Why Are Air Breather Filters Necessary for Hydraulic Systems?


Reservoir Breather Filters

In hydraulic systems, the presence of solid particulates can cause significant damage to system components and severely impact system performance. For this reason, industry professionals integrate reservoir breather filters—also referred to as air breather filters—into their hydraulic equipment to prevent airborne materials from entering through the reservoir.

The following article goes into further detail about the importance of using breather filters in hydraulic systems. It also outlines the air breather products available at DOMS Incorporated.

What Is the Function of an Air Breather in an Hydraulic Tank?

In open-circuit hydraulic systems, air moves freely into and out of the reservoir as the fluid level falls and rises. Unfiltered air can carry a variety of foreign materials—e.g., dust, dirt, and debris—all of which can contaminate the process fluids within a hydraulic system. If left unchecked, these contaminants can damage system components or reduce system efficiency. Hydraulic breather filters remove solid particulates from incoming air to ensure the hydraulic system continues to perform as intended for the duration of its expected service life.

As indicated above, air breathers play a critical role in hydraulic systems. For this reason, it is important to maintain them properly to ensure they continue to fulfill their purpose effectively and efficiently. Proper maintenance for air breather filters involves regularly changing out the filter element. Failure to do so can lead to clogging, which, over time, can lead to the formation of a partial vacuum within the reservoir. This vacuum, in turn, can cause cavitation, which often leads to premature pump failure if left unchecked.

Air breather filters integrated with pressure valves are generally used to eliminate the risk of cavitation. If the pressure rises above safe levels, the valve activates to reduce the pressure within the system.

<Find out the leading causes of hydraulic pump filters.>

Air Breathers for Hydraulic Reservoirs From DOMS Inc.

At DOMS Incorporated, we specialize in the manufacture of hydraulic filtration components. One of our core product offerings is air breather filters for hydraulic reservoirs.

Our reservoir breather filters offer air particulate protection capabilities, even in high-humidity environments. They are available in several variations to suit different hydraulic systems, including risers, dipsticks, spin-on breathers, and threaded breathers. Other design options include cast aluminum or nylon cap, with or without pressure valves, and with or without cap locks. Customers can customize various filter elements to suit their application requirements, including the basket length or pressure capacities.

Whether you require a filter breather for a hydraulic tank in the agricultural, construction, mining, or heavy-duty industrial sector, we’ve got you covered. Our experts have the knowledge and skills needed to help you identify the right filter for your hydraulic system. To discuss your application requirements with one of our representatives, contact us or request a quote today.

What Causes Hydraulic Pump Failure?


Off Road Heavy Equipment

The pump is the most expensive and critical component in any hydraulic system—it works by first creating a vacuum at the pump inlet, which generates atmospheric pressure. Liquid from the reservoir tank is then propelled through the inlet line to the pump, past a hydraulic filter or strainer, and into the hydraulic system. On a macro-level, the mechanical energy of the pump’s gears is transferred through fluid “flow” and used to power the attached hydraulic machinery.

Hydraulic systems can be used in many applications, including, for example:

  • Scissor lifts
  • Brakes
  • Vehicle gas pumps
  • Steering systems
  • Dishwashers
  • Airplane landing gear
  • Adjustable office chairs
  • Shock absorbers
  • Punch presses
  • Hydraulic power plants
  • Cranes, bulldozers, and construction equipment

Although hydraulic systems can be used in many everyday objects, they’re usually best suited for products that require high-power density or systems with changing load requirements. This simple yet elegant design offers exceptional consistency and speed compared to other driving mechanisms. Hydraulic systems are widely used across industries because they are reliable, easy to maintain, long-lasting, and safe. But despite their many advantages, hydraulic systems still require some degree of maintenance. The following guide explains what can make a hydraulic pump fail, as well as tips for extending its useful lifespan as much as possible.

5 Problems That Can Cause Hydraulic Pump Failure

Hydraulic pump failure is almost always caused by improper upkeep, which typically manifests in any of the following ways:

Hydraulic Fluid Contamination

Fluid contamination is the leading cause of pump failure and usually happens when particulates circulate through the system via a breather valve or cylinder rod, or as a result of repairs, welding slag, sealant, or refilling. Once contaminants enter the system, they can degrade parts, create buildup, change the fluid’s physical and chemical properties, corrode equipment, and lower the system’s overall efficiency.

Excess Pressure

Hydraulic pumps are designed to work within a specific pressure range. If pressures exceed the pump’s rating, it will likely overburden the pump, cause damage, and eventually halt operations completely. If the pressure changes are extreme, it could even cause an explosion.

Air in the Pump or Line

Joints and shafts must be completely sealed for the hydraulic pump to work properly. If air gets trapped inside the system, bubbles can cause pressure and temperature fluctuations, which eventually will cause the pump to break down. Usually the first sign there’s air in the pump is a high-pitched whine.

<Learn about the function of air breather filters in hydraulic systems.>


Cavitation occurs when the pump speed is inconsistent, creating air bubbles that rapidly form and then collapse. When this happens, the pump won’t completely fill with fluid, which destabilizes pressure in the system and produces the same type of high-pitched squeal as pump aeration. A blocked pipe, clogged filter, or poor system design can all cause cavitation.

Low-Quality Fluid

Hydraulic systems need high-quality cooling and lubrication oil with the right mineral content and viscosity. Purity is particularly important for high-pressure systems that operate with larger loads.

How to Prevent Hydraulic Pump Failure

The best way to prevent hydraulic pump failure is to inspect and maintain your hydraulic system. Hydraulic filters and strainers will help you avoid fluid contamination, which in turn will stabilize the temperature and pressure inside the system. Filters remove particulates that are smaller than 50 microns, and strainers work tangentially to remove contaminants larger than 50 microns. Various options are available for both filters and strainers using different ratings, mesh sizes, and materials.

When you’re selecting a new filtration system, consider the following:

  • What type of process fluid will you use?
  • What are the intended operating pressure and temperature ranges?
  • How quickly will fluids circulate through the system per cycle?
  • What volume and type of contaminants should you screen for?

After they’re installed, filters and strainers need to be routinely checked and cleaned. Operators should familiarize themselves with their hydraulic system to identify any aberrant conditions as soon as possible, if problems should arise. If you maintain your hydraulic system, it will work more efficiently, necessitate fewer repairs, require less downtime, and last as long as possible.

Contact DOMS Incorporated for Hydraulic Fluid Filtration Solutions

With over 60 years of experience manufacturing high-quality suction filters, suction strainers, gauges, and diffusers for hydraulic systems, the experts at DOMS Incorporated have the expertise to keep your operation in peak condition. We’ve worked closely with organizations from many industries, including construction, forestry, mining, energy development, industrial manufacturing, aircraft equipment manufacturing, plant processing, and more.

If you have questions about optimizing your hydraulic system, contact DOMS Incorporated today or request a quote.

Are Suction Filters Still Necessary in Hydraulic Systems?


Suction Filters and StrainersSuction filters and strainers are employed in hydraulic systems to remove contaminants from process fluids. The removal of contaminants is critical to protecting sensitive system components. The terms “suction filter” and “suction strainer” are often used interchangeably, but their main difference is the size of the contaminants they remove. As the process fluid flows through the filter or strainer, contaminating particles and pollutants are trapped. Both systems use a porous medium to remove contaminants, but filters are typically much finer than strainers and capable of capturing smaller particles.

Do Suction Filters and Strainers Cause Cavitation?

Cavitation occurs when vapor bubbles or cavities develop in a liquid, usually if the area is subjected to rapid pressure changes. The phenomenon is mostly observed in areas of relatively low pressure around an impeller. When these bubbles implode or collapse, the force triggers an intense shock wave inside the pump, which can cause significant damage to the impeller or the pump housing.

While hydraulic suction strainers and filters are critical for removing contaminants in hydraulic systems, they can also inadvertently produce cavitation if they’re improperly designed or maintained. Cavitation can occur when the filter becomes clogged with debris, thereby increasing the pressure in the suction line. No matter the cause, cavitation is a serious concern—but operators can avoid problems by using a reliable supplier and regularly cleaning or replacing the suction filter to keep the hydraulic fluid within safe pressure ranges.

Using DOMS Inc.’s filters can help alleviate pressure changes and prevent cavitation. Our filters are available with relief valves, which activate when pressure begins to escalate, thereby protecting the hydraulic system. The relief valve ensures the pump will not sustain damage, even if the filter needs to be cleaned. As a premier manufacturer of hydraulic system components, DOMS also cleans and refurbishes used filters, which helps users adhere to routine maintenance schedules and avoid premature wear.

Why Are Suction Filters Necessary in Hydraulic Systems?

The primary purpose of hydraulic suction filters is to trap and remove impurities from the hydraulic fluid. Hydraulic fluid is easily contaminated, and fluid contamination is especially prevalent right after new equipment is installed. During the initial “breaking in” period, metal flakes from the machinery can work their way into the hydraulic fluid, potentially damaging the pump or impeller and progressing into the tank.

Hydraulic oil creates a lubricating film that’s thick enough to fill the clearance between moving parts in the system. If any particles are larger than the clearance between moving surfaces, they will generate friction, which makes the equipment less effective and weakens delicate system components.

Generally, there are four main types of contamination found in hydraulic fluid:

  1. “Native” Contamination: Native contamination is caused by contaminants that are introduced into the system or its components during the manufacturing process or repairs. These contaminants include welding slag, excessive sealant, or pieces of Teflon tape.
  2. Contaminated New Oil: New hydraulic oil is typically not pure enough for advanced, high-pressure hydraulic systems. The storage, handling, and manufacturing processes can expose the oil to contaminants.
  3. Ingressed Contamination: Ingressed contamination occurs when contaminants become trapped in the air that enters the reservoir through the breather cap. Without a filter, water can contaminate the oil and enter the system, especially in humid operating conditions. Dirt particles can also penetrate the system on dirty cylinder rods; these rod seals aren’t airtight because they need to allow a certain amount of mobility. Additionally, any time the system is opened, such as when an operator disconnects a hose or adds fluid, it’s possible to introduce contaminants.
  4. Internally Generated Contamination: Internally generated contamination occurs as part of the equipment wear-generation cycle. Particles from the interior surface of components circulate in the system until they are removed with a filtration system.

<Learn about the function of air breather filters in hydraulic systems.>

Turn to DOMS Inc. for Hydraulic Filtration Solutions

Over the past 60 years, DOMS Incorporated has become one of the leading manufacturers of hydraulic filters. We offer a large selection of standard filters, with or without relief valves, and we can custom design hydraulic filters for a range of applications. Our highly skilled team also offers expert advice on safely implementing suction filters and strainers and protecting the integrity of various hydraulic systems. To request a quote or learn more about hydraulic suction strainers and filters, contact us today.

Pump Suction Strainers vs. Inline Filters


Compare pump suction strainers and inline filters to determine the best fit for your hydraulic system.

ConstructionIn hydraulic systems, the infiltration of contaminants—even minuscule particulates—can cause damage to components that ultimately results in lower system efficiency and shorter service life. For these reasons, industry professionals employ the use of hydraulic filters and strainers to remove unwanted solid and semi-solid materials from fluids before they enter or reenter the system.

Two commonly used types of contaminant removal components used in hydraulic systems are pump suction strainers and inline filters. While they serve the same function (i.e., removing solid contaminants from hydraulic fluids), they differ in regard to operating principles and positioning within the system. The following article provides an overview of the two, including how they work and when to use them in a hydraulic system.

When Should You Use a Pump Suction Strainer?

Pump suction strainers are installed onto the suction inlet or piping of a pump to protect the system from taking in solid foreign matter from the fluid reservoir. They generally feature a coarse mesh screen designed to capture and collect large particulates as the fluid flows into the pump. Compared to the finer screens of filters, they are less flow restrictive and, consequently, less likely to cause cavitation when maintained properly.

When selecting a suction strainer for a pump system, it is important to choose a size that accommodates the system’s pressure and flow requirements. Despite being not as susceptible to cavitation as filters, an improperly sized component can still lead to cavitation and, ultimately, system failure. As such, it is essential to work with a qualified suction strainer/filter designer when constructing a hydraulic system to ensure you employ the right straining/filtering solution for your needs.

When Should You Use an Inline Hydraulic Filter?

Inline filters—also sometimes referred to as return line filters or spin-on filters—are installed within the fluid return lines of hydraulic systems. They enable industry professionals to filter finer particulates from the fluid stream directly within the system, resulting in highly efficient filtration operations. The positioning of these filtration components is ideal. The return flow pressure is sufficiently high enough to push the fluid through the finer screen but not too high that the filter requires a more complex design. This quality, combined with the low velocity of the fluid, ensures the system achieves higher filtering efficiency with minimal costs.

The main drawback to inline hydraulic filters is the risk of the back pressure generated by the component causing damage to the system components and overall system. For this reason, it is vital to consult with a filter specialist who can custom-design an inline filtration solution for your hydraulic system.

<Explore DOMS Inc.’s selection of filters and strainers for hydraulic systems.>

Contact the Hydraulic Filter and Strainer Experts at DOMS Inc. Today

Improper filtration in a hydraulic system can lead to a variety of problems, ranging from loss of pressure and lowered processing efficiency to cavitation and system failure. As such, it is crucial to use the right filter or strainer for your hydraulic system. If you need assistance designing and selecting the right solution for your needs, the experts at DOMS Inc. are here to help.

At DOMS Inc., our team has extensive experience designing and manufacturing components for hydraulic systems, including suction strainers and inline filters. For additional information about our standard and custom hydraulic component solutions, contact us or request a quote today.