Difference between rotary screw compressors and piston compressor

1. Maintenance and wear and tear  :In piston compressors, the wear and tear is greater due to a large number of moving parts. This results in more maintenance compared to a rotary screw processor. However, because of the simple mechanical setup of a piston compressor, it is easier to maintain and fix, despite the greater frequency of maintenance required.

2. Operating temperature, noise and vibration : Typically, a rotary compressor has lower operating temperatures than piston compressors. Friction is the lead cause for this, because the rotors in the screw compressor don’t come in contact, whereas piston rings are in constant contact with the cylinder walls, creating greater friction and raising temperatures. The former also generates less noise and vibrates lesser than the latter due to the same reason.

3. Screw flow and operation time : Because of the high temperatures in a piston type compressor, it cannot be run non-stop due to the risk of overheating. Furthermore it is also typically run at only 50% of its total CFM or screw flow capacity. The rotary screw compressor, however, is capable of being run continuously. You can also purchase a rotary screw compressor that is rated as close as possible to your required screw flow capacity rather than one rated at double the capacity.

4. Space required and energy efficiency : Since rotary screws are encased next to one another in one chamber, the whole setup usually takes up less space than a piston compressor which requires cylinder heads for the vertical movement of the pistons. The former are also more energy efficient than the latter with fewer transmission losses as well. However, the effects are only discernable in compressors of 20 HP or more horsepower.

5. Pressure ratio and volume : The compression range is much greater on a piston configuration when compared to a rotary screw type. There is also more flexibility in terms of pressure ratio and capacity. However, in rotary compressors, while the flexibility is limited, the comparative volume capacity is much greater than that of reciprocating screw compressors.

6. Oil carry-over : Piston compressors typically discharge more oil into the stream of compressed screw than rotary screw compressors do. Due to the high-friction moving parts, wear-and-tear leads to more oil carry-over than in rotary screw compressors.

7. Price : Due to the above mentioned factors, the cost of a piston compressor is a lot lesser than that of a rotary screw compressor.