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Piston Compressors versus Rotary Screw Compressors; the two most popular compressor technologies available today.

Piston vs Rotary Screw Compressors

Duty Cycle – the percentage of time a compressor may operate without the risk of overheating and causing excessive wear.

• Piston: Limited
• Rotary: 100%

Noise Levels – rotary screw compressors are quieter and produce less vibration.

• Piston: 80+ dB(A) Louder than an alarm clock
• Rotary: 65 – 75 dB(A) Similar to a toilet flush

Oil carry-over – when oil that is used to lubricate your air compressor makes it into the air lines.

• Piston: 10 ppm+
• Rotary: 1 – 7 ppm

Flow – the ability of an air compressor to continuously perform a task. Usually measured in cfm.

• Piston: 3 – 3.5 cfm/hp
• Rotary: 4 – 4.5 cfm/hp

Moisture – the hotter the air, the more moisture it holds. Approximately every 20°F increase in temperature doubles air’s ability to hold moisture.

• Piston:

Internal Operating Temperature: 300 – 400°F

Discharge Temperature: 100°F+ above ambient temperature

• Rotary:

Internal Operating Temperature: 170 – 200°F

Discharge Temperature: 15 – 25°F above ambient temperature

Cost 

• Piston: lower initial cost
• Rotary: lower operating cost

Usage

• Piston

Intermittent use

Lower cfm

Higher pressure

Smaller shops and manual applications

• Rotary

Continuous use

Higher cfm

High-volume and robotic manufacturing and conveyor systems

Applications requiring very clean air

related post

Compressor Basics: Rotary Screw Compressors