Selection and Use of Hydraulic Filter Housings

Hydac Hydraulic Filter Assembly

Filtration is ideal for achieveing and maintaining the desired cleanliness level for hydraulic fluids. Yet, without the right filtration equipment, this will be difficult.  The following are important factors in the selection and use of Hydraulic Filter Housings.

Filter Placement Options

Hydraulic systems typically have three Filter Housings:

1. Suction Filter

This filter connects to the pump suction or is submerged in the reservoir. Since suction pressure loss can lead to pump failure, it is typically a larger mesh strainer.  Its main purpose is to protect the pump from large debris.

2. Pressure Filter

This filter is located between the pump discharge and the other components of the hydraulic system.  Smaller particulate and pump debris pass through the suction strainer and pump. The pressure filter protects the system from fouling and other damage caused by this particulate.  A bypass valve can be present or absent in the high-pressure filters. The bypass prevents filter damage in the event of over pressurization.  A well-designed pressure filter improves the performance and reliability of any hydraulic system.

3. Return Filter

This filter is in the circuit returning to the oil reservoir. It removes particulate picked up in the piping and components throughout the system. Filtering upstream of the reservoir stops sludge build up and lowers the load on the pressure filter. 

Factors to Consider

There are many factors to consider when choosing these Hydraulic Filter Housings.

Factor #1: Durability

Durability is most important because hydraulic filters must endure severe pressure cycles.  They are also subject to high pressure and temperature.  The fluid they process is often flammable.  Failure is not an option. Always select Filter Housings specifically made for hydraulic systems. These have pressure, temperature and materials specifications conducive to hydraulic applications.  They will also offer bypass valves, pressure options, manifolds and other relevant features.

General industrial filters may have some of these features but not others. As a result, there are several potential failure scenarios when using these. If a filter fails, the hydraulic system goes down.  Moreover, there is a risk of contaminating the entire circuit and all components. This will likely result in extended downtime, equipment malfunctions and safety concerns. 

Factor #2: Compact Configuration

 Compact designs allow the most filtration capacity in the smallest amount of space. 

It is common that Hydraulic Filter Housings must fit in tight spaces. They are often part of an OEM assembly made to fit in a decidedly small footprint. So, many are made with compact cast heads. These combine ports valves, circuits and manifolds in a single block.  An adjoining bowl (filter chamber) holds the element and completes the assembly. This head/cap and bowl design is very compact and easy to operate. 

In contrast, multi-component systems have loose housings, valves and piping manifolds bolted together.  They are often skid-mounted, much larger and complex to operate.

Factor #3: Ease of Operation

Filter operation generally consists of positioning valves, venting, draining and changing filter elements. All these tasks should be simple and doable in a few minutes. Hydraulic filters are often configured as duplex assemblies. This means there are two filter chambers (bowls). One is operating while the other is on standby. An integrated “switching” valve allows operators to select which filter is in service by simply turning the valve handle 90-180 degrees.   This design allows filter changes while the hydraulic system is online. 

Hydraulic filters typically have one filter element per chamber. The element should be simple to access.  Again, a cap and bowl Filter Housing is a good choice.  The bowl threads into the cap assembly or it’s adjoined with a simple clamp. A “bowl-service” filter is one where the filter element is changed by removing the bowl from the head/cap. Conversely, a “cap-service” filter is one where the cap is removed from the bowl. These are the simplest Hydraulic Filter Housings to operate.

Factor #4: Manufacturer Selection 

Working with industry leading manufacturers offers support and security. This cannot be overstated. Hydraulic filters need specialized materials and construction.  A good product demands years of product development and must pass challenging tests. The quality and reliability of hydraulic filters get advanced by those who invest in expertise and research. This offers end-users valuable filters and expertise specific to hydraulic applications. PowerFlow is an authorized distributor for Hydac.  They are one of the world’s leading manufacturers of hydraulic filters.

Reputable brands in the hydraulics industry will not fail you. Keep in mind, in technical industries it takes years of hard work and quality consistency for a company to earn a great reputation. 


Doing your homework prior to selecting hydraulic filters can prevent hydraulic system issues.  The right filters prevent fouling.  Clean fluid improves performance, productivity and reliability of hydraulic power systems. Improperly designed hydraulic filters add unnecessary risks to operations and safety. Working with a manufacturer like Hydac yields benefits.  These include superior filtration performance and helpful expertise. PowerFlow is an authorized distributor for Hydac products. Contact us for help and expertise on your fluid purification applications.

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