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What Does a Hydraulic Filter Do?

Every hydraulic system utilizes hydraulic filters to remove impurities from the hydraulic fluid to keep the system functioning optimally. In the ideal hydraulic system, you would have filters installed at every location before they enter each component.

Oil fuel or air filter for engine carHowever, this is impractical because of the costs and space needed to design such a system. Not to mention, the more filters the system has, the more it will cause an overall pressure drop. As such, it is essential to design a system that can operate efficiently while filtering impurities as best as possible.
 

What Is a Hydraulic Filter?

There are different types of hydraulic filters used in a hydraulic system depending upon the level of hydraulic filtration desired and other factors, including:
  • How easy it will be to service and replace the filters when required
  • The sensitivity of hydraulic parts and components to contaminants
  • The level of acceptable allowed for the system to still function correctly
  • The pressure required for the system to perform its functions
  • The allowable tolerances for the hydraulic parts and components
Depending on your specific needs, your hydraulic system could contain a variety of different types of hydraulic filters, such as:
  • High-Pressure Filters
  •  
  • Reservoir
  • Suction strainers
  • Reservoir Breather Filters
  • Offline Filters
Hydraulic filters will either be cartridge or spin-on type. . Cartridge filters are installed in between the parts and components and are similar to air filters. Spin-on filters screw onto a manifold connection in the line so that the fluid will pass through the filter,  they are normally suitable for low pressure applications so are used in either the suction or return lines of hydraulic circuits.
 
Of the two, spin-on filters are easier to change since you just screw it off and screw on a new one. However, the replacement filters tend to be more expensive than cartridge filters. So there has to be a tradeoff between the two and where they are used in the system.
 
For instance, spin-on filters are better suited in locations where replacing a cartridge filter would be too difficult or impossible. On the other hand, cartridge filters are better utilized in places where access is easy.
 

How Does a Hydraulic Filter Remove Contaminants?

The filters in a hydraulic system are found in various locations throughout the system to remove and prevent contaminants from being circulated through the system where they can damage parts and components. Each type of filter serves a different purpose depending on the installation location.
 
For example, low-pressure/suction filters are installed before the hydraulic pump to filter out contaminants before the fluid enters the system, whereas high-pressure filters are placed after the fluid exits the pump to help regulate the fluid power and system pressure and maintain fluid flow rates.
 
Then reservoir return line filters are installed at the end of the circuit before the fluid is returned to the reservoir. Next, strainer filters, which are also called suction strainers, are installed in the reservoir to help filter out larger items, such as rocks, nuts, bolts, insects, and other detritus.
 
Reservoir breather filters are similar to air filters. Their purpose is to remove dust and other air-borne contaminants when air enters or leaves the reservoir to help cool the fluid and regulate the reservoir pressure and fluid flow rates.
 
Another type of filtration found on hydraulic systems is an offline filter. These filters continue to filter the hydraulic fluid when the main system is offline and not being used. The offline filtration system is a sub-system consisting of a motor, pump, and filter.
 

Why Does the Filter Media Used Matter?

Filter media refers to the part of the hydraulic filter that removes and holds particulate matter and contaminants from the fluid. The level of filtration that occurs is directly related to the filter media.

suction-strainer.pngFor instance, suction strainers have larger openings, so smaller particles can easily enter the system. As such, you want to use finer filter media with low-pressure/suction filters to keep the smaller contaminants from being pumped into the system.
 

How to Use Hydraulic Filters in Hydraulic Systems

There are several benefits to using hydraulic filters in the right locations in hydraulic systems. Using the right combination of filters helps to keep the system functioning while:
  • Maintaining the overall system efficiency
  • Ensuring the system operates optimally
  • Removing the presence of contaminants from the hydraulic fluid
  • Reducing maintenance costs when filters are replaced regularly
  • Reducing the wear on system components
  • Helping , pumps, and motors last longer
 

How to Select the Right Hydraulic Filters

Even with the best filtration system, there will still be some level of contamination in the fluid. So, to select the right hydraulic filters for your hydraulic system, you need to decide what level of contamination in the fluid is acceptable.
 
Once you determine what level of fluid cleanliness you want, your next step is to determine how to achieve this objective. Ideally, you want to use a combination of low-pressure/suction filters, high-pressure filters, return line filters, and so on.
 
Next, you want to select the correct filter size and filter media type. As filters become clogged with particulate matter, their efficiency decreases and requires higher pressure levels to push the fluid through the filter, causing an overall drop in system operating pressure. As a result, the system will not operate as efficiently.

oil-filters.png
Most systems have a fluid bypass filter setting where if the pressure drop reaches a certain level, the bypass opens, allowing the fluid to bypass the filter entirely. However, this should be avoided if at all possible.
 
So, when sizing a filter and choosing the filter media, aim for a filter that only causes a pressure drop of around 10 PSI or less. This gives you more time to get to your bypass cutoff, whether it is 30 PSI or even 50 PSI. Not to mention, the higher the bypass cutoff, the longer the filter will last before it needs to be changed.
 

Why Hydraulic Oil Matters

Another factor to consider when selecting hydraulic filters is the type of hydraulic oil used in the system. Oils have different viscosities that determine how well they pass through filters. Furthermore, the quality of the oil will gradually degrade over time, requiring the oil to be changed and replaced with clean hydraulic fluid.
As can be seen, there are many factors to consider when deciding what type of hydraulic filters to use in your hydraulic system. To find the right hydraulic components for your system, please feel free to browse our selection of hydraulic filtration products and other hydraulic parts and components today.
 
Do not hesitate to contact us if you require further assistance by contacting White House Products, Ltd. at +44 (0) 1475 742500.

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