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Considerations for your rotary screw compressor solution

Choosing the right rotary screw compressor is THE crucial choice for companies that use compressed air. An informed choice will have a positive impact on energy costs, efficiency, and long-term reliability. With multiple options available, such as fixed-speed or variable-speed drives, oil-injected or oil-free systems, it is therefore essential to understand the key factors. This guide will help you make an informed and sustainable decision.

Considerations for your rotary screw compressor solution reference image

Size and pressure: Striking the right balance

Firstly, you need to start by assessing the air flow (CFM, l/s or m³/h) and pressure (psi or bar) you require. Under-sizing will compromise performance, while over-sizing will waste energy. Moreover, remember that electricity accounts for approximately 80% of the operating costs of an air compressor, so proper sizing and pressure ensure stable and efficient operation.

Here is more information on air flow and pressure:

  • Flow rate: measured in cubic feet per minute (cfm), litres per second (l/s) or cubic metres per hour (m³/h). It will vary according to your workload and how long you need a constant air flow.
  • Pressure: measured in pounds per square inch (psi) or bars. Heavy-duty tasks require higher pressure levels.

Key benefit: rotary screw compressors offer higher flow rates and higher pressure than piston compressors, making them ideal for industrial applications.

Drive types: Fixed-speed vs. Variable-speed drive (VSD)

Rotary screw compressors use two screw rotors. They are available in belt-driven, gear-driven and direct-driven models.

Fixed speed compressors

  • Operate continuously at a set speed.
  • Gear drives are more efficient than belt drives and require less maintenance.

Variable speed compressors (VSD)

  • Adjust pressure according to demand, reducing energy consumption by up to 35%.
  • Direct drive VSD models with IVR technology and iPM motors offer maximum efficiency.

Tip: It is recommended to opt for a fixed speed compressor for constant demand and choose a VSD compressor if your air requirements fluctuate.

Oil-free vs. Oil-injected systems

  • Oil-injected compressors: Require lubrication for cooling, ideal for heavy-duty industrial use.
  • Oil-free compressors: Best for applications needing pristine air quality (e.g., medical or food industries).

FAQs

Measure peak airflow and pressure requirements, then factor in your duty cycle. A properly sized compressor avoids inefficiency and premature wear.

Yes, especially for fluctuating air demand. For constant high demand, a fixed-speed model may be more cost-effective.

Oil-free is ideal for sensitive applications. On the other hand, oil-injected technology offers durability and efficiency for most industrial uses.

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