E-mail seo@sino-purification.com
Time：2025-09-22 14:43:11 Reading volume：
Choosing the filtration accuracy of an oil purifier is a highly specialized and critical issue. Choosing the right filter can significantly improve oil quality and equipment lifespan. Choosing the wrong filter accuracy can waste resources and even damage the equipment.
Selecting a filter accuracy isn't simply a matter of "higher is better." It requires a comprehensive balance of multiple factors, including oil type, equipment requirements, contamination conditions, and filtration objectives.
The key to selecting a filter accuracy lies in "matching"—matching the sensitive clearances of the equipment you want to protect and the size range of contaminants in the oil. The goal is to efficiently remove harmful particles while avoiding over-filtration (which can filter out essential additives and lead to frequent filter clogging and increased costs).
This is the primary basis for selection. Different hydraulic or lubrication system components (such as servo valves, piston pumps, and bearings) have their most sensitive internal clearances, and the filter accuracy must be able to intercept particles larger than these clearances effectively.
High-precision, critical equipment, such as the hydraulic servo systems of CNC machine tools, aviation hydraulic systems, and high-speed, high-precision bearings. These systems have very small clearances (typically 1-5μm) and require extremely high oil cleanliness levels (often ISO 14/12 or higher). Therefore, high-precision filtration (1-3μm, or even 0.5-1μm) is necessary.
Medium- and high-pressure hydraulic systems, such as those of construction machinery and injection molding machines (pressures typically >14MPa). These primarily protect components such as pumps and valves, typically requiring a filtration accuracy of 3-5μm, with a target cleanliness level of approximately ISO 17/15 or 16/14.
General low-pressure hydraulic and lubrication systems: such as general machine tools, low-load gearboxes, and circulating lubrication systems. Filters can be 10-20μm, with a target cleanliness level of ISO 19/17 or 18/16. Coarse filtration, also known as pre-filtration, serves as system oil filtration or pre-protective filtration, primarily for removing large particles and water. A precision of 20-50μm is available.
In short, the more sophisticated the equipment, the higher the pressure, and the faster the speed, the higher the required filtration precision.
New Oil Filtration: Even new oil often does not meet the cleanliness requirements of precision equipment. It is recommended to use an oil purifier with a filtration precision one level higher than the system's requirements for "purification and refueling."
Used Oil Treatment:
Highly Watery or Contaminated Oil: If the oil is severely emulsified or contains a large amount of sludge, avoid using high-precision filter elements directly. First, use a centrifugal, coalescing, or vacuum dehydration device to remove most of the water and oversized particles before performing high-precision filtration. Otherwise, the high-precision filter element will instantly clog.
Oil of Different Viscosity: High-viscosity oils (such as gear oil) experience greater resistance when passing through high-precision filter elements, requiring greater pumping capacity or a slightly lower precision requirement. A heating function can also be used to reduce viscosity.
It is important to understand the ISO 4406 cleanliness level standard. It uses three numbers (e.g., 18/16/13) to represent the number of particles >4μm, >6μm, and >14μm per milliliter of oil, respectively.
You should first consult the equipment manufacturer's manual to find their oil cleanliness requirements (ISO levels), and then ｓｅｌｅｃｔ a filter fineness that achieves that level based on this goal.
Example: To achieve ISO levels 16/14/11, an oil purifier with a filtration fineness of 3μm (β₃ ≥ 200) is typically required.
The filtration fineness (e.g., 3μm) is only a nominal value; the beta ratio better reflects the filter element's true performance.
Definition: βₓ = Number of particles larger than xμm upstream / Number of particles larger than xμm downstream
Meaning: β₃=200 means that for every 200 particles larger than 3μm, only one particle will pass downstream. Therefore, filtration efficiency = (β-1)/β 100% = (200-1)/200 100% = 99.5%.
Critical Selection: Always choose a filter element with a high β value (≥200). A filter element with a nominal 3μm filter but a very low β value may actually perform worse than a 5μm filter element with a high β value.
