An effective filtration system is a crucial element of any operation that relies on hydraulic or pneumatic machinery. Operators must pay close attention to the filter rating of that system to ensure that it’s capable of capturing any foreign contaminants that might block or damage the equipment.
In the following blog post, we’ll explain what a fluid filter rating is in the context of fluid power systems, with a specific emphasis on hydraulic and lubrication fluids. This will help you select the correct filters to maximize system performance and component protection.
Think About Particle Sizes
It’s common industry knowledge that the efficacy of any fluid power system depends a great deal on the purity of the liquid used to generate the motion. For this reason, operators must test their fluid regularly to determine its ISO 4406 cleanliness code, an industry standard that refers to the number of particles of each size present in the reservoir. Pollutants can be composed of many different materials and range in size from a few microns wide to chunks of sediment that are larger than 14 microns.
The fact that some machinery parts are more sensitive to the wear and tear caused by these particulate impurities than others is why a range of filters is available, with different ratings suited to different equipment types. The filter rating is a measure of a filter’s ability to remove specific particle sizes from hydraulic or lubricant fluid.
Micron Ratings
Once the operator determines the ISO cleanliness code of their hydraulic fluid, they can compare it to the targeted code to determine the type of filter required. Since the particulate matter that contaminates hydraulic fluid is measured in microns (millionths of a meter), many filters receive a micron rating based on their ability to capture particles of a given size. A filter with a higher micron rating utilizes a much finer mesh than one with a comparatively lower rating, meaning that it is capable of blocking contaminants of a smaller size.
There are two types of micron ratings that operators must be aware of when determining what filter they need: nominal and absolute. A filter with a nominal rating means that it will capture most particulate matter of a given size. For example, a filter with a nominal rating of 25 microns would capture over 50 percent of particles that are 25 micrometers in size or larger. However, if a more effective filter is needed, the operator should consider a filter with an absolute rating of 25 microns, which can eliminate at least 99.9 percent of impurities in the given size range.
Particularly sensitive hydraulic equipment, such as the valves used in closed-loop systems, requires higher micron ratings because any contamination in the fluid can very seriously affect the efficiency of the system.
Beta Ratios
Besides the size of the particles they can remove from hydraulic fluid, filters are also rated by their beta ratio, which refers to their overall efficiency. This is the ratio of the number of particles flowing upstream divided by the number flowing downstream. For example, a filter with a beta ratio of 100 is written 100/1, meaning that for every 100 particles that flow into the filter, only one will manage to slip through. This can also be written as a percentage: A beta ratio of 100/1 would be 99 percent since only one out of every one hundred particles makes it past the filter.
The beta ratio of 100/1 is only meant to provide an example. In real-world applications, most machinery actually requires filtration that is far more efficient than that. Ratings of 200/1, 500/1, or even 1,000/1 are not uncommon. A filter with a beta ratio of 1,000/1 would indicate 1 out of 1,000 particles of the given micron rating made it through, meaning it was 99.99 percent efficient.
Other Considerations
Contamination by rust, dirt, and other solid matter is a major contributor to breakdowns in hydraulic technologies. However, an effective filtration system must also be able to address other pollutants, including air and moisture. Air in a hydraulic system reduces the efficiency of the energy transfer, and it can easily enter the reservoir through a seal that is even slightly compromised. Operators should be able to bleed air out of the reservoir without introducing other contaminants into the system using a breather filter or similar setup.
Moisture in the system can also greatly shorten the lifespan of hydraulic fluid and the machinery using it. Moisture might enter the reservoir through compromised valves or accumulate as a result of the temperature changes that are a regular part of operating hydraulic equipment. A desiccant breather can be connected to a filtration system to capture moisture before it contaminates the hydraulic fluid.
Replacing Filters
To ensure the filtration in a hydraulic system is always operating at peak capacity, filters must be replaced regularly, before they begin to become clogged by the sediment they are designed to remove from the machinery. For this reason, it’s critical that machinery is designed in a way that allows for easy swapping of filters when the time comes. Too many hydraulic machines are designed in such a way as to render changing filters difficult, meaning that crucial maintenance is not performed as often as necessary due to the difficulty involved.
Operators who wish to maximize the efficiency of their equipment, increase output, and reduce maintenance costs should ensure they are using filters with the correct rating for their needs and that filters are changed quickly whenever the need arises. Customized parts designed by a company like Aberdeen Dynamics can help you find the right fit so your equipment runs smoothly and effectively.