The Future of Hydraulic Oil Filtration
The Future of Hydraulic Oil Filtration
The Future of Hydraulic Oil Filtration
Achieving appropriate levels of cleanliness in today's hydraulic systems requires successful capture and removal of contaminants. Filtering should be done in a way that does not disrupt oil flow or excessively increase the pressure drop in the system. It's a delicate balance between system design and efficiency.
The future of hydraulic filtration focuses on three main areas:
Development of finer fiber technology for use in filter media,
Designing various layers/arrangements of filter media for maximum effect and
Improving the overall structure and design of the filter to maximize the useful filtering area for optimum performance.
Production Efficiency in Hydraulic Filters
One of the simplest forms of filter media is the sieve or strainer. A popular choice for hydraulic filters, depth media consists of random layers of fiber strips to form a multilayer screen. Depth filtration technology is designed to have higher efficiency than strainers and retain more dirt.
There are two basic principles commonly applied to increase the efficiency of deep filters. Adding more layers to the filter and compressing it, making the pore spaces finer in order to capture particles passing through the surface layers. media during the production process.
Modern filter media design often combines layered combinations of coarse media with finer grades, with the idea that larger dirt particles are captured at the surface while finer particles are retained deeper into the media.
Increasing efficiency through increased layers or finer pore sizes can lead to undesirable results. Both methods can lead to increased differential pressure across the filter, which can shorten filter life and lead to premature filter replacement.
Finer Fiber Technology in Hydraulic Filter
To extend element life and reduce pressure drop across the filter element, filter manufacturers are constantly looking for materials with finer fibers to provide more pore space to trap dirt while increasing the fluid flow area.
Traditionally, most depth filtration was done with cellulose fibers (paper media). Many hydraulic filters today are made using synthetic fibers with smaller diameter wires. Future filter media technology will likely continue to develop finer fibers.
Evolving Filter Surfaces
Hydraulic filter manufacturers strive to create state-of-the-art filter media. Recently, a corrugated media has been developed that provides alternative flow paths and allows more filter media per unit volume. In the future, such media may replace the pleat technology found in traditional filters.
Hydraulic Filter Efficiency
Filtration efficiency is normally expressed as the ratio of dirt entering a filter compared to dirt exiting the filter, at a given micron (μm) size. Filter testing is completed in the laboratory so the results can be compared and statistically verified.
Filtration tests attempt to accurately control the quality of the test powder, flow rates, temperatures, measurement equipment, and many other variables to ensure test repeatability. The test, called multi-pass filter testing, produces a Beta (ß) rating for a given micron size filter. For example, the ß10=75 filter removes 74 out of 75 particles larger than 10 microns entering the filter.
It's understandable, but still disappointing, to see that filters in the field don't always perform exactly as laboratory tests suggest. Problems that contribute to poor filter performance may include: pulsating flows, flow rate, startup fouling, and general design flaws in the hydraulic system.
In the laboratory, filters are tested under steady-state flow conditions. The interlaced flow of real-life applications can significantly reduce performance. Therefore, it is recommended to avoid situations. Effect of pulsating flow when installing a filter in a circuit design.
Not only does efficiency vary with pulsating flow, but different media configurations can also result in different efficiencies at increasing differential pressures. For example, Figure 6 shows two elements with the same micron rating (average efficiency) but different maximum and minimum efficiencies and therefore varying dirt holding capacity. (The last point on the graph indicates element collapse.) Effective filtering is a function of good system design as well as the quality of the filter used.
Controlling Contamination Levels in Hydraulic Oil
Contamination levels in a system include the amount of contaminants in the oil during operation, contaminant entry rate, etc. It is a function of many factors such as. For most hydraulic systems, preventing contamination is more cost-effective than cleaning the system. treatment. Troubleshooting system design to control contamination will produce dramatic results. Here are a few troubleshooting tips:
Ventilation Filters
It is unfortunate that many hydraulic system breathers consist of an open cap or pipe, or at best a filler cap without a proper filter element inside. Unfiltered air should not be allowed to enter the hydraulic system.
Wherever possible, adequate ventilation filters should be installed in oil reservoirs; Ambient air carries significant amounts of pollutants.
A quality ventilation filter with an absolute efficiency of Beta 10 µm(c) = 75 or better will be sufficient in most cases.
A quality 10 µm liquid filter will generally be more efficient at capturing fine dirt particles when applied in air filtration applications. In humid conditions, breathers must evacuate water.
Reservoirs and Barrel Storage
Good cistern design will ensure that any water or heavy dirt settles in a small area or standpipe at the bottom of the cistern that can be drained periodically. Water remaining in the oil causes bacterial growth and chemical degradation.
It is best to store oil drums on their sides so that the holes are submerged. This prevents water or moisture from being drawn into the drum through breathing caused by temperature changes.
Good reservoir design will provide return line diffusers, adequate baffles, and sufficient volume to remove heavy dirt particles, water, and entrained air.
Oil should be recycled or used regularly to prevent long-term spoilage.
Ideally, oil should be filtered as it enters and exits the reservoir.
Of course, the perfect filter and perfect filter media will do wonders for the hydraulic system. However, when it comes to achieving optimum cleaning levels, filter efficiency values cannot be relied upon alone.
As discussed in this article, many other factors can affect the integrity of the system. Proper usage and solid system design go a long way in solving dirty oil problems. Every situation is different.
Climates, environments and cleaning requirements vary and should be taken into account. However, a good fluid power distributor will be able to accurately diagnose systems and recommend which media options, filter types and filter positioning are correct for each application.