How to select screw and centrifugal air compressors

The selection of screw and centrifugal air compressors needs to be combined with specific working conditions. The following analysis is carried out from three dimensions: principle characteristics, application scenarios, and key parameters of selection:

1. Comparison of core characteristics

2. Analysis of applicable scenarios

Priority screw air compressor

• Gas consumption fluctuates greatly: For example, intermittent use of gas in food packaging and pharmaceutical production lines.
• Low voltage scene: Exhaust pressure ≤1.2MPa (single stage compression can be satisfied).
• Space restrictions are strict: Small laboratory or equipment-intensive workshop.
• Sensitive to oil content: Electronic component manufacturing and painting process require oil-free models.

Priority is given to centrifugal air compressors

• Large flow continuous operation: For example, the blast furnace air supply in a steel plant is ≥80m³/min.
• high-pressure demand: Multi-stage compression is required (centrifugal three-stage compression can reach 1.6MPa).
• extreme environments: High temperature, high altitude areas (centrifugal type is more adaptable to intake conditions).
• Long-term full load: For example, gas supply to the reactor of a chemical plant (annual operation>6000 hours).

3. Calculation of key parameters for selection

1. Displacement calculation

   • formula：

Qactual​=Puse​−ΔPloss​Qtheory​×Prated​​

• parameter description：
  • Qtheory​: Equipment nameplate exhaust volume (10%-20% allowance needs to be considered).
  • Prated​: Rated pressure of air compressor.
  • Puse​: The actual working pressure of the system.
  • ΔPloss​: Pipeline pressure loss (empirical value: 0.1MPa per 100m of pipeline).

2. power matching
   • screw: Select according to specific power (kW/m³/min), and the first-level energy efficiency is ≤5.5.
   • centrifugal: The motor efficiency curve needs to be checked to ensure that the working point is in the efficient range.
3. pressure matching
   • screw: The rated pressure must be ≥ the maximum pressure of the system +0.2MPa.
   • centrifugal: The surge line needs to be avoided. It is recommended that the working flow be ≥ 80% of the rated flow.

4. Selection Decision Process

1. clear needs: Count the maximum/minimum air consumption, pressure fluctuation range, and annual operating time.
2. Primary selection model: Filter candidate models based on the gas-pressure matrix.
3. technical verification：
   • Screw type: Check specific power, noise value, oil content.
   • Centrifugal type: Verify surge line and efficiency island diagram.
4. cost analysis: Compare full life cycle costs (including energy consumption, maintenance, and spare parts).
5. On-site adaptation: Evaluate installation space, ventilation conditions, and power facilities.

example: A steel plant needs to supply gas to the blast furnace, with a flow rate of 120m³/min, a pressure of 0.8MPa, and an annual operation of 7200 hours.

• Recommended selection: Three-stage compression centrifugal air compressor (efficiency 78%, energy saving 12% compared with screw type).
• configuration recommendations: Supporting water cooling system, reserving 15% flow redundancy.

Through multi-dimensional evaluation, it can ensure that the air compressor selection is highly matched with the working conditions and reduce long-term operating costs.