Most of the industrial applications where compressed air is in use would require a pressure dew point (PDP) between +2° to +8° Celsius. For all such applications, a refrigerated type of air dryer can guarantee the best performance. For pneumatic applications, the pressure dew point should be considered over an atmospheric dew point as it will ensure the desired level of water content in compressed air, which will be harmless to the process. 

Very few industrial applications demand a quality of compressed air with PDP below +2° Celsius e.g., cryogenic applications or the manufacturing process of hydroscopic materials. For such applications, it is recommended to install a refrigerated air dryer along with a suitable desiccant dryer for reducing overall investment as well as minimize the purge-loss of the desiccant dryer.

It is necessary to remove moisture from compressed air before it enters process machinery to prevent corrosion, rust, pollutants, and germs in the user's system while ensuring the quality standards required for your industry as well as minimizing the wear & tear of your process equipment. Refrigerated dryers will increase the overall efficiency of process machinery and pneumatic tools.

Refrigerated dryer is used to remove moisture and water vapor from compressed air. They are usually an economic solution and are most suitable for safeguarding the process requirements and extending the life of the system. The latest refrigerated dryers have an in-built PDP indicator.

How does a refrigerated dryer protect equipment?

Refrigerated dryer works on the principle of cooling the compressed air to remove moisture. The heat generated by compression causes the moisture in the air to vaporize. The water vapor condenses into liquid when the air is cooled by a refrigerated dryer. Condensate is then removed from compressed air before entering the process. The process equipment may corrode, rust, and run inefficiently if the moisture is not removed from compressed air. This way, the risk of corrosion and contamination is avoided, along with increasing the overall efficiency of the system by removing moisture from compressed air.

Operating a refrigerated dryer

Refrigerated dryer resemble a house-fridge largely in its operation. Eco-friendly refrigerants are used for cooling the hot compressed air. Refrigerated dryer consists of an air-to-air heat exchanger, an air-to-refrigerant heat exchanger, a closed-loop refrigeration cycle, and a condensate drain system. 

●      Incoming hot compressed air is partially cooled by an out-going cold compressed air leaving the dryer.

●      At the same time, the out-going compressed air is re-heated around the room temperature, so condensation does not form on the outside of the piping after dryer.

●      Cooling of incoming air results in reducing the energy required by the refrigerant compressor and hence ensure further power saving.

●      Incoming air is further cooled down to required PDP level at air-to-refrigerant exchanger by eco-friendly refrigerant.

●      Water vapor in compressed air is condensed and is drained through an automatic condensate system.

●      Hot refrigerant again is passed through a close-loop refrigeration cycle for transforming into a cold refrigerant required for the next cycle. The equipment is quite simple in construction and easy to operate. The maintenance and operation too is as easy as that of a house-fridge.

In some models, users find features like intelligent drain discharge. This part eliminates condensate using electronic sensors, saving compressed air. Additionally, there are features to lower operational costs along with an optional filtering system. The compressed air’s relative humidity needs to be under 50% to be effective. There are optional PDP indicators that can help one keep track of the drying process. These gadgets measure dew point, show fan condition, and have a PDP alarm. Despite this, installing and maintaining a refrigerator drier is rather easy. To reduce operational costs as much as possible, we built machines that are durable and simple to operate.

Non-cycling

Both non-cycling and cycling variants of refrigerator dryers are available on the market. Cyclic dryer control dew point by switching on and off refrigeration cycles; hence, the PDP of the system will be maintained in the range of ± 5°C. Whereas a non-cyclic dryer controls the dew point continuously, guaranteeing a constant dew point. Non-cyclic dryer is energy efficient as it varies cooling depending on air demand, unlike over-running in the case of cyclic dryers.

No matter whatever variation in air demand, a non-cyclic Mark dryer will maintain an exact PDP at the lowest energy. The equipment is simple, safe, and reliable.

Environmentally friendly gases

CFC content in refrigerant gases affects the environment. If the ozone layer is a concern for the user, Atlas Copco’s MDS dryer employs environmentally safe gases such as R513A, R410A, and R452A.

Proper drainage

Users must utilize an oil-water separator at discharge if the refrigerated dryer is attached to an air compressor that uses oil injection. It’s crucial to properly dispose of oil, especially when awareness of environmental safety concerns is a universal problem. Additionally, when getting rid of condensate, users should implement it with caution. Oil is frequently present in the condensate water that is released from compressed air. Residual oil traces are so minute that they can’t be seen with the naked eye; hence, it is crucial to adhere to strict protocol. It is advised to never pour contaminated condensate onto the ground or into a plastic container. It is advisable to make sure that users are adhering to proper regulations and following strict EMS guidelines.

Choosing a refrigerated dryer for air compressor

It is important to select the right capacity of a refrigerated air dryer if the application is critical. The capacity of a refrigerated dryer depends on the inlet compressed air temperature, the pressure of the compressed air, and the compressor room temperature. The company’s compressed air refrigerated dryers offer great dependability and are easy to install. When it comes to quality and protecting the process & compressed air equipment, these devices will add greater value. Users should think about installation, dependability, PDP, and high-quality parts when evaluating equipment. Finding the most energy-efficient option is also crucial.

Authored by: 

Kiran Panchal

Business Manager - Industrial Air

Atlas Copco India