Ingersoll Rand Compressed Air Dryers For Sale
Schulz Compressed Air Dryers For Sale
The best-compressed air dryers are energy-efficient, affordable, and require less maintenance, all of which keep costs low. The manufacturers of compressed air dryers are constantly redesigning systems using the newest technology.
Even artificial intelligence is finding its way into the control systems on some units, enabling the dryer to learn for the most efficient operation.
These new smart compressed air dryers run cooler, use less energy, and require less maintenance.
Why Get Compressed Air Dryer?
If you run a compressed air system in your shop, no matter the size or volume, your goal should be to deliver the cleanest and driest air possible to the working end of your system.
You may already employ an array of filters that ensure the delivery of clean compressed air, but without a compressed air dryer, the water vapor content may still be damaging your tools and equipment.
Understanding the types of compressed air dryers available and how new technologies are being employed to control costs and enhance efficiency is the key to making choices on the best type and size of compressed air dryers for your application.
Making the wrong decisions can be costly in terms of operating costs and mechanical maintenance.
Types of Compressed Air Dryers
Industrial compressed air dryers typically fall into two broad categories. Each category is further divided into sub-categories depending on several factors in the design and operation of the compressed air dryer.
The two major categories are:
- Refrigerated Drying Units
- Desiccant Drying Units
The goal of each of these types of compressed air dryers is the same. At the end of the process, the goal is to remove as much water vapor from the compressed air as possible.
The engineering principles that are used in these two types of compressed air dryers both accomplish that goal using different materials and techniques that can have benefits in different applications.
We will consider each of these concepts in this article.
Refrigerated Drying Units
A survey of both industrial users and engineers who compressed air delivery systems shows that refrigerated compressed air dryers are the most popular choice in most systems.
These experts cite several reasons for making this choice.
- Cheaper upfront costs
- More economical operating costs
- Less ongoing maintenance costs.
In any industrial or manufacturing operation, costs are probably the most important factor. Controlling costs keeps prices down for the customer and increases profits for the company.
It is no wonder that industrial operators cite cost factors as the most important considerations when installing a compressed air dryer in their systems.
How do Refrigerated Dryers Work?
Think about the refrigerator in your kitchen at home. Its goal is to keep food fresh by keeping it cool.
This cooling is accomplished in large part by removing the moisture in the air inside the refrigerator.
Just like your refrigerator, a refrigerated compressed air dryer works by cooling the compressed air and driving out the water vapor.
The refrigerated compressed air dryer circulates some form of refrigerant, usually a commercial product such as R134A or R140A, around a heat sink through which the compressed air is directed.
The cooling effect causes the water vapor to condense and flow out of the heat sink before the compressed air is circulated out of the dryer. Refrigerated compressed air dryers utilize several technologies to accomplish the removal of water vapor from the compressed air in an efficient and economical manner.
Refrigerated Compressed Air Dryer Advantages
- Expense – Front end installation costs for refrigerated compressed air dryers are usually less than the installation costs of other types of compressed air dryers.
- Operation – Refrigerated compressed are dryers typically operate with fewer operating costs that other types.
Operating costs can be dependent on properly sizing the system and choosing the best system for the application.
- Maintenance – Ongoing maintenance costs for refrigerated air dryers can be lower than other types. Again, a properly sized and designed system will play a large part in how maintenance costs evolve.
Disadvantages to Refrigerated Compressed Air Dryers
Capabilities – Refrigerated compressed air dryers have a limited capacity to maintain a dew point.
This can result in elevated water vapor levels in your compressed air if the system cannot maintain the needed temperature differences in the heat sink and the compressed air.
Cycling Refrigerated Compressed Air Dryers
The operation of a cycling refrigerated compressed air dryer is closely akin to the operation of your refrigerator. The thermal mass through which the compressed air is passed to remove the water vapor is cooled by the refrigerant to a given temperature.
When the thermal mass has reached that temperature, the refrigerant compressor shuts down. This makes cycling dryers more energy efficient under certain use conditions.
Typically, cycling dryers are used in installations where the ambient air temperatures are cooler, or the compressed air usage is relatively low or sporadic. The use of cycling air dryers should be evaluated carefully based on the requirements of the environment and the job.
Pros of Using a Cycling Compressed Air Dryer
Energy Efficiency – Cycling systems tend to be more efficient energy users if they are properly sized for the needs of the system.
The cycling system only runs the compressor when the temperature of the heat sink rises above the temperature needed to be effective at removing water vapor from the compressed air stream.
Cons of Installing a Cycling Compressed Air Dryer
- Size and Weight – Cycling compressed air dryers are usually heavier and bulkier than other styles and types. The need for a massive heat sink through which the compressed air stream is passed drive up weight and size on these units.
- Costs – Initial costs of cycling air dryers are usually higher.
The need for a refrigerant compressor and extensive electronics to control the unit are the primary reasons for these elevated costs.
- Efficiency – Environmental and use must be considered when evaluating the installation of cycling compressed air dryer.
Under some conditions, refrigerated cycling compressed air dryers may simply not be able to maintain the necessary temperatures to ensure proper water vapor removal.
Non-Cycling Refrigerated Compressed Air Dryers
AS the name suggests, non-cycling compressed air dryers continually circulate refrigerant through the system.
The same sorts of heat sinks and controls are used with some new technology variations coming to the market in the last few years.
Variable controlled refrigerant valves have allowed some economies to be seen in the operation of non-cycling air dryers as have innovation in control systems.
Non-cycling compressed air dryers have some advantages and disadvantages that should be considered when planning a compressed air system
Pros of Using a Non-cycling Compressed Air Dryer
- Efficiency – Non-cycling air dryers can maintain a stable dew point capacity within the system, which allows more consistent water vapor removal.
- Capacity – Where compressed air usage is high or has rapid and marked peaks and valleys in usage, a non-cycling air dryer can more easily respond to the demands of the compressed air system.
Cons of Using a Non-cycling Compressed Air Dryer
- Economies – Non-cycling refrigerated compressed air dryers do not offer the energy savings associated with the cycling type. Because the compressor operated continually, energy savings are not realized.
Desiccant Compressed Air-Drying Units
Desiccant compressed air-drying units use a different approach to removing water vapor from the compressed air stream.
Refrigerated units use a mechanical means, the cooling of the compressed air stream, to remove the water vapor.
Desiccant air dryers use chemical processes to remove the water vapor by exposing the compressed air stream to a physical agent that either absorbs or adsorbs the moisture.
The difference in the way the moisture is removed is important to understand because it is dependent on the material that is used as the desiccant in the air dryer unit and can affect operation and costs associated with operating the unit.
- Adsorption is the process of removing water vapor from the compressed air stream in which the water vapor attaches the moisture to the surface of the desiccant material without being dissolved into the desiccant material.
- Absorption allows the water vapor to be dissolved into the desiccant material, in some cases, causing a chemical change in the desiccant material.
Type of Desiccant Compressed Air-Drying Units
Desiccant compressed are dryers that are further classified by the type of material that is used as the water trapping material in the dryer unit.
These types are classified as:
- Regenerative Units
- Deliquescent Units
- Coalescing Units
There are advantages and disadvantages to each of these types of desiccant air dryers, and some even have very specialized applications with specific industries.
Understanding the technologies and the capabilities of each of these types of desiccant air dryers is important when choosing a compressed air dryer for your installation.
Absorption vs. Adsorption
At a basic level, the type of desiccant material that is used in an air dryer system determines what kinds of additional equipment is necessary and how maintenance issues will evolve in the work environment over time.
A quick look at the advantages and disadvantages of each type of desiccant material can provide some quick answers.
- Cost – Typically, absorption air dryers have the lowest installation costs.
- Installation – Absorption compressed air dryers often have the easiest and least expensive installation costs because they do not need electrical connections.
- Operation – With no moving parts or electrical components, absorption dryers are the simplest compressed air dryers to operate and maintain.
- Maintenance – Desiccant material must be added to the compressed air dryer on a regular basis. This becomes both time and cost factor consideration
- Ecological Concerns – The dissolved desiccant that is the byproduct of the absorption process can be considered a hazardous waste material in some areas.
Removing and disposing of this material can add to the cost of the entire operation.
- System contamination – If the proper post drying filters are not installed and maintained, the byproducts of the absorption process can infiltrate equipment downstream in the compressed air system.
These byproducts can be corrosive and damaging to the piping and the equipment to which the compressed air is being delivered.
- Efficiency – The efficiency of adsorption air dryers is uncompromised with the ability in some units to reach a dew point of 0700 C, which means very dry air at the user end of the system.
- Effectiveness – Adsorption units are not affected by ambient temperatures making them extremely effective at removing water vapor in a wide range of environmental conditions.
- Filtration – The nature of the material, a dry desiccant through which the airstream passes, makes adsorption style units act as filtration units as well.
- Energy consumption – Adsorption units typically involve some sort of regenerative mechanism which requires a lot of electrical energy to operate. This equates to increased operating costs.
- Maintenance – Periodic replacement or addition of the adsorption material may be necessary. This can be a time consuming and expensive proposition for some installations.
- Noise – This type of compressed air dryer can be extremely noisy to operate and may require that the installation be distanced from the workplace or enclosed in specially built containment areas to suppress the noise.
To further complicate the situation, is the issue of desiccant regeneration. Many desiccants compressed air dryers incorporate systems that allow the desiccant material to be dried, or regenerated, automatically by the system.
These regeneration systems come in two styles, heated and heatless.
Heated Regeneration Systems
Heated regeneration compressed air dryers utilize heating systems to drive off the trapped water vapor from the desiccant material and restore the effectiveness of the desiccant to continue to capture water vapor from the compressed air stream.
These heating systems can be either internal or external and are usually electrically operated.
In addition to heat, heated regeneration systems require some means to circulate the heated are inside the vessel that contains the desiccant material to ensure that the material furthest from the heat source gets the same regenerative effect as the material sitting in close proximity to the heat source.
Advantages of Heat Regenerative Systems
- No freeze-up danger even when low dew points are maintained
- Reduced levels of purge air are required to keep the system operating optimally
Disadvantages of Heat Regenerative Systems
- Desiccant material replacement required periodically
- Oil contamination of the desiccant material can effectively neutralize the water vapor adsorption properties unless proper pre-filtration is maintained.
- It requires a purge air system to circulate and remove hot air in the desiccant chamber.
Heatless Regeneration Systems
Heatless regenerative air dryers do not depend on internal or external heaters to drive the water vapor from the desiccant material. Instead, these systems use only the flow of purge air through the desiccant material to remove the collected water vapor.
This can use as much as 18% of the flow capacity of the compressed air system and the design of the system must take this into consideration.
Heatless regenerative systems can be used in situations where access to the compressed air dryer is difficult or limited such as hazardous areas or in remote locations.
The simplicity of their operation is attractive to many operators.
Advantages of Heatless Regeneration
- Very low dew points can be easily maintained without the problems associated with freeze-up
- Easy design for mobile, remote, or hazardous area operation. The ability to operate the system on air pressure alone eliminates many installation problems
- Lower initial unit cost due to the absence of expensive heating units and control systems
Disadvantages of Heatless Regeneration
- Desiccant material must be replaced periodically. This is typically on a three to five-year cycle.
- Purge air needs can be large, which can affect the overall expense to operate the system. Compressors must be sized to provide not only working airflow but also the additional capacity to operate the purge system.
- The desiccant materials used are sensitive to exposure to oil. The incoming compressed air stream must be properly filtered to remove any aerosolized oil or oil droplets.
The Twin Tower Concept
Regenerative compressed air dryers usually involve a twin tower design. Each tower is, in effect, a compressed air-drying system.
The design allows one tower to be working to trap water vapor while the other is being regenerated. This system is effective for both heated and unheated regenerative systems.
The advantage of the twin tower design is always the ability to maintain the full operation of the system. There is never a need to shut down the compressed air delivery system in order to maintain or regenerate the desiccant material.
This is much more efficient and cost-effective over time despite the added expense on the front end.
Deliquescent Compressed Air Dryers
A specialized type of desiccant compressed are dryer is the deliquescent models. These dryers are usually of single tower construction and utilize a special type of desiccant know as Dry-O-Lite.
Dry-O-Lite is a proprietary product that is primarily sodium chloride. Water vapor reacts with the material in the dryer dissolving the desiccant material into a brine that collects at the bottom of the tower.
This brine must be periodically removed, and more desiccant material added. This single tower construction is simple and straightforward.
This makes deliquescent air dryers less expensive to install and to maintain than other styles.
Advantages of Deliquescent Compressed Air Dryer
- Low installation and acquisition costs
- Very low-pressure drop across the system
- Simple and efficient operation
- No electrical power required
- No moving parts
Disdvantages of Deliquescent Compressed Air Dryer
- Dew point is directly affected by ambient air temperature and the temperature of the compressed air entering the system
- Regular and periodic maintenance required to purge the brine from the system and replace the desiccant material.
- Post filter installations are required to keep desiccant material from reaching downpipe areas.
Coalescing Compressed Air Dryers
Some applications where compressed air is delivered to equipment that is considered essential to health and safety can require an even higher level of air purification.
One example of this is the trucking industry. Large trucks depend on air pressure to operate the braking system.
These brake systems are particularly vulnerable to both water and oil contamination.
The nature of the installation also requires much smaller air-drying systems that would be found in an industrial installation.
Coalescing compressed air dryers are normally found as cartridges that fit into the compressed air delivery system and undergo periodic inspection and replacement.
These cartridges contain a pre-filtration system, an oil capturing filter material, and a desiccant material to trap water vapor. Outside the vehicle industry, coalescing filters are often installed in medical compressed air delivery systems such as in dentists’ offices and medical clinics.
Membrane Compressed Air-Drying Units
One of the newest technologies to find its way to compressed air dryers is membrane permeability. That sounds complicated, but you are probably using the same sort of technology every day.
Reverse osmosis water filtration is a form of membrane permeability. When used in compressed air dryers, the concept is the same.
The membrane compressed air dryer uses a membrane that will allow gas molecules to pass through but traps the larger water molecules in the membrane where they are collected and vented to the exterior of the air dryer.
Membrane technology is efficient. There is virtually no pressure loss across the system, no moving parts, easy maintenance, and high reliability.
The membrane system typically doesn’t require any electrical power to operate, making them cost-efficient as well.
It’s All About Air Quality
It is the quality of the air at the end of your compressed air delivery system that is the goal. Dry, clean air to protect tools, equipment, and personnel is the reason for the expense of installing a top-quality compressed air dryer in your system.
I hope that this article has provided you with an understanding of compressed air dryer technology and some leads to finding the best equipment to meet your needs.