Air Dryer A to Z

• What is compressed air, and where is it used primarily?

Today, it is a major power source for factories and industrial sites in all fields.

Generally, electricity is thought to be the whole power source, but when you know it, there are many places where compressed air (pneumatic) is used as a power source. As you may already know, there are a lot of familiar cases in our lives. For example, bolt loosening and tightening tools for replacing tires are not electric wrenches that use electricity, but pneumatic wrenches that are powered by compressed air. The air used for injection is also compressed air. It is also used in automation equipment used for planting small chips in semiconductor production line that can be seen in news, automatic loom weaving machine, robots assembling automobile, etc. Now automation means that pneumatic system equality is established. Compressed air is also used for painting, which is a necessary process for manufacturing most industrial products such as furniture and ships. In addition, it covers all industries such as electric and electronic products, machinery, chemicals, precision processing, and even food and beverage manufacturing and medical equipment.

• Why is pollution in the compressed air a problem?

In the process of compressing the atmospheric air, various impurities such as moisture, dust, and pollutants contained in the air are sucked into the air and concentrated in the compressed air.

These contaminants can cause serious damage to the elements of the compressed air system, such as piping corrosion, valve clogging, clogging of the instrument, malfunction of various pneumatic equipment, poor coating, etc., After all, these serious contaminants make such as product failure, production line interruption, and quality degradation. For example, when water is impregnated into the semiconductor manufacturing process, defective products are produced, or the automation line stops operating due to moisture. In addition, the surface of the automation line is damaged due to the formation of blisters during the coating operation. The contact area of the compressed air caused by corruption and product failure causes damage, and the range of damage caused by the moisture is so large that installation of an air dryer is essential in almost every factory that uses compressed air.

• Why does condensated water appears?

Normally compressed air is compressed to 8 times the atmospheric pressure.

After compression, the volume is reduced to 1/8, but the relative humidity is increased 8 times and a large amount of water is generated.
Moisture changes its shape from liquid to gas, that is, water vapor, as the temperature increases or the pressure decreases. However, if the temperature is high or the pressure is low, it can not be changed into water vapor indefinitely. The amount of water vapor that can be contained per unit volume at any temperature and pressure condition is determined by natural law, and this value is called saturated water vapor amount. The ratio of current water vapor and saturated water vapor is called relative humidity. When the relative humidity is 100%, the entered water vapor that flows in is changed into water instead of water vapor. In the process of compressing air sucked with water vapor in the atmosphere, but the relative humidity is increased because the water content remains unchanged.
Normally compressed air is compressed at 8 times the atmospheric pressure. This story tells us that the volume after compression is reduced to one-eighth, but the concentration of water is increased eight times. Even in very dry winters, the relative humidity is about 30%, and in normal cases, the relative humidity that people feel comfortable is about 40% to 60%. When the relative humidity is 60%, when this air is compressed, the concentration of water becomes 480%, 100% is present as water vapor, and the remaining 380% is converted into condensate (water).

• How can moisture be removed?

Refrigerated air dryers use the simplest way to essentially remove water vapor by cooling compressed air and condensing the water vapor contained in it.

The method of using the principle, the lower the temperature at a certain pressure is, the smaller the amount of saturated water vapor is, is the most widely used refrigerated air dryer in industry. Refrigerated air dryers have a heat exchanger that cools compressed air and a refrigeration compressor that circulates the refrigerant. This type of refrigerated air dryer operates the refrigeration compressor continuously for 24 hours regardless of the compressed air load.

• What is the PCM dryer?

It is a product that saves energy while controlling the On/Off operation of refrigeration compressor by applying phase change material that freezes and melts at constant temperature.

The PCM dryer adopts a phase change material that freezes and melts at a specific temperature in the heat exchanger. When the refrigerant sent from the refrigeration compressor through the condenser to the heat exchanger freezes the PCM, the refrigeration compressor stops operating. Even if the refrigerant does not circulate, the frozen PCM continuously dehydrates the compressed air by cooling it continuously, and there is no power consumption during this time, so energy is saved evenly. When the compressed air continuously comes in, the PCM gradually melts. When the PCM is completely melted, the refrigeration compressor is operated again, and the process of freezing PCM is repeated.

• What is the energy saving efficiency of the PCM dryer?

It is 85% ± 10%.

Of course, because the operating conditions are different for each site where the air dryer is installed, it is difficult to calculate uniformly. However, since the launch of PCM dryer in 2016, about 300 PCM dryers have been installed in Korea over the past year, showing an average energy saving efficiency of over 85%.

• It looks like an exaggerated figure because energy saving efficiency is 85%?

Actual energy saving rate of PCM dryers are verified over 80% throughout the year.

As shown in the graph below, the energy saving efficiency is over 65% even when operated at 100% flow rate in the average seasonal temperature conditions of South Korea. Very few sites use 100% compressed air at all times, and even in very heavily used areas, the maximum instantaneous flow rate is rarely greater than 80%, and the cumulative average flow rate is less than 40 to 50% of the rated flow rate.

• Comparing the power consumption for the 100 horsepower air dryers, other makers’ air dryers have higher power consumption than SPX FLOW’s, but there are more products with lower power consumption than SPX FLOW’s. Even, power consumption of some air dryers are 1.5kW while the PCM dryer is about 2.6kW. Is not the PCM dryer ineffective due to high power consumption figures under the same rated conditions?

If the air dryer is designed for 100 horsepower capacity, the suitable power consumption is about 2.55kW.

If it is 1.5kW, it is likely that the product is not qualified enough to handle the flow rate for 100 horsepower air compressor. In order to reduce the cooling heat load of the refrigeration cycle, the general refrigerated air dryer adopts a structure that passes the pre-cooler that is cooled by the heat exchange with compressed air at the outlet before the compressed air flows into the evaporator.
The cooling capacity of the air dryer is determined by the heat exchange efficiency of the pre-cooler. The heat amount for 100 horsepower refrigerated air dryer is about 35,800 Btu/h, and the heat sharing ratio of the precooler and the chiller is 50:50. The cooling heat required for the refrigeration cycle is 17,900 Btu/h, and the rated power consumption of the refrigeration compressor varies by the manufacturer, the refrigerant used, and the compressor type, but it is usually distributed in the range of 2.5 to 3.5 kW. Therefore, considering the power consumption of the condenser fan, it is normal that the rated power consumption of the air dryer is 2.5kW or more, and if the product is far less than this, it is very likely that the refrigeration cycle that can not handle the 100 horsepower compressed air flow rate is applied.

• Is there any case where PCM is applied to other air dryer makers, or similar product manufacturers such as air conditioners?

SPX FLOW Korea is the first in the world to succeed in the development and commercialization of air dryer with PCM.

There have been numerous efforts to develop a phase change type air conditioner applying the same technology to the air dryer maker in the United States and Europe as well as Korea’s representative S electronics. However, there are no cases that have succeeded due to technical limitations. We have developed the PCM dryer using this dream technology, and it is the first time in the world that we commercialize it as a product that saves energy by 80 ~ 90% over the entire capacity from 20 horsepower to 3,000 horsepower.

• Is the energy saving efficiency of the air dryer low compared to the air compressor?

VSD air compressors have energy saving efficiencies of only 10~15%, but PCM dryers can save energy over 80% to 90%, so efficiency is not comparable.

The variable speed control type VSD system has a great limitation on energy saving because it requires energy consumption of at least 40% for oil circulation. On the other hand, since the PCM dryer consumes energy only when the refrigeration compressor is operated by the on/off control method, the actual operating time for one hour is about 5 to 10 minutes in total. Energy saving is achieved during the “Off” period. The energy saving rate on 100 horsepower VSD air compressor is 10~15% only (about 10kW), however the PCM dryer saves 80 to 90% more energy.

• There are many products using inverter technology as energy saving products. What is the difference?

Inverter type has to consume a certain amount of energy eventually, since it must be operated at minimum speed (about 40%) for lubricating oil circulation in refrigeration compressor even when no load is applied.

Simply put, if the gasoline car that consumes the fuel while the engine is still idling in the signal waiting mode is an inverter type air dryer, the PCM dryer is like an electric car that is shut off when waiting for the traffic signal for a long time. However, in the case of automobiles, the idling time during signal waiting is less than the total running time. (There is a gasoline car with ECO mode, which turns off the engine to save even a small amount of energy waste.) In the case of air dryers, considering the average compressed air usage versus capacity and the average heat load per season (Inlet air temperature and ambient temperature), the average idling time is 85%.
The reason is that the annual average temperature of South Korea, which can be called the actual operating condition, is less than 15 ℃. In fact, when the condition of using the air dryer is examined, the average compressed air usage is much smaller than the maximum capacity. Furthermore, since it is necessary to be capable of stable dehydration even under the most heat load conditions during the year, it is necessary to design the air dryer based on the summer condition of 38°C as the designing conditions for determining the capacity of the air dryer. Therefore, if you look at the yearly average, there are many times when there is room for cooling capacity. These are the reasons why the PCM dryer can save 85% energy. For this reason, ‘high temperature air dryer’, which set the dryer inlet temperature at 50 ℃ as the design condition, is wasting more energy.
On the other hand, the difference of power consumption of air compressor based on the ambient temperature is very small. Therefore, even if the inverter air compressor is used for energy saving, the saving rate is only 10 ~ 15%.

• What is the payback period when replacing a non-cycling refrigerated air dryer with a PCM dryer?

It is about 2.6 years.

Here’s an example of an air dryer for 100 horsepower air compressor. The power consumption of the PCM dryer for 100 horsepower is about 2.6kW. If we assume that the average energy saving efficiency of PCM is 85%, and that it operates full 300 days, at three shift factory like automobile parts manufacturers, and the electricity rate is 110 KRW, then the annual electricity saving cost is 1,750,000 KRW. (2.6 x 0.85 x 24 x 300 x 110 = 1,750,320)
If the PCM dryer for 100 horsepower air compressor costs about 4,620,000 KRW, so if you divide it by the annual saving cost, it takes about 2.6 years until your investment pays off. (4,620,000/1,750,320 = 2.6)

• When you newly installed or expanded, what is payback period of difference between PCM dryer and non-cycling refrigerated air dryer?

It is about 2.8 months.

Here’s an example of an air dryer for 100 horsepower air compressor. The power consumption of the PCM dryer for 100 horsepower air compressor is about 2.6kW. If we assume that the average energy saving efficiency of PCM is 85%, and that it operates full 300 days, at three shift factory like automobile parts manufacturers, and the electricity rate is 110 KRW, then the annual electricity saving cost is 1,750,000 KRW. (2.6 x 0.85 x 24 x 300 x 110 = 1,750,320)
If the price of 100 horsepower non-cycling refrigerated air dryer is about 4,200,000 KRW, and the price of PCM dryer is 4,620,000 KRW, so if you choose PCM dryer, you need to invest the difference, 420,000 KRW. This is payback cost for 2.8 months, divided by the annual savings. (420,000 / 1,750,320 x 12 = 2.8)

• Why is the price of a large size PCM dryer high?

It is energy-saving and oil-free product that provides oil removal efficiency up to 99.8%.

There are many other products in the market, ignoring even the stable dew point and dehydration performance, which is the basic performance that air dryers must provide. The PCM dryer provides 4±2°C dew point as well as complete dehydration performance. In addition, a cold coalescing filter is built into the dryer to effectively remove oil from the compressed air. The cooled air from the rear of the separator contains a considerable amount of liquid oil, which is removed through the Cold Coalescing filter.
If the oil removal filter is installed at the downstream of the dryer, the temperature of the air at the outlet of the dryer is high, so there is a lot of oil present in the vapor state and it is difficult to remove it.

Even though, I guess it’s too expensive.

Please compare the total cost of purchasing and installing a filter separately from the dryer and the cost of purchasing one large PCM dryer in order to install a system where the oil removal efficiency is at most 70%.

In the field where the oil removal is concerned about the compressed air, install an air dryer and an oil removal filter at the rear end. This requires piping to connect the dryer to the filter, which requires additional cost and space. Loss of operating expenses due to differential pressure can not be excluded. However, if you have a large PCM dryer with a built-in Cold Coalescing filter inside the product, all these hassles will be resolved, and it will be much more profitable just to compare it in cost.

 

• Why does Cold Coalescing need?

There is a growing demand for complete oil removal in industries such as electricity, electronics, semiconductors and paints where oil free is required, as well as in all other industries seeking high quality.

However, if you have to pay for the costly oil free compressors, we recommend Cold Coalescing, which allows for complete dehydration at low cost and close to the Oil Free level of the compressed air in the oil-fed compressors.

• What is the difference between PCM and PCM PLUS?

If PCM dryer is a standard dryer, PCM PLUS can be described as a filter-integrated high-temperature integral dryer.

The PCM PLUS has a rated inlet air temperature of 50°C and an ambient air temperature of 35°C, enabling inlet air temperature up to 60°C, while maintaining the high energy efficiency of up to 99% provided by the PCM series. The pre and after filters are built into the dryer, making it easy to install, maintain and repair the product.

• PCM PLUS is an all-in-one type, why is there no aftercooler?

If you use a proper dryer, you do not need an after cooler on the front of the dryer.

Generally, if the product satisfies the inlet air temperature condition and the flow rate of the inlet air to the air dryer, the dryer itself provides sufficient cooling and dehydration functions, so there is no need to install after cooler after the air compressor and before the air dryer. Wrong common sense is wasting customer’s valuable money. The same applies to high temperature products. It is necessary to provide dehydration performance without installing the after cooler within the range of the conditions that the air dryer guarantees. However, some cheap and underperforming air dryers require dehydration of the after cooler at the front end so that residual moisture can only be removed from the dryer. Therefore, it is common to install after cooler. Air compressors over 30 HP are screw type in general and usually have after cooler built-in. The high temperature discharge air is only from a small reciprocating air compressor less than 30HP, and the high temperature dryer was originally developed for this small reciprocating air compressor less than 30HP in the USA that does not have an after cooler. In Korean market, it is common that the istallation of high temperature air dryer which has built in after cooler for the screw compressor which also has an after-cooler in it which makes the duplication installation of after cooler. This is due to the distrust of air dryer products that cannot perform properly due to the terribly wrong practices which is difficult to see in other countries. PCM PLUS is a solid air dryer that provides stable dew point and dehydration performance even in high-temperature working condition.

• What is PCM? I wonder what raw material is for PCM, and whether it is harmful or not.

PCM is a common name for phase change materials, and it is harmless organic compounds.

It is a common name for a substance whose phase changes at a constant temperature. Typically, it is water. (For 0 °C ~ 100 °C at atmospheric pressure, latent heat is released or absorbed when a phase change occurs from ice ↔ water ↔ water vapor.)
PCM has been developed as a filling material to protect spacemen exposed to extreme environments, and is now a very familiar material used mainly for ice packs and heat packs .There are many different types of PCM classified its melting point & latent heat amount.
The PCM designed to cool and condense compressed air and optimize drain discharge is applied on our PCM dryer, and it is harmless to the human body. (But, it’s not allowed to eat it, though)

• What is the life span of PCM, and can it be objectively proved?

The lifetime of PCM is semi-permanent.

In general, when the manufacturer refers to the lifetime of the product, the lifetime of the product depends on the lifetime of the product depending on the lifetime of the parts that are worn out or decrease in performance over time. However, since PCM is a material that repeats freezing and melting with a simple physical action inside a totally enclosed heat exchanger, it is not a substantially driven component, and the state of the PCM emits or absorbs latent heat, It is not a factor that determines the life of the dryer. Even if water is freezing and melting thousands of times, it is like a reason not to worry about the change in water properties.
However, when the temperature of the PCM is rapidly increased to 120 ° C or exposed to the external environment for a long time (when the lid is opened and kept for a long time without sealing), the properties and latent heat capacity of the PCM may be changed. But, the PCM life is semi-permanent because it is filled in a completely enclosed space in the heat exchanger that is shut off from the outside environment by the heat insulation and uses only the phase change effect.

• If PCM freezes, does it increase in volume like water and become frozen and burst?

PCM is free from frozen & burst because it is reduced in volume when frozen.

Water is the only material on the earth that increases in volume when frozen. Because we are so familiar with water in everyday life, it is common sense that the volume increases when frozen in general. The increase in the volume of ice is due to hydrogen bonding between water molecules. Water molecules have a hydrogen bonding rate of less than 15%. When they are frozen, the hydrogen bonds become completely (100%), making regular ice crystals and increasing the volume of voids between these crystals. However, since PCM does not increase in volume when frozen along with its general physical properties, it is free from the phenomenon of freezing.

• Is there any possibility of PCM leaking inside the heat exchanger?

You can rest assured that all of our heat exchangers will be applied to your product after helium leak test.

The total amount of heat exchanger that we use in air dryer is applied to the dryer only with the most reliable Helium leak test, and we have been exporting it to overseas for more than 10 years. The reason why we declare the heat exchanger warranty period to be the industry’s highest level of 5 years is the expression of pride that we have accumulated 30 years of know-how as a manufacturer of dryers and thoroughly inspect all heat exchangers.