How many meshes are used for hydraulic oil filtration?

Hello! This is a very professional and important question. Simply answering with a "mesh number" isn't accurate, as the filtration requirements for hydraulic systems primarily focus on filtration accuracy (measured in microns, μm), not mesh number.

Mesh number and microns are different units that describe the size of filter pores. There's a corresponding relationship between them, but in the hydraulic field, professionals consistently use microns (μm) as the standard.

Core Answer: Consider microns first, then convert to mesh number.

The filtration accuracy requirements for hydraulic oil depend on the cleanliness requirements of the hydraulic system itself. Generally speaking:

1. Suction Filter (Low-Pressure Side):

Filtration Accuracy: 100-250 μm

Approximate Mesh Size: 60-150 Mesh

Purpose: Protects the hydraulic pump by filtering larger contaminants. Because it's installed at the pump's suction port, where pressure is low, a coarser filter is used to ensure unobstructed flow and prevent cavitation.

2. Pressure Filter (High-Pressure Side):

Filter Accuracy: 10-25 μm

Approximate Mesh Size: Since mesh sizes are no longer commonly used in fine filtration, they are generally above 500 mesh; however, the micron value should be of particular concern.

Purpose: Protects delicate valve components in the system (such as servo valves and proportional valves). This is the most important filter, capturing the most dangerous fine particles.

3. Return Oil Filter:

Filter Accuracy: 10-40 μm

Approximate Mesh Size: Similarly, approximately 400-800 mesh (reference value, prioritize μm).

Purpose: Captures wear particles generated during system circulation and external contaminants before the oil returns to the tank.

4. Circulation Filter (Offline Filter):

Filter Accuracy: 1-10 μm or even higher

For filters outside the effective mesh size conversion range, high-precision filter media is typically used.

Purpose: Continuously filters the oil in the tank independently of the main system, effectively controlling the oil cleanliness level.

Why shouldn't we just focus on "mesh size"?

Different standards: "Mem" itself is an imperial unit, referring to the number of holes per inch. However, it cannot accurately describe a filter's depth of filtration, uniformity, flow characteristics, and other aspects. Two 100-mesh filters can have significantly different filtration accuracy due to differences in weave and wire diameter.

Industry practice: All standards in the hydraulic and lubrication industries (such as ISO 4406 cleanliness standards) and equipment manufacturers' specifications are defined using microns (μm). When communicating with others, saying "I need a 10-micron filter" is much more professional and accurate than saying "I need an 800-mesh filter."

Micron (μm) to Mesh Size Conversion Reference Table

To help you understand, here is a very rough conversion relationship for reference only:

| Filtration Fineness (μm) | Approximate Mesh Size (Mesh) |                         Main Application Scenarios                              |

| :------------------------- | :---------------------------------- | :------------------------------------------------------------------ |

| 250 μm                          | 60 Mesh                                      | Coarse Filtration, Suction Filter                                                 |

| 180 μm                          | 80 Mesh                                      | Coarse Filtration, Suction Filter                                                 |

| 150 μm                          | 100 Mesh                                    | Coarse Filtration                                                                        |

| 106 μm                          | 150 Mesh                                    | Coarse Filtration                                                                        |

| 75 μm                            | 200 Mesh                                    | General Pressure Filtration, Return Oil Filtration Pre-Filtration |

| 45 μm                            | 325 Mesh                                    | Return Oil Filtration                                                                   |

| 25 μm                            | ~500 Mesh                                  | Common Pressure/Return Oil Filtration Fineness                     |

| 10 μm                            | ~1250 mesh                                | High-precision pressure/return oil filtration                             |

| 5 μm                              | ~2500 mesh                                | Fine filtration for demanding systems                                      |

| 3 μm                              | ~5000 mesh                                | Ultra-fine filtration, such as servo systems                               |

Please note: The above table is an estimate based on standard wire diameters. The actual product accuracy (μm) must be based on the manufacturer's stated absolute accuracy.

Summary: Forget "mesh size," remember "micron (μm)." For most industrial hydraulic systems, using 10 μm or 20 μm filters for both the pressure and return lines is a common starting point. However, the most reliable approach is always to follow the equipment manufacturer's recommendations.