Every industry, machine, and component within a hydraulic system brings its own set of requirements, each affecting the other to eventually influence selection of a seemingly simple filter element. Before setting yourself up for unintentionally higher operating costs, you should not only select a filter based on pressure, flow, and cleanliness level required, but have a good feel for the big picture. Described here are five crucial pieces of information to know before sizing and selecting a filter.
1.Know the Application
Let’s start broad. First and foremost, understand the performance requirements of the filter. When it comes to accurately sizing a filter, performance requirements are often expressed in terms of Beta ratio, which is simply the ratio of particles entering the filter versus those exiting. Beta ratios can also be expressed as an efficiency percentage.
Today’s hydraulic filters are designed with media to trap and hold more contamination particles than ever for long life and low pressure drop.
For example, an application requiring a high-performance element will often have a Beta ratio exceeding 1,000, where 1,000 particles enter the filter but only one particle makes it out. Element performance in this scenario would be expressed in terms of a 99.9% efficiency. A reputable filter manufacturer will have documentation defining their element performance by the element’s pore-size rating. But having a strong understanding of the application’s performance requirements empowers you to enter the filter sizing and search stage equipped for success.
2. Know the Hydraulics
Once you’ve established the performance requirement of the application, it’s time to evaluate the hydraulic system. The hydraulic components installed in the circuit directly affect the type of hydraulic filter needed to function according to industry standards. This criterion drives an ISO-cleanliness code requirement that helps dictate the proper filter element type. As an example, a proportional valve in the circuit might require a 20/18/15 ISO-cleanliness code. To meet the standard set by the ISO code, this circuit requires a filter with either 3 or 6 µm absolute filtration.