Air Properties

Components of air

Our Planet has air, a mixed gas for which nitrogen and oxygen are main components.
However this table refers to air state, and our actual atmosphere includes moisture, dust and contaminants other than items shown in the table


Item/Component Nitrogen(N2) Oxygen(O2) Argon(Ar) Carbon Dioxide(CO2) Hydrogen(H2) Neon(Ne) Helium(He) Others
Volume(%) 78.03 20.99 0.933 0.03 0.01 0.0018 0.0005 -
Weight 75.47 23.2 1.28 0.046 0.001 0.0012 0.00007 -

Also, as the status of air changes according to altitude, temperature, located on and time, standards are needed for applications pneumatic devices. The flowing table represents air under the standard state.


Name of Standard Reference State Flow Notation
ASME Power Test Code 68℉ 14.7psia RH 36% S㎥/h
Sℓ/min
SCRM
SCFH
Compressed Air Institute 68℉ 14.7psia DRY
atural Gas Pipeline Field 14.7psia - >Suction Temperature
Japan Industrial Standards (JIS) 20℃ 760mmHg RH 65%
Korean Industrial Standards ㉿ 20℃ 760mmHg RH 65%

o Normal air: air at O°C, 1 aim and 0% relative humidity
o Normal air notation: Nm3 /h,NQ /min, m3 /hfntp), Q /min(ntp),etc


Conversion of measured air

Performance of different compressors is compared by discharged air volume, pressure, etc. Here, the correlation between discharge air volume, normal air volume (Nℓ/ min) and standard free air volume (Iℓ /min) require special attention. Normal air volume is in the unit of Nℓ/min or NTP, and NTP stands for normal temperature & Pressure. This value represents ideal air volume in the academic state, On one hand, the standard air volume is shown as a unit of ℓ /min, This value represents air volume in the industrial standard state for commercial use. The following table shows the two conditions,

Item Normal Air Standard Air
Unit Nℓ/ min ℓ/ min
Reference Temperature 0℃ 20℃
Absolute Pressure 760mmHg (1kg/㎠) 760mmHg (1kg/㎠)
Relative Humidity 0% 65%
Air Weight 1.29kg/㎥ 1.2kg/㎥

o Normal air: air at O°C, 1 atm and 0% relative humidity
o Normal air notation: Nm3/h,Nℓ /min, m3/h(ntp), ℓ /min(ntp),etc



Float area flowmeter generally used measures flow in a normal state, Since discharge air volume of each manufacturer indicates air volume in the standard state, conversion between the two air states is done according to the following equations

1. Qt = Qn x (273 + t) / 273 x (760 / pt)
2. Qn = Qt x {273 / (273 + t)} x (pt /760)

o Qt :actual discharge air volume( ℓ/min) in suction state
o Qn :actual discharge air volume( ℓ /min)in normal sate
o t :temperature in suctionstate( °c)
o pt :absolute pressure (mmHg) or inhaled gas


⌽ Ex)Conversion of air volume
What is converted air volume { ℓ /min) when air demand is 1OON ℓ/min, inhaled air temperature is 30'C and absolute pressure in the inhaled state is 750mmHg (local atmospheric pressure)?

Explanation :Qt = 100Nℓ /min x {(273 + 30 °C) / 273} x (760mmHg / 750mmHg) = 112.4 ℓ/min

Selection of compressor

When selecting an air compressor, a model with appropriate capacity and specification must be selected with consideration on installation area. noise and maintainability. Taking into account calculation error in the computation of capacity, correct on of frequency (load rate), pressure drop in air cleaner and pipe, leakage in pipe joints, and maintenance according to life span of compressor,it is desirable to select a compressor with capacity 1.5 ~ 2 times as large as design capacity.
1)Air pressure required by consumer
2) Necessary air volume (converted to air volume in the atmosphere: free air)
3) The frequency of air use (load rate %)
4) Cleanliness of air (moisture and oil content)

While computers on of air volume for selection of air compressor differs according to conditions of use, the standard described here was set forth based on the most frequently used nozzle and air cylinder.


Air discharge volume in the nozzle


As air discharge volume in the nozzle is maximized when the discharge rate reaches a speed of sound (this is referred to as the critical condition), it is computed by finding flow rate with maximum mass. When a specific heat ratio of air is k=1.4, discharge volume ( ℓ/min) a=rding to maximum mass flow rate is:

Mmax = 0.686 x ((,x d2/ 4 x P2 }} I ( √ (R x t2 ) ) x (60 x 1000) / 1.2

d :diameter of nozzle (converted to m)I PO: absolute pressure (converted to Pascal) /
R :gas constant of air (conver1ed to Nm/kg°K) / TO:absolute temperature of air (°C+273)



When the above equation is rearranged, discharge volume Q (m3/min) is:

Q = (273.15 / p ) x ( (πd2/4) x c x Pa) /√ T

d: diameter of the nozzle (converted to mm)/ C : flow constant (1if air)I p: specific weight of air (1.2k9/m3) I TO : absolute temperature of air (°C + 271.15) / Pa:absolute pressure of air (pressure on gauge + 1.0332 kg/cm2)

Using the above equation, air injection volume in the nozzle at 20°C can be expressed as a table as follows.

[Table of air Injection volume In nozzle]

NOZZLE
0m
GAUGE P (kgf/㎠) (m:t:ℓ / min)
1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0
0.2 0.7 1.3 1.5 1.9 2.2 2.6 2. 3.4 3.6 4.0
0.4 3.0 4.4 3.9 7.3 9.2 10.2 11.7 13.1 14.6 16.0
0.6 5.4 10.0 13.2 15.4 19.7 23.0 26.2 29.9 32.8 36.0
0.8 11.8 17.6 23.4 29.2 38.0 40.3 49.6 52.4 58.3 64.1
1.0 18.4 27.8 36.4 46.7 54.9 63.8 72.9 81.9 91.0 100.1
1.3 31.2 48.5 61.8 77.1 92.5 107.8 123.3 128.5 153.8 160.3
1.5 41.3 61.8 82.3 102.7 123.1 143.8 164.8 184.9 204.8 225.2
2.0 73.8 110.1 146.3 182.6 219.0 255.2 291.5 327.8 364.1 400.4
3.0 166.0 247.8 329.3 410.9 492.6 574.2 655.9 737.5 819.1 900.8
3.4 213.2 318.1 422.9 527.8 632.7 737.5 842.4 947.3 1052.1 1137.0
3.8 266.2 397.3 528.3 639.3 790.0 821.3 1052.3 1183.3 1314.3 1445.3
4.0 285.1 440.2 583.4 730.5 873.7 1020.8 1165.5 1310.5 1455.6 1601.4
4.7 407.4 607.2 808.2 1008.6 1208.8 1408.4 1609.7 1810.1 2010.2 2210.9
5.0 481.4 687.9 814.6 1141.4 1366.2 1598.0 1821.8 2046.6 2275.4 2603.7
6.0 683.9 990.5 1317.4 1643.7 1970.2 2296.8 2623.4 2650.0 3276.5 3603.1
7.0 903.7 1348.2 1792.7 2233.2 2684.7 3126.2 3570.7 4015.2 4459.7 4904.2
8.0 1180.3 1760.9 2341.6 2922.0 3502.6 4083.2 4653.2 5244.4 5835.0 6405.5
9.0 1493.8 2228.6 2963.4 3693.3 4433.0 5167.8 5908.5 6837.4 7372.2 8107.7

Air consumption If using an air cylinder

Since air cylinder discharges compressed air into the atmosphere when the backstroke is performed as force is applied on the piston, air corresponding to cylinder volume x compression ratio is consumed during one-way 1 stroke. Air volume for cylinder operation(1stroke) is:

Q ={(π d2 / 4) x S x P} / 1000 (ℓ /min)

d:inner diameter of cylinder (co) / S: cylinder stroke{on)/ P:absolute pressureolcompressed air (gauge pressure + 1.03323kg/cm2



Air volume olreciprocating type inwhich cylinder operation is repeated severaltimes every minute:

Q= {{ π d2 / 4) x S x (No. of operations per minute ) x P x 2} / 1000(ℓ /min)

Ex) What is air volume consumed when a cylinder with an inner diameter of 50mm and stroke of 200mm is operated 20 times per minute under air pressure of 61kg/cm2(g)? (single-acting cylinder: returning spring)

Q = [π x {(π 52 cm) / 4) x 20cm x 20 times/min x 7.03323 kg/Cm2(a)] ÷ 1000=55ℓ /min
*Incase of reciprocating cylinder : 55ℓ /min x 2 = 110ℓ /min

Air consumption by air tools

When computing air volume consumed by air tools that use compressed air as power source, determine the capacity of the compressor based on the table below.

Name of Air Tool Specification Air Port Air Consumption(㎥/min) Appropriate Air Pressure(kg/㎠G) Note
ANGLE GRINDER 4 inch WHEEL PT 1/4 0.6 6.0 - 6.5  
7 inch WHEEL PT 3/8 1.5 6.0 - 6.5  
Grinder 11-1/2 inch WHEEL PT 1/4 0.3 6.0 - 6.5  
SCREW DRIVER 12 - 4 PT 1/8 0.28 - 0.32 6.3 - 6.5  
15 - 6 PT 1/4 0.3 - 0.5 6.3 - 6.5  
IMPACT WRENCH 116 PT 1/4 0.5 6.3 - 6.5  
132 PT 1/2 0.9 6.3 - 6.5  
Air Drill 1¢10 PT 1/4 0.5 - 0.7 6.3 - 6.5  
라Ratchet Wrench 112 PT 1/4 0.5 6.3 - 6.5  
SANDER 1PAD SIZE 100 x 175 PT 1/4 0.6 6.3 - 6.5  
Polisher 1¢205 PT 1/4 0.8 6.3 - 6.5  

Note: Air tools of Daewoo Precision (88)

However, since air consumption is a value indicating continued operation of air tool under a no-load condition, air consumption can be changed according to conditions of use.Appropriate air volume must be computed by reviewing conditions of use (time during which itis actually used per minute).

Computation of Air Tank Capacity

Generalpiston type compressor requires an air tank to absorb pulsation (vibration of air) and storage of appropriate air, but screw air compressor does not require an air tank because it has almost no pulsation and discharges compressed air using internal compression.

However, when air volume used is temporarily and discontinuously higher (or load in the air quickly fluctuates) than discharge air volume per unit time of compressor, a separate air receiver needs to be installed to promote the efficient operation of compressor.
The equation for computing capacity of air receivers as follows.

V = ( P1 X (01 -02 ) X t } / ( P2 - P3 )

v :capacity of airreceiver (m')
Pl :inhaled air pressure of compressor (kg/cm2) / P2 :pressure inside air receiver(kg/cm2(a))/ P3 :demanded pressure(kg/cm2(a))/QI :demanded air volume(m2) / Q2:discharge air volume(m2) / t:time during which capacity is temporarily exceeded (MIN)

However, demanded air volume (Q1: m2) indicates air volume required in time during which capacity is temporarily exceeded. The discharge air volume of compressor indicates the value computed by dividing discharge air volume per minute by time tor temporary excess of capacity (when the time of temporary excess is less than 2m)
Ex) What should the capacity of air receiver be when discharge air volume of the compressor is 550ℓ /min and 1,500 ℓ of air with discharge pressure 8.5cm2 is to be discharged in 40 seconds? (Here, pressure inside air receiver is assumed to be the same as discharge pressure of compressor)

Using the equation on above:

V = ( Pl X (Q1 -Q2 ) X t } / ( P2 - P3 )

o Pl : 1.03323 kg/cm2 (a)
o Ql : 1.5 m2 / Q2 :0.55 m2X40sec/60sec=0.37 m2 / P2: :9.53323 kg/cm2(a) / P3 :6.03323kg/cm2 (a) / t :0.67 min(40sec)

V=(l.0332 x (1.5 -0.37 ) x 0.67 } / ( 9.5332 -6.0332 ) = 0.223 ( m2 ) = 223 (m2)= 230ℓ

Air receiver with capacity ol230 ℓ or above is installed.

Installation And Piping

Precautions for installation of the compressor

Selection of installation place and foundation for the compressor are greatly restricted by surrounding facilities, and the following matters require special attention. Perform installation work according to the installation guideline provided by the manufacturer of the compressor.

1.Installation place
  • o No rapid temperature change between seasons and day I night
    As explained earlier, the performance of compressoris extremely sensitive to temperature. When such on air temperature and heal dissipate on in the compressor, especially when attached with air-cooling intercooler, alter cooler and air dryer, the installation place must be maintained at or below 40°C. In places with low-temperature of 0°C below, the high viscosity of lubricant can cause overcurrent during initial start-up. In case of the air-cooling air dryer, condensate can freeze due to lowering evaporation temperature.
  • o To be installed outdoors to avoid exposure to snow, rain, strong wind, direct sunlight and contamination of inhaled air
  • o To prevent vibration and impact
  • o To secure space necessary for transport road,hatch and disassembly inspection
Most compressors require regular inspection. Bearings, valves and seals have prescribed life span and need to be replaced alter operation. Space must be secured with consideration on these during installation of the compressor.
2.Foundation
Foundation may be directly installed on the ground surface for small products, but in general, foundations installed in places that satisfy the following requirements by manufacturing concrete and steel frame.

  • o To have sufficient durability against the weight of machine and operation load
  • o To have a natural frequency of foundation avoid the range of resonance with excitation force of the machine
  • o To be careful and perform insulation prevent impact of vibration onbuilding
3.Selection of pipe
The necessity of compressed air is gradually increasing with rationalization on automated manufacturing facilities, and areas of usage are increasing as well. Each manufacturing facility requires a certain amount of compressed air, which is supplied and distributed from the engine room through the pipeline. Determination of diameter of compressed air supply pipe has become an important problem. The diameter of compressed air supply pipe must be selected with consideration on flow and pressure loss of compressed air in the pipe, and it is desirable to set pressure loss between air pressure storage unit and machine to be 0.1kg/cm2(g) or below. Diameter should be thoroughly reviewed to consider future expansion. Matters to be reviewed during the determination of pipe diameter are as follows.

  • o Air usage -air usage must be calculated as a momentary load condition. When maximum momentary load condition is not taken into account, lack of pneumatic pressure can lead to malfunctioning of the product.
  • o Length of pipe- length from air cleaner to final manufacturing facility is computed.
  • o Allowable pressure drop (pressure loss) - allowable pressure loss occurring is determined based on pipe length. (Pressure loss only in the pure pipe)
  • o Work pressure of final demand -work pressure at the end of pipe or final place of use is reviewed .
  • o Conditions of air cleaner use and quant ty of auxiliary materials -since pressure loss occurs as pressure supplied from compressor passes through the air cleaner, primary pipe pressure needs to take this into consideration. It must also include throttle loss from pipe fittings and valves applied to pipe.

The standard flow of compressed air in pipe differs according to the size of pipe, but desirable f flow is to be 12m/sec or below. A standard flow for pipe diameter of 60mm or below should be 1Om/sec or below. Also when selecting pipe diameter, refer to the following table after determining demanded pressure, flow (free air volume condition) and demanded length of pipe (demanded length pipe includes a pure length and correction length for various throttle elements).

Pipe Fittings Correction Length Valves Correction Length
90℃ Elbow d=3/8"~ 21/2"
d=3"~ 6"
d=7"~ 10"
30times d
40times
50times
Globe Valve d=1"~ 21/2"
d=3"~ 6"
d=7"~ 10"
45times d
60times
75times
90℃ Band
45℃ Elbow
T Fitting
+ Fitting
R/d = 3 ~ 5
d = 1"~ 3"
10~20times d
15~20times
40~80times
50times
Butterfly Valve 100% open
75% open
50% open
25% open
0times d
10times
100times
900times
90℃ Angle Valve 100~120times pipe diameter d

When using pipe diameter selection table, find the calculated pipe length (a) axis and demanded air volume (b) axis to cross a line to a (b) axis. Then, draw a line connecting the point of pressure 8,0kg/cm2on (e) axis and point of pressure drop 0.1kg/cm2 on (g) axis across (f) axis.When a line is drawn to connect the crossings of (c) and (f) axes, the point of this line that crosses (d) axis is the inner diameter of pipe.(⌽.88mm)
On one hand, as pressure drop in the pipe occurs according to pipe length and diameter, pipe length from the discharge port of the air compressor to the place of final demand and demanded air volume must be considered, as well as standard pressure loss of each device (AIR DRYER, AFTERCOOLER, FILTER, AIR RECEIVER) when pneumatic cleaning devices are used. The discharge pressure of compressor should be determined with sufficient consideration on secondary pressure loss from bending of pipe and installation of valves.
Pressure drop in the pipe can be expressed using the following equation.

ΔP=4 x fx { L x p x v2 } x (d x 2 x g } + Correctionlength

ΔP:pressure dropin kg/m2, f:friction coefficent , L:tength of pipe in m, p:density of fluid in kg/m2,v:mean velocity of fluid in m/sec m/sec,d :inner diameter of pipe in m,g:gravitational acceeration - 9.81 m/sec2




[Table for Selection of Pipe Diameter]
graph

[Value of Friction Coefficient f of Air Flowing in the Pipe]

Inner Diameter of Pipe f Inner Diameter of Pipe f Inner Diameter of Pipe f Inner Diameter of Pipe f
25.4 0.01242 228.6 0.00378 431.0 0.00327 635.0 0.00309
50.8 0.00756 254.0 0.00367 457.2 0.00325 660.4 0.00307
76.2 0.00594 279.4 0.00358 482.6 0.00321 685.8 0.00306
101.6 0.00513 304.8 0.00351 508.0 0.00319 711.2 0.00304
127.0 0.00464 330.2 0.00345 533.1 0.00316 736.6 000304
152.4 0.00432 355.6 0.00340 558.8 0.00314 762.0 0.00302
177.8 0.00409 381.0 0.00335 584.2 0.00312    
203.2 0.00392 406.4 0.00331 609.6 0.00310    

[Resistance Length of Pipe Fittings]

Fittings n Valves n
90℃ Elbow d=3/8"~ 21/2"
d=3"~ 6"
d=7"~ 10"
30
40
50
Globe Valve d=3/8"~ 21/2"
d=3"~ 6"
d=7"~ 10"
45
60
75
Standard90℃ Band
Elbow
45℃ Elbow
T Fitting
+-shaped Fitting
R/d = 3 ~ 5
d = 1"~ 3"
d = 1"~ 3"
10~20
15~20
15~20
40~80
50
Butterfly Valve Fully open
3/4open
1/2open
1/4open
0
10
100
900
90℃ Angle Valve   100~120

Operation And Lubrication Management

Trial Operation

Tiral operator in compressor is generaly performed by manufactor or installer according to the following seequence:

1. Before Operation

Operation Sequence Precaution
Check connection of power and grounding, and make sure that voltage is within the regulated value. Prevent malfunctioning by connecting power grounding to the ground surface.
Supply lubricant until it reaches upper limit of oil level gauge. When lubricant becomes insufficient after starting the device as it flows into oil cooler, stop the compressor and check that pressure reaches 0kgf/㎠(G) before resupplying oil.
Check tension on V-belt (in case of motor V-belt type). Check suspension of power.
Supply cooling water to cooler (in case of water-cooling type).  
Stop (power) lamp is turned on when power is supplied. In case of reverse phase, reverse phase relay is operated to turn “reverse power phase” lamp on. The compressor cannot be operated.

2.Operation

Operation Sequence Precaution
Completely open the discharge valve and press start button. Pressure suddenly rises when the machine is started with the valve closed.
During no-load operation, slowly close the discharge valve at discharge pressure of 4kg/㎠(G). If discharge pressure is higher or lower than 4kg/㎠(g) when the discharge valve is completely open, adjust holding pressure valve.
  Check vibration, noise and oil leak.

3.During Operation

Operation Sequence Precaution
Allow discharge pressure to reach discharge pressure in the specification.
Check the meter values under full load operation.
When no-load operation starts, pressure inside oil separation tank is discharged to reduce discharge pressure (inside unit). No-load operation is carried out while maintaining discharge pressure of 1~2.5kg/㎠(g).
Pull the safety valve ring to check its operation.
(Open the inspection door on the front of package or inspection hole on the side)
Setting pressure of safety valve is as follows.
For 7.0kg/㎠(g) specification: 8.5kg/㎠(g)
For 8.5kg/㎠(g) specification: 9.5kg/㎠(g)
For 9.5kg/㎠(g) specification: 9.9kg/㎠(g)

4.Stop

Operation Sequence Precaution
Press stop button. As soon as the motor stops, auto air discharge valve discharges compressed air from oil separation tank to the atmosphere, which generates a sound for about 30 seconds.
Make sure that pressure gauge indicates 0kg/cm2 (g) after the machine comes to a stop.  


Routine Operation

1) Operation Seequence

1️⃣ Before operation
Open the condensate drain valve at the bottom of front side of the cabinet to drain condensate out of oil separation tank. After draining condensate, inspect oil level gauge to make sure that lubricant is within the gauge limit. Check whether power lamp is turned on. Supply cooling water to the cooler. (For water-cooling type)
2️⃣ Operation
Completely open the discharge valve and press the start button to start the compressor. Slowly close the discharge valve to increase pressure.
3️⃣ During operation
Inspect meter values under full load state. Check for abnormalities in meter lamps. (Record meter values onDaily InspectionRecord) Pull the safety valve ring to confirm proper operation(checked at every 500 hours).
4️⃣ Stop
Press the stop button. Make sure that pressure gauge indicates Okgf/cm2 (g) after stopping. Block cooling water and discharge cooling water inside the cooler. (For water-cooling type)

2. Precautions for Winter Operation
When operating the compressor under low atmospheric temperature (surrounding temperature), the compressor may not rotate smoothly or automatically stop as soon as it starts. (Overcurrent display: EOCR) This is caused by increased viscosity from a low temperature of lubricant. In this case, increase the temperature of lubricant by repeating the operation of the compressor 2 ~3 times.

Lubricant management
Functions of oil include lubrication, cooling, sealing, rust prevention and stress dispersion. When an inappropriate lubricant is used, bearing fixation, damaging of the valve from the generation of hard carbon, and leakage from each sealing part (between rotor and casing, piston, piston ring and cylinder part) can result in reduced performance and reduced life span. On one hand in refrigerant compressor, the inappropriate lubricant can prevent ideal separation from the refrigerant. reduced stability . and clogging of capillary tube or expansion valve. Functions are as follows.
1️⃣ Lubrication: forms an oil film on the friction surface to reduce friction between metals
2️⃣ Cooling: cools compression heat during air compression to prevent overheating
3️⃣ Sealing: prevents leaking of pressure
4️⃣ Rust prevent on: prevents oxidization by preventing contact with oxygen, water and corrosive gas using oil film formed on the metal surface
5️⃣ Stress dispersion: load on the friction surface is evenly dispersed to reduce impact and wear

Type of lubrication is divided into complete lubrication and boundary lubrication depending on the lubrication state. Complete lubrication (fluid lubrication)is the most ideal case in which two adjacent objects are completely separated by oil. Boundary lubrication(thin film lubrication) is the case in which two moving objects show partial friction as they contact each other through thin oil film. Most objects are operated in boundary lubrication state. Another type of lubrication is called extreme pressure lubrication. The friction surface is sometimes destroyed by excessive load or high temperature of the friction surface, and extreme pressure lubrication forms an extreme pressure film using an additive to prevent this destruction phenomenon.

In general, lubricants exhibit optimal performance at 50-60°C, and oil film becomes thin or is decomposed at or above 65C. (Actual decomposition temperature differs for each lubricant, but it is mostly around 120C. Since this refers to the local temperature of the lubricated part, general upper Jim of tank temperature should be set to 105C.)

Management of lubricant is an item of inspection before starting of the compressor. 1/4 position of oil level gauge is considered as the lower limit. When a new compressor is to be used, the lubricant must be completely drained and replaced after 500~600 hours of use. When the lubricant is to be continuously used, lubricant recommended in the compressor manual must be used for 2,0003.000 hours. If it is difficult to purchase the recommended lubricant, the same type of base oil with same viscosity must be selected (be careful as there are many different types of commercial base oil including alkylbenzene, synthetic lubricant, paraffin, naphthene, silicon, olefin, ester, polyester, and poly alpha glycol).

Dehumidification

Dehumidification comprehensively refers to the work of removing moisture in the air and various gases and converting air or gas to dry state. General types of dehumidification include cooling dehumidification and compressed dehumidification, and chemical dehumidification.

Cooling dehumidification


Cooling dehumidification is a method in which air is cooled below dew point to condense moisture in the air into water and reheated alter removing condensed moisture to obtain air with low humidity. Refrigerant, cooling water and brain of the refrigerator are used as cooling sources of air, and it has the following characteristics. [Characteristics of cooling dehumidification]
1) When the surface temperature of cooling coil drops below O'C, condensed moisture freezes on the surface of the coil and reduces cooling efficiency, making it difficult to obtain constant humidity.
2) Cooling efficiency is reduced when relative humidity is high, such as during the rainy season.
3) Limitation of this dehumidification method in general use is dew point temperature of O°C or above.
4) Size of the facility is increased with power consumption, resulting in increased cost of operation.


Compressed Dehumidification

Compressed dehumidification is a method in which air is compressed to reduce its volume and cooled. Moisture in the air is condensed into moisture. Air is reheated alter removing moisture to obtain air with low humidity. it has the following characteristics. [Characteristics of compressed dehumidification]
1) This method is applied for dehumidification with small wind and low humidity.
2) This method requires high power cost for compression,
3) This method is applied when high pressure dehumidified air is needed tor instrumentation, etc.
Compressed dehumidification method uses cooling cycle facilities using compressed air to cool air down to pressure dew point of O°C.

Chemical Dehumidification

Chemicaldehumidification is divided into absorbent batch type and absorbent liquid type, and each has the following characteristics.
Absorbent batch type uses two or more towers by filling solid adsorbent (silica gel, active alumina, zeolite, etc.)into the cylindrical tower. When there are two lowers, one top is used to absorb dehumidified air. Regeneration is performed by switching to the other tower alter certain time. Dehumidification is carried out by capillary tube acting on the surface of absorbent.
[Characteristics of chemical dehumidification - absorption bath type]
1) Dehumidified air with low dew point can be obtained depending on the solid absorbent selected.
2) As dehumidification and regeneration are switched at a prescribed timing, dehumidified air cannot be obtained continuously.
3) Regular replacement of absorbent is required.
4) The device shows a large pressure loss.
5) Regeneration temperature is high.

Absorbent liquid type uses lithium chloride solution as absorbent and consists of dehumidification part and regeneration part. When absorption solution sprayed inside dehumidification part contacts air to be dehumidified, moisture in the air is absorbed by solution due to the difference in partial pressure between the absorbent solution and water vapour in the air. Condensation heat and absorption heal occurring from absorption are removed by the cooling coil. The solution that absorbed moisture is returned to the regeneration part using liquid circulation pump contact air heated by heat coil. Here, moisture in absorbent solution is evaporated into the atmosphere. The concentrated solution is sent back to the dehumidification part alter regenerate on for circulation.

[Characteristics of chemical dehumidification - absorbent liquid type]
1) As dehumidification and regenerate on are continuously carried out, dehumidified air can be constantly obtained.
2) Carry-over (the phenomenon in which solution is discharged with wet air being discharged from regeneration partly atmosphere) of the solution must be prevented.
3) As deposition of lithium chloride can occur depending on concentration and temperature of the solution, the concentration of solution needs to be managed
4) Regular supplementation and replacement of solution are required.

Compressor Test Standerds

Test methods for air compressor and refrigerant compressor shall follow methods regulated in KS. Testing method and conditions for each compressor regulated in KS are in the following table.
[ Test standards for compressor in KS ]

Name of Standard Standard No. Test Conditions
Testing and inspection methods for volumetric compressor KSB 6351 Repetitive and rotary compressor with pressure ratio of 2 or higher
suction temperature 20°C, suction pressure 101.3kPa, relative humidity 65%
Testing and inspection methods for turbo type blower and compressor KSB 6350 Turbo type ventilator and compressor with pressure ratio of 1 or higher
suction temperature, suction pressure and relative humidity same as above

Guid For Purchasing Genuine Parts

Air compressor is extremely important and sensitive equipment used as essential power source in factories. You must use genuine parts to extend the life span of equipment and receive various services from our company.



Genuine parts of COAIRE are the same parts used in new products of our company, and the quality of genuine parts is guaranteed by strict inspection process. Genuine parts may and may not have our company's logo, so please consult with an official agency for confirmation. You can purchase parts through a network of 36 agencies around the nation.
Attention!!
Please be care full as failures caused by use of parts other than our genuine parts are exceptions to the free maintenance service during the warranty period,

Service Guiidance

[Service guidance]

  • You can check details on service on User Manual.
    Some problems that our customers regard as failure can be resolved by simple adjustment or change in setting. Please refer to the page on cause and measure on failure and FAQ to search for a solution or read user Manual.
  • You can easily find the solution to your problem through cause and measure on failure menu and FAQ menu on our web site.
  • FAQ

    [Service Request]

    • Please contact our agency or store from which you purchased the product. If you cannot find the answer to your question on User Manual and our web site, you can contact our professional counsellors. When your product is determined to be in need of maintenance service after confirming a few symptoms. you can visit our company or agency to receive maintenance service by a technician of COAIR.


    Free Service

    • Failure or defect which occurs in normal state during quality assurance period of the product
    • New products are warranted for one year since the trial operation (warranty period may differ for each product).


    Service Handling and Period

    • To apply for service, please send "product name, model name, manufacturing number, place of purchase, details of the failure, etc," through customer inquiry (web site) or phone, fax and e-mail of AS Team at our headquarters, agency or store.
    • Headquarters: TEL(031)4962060, 62, 64 I FAX (031)319-4910
    • For accurate and prompt handling of the service request, please make use of our online service.
    • All service requests are handled immediately or at least on the day of request depending on the severity of the failure, distance and conditions of agency or store. Under special circumstances, it may take up to 1 3 business days to handle a request.


    • Quality Warrenty Period

      • Quality warranty period refers to the period for which a manufacturer or seller guarantees free repair of any quality, performance or functional defect naturally occurring under normal condition of use based upon Quality Assurance.
      • Quality assurance period is one year from the dale of purchase (it may differ for each product and according to special contracts).
      • Exceptionslo quality assurance period: when used product is purchased, consumable parts, failure caused by mistake of the consumer, when the product is repaired or remodelled by the customer, failure caused by naturaldisasters
      • Quality assurance period is computed based on the date of purchase and confirmed by date of purchase and Quality Assurance form. When the date of purchase is not specified on Quality Assurance form, Quality Assurance form is not received, Quality Assurance form is lost, or it is otherwise difficult to confirm the dale of purchase, the date of purchase is calculated by considering manufacturing number of the product, manufacturing dale or 6 months (based on expiration period) from the date of import clearance.

History of Scroll Compressor (Air End)

The concept of scroll compressor was first proposed by Leon Creux of France in 1905, but it was not commercialized at the time due to lack of processing technology and measure on the gas leak.
In Korea, Kyungwon Machinery started assembly production in 1993 and successfully developed a commercial oil-free scroll air compressor for the second time. a nation and third time as a maker in October 2004, It has become an oil-free scroll air compressor manufacturer with high added value,

1979
  • It was processed and developed by HITACHI of Japan, and commercialization was done as an air conditioner for cars by Sanden of Japan in 1981.
1983
  • After successful commercialization by HITACHI of Japan as a home package air conditioner, COPELAND of the United States commercialized the product to vitalize scroll compressor market.
1987
  • ◦ Japan began development of oil-free air compressor, but actual commercialization was delayed.
    ◦ Delay in commercialization was caused by lack of technology to effective, resolve axial gas leak in turning scroll, wear loss between scroll wraps, and accurate processing of scroll shape.
1991
  • ◦ ANEST-IWATA and HITACHI of Japan succeeded in the commercialization of oil-free scroll air compressor. Higher level cam processing technology and Sealing technology were applied compared to air conditioning scroll refrigerant compressor developed in the 1980s.
    ◦ Major air compressor manufacturers in the United States and Europe recently attempted to develop oil-free scroll air compressor, but they failed to commercialize it due to patent technology of ANEST-WATA and HITACHI.
1991
  • ◦ Kyungwon was the second as a nation and third as a maker to develop and commercialize oil-free scroll air compressor. It has become an oil-free scroll air compressor manufacturer with high added value.
    ◦ Oil free scroll air compressor exhibited high efficiency, low noise, small size a. lightweight. It was commercialized in the range of 1.5kW ~ 30kW and is widely used in diverse fields.
    ◦ In the future, efforts for development of large capacity technology are expected.
2010
  • ◦ Obtain. ISO 8573-1: 2010 Class 0 certification
    As a certification on contaminants and purity level of compressed air, the 2010 revision reflected dust on contaminants to define Class 0 as the cleanest air.
2010
  • ◦ Obtained CE certificate
    Attachment of CE mark on a product means that the product or its manufacturer satisfies essential requirements in the relevant regulations or directives of the EC Board of Directors. In other words, conformity lest was performed on the product by the manufacturer, importer or a third party (certification authority) for distribution of the product in the market without limits. Accordingly, products related to the health of consumers, safely and environment are obligated. to attach CE mark.Marked products can be distributed freely without inspection or testing in EU and EFTA regions.
    That is, it is a unified product certification mark acknowledged by EU and EFTA nations (members of the European Union and European Free Trade Agreement).

Operating principle of scroll air compressor

Fixed scroll and turning scroll in the operating part are combined by turning the phase of both warps by 180°. Turning scroll turns along the rotation of the crank axis as shown in the figure, Suction compression and discharge are performed simultaneously, and four enclosed spaces (compression rooms) with the shape of the crescent moon are formed

Enclosed volume of space in shape of crescent moon is gradually compressed. compressed air moves to the centre and is discharged out through outlet at the centre of the fixed scroll

Structure of scroll air compressor

Characteristics of scroll air compressor

High efficiency during compression process through prevention of gas leak

◦ Since pressure difference between two compression pockets of fixed and turning scrolls is smaller than overall pressure difference calculated by subtracting suction pressure from discharge pressure. compared gas is never recompressed. This results in smaller power loss compared to other compressors.
◦ In the case of reciprocating compare and rolling piston compressor, the recompression process is repeated to reduce the efficiency of the compressor



Suction compression and discharge are continuously performed.

◦ It involves low vibration and noise as compression is continuously performed with a slower speed of pressure increase compared to other compressors.
◦ Change in torque of scroll compressor is about 1/10 of torque change shown by other the compressors, exhibiting a significant reduction in vibration and noise1.
◦ Rotation and compression torque of the crank axis (figure on the right)

Suction valve and discharge valve are unnecessary

◦ Since suction room inhaling gas and discharge room performing discharge are not directly connected, suction and discharge valves are unnecessary. As a result, there are no problems related to fluid loss. noise and damaging. The product obtained high efficiency, low noise and high reliability.

Advantages of oil-free air compressor

◦ It supplies clean air.
◦ It is appropriate for the purpose as described below as compressed air does not include oil mist.
   -food manufacturing machinery, beverage manufacturing machinery, medical device. a dental device, analyzer chemical industry, chemical industry, particulate return, painting. printing machinery. paper processing, water quality improvement
◦ Oil management such as oiling unnecessary
   - Oil management such as routine oiling is unnecessary, and there is no cost for oil replacement and filling.
◦ Excellent environmental protection (no oil mist)
  -Since oil mist is not discharged, the surrounding environment is not polluted.
◦ Oil mist filter does not need to be installed and managed.
  - Costs for installation and element replacement of oil mist removal filter are unnecessary.
◦ There is no cost for treatment of waste oil.
  - No industrial waste and wastewater is generated.
  - There is no cost that occurs to industrial waste management business.
◦ here is no cost for management of drain.
   - Oil injection drain contains oil in water and involves a cost for wastewater treatment. but oil-free type does not have such cost.
◦ Pressure loss from contamination on the interior of the pipe is low.
  - When used for a long time. contaminants inside the pipe can be increased to cause pressure loss and failure of devices such as auto trap, increasing the cost burden compared to the initial electric charge.
◦ Simple air circuit compared to forced oil injection circuit
  - Low failure rate