspect and Service
Monitor drains, separator media, outlet condition and service indicators to prevent overflow or untreated discharge.
Need Help Designing the Complete System?
Provide your compressor CFM, pressure, inlet temperature, application, required dew point, compressor type and operating schedule. A compressor specialist can help confirm the complete treatment train.
Related Air Treatment Resources
Air Treatment System Design FAQs
What is the correct order for compressed air treatment?
A common order is compressor, aftercooler, receiver and drain, water separator, prefilter, dryer, final filter and point of use. Exact placement depends on the equipment and application.
Should the receiver be before or after the dryer?
Many systems use a wet receiver before the dryer to collect bulk moisture and stabilize demand. Some systems also use dry storage after the dryer. Final design depends on control strategy and air-quality requirements.
Does a refrigerated dryer need a prefilter?
Many systems benefit from upstream filtration, especially where oil aerosol and particulate loading could contaminate the dryer.
Why does a desiccant dryer need an after-filter?
An after-filter captures desiccant dust before it enters the distribution system.
Where should a water separator be installed?
A water separator is commonly installed after cooling and before fine filtration or the dryer so it can remove entrained liquid water.
Do I need an oil-water separator?
Oil-lubricated compressors can produce oily condensate that may require treatment before discharge. Requirements depend on the system and applicable regulations.
How much pressure drop is acceptable?
Acceptable pressure drop depends on the system, but each component should be sized and maintained to keep total differential pressure as low as practical.
Can one dryer serve multiple compressors?
Yes, if the dryer is sized for the maximum combined corrected airflow and the control strategy prevents overload.
Should I use centralized or point-of-use treatment?
Centralized treatment is efficient for common plant requirements. Point-of-use treatment is useful when one process needs cleaner or drier air than the rest of the facility.
What is the best system for outdoor air lines?
A desiccant dryer with proper prefiltration and after-filtration is a common starting point when lines may be exposed below freezing.
What is the best system for a paint booth?
A paint booth commonly needs a dryer, coalescing filtration and point-of-use final filtration. The dryer type depends on finish requirements and the coldest piping temperature.
Is a dryer alone enough for food or medical air?
No. These applications may require engineered purification, monitoring, validation and compliance with applicable standards.