In Industrial Applications, Is It Necessary To Equip A Screw Air Compressor With A Refrigerated Dryer?

Is a refrigerated dryer necessary for screw air compressors in industrial applications?Let's discuss this in detail.

First, we need to understand why a refrigerated dryer is necessary.

The air compressed by the air compressor contains a significant amount of moisture. The ambient air drawn into the compressor contains water vapor (humidity). When air is compressed, the pressure increases and the volume decreases, but the total amount of water vapor drawn in remains constant. According to Dalton's law of partial pressures, the partial pressure of the water vapor also increases significantly.

The compression process generates a significant amount of heat (screw compressor exhaust temperatures are typically above 70°C to 100°C). During this time, the water vapor is superheated and does not condense. Before entering the pipeline network, the compressed, high-temperature air passes through an aftercooler (usually integrated into the compressor) and an air receiver for cooling. As the temperature decreases, the saturated water content of the air drops dramatically. When the air temperature drops below the dew point at its current pressure, the excess water vapor condenses into liquid water. If this liquid water is not removed, it will enter the downstream pipelines and equipment with the compressed air, causing many hazards, such as:
(1) Corrosion: rusting pipes, valves, cylinders, tools, etc.
(2) Damage to equipment: washing away lubricants, causing pneumatic components to jam, and water hammer damage to equipment.
(3) Contamination of products: affecting the quality of paint, food, medicine, and electronic products.
(4) Reduced efficiency: increasing pipeline pressure drop, clogging filters and small holes.
(5) Instrument failure: clogging or damaging precision instruments.

What is the main function of a cold dryer?
The function of a cold dryer is to further reduce the temperature of the compressed air (usually to a dew point temperature of 2°C - 10°C) by forced cooling before the compressed air enters the pipeline network, so that most of the water vapor in it condenses into liquid water and is discharged through an automatic drain. This can significantly reduce the water content (pressure dew point) of the compressed air and protect downstream equipment and processes.

What are the key factors that determine whether to equip a cold dryer?

1. Compressed air quality requirements (especially requirements for moisture):
Must be equipped: If your air-using equipment or process is very sensitive to the moisture content in the compressed air, then a cold dryer (or more advanced drying equipment) is essential. These scenarios include:
(1) Painting/coating: Moisture can cause blisters, orange peel, decreased adhesion and other problems on the paint surface.
(2) Precision pneumatic tools/instruments: Moisture can cause rust on internal parts, lubrication failure, inaccurate movement and even damage.
(3) Instrument air: Moisture can clog small instrument pipes and valves, causing control failure or inaccurate measurement.
(4) Electronics manufacturing/semiconductors: Extremely strict, moisture may cause short circuits, oxidation or affect the process.
(5) Medicine, food and beverages: There are strict requirements for cleanliness and pollution-free, and moisture can easily breed bacteria.
(6) Pneumatic conveying: Moisture can cause powder materials to clump and clog pipes.
(7) Equipment using air bearings: Moisture can damage the bearing surface.

2. Location Humidity and Temperature:
The higher the ambient humidity, the more liquid water is produced after compression.
In hot and humid regions, it's almost impossible to operate without a refrigerated dryer, and the water production will be very high.

3. Compressed Air Usage Pattern:
Intermittent use is more likely to cause condensation to accumulate in the pipes than continuous use.

4. Maintenance Capacity and Cost Considerations:
Not having a refrigerated dryer means you'll need to drain and maintain the air storage tank, pipes, and gas-consuming equipment more frequently. Otherwise, problems like corrosion and blockage will quickly arise. In the long run, repair costs and downtime losses may far exceed the investment in the refrigerated dryer.

The refrigerated dryer itself has a certain purchase cost and operating energy consumption (albeit relatively low).

Thus, from the perspectives of protecting equipment, ensuring process quality, and reducing maintenance costs, equipping most industrial screw air compressor systems with a refrigerated dryer is a highly recommended and essential standard feature. It is one of the key components to ensure the reliable, efficient, and long-lasting operation of the compressed air system.