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The difference between oil-free screw compressor and oil injector

2026-04-15Views:

Oil-free screw compressor and oil-injected screw compressor are two common types of air compressors, which are significantly different in terms of working principle, performance characteristics, application scenarios, advantages and disadvantages. Here are the differences between them:

1. working principle

  1. oil-free screw compressor:
    • compression process: Two precision-machined spiral rotors (a male rotor and a female rotor) rotate in opposite directions in the compression chamber, gradually compressing the air sandwiched between the screw and the housing.
    • Lubrication method: oil-free lubrication, Relying on the strict tolerance of the rotor and advanced sealing technology to prevent air leakage.
  2. oil-injected screw compressor:
    • compression process: The screw is used to compress the air, and lubricating oil is injected during the compression process to cool and lubricate the compression cavity.
    • Lubrication method: oil injection lubrication lubricating oil plays multiple roles in the compression process, such as cooling, lubrication and sealing.

2. performance characteristics

Performance oil-free screw compressor oil-injected screw compressor
compressed air quality no oil pollution, high cleanliness contains trace oil, need to match the oil separator
noise level low (oil-free lubrication reduces friction noise) lower (lubricating oil noise reduction)
heat dissipation performance dependent cooling system lubricating oil takes away heat, good heat dissipation performance
maintenance complexity complex maintenance (seals need to be replaced regularly, etc.) easy maintenance (lubricating oil takes into account cleaning function)
efficiency high energy efficiency high energy efficiency (near isothermal compression)

3. Application Scenarios

  1. oil-free screw compressor:
    • high cleanliness demand industry: Such as food, beverage, medical, electronic, pharmaceutical, etc., to avoid oil pollution affecting product quality.
    • Special process such as laboratory gas supply, precision instrument manufacturing, etc.
  2. oil-injected screw compressor:
    • general Industrial Field: Such as factories, mines, construction, petrochemicals, tire manufacturing, electricity, etc., to provide compressed air for pneumatic equipment.
    • Refrigeration industry: Provide compressed refrigerant for cold storage, refrigerated trucks, etc.

4. advantages and disadvantages

Type advantages disadvantages
oil-free screw compressor compressed air is clean and oil-free, suitable for high cleanliness demand scenarios; oil-free lubrication reduces the risk of environmental pollution. The initial cost is high; maintenance is complex and seals need to be replaced regularly; heat dissipation relies on an external cooling system.
oil-injected screw compressor high energy efficiency, easy maintenance, low cost; low noise, suitable for general industrial scenarios. Compressed air contains a small amount of oil and is not suitable for high cleanliness demand scenarios.

5. Summary

  • selection basis:
    • if required high cleanliness compressed air(e. g. food, medical, electronic industries), choosing oil-free screw compressor.
    • If required high-efficiency, low-cost compressed air(e. g. general industrial scenario), select oil-injected screw compressor.

The two compressors have their own advantages and disadvantages. Users should choose the most suitable type according to actual needs (such as air quality requirements, budget, and maintenance capabilities).

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