What are Compressed Air Dryers?
An air dryer is a piece of essential equipment for removing excess moisture, oil, and toxins from compressed air systems. Removing moisture from the compressed air extends the lifespan of your industrial equipment such as pneumatic tools significantly, reducing your maintenance costs in the process. In some industries, such as pharmaceuticals and food production, a compressed air dryer is critical to maintaining compliance with strict hygiene and quality standards.
In this guide, we introduce you to the different types of compressed air dryers and explain how they work. We’ll also help you determine which compressed air dryer to buy and how to maintain it.
If you’re in doubt and need a professional’s insight, don’t hesitate to contact our compressor and dryer specialists – it’s always better to choose the correct dryer the first time, when it comes to the safety of your valuable equipment. Choosing the right compressed air dryer depends on your specific air quality requirements and operating environment.
How Do Compressed Air Dryers Work?
To understand how compressed air dryers work, we must first look at why moisture is present. Compressed air dryers reduce the amount of toxins, oil and moisture within compressed air systems. They pull out and remove any moisture in your compressed air, essentially “drying” it.
The basic air dryer working principle varies by type, but generally, the compressed air passes through a system that separates water vapour from the air stream.
While some air compressors include built-in aftercoolers capable of removing up to 70% of moisture, this alone may not suffice in high-humidity environments or applications requiring extremely dry air. In these cases, additional dryers become indispensable. If you use compressed air for critical applications, relying solely on an aftercooler is rarely enough.
Why You Need Compressed Air Dryers
Atmospheric air, as in the air all around you, naturally contains some water vapour. The temperature of the air has a significant impact on how much moisture it contains (the hotter the air, the more moisture).
As air rapidly pressurises inside a compressed air drying system, heat and water vapour are released, which can cause condensation to form inside your machinery. For example, if the air is 20°C and humid, using a compressor at 7 bar pressure can release up to ten litres of water per hour. This moisture in the air causes rust and contamination in the pipework.
This moisture damages equipment and can compromise sensitive industrial processes, leading to product defects, increased maintenance, and reduced operational efficiency. Therefore, efficient air treatment is vital to remove moisture from the air before it reaches your tools.
The Pressure Dew Point (PDP)
The temperature at which the moisture in the compressed air system becomes water vapour is called the pressure dew point (PDP). Air dryers suppress the dew point to ensure condensation does not occur. A low PDP value indicates a small amount of water vapour in your compressed air system. You’ll need to pay attention to the PDP when choosing the most appropriate unit for your needs.
Maintaining a low PDP is critical in sectors like food processing, where contamination risks are high. Modern desiccant dryers can achieve PDP levels as low as -40°C or even -70°C, ensuring superior moisture control. If the dew point of the air is not managed, the air becomes saturated, leading to system failure.
The Four Main Types of Air Dryers
There are four main types of air dryers available, though the most common in industrial settings are refrigerant and desiccant. We also cover membrane dryers below. Which one you should buy depends on your budget, your compressed air system, and the specific tasks you need to carry out.
Remember, if you need any assistance at all, we’re just a phone call away.
Pro tip: Consider conducting an AIRScan analysis to assess your system’s needs and identify the most energy-efficient dryer for your operations.
Refrigerant Air Dryers
Refrigerated air dryers are the most commonly used dryers in general industry. They cool the temperature of the compressed air to about 3°C (37°F), which turns the water vapour into dry air. The working principle is simple: they work by cooling the compressed air to force moisture to condense.
The two main categories of refrigerant dryers are cycling and non-cycling; non-cycling dryers are simple and cost-effective, but less energy efficient than their cycling counterparts.
Applications
Refrigerant air dryers work well with most rotary screw compressors, though we recommend high-temperature versions for piston air compressors. Especially non-cycling versions, refrigerant air dryers tend to be budget-friendly, simple to install and easy to operate. This accessibility makes them the industry standard for most settings. These dryers are widely used in general industrial applications, automotive manufacturing, and woodworking. Common models like the Atlas Copco FD and FX series are ideal here.
Pros and cons
Non-cycling dryers are cost-effective and dependable, but because they use about the same amount of energy, whether you need a lot of air or just a little, they can lack efficiency. Cycling dryers, often equipped with Variable Speed Drive (VSD) technology, use extra components to automatically turn on and off as needed, making them more energy efficient. They generally cost more to purchase but can result in savings in the long run. In these systems, the dry air is then reheated to prevent sweating on pipes.
Desiccant Air Dryers
If you need dryers that deliver the air quality you need to manufacture food or pharmaceuticals, you’ll need desiccant air dryers. These are a type of adsorption air dryer.
Rather than cool down the air, desiccant air dryers use chemicals that bind to and remove moisture. Desiccant air dryers use desiccant materials such as activated alumina or silica gel. Desiccant air dryers can reach a PDP as low as -40°C, making them much more effective than their refrigerated counterparts. Advanced desiccant dryers, such as Atlas Copco’s heatless and heated variants (CD, BD, and XD series), can reach PDP levels of -40°C or lower, providing exceptional moisture control.
Applications
Desiccant air dryers are most commonly used in industrial applications where the quality of the compressed air is crucial, such as in the manufacturing of pharmaceuticals, food and drinks, electronics, dental and medical equipment, and painting and coating. They are also essential for outdoor lines where compressed air can cause freezing issues in winter.
Pros and cons
If high-quality air is a priority, desiccant air dryers are hard to beat. Plus, thanks to their efficiency, they boast relatively low running costs. However, they are more expensive to purchase upfront than refrigerated dryers, and the additional expense isn’t always warranted. Further, many rely on purge air for drying the desiccant media, which can result in costly waste if not managed by smart controls like Elektronikon®. The main types of desiccant dryers include heatless, heated purge, and blower purge (zero purge) models.
Membrane Air Dryers
Membrane dryers are a compact solution for specific point-of-use applications. They work by passing the incoming air over a hygroscopic membrane. Water vapour permeates the membrane fibers faster than air, removing moisture from the compressed air efficiently.
Applications
These are ideal for laboratories, dental offices, or small-scale operations where a quiet, low-maintenance solution is required. They require no electricity to operate.
Pros and cons
Membrane air dryers are silent and have no moving parts. However, they can have higher purge air losses compared to other compressed air dryer types.
Deliquescent Dryers
While less common in precision industries, some dryers use soluble salt tablets to absorb moisture. As the tablets absorb water, they dissolve (deliquesce) and must be replaced. These are typically used in remote locations like mining where electricity is unavailable.
Technical Specifications: Atlas Copco Air Dryers
When selecting a dryer, understanding the capabilities of your equipment is key. Here is a quick overview of the range we offer:
- Refrigerated Dryers (FD/FX Series): Achieve a dew point of +3°C. The FD VSD models offer energy savings of up to 50% by adjusting cooling to demand.
- Desiccant Dryers (CD/BD/XD Series): capable of dew points down to -40°C or -70°C. Features like zero-purge cooling ensure you don’t waste compressed air during regeneration.
- Compliance: These dryers help you meet ISO 8573-1 air quality standards (Class 4 for refrigerant, Class 1 or 2 for desiccant), ensuring your process air is safe.
The Importance of Regular Professional Check-Ups
By allowing a trained professional to inspect your compressed air dryers from time to time, you can catch small problems before they exacerbate. Maintenance tasks may include checking desiccant beds, changing filters, and verifying the performance of cooling systems in refrigerated dryers.
Advanced tools like SMARTLINK monitoring systems can provide real-time data on dryer performance, making it easier to schedule timely maintenance.
While it can be tempting to delay inspections – particularly when you need to keep a close eye on cash flow – specialist maintenance can help you save hundreds (if not thousands) of pounds in the long run.
Compressed Air Dryer Preventive Maintenance Tips
In between professional check-ups, doing your own maintenance will go a long way at minimising problems before they escalate.
- Regularly Check and Replace Filters: Filters are the first line of defence against dirt and debris. They filter the air to prevent contaminants from reaching the dryer. Inspect them frequently and replace them according to the manufacturer’s recommendations.
- Monitor Condensate Drains: Ensure that condensate drains are functioning properly and free of clogs. Accumulated moisture can lead to corrosion and reduced dryer efficiency.
- Inspect Desiccant (if applicable): For desiccant dryers, check the desiccant material regularly for signs of degradation or saturation. Replace it as needed to maintain optimal drying performance.
- Check for Leaks: Air leaks can significantly impact dryer performance and lead to energy waste. Regularly inspect all connections and fittings for leaks and repair them promptly.
- Schedule Professional Maintenance: Consider scheduling annual or bi-annual maintenance visits from a qualified technician. They can perform thorough inspections, identify potential issues, and perform necessary repairs or adjustments.
By investing a little time and effort in preventive maintenance, you can extend the life of your compressed air dryer, reduce downtime, and save money on costly repairs. Remember, a well-maintained dryer means clean, dry air and a more efficient operation for your business.
Common Issues and Solutions
- Desiccant Replacement: In desiccant dryers, the desiccant material has a limited lifespan, which means it needs replacing periodically for your dryer to maintain efficiency.
- Clogged Filters: Filters in air dryers can become clogged over time, adversely affecting their performance. Keep your dryer in full working order by changing the filters regularly.
- Cooling System Problems: In refrigerant dryers, the cooling system is critical. If the air is cooled insufficiently, condensation will occur downstream. Problems with the refrigeration components can lead to reduced drying efficiency.
- Leak Detection: Air leaks in the system can reduce the effectiveness of the dryer. Don’t forget to check for and repair any leaks frequently.
Find the Most Suitable Air Compressor Dryer for You
Air compressor dryers play an indispensable role in maintaining the quality and performance of your compressed air systems. By purchasing modern and reliable compressed air drying systems, you can minimise your operating costs, while maximising operational efficiency and mitigating business risks. Since your air dryer will be essential in the day-to-day running of your business, you should ask a specialist for advice. Clean air is essential for modern manufacturing.
Atlas Copco’s range of energy-efficient air dryers, including the CD and FD series, offer cutting-edge performance, ensuring reliability and compliance with ISO standards.
At Anglian Compressors, a Branch of Atlas Copco Compressors, we’ve been a leading distributor and installer of compressors, compressed air dryers and related equipment since 1977. If you need advice or want to find out how our solutions can help you save energy, cut costs and improve your bottom line, don’t hesitate to contact us for a no-obligation chat.