Hydraulic Oil Filtration System – Process, Types & Benefits

Martin Wilson
Jun 26
3 min read

Hydraulic systems are the backbone of modern machinery across industries like manufacturing, construction, aerospace, and agriculture. However, their performance and longevity heavily rely on hydraulic filtration—the process of removing contaminants from hydraulic oil. Without proper filtration, even the most advanced systems can suffer from wear, failure, or total breakdown.

In this blog, we’ll explore the hydraulic oil filtration system, how the hydraulic filtration process works, the types of filters used, and where they should be placed for optimal performance.

What is Hydraulic Filtration?

Hydraulic filtration is the process of removing dirt, metal particles, and other contaminants from hydraulic fluid. These impurities, if left unchecked, can damage components like pumps, valves, and actuators, leading to system failure.

The filtration system keeps hydraulic oil clean, ensures efficient energy transmission, and extends the life of the entire system.

How Does a Hydraulic Filter Work?

A hydraulic filter works by trapping contaminants in a porous medium as the fluid passes through. This medium can be made from synthetic fiber, paper, or metal mesh. Filters can remove particles of varying sizes, measured in microns (1 micron = 1/1000 of a millimeter).

Depending on the system's configuration, filters can be installed in different locations such as:

Suction line filters – Before the pump
Pressure line filters – After the pump
Return line filters – Before fluid returns to the reservoir

Hydraulic Oil Filtration System: Key Components

Filter Element: The heart of the system that removes particles.
Filter Housing: Protects the filter element.
Indicators/Sensors: Show when the filter is clogged.
Bypass Valve: Prevents flow restriction if the filter is blocked.

The efficiency of a hydraulic filtration system is often defined by its beta ratio (filtration efficiency), which measures how effectively it removes particles of a certain size.

Hydraulic Filtration Process

The process typically includes:

Suction Filtration: Fluid is drawn from the reservoir through a coarse filter.
Pressure Filtration: High-pressure filters clean the oil after the pump to protect downstream components.
Return Filtration: Filters capture particles before fluid returns to the reservoir.

This multi-stage filtration ensures that contaminants are constantly removed during the fluid’s circulation.

What Are the Three Types of Hydraulic Filters?

Suction Filters – Located before the pump to catch large contaminants.
Pressure Filters – Installed after the pump to protect sensitive components.
Return Line Filters – Positioned before the reservoir to catch particles coming from actuators or valves.

Some systems may also include off-line filters (kidney loop systems) for continuous filtration without interrupting the main flow.

Do Hydraulic Filters Go Before or After the Pump?

Hydraulic filters can be placed both before and after the pump depending on the type and purpose:

Before the Pump: Suction filters prevent large particles from damaging the pump.
After the Pump: Pressure filters protect valves and actuators from smaller contaminants.

The correct placement depends on the system’s design and sensitivity of the components.

Conclusion

A reliable hydraulic oil filtration system is essential for smooth operation, reduced downtime, and extended equipment life. By understanding the hydraulic filtration process, selecting the right filter type, and maintaining the system regularly, you can significantly improve system reliability.

For premium filtration solutions, visit Harvard Filtration—a trusted name in hydraulic filtration systems and filter elements.

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