Hydraulic System Oil Pollution Level Standards and Pollution Control
1. Pollution level
Pollution degree refers to the content of solid particulate pollutants in a unit volume of oil, that is, the concentration of solid particulate pollutants
contained in the oil. The degree of contamination of the working medium in hydraulic systems can be quantitatively represented by the degree of contamination.
2. Pollution level standards for hydraulic system fluids
①. ISO4406 Pollution Level Standard
This standard is the "Hydraulic Transmission Oil Solid Particle Pollution Level Code Method", which uses two digits to represent the pollution level of the oil. The preceding digit represents the particle number level with a size greater than 5 μ m in 1ml of oil, and the following digit represents
the particle number level with a size greater than 15 μ m in 1ml of oil. The two digits are separated by a diagonal line.
②. GB/T14039 Pollution Level Standard
GB/T14039-2002 is the "Hydraulic Transmission - Fluid - Solid Particle Pollution Level Code Method" formulated in China, which is equivalent to
the ISO4406 standard. As a cleanliness standard for hydraulic fluids.
③. NAS1638 Pollution Level Standard
This standard is based on particle concentration and is divided into 14 pollution levels according to the maximum allowable number of particles in a given range of 5 particle sizes in 100ml of oil. The cleanest level is level 00, and the highest pollution level is level 12.
3. Methods for measuring pollution levels
① Visual inspection method;
② Colorimetric method;
③ Quality Law;
④ Pollution index method (sedimentation index method);
⑤ Particle counting method.
4. Pollution control of hydraulic systems
The pollution of hydraulic systems is twofold: firstly, the deterioration of the working medium itself leads to changes in viscosity and acidity;
secondly, external pollutants mix into the working medium.
5. Ways of hydraulic system contamination
① Originally lurking;
② External intrusion;
③ Internally generated.
6. Types of hydraulic system contamination
① Pollution of solid particles
Solid particulate pollutants mainly include chips, casting sand, welding slag, dust, burrs, etc.
② Gas pollution
Gas pollutants mainly include air mixed into the system from the atmosphere and gases separated from oil.
③ Pollution of liquids
Liquid pollutants mainly include water, cleaning fluid (oil), or other types of hydraulic working media.
④ Oxidation of working oil
The harmful chemicals produced by the oxidation of working oil can accelerate the deterioration of the oil.
7. Control of hydraulic system pollution
⑴ Pollution control of new oil
Through inspection, it was found that the pollution level of unfiltered and purified new oil often exceeds the specified requirements. Therefore,
effective management measures must be taken to control the pollution of new oil. After purchasing hydraulic oil, its cleanliness and main physical and chemical properties should be tested. New oil that does not meet the cleanliness requirements must be filtered and purified before use.
⑵ Pollution control of hydraulic systems
① Reduce residual pollutants in the system
Before assembling the hydraulic system, it is necessary to carefully clean the components and pipelines. Before putting it into use, the system
must be cyclically flushed to thoroughly remove any remaining impurities in the system.
② Prevent pollutants from entering the system
The fuel tank should be properly sealed and equipped with an air filter to prevent dirt from entering the system through the tank. When refueling,
it must be filtered according to regulations, and cleaning procedures must be strictly followed during maintenance.
③ Remove pollutants from the system
Properly select, use, and maintain filters, regularly inspect, clean, or replace filter elements based on usage, and regularly clean fuel tanks.
④ Control emerging pollutants
Strictly follow the operating oil usage and maintenance regulations, and pay special attention to controlling the temperature rise of the system.