Oil content grade of compressed air at air compressor outlet

The oil content level of compressed air at the outlet of an air compressor is an important indicator to measure the quality of compressed air. It is directly related to the applicability and safety of compressed air in various industrial applications. The following is a detailed explanation of the oil content level of compressed air at the outlet of the air compressor:

1. International standard (ISO 8573-1)

The ISO 8573-1 standard formulated by the International Organization for Standardization (ISO) clearly defines the oil content in compressed air. This standard divides oil content into multiple levels, including:

• Class 0: The oil content in the air is required to be less than 0.01mg/m³. This level is considered to be oil-free and suitable for applications with extremely high air quality requirements, such as pharmaceutical, food, electronics and other industries.
• Class 1: Oil content is required to be less than 0.1mg/m³. This level is considered to be a low-oil state and is suitable for industrial production occasions with high requirements for air quality.
• Class 2: Oil content is required to be less than 1mg/m³. This level is considered a regular state and is suitable for general industrial production situations.

2. National standards (GB/T 13277.1-2023)

In China, the national standard GB/T 13277.1-2023 “Compressed Air Part 1: Purification Levels of Pollutants” also stipulates the oil content in compressed air. This standard stipulates the purification levels of particles, water and oil in compressed air, as well as methods for describing active microorganisms and gaseous pollutants. Among them, the total oil content levels are divided into different levels, which is crucial to ensuring that compressed air meets the cleanliness requirements of specific applications such as the food and pharmaceutical industries.

3. Oil content ranges of different types of air compressors

1. Oil injection screw air compressor：

   • The oil content of its exhaust gas is generally no more than 3ppm (i.e. 3mg/m³).
   • When the oil content of compressed air exceeds this standard, it is usually called high fuel consumption, commonly known as running oil or flying oil. This is one of the more common fault phenomena among users.

2. Micro-oil air compressor：

   • The oil content in the outlet air shall not exceed 0.01mg/m³, which is suitable for occasions with high requirements for air quality.

3. oil free compressor：

   • It is generally believed that its oil content is about 0.01ppm.
   • High-quality oil-free air compressors can have an oil content of less than 5ppm or even lower. This type of air compressor is widely used in the food, pharmaceutical and electronics industries to meet high requirements for compressed air quality.

4. Industry norms

• In China, national standards stipulate that the liquid oil content in compressed air shall not exceed 5mg/m³, and the oil vapor content shall not exceed 0.5 mg/m³.
• For the pharmaceutical and food processing industries, the oil content in compressed air must be strictly controlled. China Pharmacopeia and GMP (Good Manufacturing Practice) require the oil content of compressed air to be ≤0.1mg/m³ or even lower to ensure product quality and safety.

V. Test Method

In order to accurately evaluate the oil content in compressed air, the partial flow (B2) test method and the full flow (B1) test method are specified under the ISO 8573 standard. Both test methods comply with ISO 8573 standards, but there are essential differences in practical applications:

• Partial Flow (B2) Test Method: Mainly focusing on the detection of the central airflow, only mist oil can be identified, but liquid oil flowing along the pipe wall cannot be detected.
• Full Flow (B1) Test Method: Comprehensive analysis of the entire airflow can detect mist oil and liquid oil at the same time, providing a more accurate assessment of oil content.

6. The importance of post-processing equipment

Even if oil-free air compressors are used, post-treatment equipment (such as filters, dryers, etc.) still plays a crucial role in ensuring the quality of compressed air because the ambient air may contain pollutants such as oil vapor. Through the treatment of post-treatment equipment, the oil content and other pollutants in the compressed air can be further reduced to meet the high requirements of specific applications.