In this article, we will see the difference between Oil Free Screw Compressor and Oil Lubricated Screw Compressor.
Oil Free Vs Oil Lubricated Screw Compressor
| S.no | Description | Oil-Free Screw Compressor | Oil Lubricated Screw Compressor |
| 1 |
Process Gas Compatibility |
The process gas is completely free of oil, there is no contamination and therefore any gas can be handled. | In oil-free screw compressors, due to the positive displacement compression, even polymer gas or dirty gas can be compressed |
| 2 |
Rotor speed |
The rotor speed is higher | Rotor speed is lower because the oil turbulence in the rotor chamber will be high |
| 3 |
Discharge temperature |
Discharge temperature is typically high because of compression heat. To avoid excessive heat deformation, cooling is required. | Discharge temperature is low because of lubrication |
| 4 |
Pressure Ratio Limitation |
Due to rotor clearance and discharge temperature limitation, high-pressure ratio cannot the achieved in Oil-free screw compressor
The maximum pressure ratio obtained in this compressor is 3:1. |
Due to the user for oil injection, the rotor clearance is the minimum and discharge temperature can increase in the compressor.
The maximum pressure ratio obtained in this compressor is 50:1. |
| 5 |
Timing Gear |
Due to rotor clearance, timing gear is used for proper meshing of male and female rotors. | In this type of compressor the male and female rotor in close clearance. Hence timing gears are not utilized. |
| 6 |
Maintenance Cost |
High maintenance cost. Because the rotors are not lubricated. Hence rotor has life very short life when compared with oil-lubricated screw compressor. | Low maintenance cost. It is because most parts are properly lubricated. Also, the life of rotor long enough so that a spare requirement is not needed. |
| 7 |
Compressor Casing Cooling Jacket |
During gas compression more heat generated, it reduce compressor efficiency and rotor life. To overcome this problem casing cooling jacket is envisaged for this compressor | Casing cooling jackets are not required. Because the oil inside the compressor will act as a cooling medium |
| 8 |
Sliding Valve arrangement |
The sliding valve arrangement is not used in this type of compressor | The sliding valve arrangement is used for capacity control of this compressor |
| 9 |
Compressor Skid Size |
The skid size is larger when compared with oil-lubricated screw compressor for the same capacity and compression ratio. | The skid size is very small, when compare with oil-free screw compressor for the same capacity and compression ratio. This is due to the high compression ratio will be achieved in a single stage of this compressor. |
| 10 |
Intercooler and Aftercoolers |
Both Intercooler and After-coolers are required for this type of screw compressor | Intercooler and After Coolers are not required. Because oil will cool the compressed gas. |
To read about Reciprocating Compressor, click Here.