The difference between oil-free screw air compressor and oil-injection screw air compressor

The main differences between oil-free screw air compressors and oil-injection screw air compressors are reflected in the following aspects:

1. Working principle and lubrication method

• Oil-free screw air compressors:

  • Working principle: Use two inter-meshing screws to compress air. The screw is made of high-strength alloy material and is precision-processed to form a closed compression chamber when rotated. Air enters the cavity through the inlet port, compresses and gradually increases as the screw rotates, and is finally discharged in the form of high-pressure gas.
  • Luction method: Oil-free lubrication technology is used, and it does not come into contact with oil during compression. The bearings, synchronous gears and other parts that need lubrication are isolated from the compression chamber through an effective shaft seal and are lubricated with special lubricating oil. Some high-end models use water lubrication technology to achieve complete oil-free.

• Food injection screw air compressor:

  • Working principle: Air compression is also performed through two inter-meshing screws. During the compression process, lubricating oil is sprayed into the compression chamber and mixed with air to act as cooling, lubricating and sealing.
  • Luction method: Use oil lubrication technology, and the lubricating oil comes into direct contact with the air during compression.

2. Compressed air quality

• Oil-free screw air compressor:

  • Air quality: Since there is no contact with oil during the compression process, the compressed air quality is high, and there is no oil stains, and it meets the industry standards with high requirements for air quality.
  • Application field: Widely used in industries such as food, medicine, and electronics that have strict requirements on air quality.

• Food injection screw air compressor:

  • Air quality: The compressed air contains a certain amount of oil stains and needs to be post-treated through oil and gas separators and other equipment to remove oil.
  • Application field: Applicable to general industrial fields and occasions where air quality requirements are not particularly strict.

3. System structure and maintenance costs

• Oil-free screw air compressor:

  • System structure: The system structure is simple and does not require the use of oil and gas separators and other post-treatment equipment.
  • Maintenance cost: Due to the oil-free design, oil consumption and replacement are reduced, and maintenance costs are reduced. At the same time, it also reduces the hassle of cleaning and disposing of waste oil.

• Food injection screw air compressor:

  • System structure: The system structure is relatively complex and requires the use of oil and gas separators, coolers, dryers and other post-treatment equipment.
  • Maintenance cost: It requires regular replacement of parts such as engine oil and filters, and the maintenance cost is relatively high.

4. Performance parameters

• Oil-free screw air compressor:

  • Single-stage pressure ratio: generally lower, usually less than 3. Two-stage compression may be required for power compressors.
  • Exhaust pressure: usually less than 2.5MPa.

• Food injection screw air compressor:

  • Single-stage pressure ratio: higher, can reach more than 13.
  • Exhaust pressure: The range is wide, usually between 0.8 and 4.5MPa.

5. Other features

• Oil-free screw air compressor:

  • Operational efficiency: Due to the oil-free design, internal leakage is reduced and energy use efficiency is improved.
  • Environmental protection and energy conservation: Comply with environmental protection requirements, energy conservation and emission reduction.

• Food injection screw air compressor:

  • Operation efficiency: Although it also has a high energy efficiency ratio, it may be slightly inferior in energy use efficiency compared to oil-free screw air compressors.
  • Environmental protection and energy conservation: Effective post-treatment measures are required to reduce environmental pollution.

To sum up, there are significant differences in the working principle, compressed air quality, system structure and maintenance costs, performance parameters, etc. of oil-free screw air compressors and oil-injected screw air compressors. When choosing, trade-offs and choices should be made based on actual needs and budget.