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Compressed Air Dryers Guide – Which Type of Air Dryer Do I Need?

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Compressed air is considered by many as the fourth utility in industry. To produce effective and efficient air, moisture removal is required in compressed air systems.

Compressed air dryers are frequently used to remove the moisture from the air, and so this page will provide you with all the relevant information on air dryers and the different types.

Table of Contents

What is a Compressed Air Dryer?

A compressed air dryer is a machine designed to significantly reduce the amount of moisture in compressed air. Not only this, but they promote high-quality products, minimize compressed air contamination and create a safer environment for employees or workers.

In humid work environments, air dryers can be the difference between stalling or successful operations.

Why is it so important to reduce the moisture in compressed air? Too much moisture can cause rust, corrosion and even contaminate the quality of the compressed air. Poor quality compressed air will then damage your final end-use.

Therefore, to reduce the amount of moisture in your compressed air – and inevitably prolong the life of your machine – a compressed air dryer is essential.

Moisture will enter the air and the air compressor in several ways. An undersized or overworked air compressor may absorb more moisture from the air surrounding it! The environment it operates in can also make a massive difference. High-humidity atmospheres are capable of holding a lot more moisture than non-humid atmospheres.

Note: when air reaches a temperature conducive to moisture saturation and condensation, it is known as the dew point

Types of Compressed Air Dryers

People ask, which type of air dryer do I need? Well first of all, you need to know the following:

  • How often the compressed air will be used
  • The kind of environment the air compressor is operating within
  • The required temperature of the air
  • The specific uses of the compressed air
  • Your desired pressure dew point

There are 4 main types of air compressor dryers available, and the key difference between them is the agent inside the machine that dries the incoming air:

  1. Refrigerated air dryers
  2. Desiccant air dryers
  3. Deliquescent air dryers
  4. Membrane air dryers

Now let’s take a look at these in greater detail!

Refrigerated Air Dryers

The refrigerated dryer out of all the various types, is the most popular. This type of air dryer functions in a similar way to home refrigerators or air conditioning units in that a cooling process is employed which prevents moisture.

In refrigerated dryers, the compressed air is cooled to around 35 F! When air enters this dryer, the moisture is extracted and drain before the newly dried air is reheated. Upon completion of its cycle, the compressed air flowing out the outlet will have a dew point of between 35 F and 40 F.

Refrigerated air dryers are available as either cycling or non-cycling types, for more information visit our Refrigerated Air Dryer Guide.

Advantages of Refrigerated Air Dryers

  • Generally inexpensive to set up compared to other dryers
  • Operation and maintenance costs are low
  • Resistant to airborne particles

Disdvantages of Refrigerated Air Dryers

  • Have a minimal dew point capacity
  • Not recommended for sub-freezing temperatures as the moisture may freeze and damage the system

Desiccant Air Dryers

Desiccant agents are used to dry compressed air in a process called adsorption – where moisture attaches itself to the desiccant without being dissolved. Compressed air is sent through a vessel containing two towers, both filled with a desiccant agent such as activated alumina or silica gel.

This desiccant drying agent sucks the moisture out of the compressed air through the adsorption process. For further information on how they work visit our Desiccant Compressed Air Dryer Guide!

Desiccant dryers are important in a vast amount of industrial applications, where the drying process is needed to maintain the crucial integrity of operations as well as maintain the quality of products.

They make it possible to maintain controlled humidity environments, with their types being either heatless, heated internally or heated externally. Depending on the type, the dew point can reach as low as -40 F or even -100 F.

Advantages of Desiccant Air Dryers

  • Employable in remote and hazardous environments
  • Low dew points
  • Operate at a reasonable cost

Disadvantages of Desiccant Air Dryers

  • Airborne oil particulates can degrade the desiccant agent
  • Desiccant bed must be replaced every 3 to 5 years
  • Desiccant dryers often need purge air
  • Set up costs can be high

Deliquescent Air Dryers

Compressed air is passed over a bed of deliquescent chemicals that saturate with the excess moisture from the air. As these chemicals attract and collect the moisture, they’re disposed of along with the water.

Typical chemicals used in this type of air dryer are sodium, calcium chloride and lithium as they all have a natural capacity for water attraction. A high-quality filtration system is crucial for the successful operation of the deliquescent dryer otherwise you run the risk of chemical build up which can cause problems for you.

For more information on these types of dyers visit our Deliquescent Compressed Air Dryer Guide!

Advantages of Deliquescent Air Dryers

  • Initial set up is inexpensive
  • No moving parts to maintain
  • Operation is relatively straightforward and requires little attention thereout

Disadvantages of Deliquescent Air Dryers

  • Depend on high-quality filtration to operate efficiently
  • Replacing chemicals is costly (especially with frequent use)
  • Saturated chemical disposal can be complicated and expensive

Membrane Air Dryers

Membrane air dryers are often used for dehumidification and for applications that require gas separation like food production. When compressed air passes through a membrane dryer, it moves across a bundle of semi-permeable membrane fibres.

These fibres allow certain materials, such as oxygen to pass through the membrane, separating it from the desired gas. Membrane air dryers are typically for smaller projects and single points of use.

Advantages of Membrane Air Dryers

  • Easy and affordable to maintain
  • Operation is quieter than other dryers
  • Require no electricity

Disadvantages of Membrane Air Dryers

  • Require consistently clean air (free of oil and particulates)
  • Require a pre-filter that must be changed frequently to avoid blockage

Air Dryer Applications

Air dryers are commonly used a wide array of industries and applications that include:

  • Food drying (desiccant)
  • Health care (desiccant)
  • Low-flow unattended applications (membrane)
  • Material processing (desiccant)
  • Manufacturing plants (refrigerated)
  • Media blasting (deliquescent)
  • Metal surface preparation (deliquescent)
  • Point of use applications (membrane)

These are just tiny fractions of the compressed air dryer applications across all industries!

Air Dryer Maintenance

Preventive maintenance must be scheduled on your air compressor. It’s all well and good having an efficient air drying system, but it means very little if the air compressor itself is not working correctly.

To avoid setbacks, schedule regular preventative maintenance checkups on both your air compressor and air dryer systems. You should also implement a monitoring system that allows you to stay up-to-date on the status of your equipment and the quality of the air being produced.

Improve the quality of your intake air! The less polluted your intake air, the less your air compressor and air dryer will have to work to purify it. Promoting a clean workspace by taking steps to minimize contamination by introducing a filtration system to the compressed air cycle will help significantly.

What to Look For When Buying an Air Dryer?

You must be wondering how they’re sized, but first you must decide what type best suits your application. Once you have done that, you can start to think about how you might size them. There are 4 extremely important parameters to investigate when considering what size air dryer you need, and these aren’t the physical size.

You must consider the following 4 factors which depict your air dryer size:

  1. Maximum Pressure
  2. Maximum Flow
  3. Inlet Temperature
  4. Ambient (Room) Temperature

Maximum Pressure

A key number to look at is the maximum pressure the dryer can withstand. When buying an air dryer please ensure that the dryer has a higher maximum pressure than your air compressor, otherwise you’re in trouble!

Maximum Flow

Think about the maximum flow size of your dryer, it must be higher than the amount your air compressor can deliver. If you were to choose an air dryer with a smaller/lower CFM than that of your compressor, you will have a big pressure-drop across the dryer.

This big pressure-drop will then need to be compensated for by setting your compressors pressure higher, resulting then in a higher energy bill. Or worse, having too small CFM dryer might mean its unable to reach its desired dew point.

Inlet Temperature

All air dryers will have a specified maximum inlet temperature. If you were to exceed this temperature, you could easily damage parts of the dryer or cause the dryer to not reach its dew point.

If you will be working with hot air, you can obtain specific high inlet temperature dryers in the market!

Ambient (Room) Temperature

The final factor you must consider is how hot of a room are you compressing your air in? You must find out what the maximum temperature on the hottest summer day is, and ensure the dryer is capable of working in that without over-heating and shutting down.

Air Dryers Readily Available on Amazon

I have picked out an example of each of the different types of air dryers readily available on Amazon so I can discuss the differences. However, I unfortunately could not find a deliquescent air dryer available on Amazon.

First up is this Ingersoll Rand refrigerated type air dryer. It’s overall dimensions are 16.5 x 16.5 x 14 inches and would be installed after the air compressor.

When looking at those 4 key parameters for buying the right one:

Maximum pressure: 203 PSI
Maximum flow: 15 CFM
Maximum inlet temperature: 140° F
Maximum ambient temperature: 115° F

Next up we have a Desiccant air dryer which is an in line component for a very reasonable cost compared to the refrigerant dryer.

This air dryer is only 6.5 x 3 x 3 inches which is a lot smaller than the refrigerant air dryer and will certainly be easier to install.

This desiccant air dryer has a maximum pressure of 215 PSI, a maximum flow of 88 CFM and a maximum inlet temperature of 140° F. Unfortunately it is unclear what maximum the ambient temperature is.

Note: This is not the Desiccant twin tower previously described, the in line desiccant air dryer process is slightly different but works on the same principles. The twin towers are far greater in size and cost a significant amount more.

Finally we have this in line Membrane air dryer. Similar size to the desiccant air dryer I presented, but fairly more expensive!

The maximum operating pressure for this type of drier is 123 PSI (converted from 0.85 MPA).

Hopefully this page has provided you with a better understanding of the different types of air dryer, and what you should be looking at when selecting to buy one!

FAQs (Frequently Asked Questions)

What does an air dryer do?

An air dryer suppresses the dew point of compressed air by remove the water moisture from it. If this moisture was not removed, damage could be caused the the air compressor system.

Do air dryers work?

Yes, air dryers work by removing the moisture from compressed air so that your end application receives the best purified air you can possibly get.

How many types of air dryers are there?

There are four main types of compressed air dryers which are refrigerated, chemical, desiccant, and membrane.

Do I need an air dryer for my compressor?

If you want to prevent damage to your air compressor system, it’s components and your end use applications then yes, you need an air dryer. Moisture creation in a compressor is completely unavoidable, so the only thing you can do is work to remove this moisture.

If you have any questions regarding compressed air dryers then please leave a comment below with a photo if applicable so that someone can help you!

By Aidan Weeks

A passionate Mechanical Engineer with endless enthusiasm for fluid power - building off the back of over 18 years of high quality contribution and discussion stimulated by Bill Wade here at About Air Compressors. With both practical and theoretical experience in pneumatics and hydraulics, I'm putting my knowledge to work - and working my grey-matter through my research, assistance and publishing work here at About Air Compressors. Feel free to reach out any time! P.S. A HUGE shout out to Doug who really offers such great value to all visitors to About Air Compressors - once again, feeling like I'm standing on the shoulders of GIANTS by getting to work alongside such a great community

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