What are the lubrication requirements for oil-free compressors?

Oil-free compressors achieve oil-free lubrication through special design or materials, and their lubrication requirements mainly focus on material selection, lubrication method, sealing and cooling, maintenance management four core expansion, as follows:

1. material selection: wide application of self-lubricating materials

oil-free compressors are self-lubricating through the use of special materials to reduce dependence on traditional lubricants:

• piston ring and cylinder wall: Use polytetrafluoroethylene (PTFE), carbon fiber or composite materials containing filling components, which can produce self-lubricating effect and reduce friction and wear when in contact with each other. For example, in a miniature reciprocating piston compressor, the piston ring and the aluminum alloy cylindrical surface are self-lubricated to achieve efficient operation.
• rolling bearing: In the oil-free centrifugal compressor, the use of hybrid ceramic bearings (such as steel ring and silicon nitride ceramic ball combination), the use of refrigerant fluid elastic dynamic lubrication mechanism to form a very thin lubricating film, to achieve oil-free lubrication.

2. lubrication mode: application of water lubrication and special medium

oil-free compressors replace traditional oil lubrication with innovative lubrication:

• water lubrication technology: Single-screw or twin-screw oil-free air compressors use pure water or softened water as lubricants to achieve the four functions of lubrication, cooling, sealing and noise reduction. The water lubrication system needs to use special stainless steel to make the body parts to resist the corrosion problem that may be caused by long-term contact with water.
• pure refrigerant lubrication: In oil-free centrifugal compressors, refrigerants (such as HCFC-123 and R1233zd) are used as lubricants to form a lubricating film through a fluid elastic dynamic lubrication mechanism. This technique requires precise control of refrigerant viscosity, pressure-viscosity characteristics and contact body roughness to ensure lubrication.

3. sealing and cooling: preventing contamination and ensuring performance

oil-free compressors need to ensure that the compressed air is pure and oil-free through sealing and cooling design:

• seal Design: Piston rings or sealing packings made of labyrinth seal structure or anti-wear materials such as graphite and polytetrafluoroethylene to prevent gas leakage and external lubricating oil mixing. For example, piston compressors that compress high-purity gases are oil-free lubricated by labyrinth seals.
• Cooling system: Oil-free compressors need to control the operating temperature through an efficient cooling system to prevent damage to components due to frictional heat generation. The water-lubricated compressor uses the cooling effect of water to achieve ideal isothermal compression and improve compression efficiency.

4. maintenance management: regular inspection and water quality control

the maintenance of oil-free compressors needs to focus on material wear and lubricating medium status:

• material wear monitoring: Regularly check the wear of self-lubricating materials and replace worn parts in time. For example, the scale and corrosion problems of water-lubricated compressors need to be solved by regular cleaning and water treatment.
• Lubricating medium management for the water lubrication system, the water quality (such as pH value, hardness) should be regularly tested to prevent corrosion and scaling; for the pure refrigerant lubrication system, the refrigerant pressure and viscosity changes should be monitored to ensure the lubrication effect.