Hydraulic filter

Hydraulic filter are the mediums in oil Hydraulic system used to arrest impurities and purify the oil to improve the operational efficiency of hydraulic components. 

A hydraulic filter is a component used in hydraulic systems to remove contaminants from the hydraulic fluid. Hydraulic systems are widely used in various applications, such as in industrial machinery, construction equipment, aircraft, and automobiles. The hydraulic fluid in these systems serves as a medium for transmitting power and lubricating moving parts.

Contaminants in hydraulic fluid can include particles, dirt, metal shavings, and other debris that can damage hydraulic components, reduce efficiency, and lead to system failures. The hydraulic filter plays a crucial role in maintaining the cleanliness of the hydraulic fluid by trapping and removing these contaminants.

Need of the Hydraulic filters 

The hydraulic oil may contain various contaminates like welding scales, metal chips, tapping compound, sand particles, sludge, rust, water and dirt etc which may result in wear, corrosion, poor performance and ultimately failure of the equipment. 

Hence it is necessary to use filters to remove contaminants and supply pure oil to the system. The function of the filter is to separate out contaminants from the oil and clean it. 

Principle of filter 

Oil filter is a hydraulic element which removes impurities from the oil and supply clean oil to the system. 

Most of the filters work on the principle of trapping the particles in small holes. The fluid may pass through filter element and particles above a certain size become trapped. 

What is Hydraulic filter – Principle, Types and More

Classification of hydraulic filter 

Oil filters are classified on the basis of –

A) According to construction of filter medium 

1) Surface filter 

It is a thin screen of filter material. 

Surface filters are normally constricted from thin sheets of material folded in many sections and turned into multipointed star shape. 

There is a large surface area available in a small space. The filter is fitted inside a bowl. 

The thin sheets full of holes traps the solid particles as the oil passes through them. 

The material used for surface filters are cellulose, woven, steel fibers etc. 

Hydraulic filter

2) Depth filter 

It is a thick layer of material. 

Depth filters are constructed with a thick layer of material with small passages through which the fluid must pass. 

The passages may be formed from granules compacted into thick cylindrical layer compacted into a tube. 

The particles become trapped in the passages and oil is filtered out. 

The capacity of depth filter is more than the surface filter as well as it also arrest finer materials which can not separated by surface filters. 

The filter materials used in depth filter are cellulose, synthetic fiber, metal fibers, glass fiber etc. 

Hydraulic depth filter

What is Hydraulic filter – Principle, Types and More

B) According to quantity of oil to be filtered 

1) Full flow filter

The entire oil flow is filtered. 

Full flow filter is used to filter out the entire flow of oil from inlet to the outlet of filter. 

Full flow filter consists of thick depth filter element formed into cylindrical shape and it is placed in a bowl. 

The filter has inlet for impure oil and outlet for clean oil.  

Full flow filter

2) By pass filter

Only a portion of oil is filtered. 

When only a portion of the oil is passed through the filter element and main portion of oil is directly passed without filteration. It is called as by pass filter. 

In this filter, due to pressure difference between the inlet and restricted passage, a portion of oil is drawn towards the filter cartridge for removing contaminations. 

In this the valve opens to bypass the large quantity of oil and only small portions is allowed for filtrations. 

What is Hydraulic filter – Principle, Types and More

Hydraulic filter advantages and disadvatages

Hydraulic filters play a crucial role in hydraulic systems by removing contaminants from the fluid, ensuring smooth operation and extending the life of the components.


Contaminant Removal: The primary function of hydraulic filters is to remove particles and contaminants from the hydraulic fluid. This prevents damage to sensitive components such as pumps, valves, and actuators.

Extended Component Life: By removing contaminants, hydraulic filters contribute to the longevity and efficiency of hydraulic system components. Clean fluid reduces wear and tear on seals, bearings, and other parts, leading to longer equipment life.

Improved System Reliability: Clean hydraulic fluid ensures reliable operation of the entire hydraulic system. It helps maintain consistent pressure levels and prevents malfunctions that can occur due to contamination.

Enhanced Performance: Hydraulic filters help maintain the efficiency and performance of hydraulic systems by ensuring that components can function optimally without being hindered by contaminants.

Reduced Downtime: Preventing damage to hydraulic components through effective filtration reduces the need for maintenance and repairs. This, in turn, leads to decreased downtime and increased overall system productivity.

Environmentally Friendly: Properly maintained hydraulic filters contribute to environmental protection by reducing the likelihood of hydraulic fluid contamination, which can be harmful if released into the environment.


Pressure Drop: Hydraulic filters can introduce a pressure drop in the system as the fluid passes through the filter media. This pressure drop needs to be considered in system design to ensure that it does not negatively impact performance.

Maintenance Requirements: Filters need regular monitoring and maintenance to ensure they are functioning correctly. This includes replacing filter elements or cartridges at specified intervals.

Initial Cost: High-quality hydraulic filters can have a relatively higher initial cost. However, the long-term benefits, such as reduced maintenance costs and increased system reliability, often outweigh the initial investment.

Size and Weight: In some applications where space and weight are critical factors, the addition of hydraulic filters may pose challenges. Compact systems may require careful consideration of filter size and placement.

Fluid Compatibility: Not all hydraulic filters are suitable for use with all types of hydraulic fluids. It’s important to select a filter that is compatible with the specific hydraulic fluid used in the system.

What is Hydraulic filter – Principle, Types and More

Application of hydraulic filter

Hydraulic filters find application in various industries and equipment where hydraulic systems are used. The primary purpose of hydraulic filters is to remove contaminants from hydraulic fluid, ensuring the smooth and efficient operation of hydraulic components.

Construction Equipment:
Hydraulic filters are widely used in construction machinery such as excavators, loaders, bulldozers, and cranes. They help protect hydraulic pumps, valves, and cylinders from damage caused by dirt, debris, and other contaminants.

Industrial Machinery:
Hydraulic systems are prevalent in industrial machinery, including manufacturing equipment, metal presses, and machine tools. Hydraulic filters play a crucial role in maintaining the cleanliness of hydraulic fluid to prevent wear and damage to critical components.

Automotive Applications:
Some vehicles, especially heavy-duty trucks and specialized vehicles, use hydraulic systems for functions such as braking, suspension, and steering. Hydraulic filters are employed to keep the hydraulic fluid clean and maintain the proper operation of these systems.

Aircraft Hydraulic Systems:
Aircraft utilize hydraulic systems for various applications, including landing gear operation, flap movement, and brake systems. Hydraulic filters are crucial in aviation to ensure the reliability and safety of these systems.

Marine Applications:
Hydraulic systems are employed in marine equipment such as cranes, winches, and steering systems on ships. Hydraulic filters help prevent contamination and maintain the integrity of the hydraulic fluid in marine environments, where exposure to water and other contaminants is common.

Material Handling Equipment:
Forklifts, conveyor systems, and other material handling equipment often incorporate hydraulic systems for lifting, positioning, and transporting goods. Hydraulic filters help ensure the smooth and reliable operation of these systems.

What is Hydraulic filter – Principle, Types and More


What is a hydraulic filter?
A hydraulic filter is a component within a hydraulic system that removes harmful particles by forcing hydraulic fluid through a porous filter element. The filter element traps contaminants and prevents them from re-entering the fluid flow and damaging other downstream equipment.

What material is used for hydraulic filters?
Common materials used in hydraulic filters are glass microfiber, phenolic-impregnated cellulose, and polyester. Many systems simply require specific replacement filters, which can be ordered through filter manufacturers and suppliers, or through the machine or device system manufacturer.

What micron is a hydraulic filter?
Hydraulic Filtration – Screw-on filters, 10, 20 and 25 micron filters.

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By Aditya

Hi, I’m Aditya Sharma, a professional blogger from Gurgaon, India and I launched this blog called aadityacademy on July 2021. aadityacademy.com is a mechanical Project-oriented platform run by Aditya sharma and I got the motivation to start aadityacademy blog after seeing less technical education information available on google.

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