The Importance of Filtration In Hydraulics

In this article, we’ll explore the importance of filtration in hydraulics, and how choosing the right filtration products and elements can minimise breakdowns and maintenance requirements, thereby optimising operational performance.

The Importance of Filtration in Hydraulic Systems

Just as kidneys filter out waste from our blood, hydraulic systems require filtration to remove contamination from the hydraulic fluid.

Contamination can severely impact machine performance, hydraulic system and component longevity and reliability. Particles such as dirt ingress, metal shavings, or a degraded fluid will cause wear and tear on hydraulic components, leading to system failures, decreased efficiency, and reduced component lifespan. Maintaining your hydraulic fluid will save you money and downtime.

By ensuring that hydraulic fluids are kept clean and free of contamination, the risk of damage to pumps, valves, and other components caused by contamination is reduced significantly.

Choosing the right filtration element

Choosing the right filtration element for your application may seem like a very basic task. However, it can be confusing and there are several factors that need to be considered and some are often missed.

Let’s take a look:

Knowing The Application & Understanding System Requirements: Understanding the hydraulic system’s requirements is imperative and is the first step when choosing the correct filtration elements. By knowing parameters such as fluid type and viscosity, operating temperature, pressure, and flow rate, helps our system designers, project engineers and hydraulic technicians in selecting a filter that can perform efficiently under the expected working conditions, without hindering the system’s operation.

Choosing The Correct Filter Type:

There are five main types of filters, all of which have a very specific jobs within a hydraulic system.

Suction line filters – The most basic filter type, suction line filters are located within the tank and are coarse filters, typically 125 micron nominal with a 0.2 bar bypass used to protect the pump inlet from large contaminant and items such as bolts and rags that may have dropped into the systems reservoir. Sizing is important to ensure minimal pressure differential across the filter element. The use of suction strainers needs to be considered very carefully so as not to impose any unnecessary strain on the pump that would cause premature failure often associated with cavitation. Particular attention needs to be made to the maximum ‘absolute’ pressure rating of the pump, typically 0.8 bar for piston pumps. You will often see suction strainers on gear pumps, for vane and piston pumps our preference is to avoid these all together and to offline condition the hydraulic fluid and to adopt a magnetic suction strainer with zero pressure differential that is there to simply remove submicron ferrous contamination associated with accelerated pump wear leading to a reduce in pump life.

Return line filters – Return line filters are commonly used in open loop systems. They filter the oil before it returns to the reservoir, keeping the reservoir free of particulate that could potentially enter the system from component wear and tear and to maintain the recommended cleanliness levels. Selection of the element is important to achieve the necessary NAS/ISO/SAE code for the installed components. Return line filters in offline or circulating circuits are used to ensure new oil is conditioned to the correct cleanliness level during commissioning of new plant or following servicing of existing systems requiring an oil change. As with suction strainers it is important to ensure correct sizing to maintain a low-pressure differential and maximum dirty holding capacity.

Pressure line filters – Pressure line filters are found across a vast range of applications, In both mobile and industrial hydraulics. Placed after the pump, they protect the hydraulic components in the event of pump failure by catching all the particulate before it makes its way through the system as well as ensuring each circuit and expensive components are protected. Depending on the technology installed, proportional, servo, poppet and seated valves pressure filters can prove invaluable to protection high cost, high precision components requiring a high-level NAS/ISO/SAE filtration rating. It is common to see pressure filters installed with high pressure collapse elements, no bypass, and visual and electrical clogging indicators. On machines operating 24/7 duplex pressure filters are commonplace to ensure elements can be changing without shutting down the machine or process.

Breather filters – Breather filters prevent airborne particulate such as dust and dirt from entering hydraulic reservoirs and contaminating the hydraulic fluid. Breather filters are designed to stop particles at 3 microns or larger from entering the system. In addition to traditional breathers, desiccant breathers are also used when it is important to protect the hydraulic fluid from the ingress of water as well as airborne particulate contamination.

Offline filters – Operating separately from the main hydraulic or lubrication system, offline filtration offers continuous filtration and conditioning of hydraulic fluids in any system. By maintaining flow, this additional filtration prevents particulate and water build up over time. Offline filtration through the selection of the correct elements and flows relative to system volume will maintain a high-level of cleanliness, therefore minimising early component wear and ensures maximum life and performance.

Determine Filtration Level Needed:

Understanding the level of filtration needed is crucial in choosing the right element. If not followed, this could have catastrophic consequences. The level of filtration required is often determined by an NAS/ISO/SAE cleanliness code required, this outlines the cleanliness levels needed for different types of systems. The cleanliness code required is usually provided by the original equipment component manufacturer, unfortunately most systems are application specific, and each system will need to be assessed by an experienced fluid power applications engineer. Our engineers are on hand to help and guide you with the correct selection. Choosing a filter that meets or exceeds the NAS/ISO/SAE cleanliness code is essential for protecting your components from premature wear or failure.

Select the Appropriate Filter Media:

The choice of filter media has a significant impact on the effectiveness of system filtration. The most popular options are cellulose (paper) or glass fibres. Both have different properties in terms of filtration efficiency, dirt-holding capacity, and resistance to chemicals. Glass fibre filters are much more efficient, offer exceptional durability under high-pressure conditions, allow for greater fluid compatibility, and are better suited for removing finer particles with absolute ratings. Paper filter elements are much less efficient, are nominal rated as opposed to absolute and are slowly being replaced. Each filter element is made up of multiple layers and filter element manufacturers are continuously looking for ways to improve standards and element technology to benefit component life and system performance. New technology and materials are pushing the boundaries to reduce differential pressures across elements relative to size and flow, pushing for greater dirt retention capacity and improving contamination separation performance and well as having to deal with new challenges as fluids evolved, such as the increasing need for stat-free properties.

Conclusion

Selecting the correct filtration products and filter elements requires a much deeper understanding than the above, and sometimes initially thought. Filtration is an integral part of any fluid power system. When a system is correctly designed with the right filtration products and elements taking into consideration the fluid, environment and technology installed as well as being optimally sized for system performance and dirt holding, and or water ingress management you will ensure maximum machine and plant uptime, optimal system performance, and a reduction in component wear and system longevity.

HYQUIP’s experienced application and project engineers will help you choose the right filtration products and solutions for your project.

If you’re unsure or need any assistance call 01204 699959 or email enquiries@hyquip.co.uk