Moisture in compressed air is troubling for manufacturing and production facilities. Manufacturing quality becomes an issue when excess moisture is present in production facilities. Inferior products create reliability concerns and entire production batches may become invalidated.
Humid compressed air affects pneumatic equipment, too. Machinery suffers from corrosion, reliability problems, and equipment failure.
Air compressor dryers remove moisture from compressed air before it is used inside the plant. Several types of compressed air dryers exist:
- Refrigerated air dryers are the most common and affordable drying system. They can drop air temperatures to as low as 3° Celsius (approximately 37° Fahrenheit).
- Desiccant dryers absorb moisture, sometimes include internal heaters, and can achieve sub-zero air temperatures. These are ideal for low moisture tolerance manufacturing and related operations.
- Membrane dryers capture moisture usually without requiring energy to operate. Overall, they are less capable yet offer substantial potential energy savings.
So… let us start with the basics.
What is an Air Compressor Dryer?
An air compressor dryer removes moisture from compressed air. When air is compressed, water vapour concentrates. This water then condenses as the air cools, causing problems in pipework and equipment.
Most UK workshops use refrigerant dryers, which cool the air to about 3°C. At this temperature, water condenses and drains away. These units need their condensate traps emptied weekly. The cost for a standard 50 cfm refrigerant dryer starts at around £650 plus VAT.
Desiccant dryers use materials like activated alumina to absorb moisture. These are common in pharmaceutical factories near Cambridge, where very dry air is needed. The desiccant beads need replacing every 3–5 years at approximately £200 for a small unit.
Membrane dryers separate moisture using selective membranes. These are less common but useful where electrical power is not available. Several North Sea platforms use them for instrument air systems.
Most manufacturers size dryers based on the worst summer conditions. A dryer that works well in January might struggle during the humid August days in Manchester. Installation typically requires 1-metre clearance for service access, something often overlooked in crowded plant rooms.
Types of Air Compressor Dryers
Below, we explain the main types of air compressor dryers:
Refrigerated Dryers
Refrigerated dryers use condensation to remove moisture. Heat exchangers process heated compressed air, cooling it down. After cooling, water separates and is released through a special drain.
These dryers are efficient, achieve reasonable reductions in temperatures (near zero degrees), and run economically. When sub-zero compressed air temperatures are not required, they are often sufficient for industrial operations.
Cycling refrigerated dryers optimise energy use by shutting down when the demand is low, enhancing efficiency.
Desiccant Dryers
Desiccant dryer systems use heated desiccant material to collect moisture from the air that passes through. The material is similar to the tiny packets of absorbent silica found inside new luggage and apparel. Some of these desiccant dryer systems also include internal heaters or blower purge features to further enhance their capabilities.
These dryers may achieve temperatures of minus 20°C (minus 4°F) to minus 70°C (approximately minus 94°F). Desiccant dryers are the best option for industries requiring cooled compressed air with minimal moisture. Heated desiccant dryers are commonly used in pharmaceuticals, electronics, and food packaging industries where ultra-low moisture content is essential.
Membrane Dryers
A membrane dryer relies on membranes to dry air efficiently. Water vapour is captured before it condenses into H2O. This prevents contamination and moisture damage to equipment.
While membrane dryers do not require electricity to operate and are fairly quiet, they have capacity flow limitations and may not be suitable in all situations. They are ideal for point-of-use applications in laboratories, medical equipment, and small-scale manufacturing processes.
It is important to understand which air compressor dryer system is right for you. Get free air system advice by talking with our specialists at J LL Leach.
How Air Compressor Dryers Work
Air compressor dryers process air. They remove moisture and lower the dew point, enabling dry compressed air distribution to downstream equipment and elsewhere. Operators seek the most appropriate air compressor dryer based on specific needs.
Dryer systems use different cooling and moisture extraction mechanisms:
Refrigerated Dryers: heat exchangers cool the compressed air, condensing water and expelling it. They manage above-freezing air temperature levels and remove moisture well. Medium air flow capacity is achievable. Energy efficiency is reasonable, too.
Desiccant Dryers: moisture-absorbing desiccant material captures water vapour content. This material is recycled. High air cooling capacity is possible at sub-zero temperatures. Moisture is successfully captured almost in its entirety, making desiccant dryers applicable for manufacturing facilities that require extremely dry air.
Membrane Dryers: permeable replaceable membranes strip water vapour while allowing cooled air through. As a lower-capacity dryer, maintenance is reduced, installation is more straightforward, and no electricity is required. Membrane dryers are primarily applicable for low flow, direct applications for isolated purposes, not as part of large commercial air systems.
Choosing the Right Air Compressor Dryer
To select the right air compressor dryer, it is necessary to have a clear understanding of current and future compressed air needs. Factors such as the operational environment, air quality requirements, energy usage, ongoing costs, maintenance, and other aspects are highly relevant.
Improved selection guidance
For example –
- Low-cost options for moderate requirements: a non-cycling refrigerated dryer.
- High precision, ultra-dry air: heated desiccant dryers are optimal.
- Eco-friendly and energy-conscious operations: membrane dryers provide significant energy savings without compromising reliability.
Maintenance and Troubleshooting
Air dryers need regular checks to work properly. Without maintenance, moisture gets into the air system and damages tools and pipework.
Basic maintenance includes:
- Change filters every three months. Most Manchester factories mark the filter housings with the next due date.
- Check automatic drains weekly. The small plastic drain tubes often kink where they exit the cabinet.
- Look for pressure drops across the dryer. More than 0.5 bar indicates a problem.
For refrigerant dryers, clean the condenser fins yearly with a soft brush. Dust buildup is common in woodworking shops around Leeds. The standard R134a refrigerant used in most units needs checking if the dryer struggles to maintain temperature.
Desiccant dryers require more attention. Check the colour indicator beads monthly – they turn from blue to pink when saturated. At the Cadbury factory in Birmingham, they schedule tower changeovers every six years regardless of condition. Heater elements often fail first, showing as inconsistent regeneration cycles.
Membrane dryers need little maintenance but suffer from oil contamination. If installed after an older compressor in Coventry’s automotive plants, they typically last 18 months before needing replacement.
If water appears in the lines, check the dryer sizing. A unit rated for 250 cfm cannot handle 300 cfm, even for short periods. Most system problems occur when air demand exceeds design capacity, particularly during summer afternoons when ambient humidity rises.
Industry Applications and Case Study
Moist air enters industrial air equipment and requires either cycling or non-cycling dryers to reduce moisture levels. A wide range of industrial applications is possible for air systems, but moisture level requirements are a critical factor.
Heated desiccant dryers and heatless desiccant dryers reduce water vapour in the air. Industrial operators, such as food producers and pharmaceuticals, require extremely dry air, and these dryers are ideal for them. Dryers are critical equipment within high-quality air systems. With pressurised air, proper dryer selection is essential.
Case Study
A boutique UK jam manufacturer required a robust compressed air system to improve their jam-filling capacity. After evaluating their needs, a refrigerated dryer was installed. This system met the increased demand and ensured hygienic, moisture-free compressed air, vital for food safety compliance.
Conclusion
Air dryers are essential to complete air systems. They ensure high-quality, moisture-free compressed air, extending the life of the equipment and improving production quality. With Atlas Copco’s advanced solutions, industries can achieve sustainable and cost-effective operations. Always consult an air systems professional to determine the right solution.
Selecting the most appropriate air dryer requires an air systems professional. J LL Leach employs a team of knowledgeable staff to review your requirements and confirm the dryer type needed. Get in touch with us today.
FAQ
What does an air compressor dryer do?
An air dryer removes moisture from compressed air. When air is compressed, water vapour concentrates and condenses as the air cools. Most workshops in Leeds report that water problems increase during the summer months when humidity rises.
Without drying, water collects in pipework low points and eventually reaches tools. This causes rust in air motors and sticky operation of valves. A basic dryer for a small 15 cfm compressor costs about £375 plus VAT and needs an annual service.
Do I need an air dryer for my compressor?
Most industrial and workshop applications need a dryer. The exceptions are some construction uses and temporary setups. Garages in the Birmingham area typically run without dryers for tyre inflation but add them for spray painting. Water in compressed air leaves spots on paintwork and reduces finish quality.
Systems left running overnight in unheated buildings often build up significant condensate that needs to be drained each morning before work starts.
What is the difference between a refrigerant and a desiccant air dryer?
Refrigerant dryers cool air to about 3°C, causing water to condense. They achieve a pressure dew point of +3°C, suitable for general factory use. A standard unit draws about 0.8 kW of power for a 100 cfm system. Most Midlands manufacturers use refrigerant dryers.
Desiccant dryers use absorptive materials like activated alumina. They typically achieve -40°C dew points, which is needed for outdoor applications where freezing is a risk. The National Grid uses them for pneumatic controls on gas pipelines in Scotland. They cost roughly twice as much as refrigerant types and need material replacement every few years. A 100 cfm desiccant dryer uses about 15% of the compressed air for regeneration, which increases running costs.
