Choosing the Best Hydraulic Oil Filtration Equipment for Your System

Hydraulic Oil Filtration Equipment: Types and Selection Guide

Maintaining hydraulic oil cleanliness is essential for equipment reliability and system longevity. Various filtration systems are used depending on contamination type, operation mode, and maintenance needs. They are generally divided into online filtration equipment and offline purification equipment.

1. Online Filtration Equipment (Continuous Operation)

Online filtration runs while the hydraulic system operates, maintaining stable oil cleanliness and protecting precision components.

(1) System-Built-in Filters

These are installed directly in the pressure, return, or circulation lines.

Types: Suction filters, high-pressure filters, return filters, circulation filters

Features: Control daily oil cleanliness; compact and reliable as part of the system.

(2) Portable Filtration and Refilling Cart

Also known as a portable oil filter cart, it’s the most versatile maintenance equipment.

Principle: A pump draws oil from the tank, filters it, and returns it through an independent circulation loop.

Uses:

Clean new oil during refilling

Periodic purification during operation or shutdown

Advantages: Mobile, multifunctional, high precision (3–5 μm or better)

(3) Independent Circulating Filtration System

Used in large systems requiring ultra-clean oil, such as machine tools, injection molding machines, and power plants.

Features: 24-hour continuous filtration, strong particle and moisture control, independent of the main system.

2. Offline Purification Equipment (For Severe Contamination)

When oil contains water, air, or sludge, specialized purification is required.

(1) Vacuum Oil Filter

Removes dissolved water, free water, and gas, while also filtering particles.

Principle: Heated oil is vacuum-treated and atomized, evaporating moisture and gases. The dried oil passes through a fine filter before returning to the tank.

Best For: Water-contaminated, milky, or foamy oil.

(2) Centrifugal Oil Filter

Separates substances by density using centrifugal force.

Principle: A rotating drum expels water and heavy solids to the wall.

Best For: Large water content or heavy particles.

Limitation: Less effective for fine particles and dissolved water.

(3) Coalescing Separation Oil Filter

Designed for efficient water removal.

Principle: Coalescing elements merge tiny water droplets into larger ones, which then settle and separate from oil under gravity.

Best For: Free and emulsified water removal.

How to ｓｅｌｅｃｔ the Right Filtration Equipment?

1. Type of Contamination

Solid particles → High-precision or upgraded system filters

Water → Vacuum or coalescing purifier

Air → Vacuum oil filter

Metal debris → Magnetic filter

2. Required Filtration Accuracy

Standard systems: 10–15 μm

Precision/servo systems: 3–5 μm or finer

Accuracy depends on component sensitivity and is measured by absolute rating and β value.

3. Oil Viscosity and Flow Rate

Ensure flow rate matches tank capacity and oil viscosity. High-viscosity oil may require stronger pumps or preheating.

4. Application Scenario

Routine maintenance or shared use: Portable filter cart

Continuous purification: Built-in circulation system

Severe contamination or oil recovery: Vacuum or coalescing purifier

Summary and Recommendations

For most factory applications, a portable, high-precision oil filtration cart offers the best performance and cost-effectiveness. It supports new oil filling, regular maintenance, and troubleshooting, ensuring long-term oil cleanliness.

If the system frequently encounters water ingress, add a vacuum oil purifier or coalescing separator to maintain hydraulic reliability and extend component life.