Oil content of compressed air from ordinary air compressor

The compressed air produced by ordinary air compressors will contain a certain amount of lubricating oil, usually between 5 mg and 50 mg per cubic meter, depending on the type of equipment, operating conditions and maintenance level. The following from a professional point of view for you to resolve:

1. Sources and influencing factors of oil content

• lubrication method: Ordinary air compressors mostly use oil lubrication technology. During the compression process, lubricating oil will form an oil film to reduce friction, and part of the oil may enter the compressed air in the form of aerosols.
• Device Type: Piston compressor due to reciprocating motion characteristics, the oil content is usually higher than that of screw compressor; micro oil screw machine oil content is significantly higher than that of oil injection screw machine.
• Operating parameters: The higher the exhaust pressure, the greater the oil evaporation; For every 10 ℃ increase in ambient temperature, the oil carrying capacity may increase by 20%-30%.
• Maintenance condition if the filter element of the oil separator is not replaced in time (usually every 2000 hours), the oil removal efficiency may drop from 99% to less than 80%.

2. Oil content performance of typical application scenarios

• machining: When used in pneumatic tools, the oil content is 30-50 mg/m & sup3; acceptable, oil mist can play a certain lubricating effect.
• Painting operation: The oil content shall be controlled below 5 mg/m & sup3, otherwise the paint film will have defects such as shrinkage cavity and pinhole.
• Food Packaging: It must reach 0.01 mg/m & sup3; Below, it is necessary to install an activated carbon filter or a catalytic oxidation device for deep degreasing.

3. Detection and control of oil content

• detection method: The laser particle counter can be used to monitor the concentration of oil droplets above 0.1μm in real time, in line with ISO 8573-5 standard.
• means of control:
  • primary filtration: centrifugal oil-water separator can remove 80% of liquid oil droplets
  • precision filtration: the coalescing filter element filter can reduce the oil content to 0.1 mg/m & sup3;
  • deep purification: Adsorption dryer with carbon fiber filter element can achieve ultra-low oil content of 0.003 mg/m & sup3;

4. Economic trade-offs

• direct cost: The purchase cost of oil-free air compressors is 30%-50% higher than that of ordinary models, but it can save subsequent filtration costs.
• hidden cost: If ordinary compressors are used in precision manufacturing, the rework rate due to oil pollution may increase by 5%-10%, far exceeding the equipment price difference.
• Energy Efficiency Comparison oil-free models do not require lubrication systems, energy efficiency is usually 8%-12% higher than ordinary models, and long-term operating costs are lower.

Selection recommendations:

• for scenarios with no special requirements for the oil content of compressed air (such as general power gas), ordinary air compressors can be used, but the oil content needs to be checked regularly.
• When used in precision manufacturing, food and medicine and other scenes, it is recommended to directly use oil-free air compressor, or configure multi-stage filtration system to ensure the quality of gas.
• When the oil content is ≤ 0.01 mg/m & sup3;, catalytic oxidation technology or membrane separation technology is required for ultimate purification.