The residual oil content of compressed air refers to the concentration of small particles of lubricating oil remaining in compressed air. It is an important indicator to measure the cleanliness of compressed air, and directly affects the service life of downstream equipment and product quality. The following detailed analysis from a technical point of view:
1. generation mechanism
- oil-lubricated air compressor
- the lubricating oil is atomized by high temperature and high pressure during the compression process, and some oil molecules enter the exhaust pipe network through the oil separation core.
- When the efficiency of the oil core decreases (such as blockage and breakage), the residual oil content increases exponentially.
- Oil-free air compressor
- use self-lubricating materials or labyrinth seals, but may still produce trace residual oil (usually <0.01 mg/m & sup3;) due to volatilization of bearing grease.
2. detection standard
| Application areas | ISO 8573-1 level | requirements for residual oil content |
|---|
| general industry | Class 3 | ≤5 mg/m³ |
| spraying/Medicine | Class 2 | ≤1 mg/m³ |
| electronics/Semiconductors | Class 1 | ≤0.01 mg/m³ |
3. influencing factors
- air compressor type
- piston machine> Screw machine> Scroll machine (oil mist control difficulty is different due to structural differences)
- filter Configuration
- the three-stage filtration system (pre-filtration + precision activated carbon) reduces the residual oil content by 90% compared with single-stage filtration
- environmental parameters
- for every 10 ℃ increase in temperature, the efficiency of the oil core will decrease by 5%-8%.
- Increased residual amount due to enhanced adsorption of oil molecules at relative humidity> 70%
4. detection method
- online monitoring
- capacitance method sensor real-time measurement of oil molecular concentration (accuracy ± 0.5 mg/m & sup3;)
- infrared spectrometer: Can distinguish between oil mist and particulate pollutants (response time <1 second)
- laboratory Analysis
- weighing method: Collect 1m & sup3; weigh oil droplets after compressed air is condensed (ISO 12500 standard)
- gas chromatography quantitative analysis of oil components (can detect C10-C40 hydrocarbons)
5. control strategy
- proactive prevention
- install the differential pressure sensor to monitor the state of the oil core (the differential pressure> 0.7bar needs to be replaced)
- use of synthetic lubricants (oxidation stability 5 times higher than mineral oil)
- end treatment
- add super oil mist filter (0.01μm accuracy)
- configuration of catalytic oxidation units (converting oil molecules to CO₂ and H₂ O)
- intelligent operation and maintenance
- deployment of air compressor Internet of Things system, combined with big data to predict the trend of residual oil content
for key applications such as food packaging and medical devices, it is recommended to conduct ISO 8573-1 full-item testing every quarter, and establish a preventive replacement mechanism for oil separation cores and activated carbon filters.
