To assess whether an air compressor's output meets quality standards, the key lies in evaluating three critical parameters: oil content, dust content, and moisture content. This assessment must also consider specific requirements of end-use scenarios (e.g., hygiene standards in food and pharmaceutical industries). The methods include on-site rapid evaluation and professional instrument testing, as detailed below:
## 一. On-site Quick Assessment Method (For Routine Inspections)
This method requires no specialized equipment and can quickly assess whether there are obvious air quality issues, making it suitable for routine workshop inspections.
1. **Water Content Assessment**
- **Filter paper test method**: Take a clean qualitative filter paper and align it with the air compressor's exhaust port (or terminal air usage point), then exhaust for 30 seconds to 1 minute.
-Standard compliance status: The filter paper surface shows no visible water stains or moisture marks, with only slight airflow imprints remaining.
-Non-compliant condition: If filter paper shows water stains, dampness, wrinkling, or dripping, it indicates excessive moisture content in the compressed air.
- **Indirect dew point detection**: Monitor the operation of the cold dryer/absorber. If the equipment functions normally but the air receiver bottom frequently accumulates water, or if rust appears on the pipeline inner walls with condensation leakage, this indicates the compressed air dew point exceeds ambient temperature and fails to meet moisture content standards.
2. **Oil Content Assessment**
- **White Paper Wiping Method**: Use a clean white paper towel or white paper to wipe the inner wall of the terminal's air inlet, or direct it at the exhaust port for 10 seconds.
-Standard compliance: The white paper surface is free of oil stains, yellowing marks, and greasy texture.
-Non-compliant condition: Oil stains or greasy appearance on the white paper indicate excessive oil content.
- **Odor detection method**: If the compressed air emitted carries a distinct lubricant odor, it likely indicates incomplete oil-gas separation and excessive oil content.
3. **Dust Content Assessment**
- **Filter interception method**: Install a fine-mesh filter (e.g., 1μm precision filter) at the terminal gas outlet and observe after continuous ventilation for 1 hour.
-Compliance status: The filter surface shows no visible dust or impurities.
-Non-compliant condition: The filter screen surface is heavily coated with dust and black particles, indicating excessive dust content.
- **Equipment observation method**: If terminal pneumatic components (e.g., cylinders, spray guns) frequently exhibit valve core sticking or nozzle clogging, and disassembly reveals significant internal dust accumulation, this indicates substandard dust content in the compressed air.
## 二. Special Compliance Requirements for Different Industries
The 'compliance' of compressed air quality is relative and must align with specific industry gas usage standards.
- **Food and Pharmaceutical Industries**: Must comply with **ISO 8573-1 Class 1** standards, requiring oil content ≤0.01mg/m³, dust content ≤0.1μm, dew point ≤-20℃, and must obtain food-grade certification (e.g., FDA certification).
- **Spray and precision electronics industries**: Oil content must be controlled to ≤0.1mg/m³ to prevent coating detachment and component short circuits caused by oil contamination.
- **General mechanical processing industry**: Oil content ≤5mg/m³ and dust content ≤5μm are sufficient to meet basic requirements.
