Are particulate matter in hydraulic oil harmful?

Particulate contaminants in hydraulic oil are the leading cause of hydraulic system failures, and their harm is extremely significant. Statistics show that over 70% of hydraulic system failures are related to oil contamination.

How harmful are particulate matter particles in hydraulic oil?

The harm of particulate matter primarily manifests in the damage it causes to precision components in hydraulic systems. The severity depends on the material, hardness, size, and shape of the particles.

1. Accelerated Wear and Surface Scratching (The Most Common Harm)

Principle: Driven by high-pressure hydraulic fluid, particles scrape at high speed between moving parts of components (such as the distributor plate and cylinder of a pump, or the valve core and valve sleeve), abrading metal surfaces like sandpaper.

Consequences: This leads to increased internal leakage in components, decreased efficiency (e.g., insufficient pump output flow), and the generation of more new wear particles, creating a vicious cycle. Ultimately, this results in component failure.

2. Causes Component Jamming and Malfunction

Principle: Larger particles or fibrous impurities may become stuck in the radial clearance of a spool valve or block the throttling groove of the valve core.

Consequences:

1. Impact on Valve Core: This obstructs valve core movement, causing slow, non-functional, or irregular operation of the hydraulic cylinder or motor, severely impacting the accuracy and reliability of equipment control.

2. Clogging of Throttling Orifices and Filters:

Principle: Small particles accumulate and clog tiny throttling orifices, damping orifices on the valve body, and filters within the system.

Consequences:

This leads to unstable system pressure and delayed response. Filter clogging increases pressure differential, potentially causing bypass valves to open and allowing unfiltered oil to enter the system directly, causing wider contamination and damage.

3. Accelerated Oil Performance Deterioration:

Principle: Metal wear particles (especially copper and iron) catalyze oil oxidation, accelerating oil deterioration. Simultaneously, the heat generated by wear also promotes oil oxidation.

Consequences:

This results in changes in oil viscosity, increased acid value, the formation of more sludge and deposits, and a shortened oil lifespan.

The Relationship Between Hazard Severity and Particle Size

1-5 micrometers (µm) particles: These are the most numerous and the main cause of abrasive wear. Their small size allows them to easily enter the tiny gaps between moving parts, causing slow but continuous wear.

15-40 micrometers (µm) particles: These easily cause component jamming and orifice blockage.

Particles larger than 40 micrometers (µm): These usually cause severe valve jamming or instantaneous severe scratches.

Of particular note: The most dangerous particle sizes are very close to the gaps between moving parts (typically 1-5µm), as they easily get stuck in these gaps, causing severe abrasive wear.

Particulate matter in hydraulic oil is by no means "harmless impurities"; it is a "hidden killer" lurking in the hydraulic system.

To ensure reliable equipment operation and extend the life of components and oil, strict contamination control measures must be taken:

1. Regularly test the oil to monitor particulate contamination levels (e.g., according to ISO 4406 standard). 2. Use high-precision oil purifiers to filter the hydraulic fluid online or offline, controlling its cleanliness within the target level.

3. Strengthen maintenance management, such as filtering new oil before adding oil, maintaining a clean maintenance environment, and replacing filter elements promptly.

Proactively controlling particulate contamination can significantly reduce the failure rate of hydraulic systems, making it a highly profitable investment.