Filtration & filter media: maximum performance

The demands placed on modern hydraulic systems are constantly increasing: smaller components, extreme flow rates, and highly refined oils require a filtration system designed without any compromises. For design engineers and technical managers, selecting the optimal filter media is critical to system efficiency, as it helps to proactively address issues such as unexpected downtimes, high differential pressure, and rapid oil degradation. RT Filtertechnik GmbH combines decades of development expertise with innovate filtration technology to deliver tailor-made modular systems and application-specific solutions.

The evolution of filtration and modern material expertise

Since the early days of industrial fluid conditioning, filtration technology has advanced rapidly. At the dawn of industrialisation, simple metal wire meshes or cellulose-based paper materials were commonly used. However, as cleanliness requirements became more stringent in the 1970s, there was a growing need to adopt micro glass fibre media on a larger scale. Today, advanced nonwoven fabrics produced through the precise melt-blown process dominate modern hydraulic media filtration.

In practice, a highly efficient filter medium is rarely made up of a single layer; instead, it employs the principle of depth filtration with an intelligent, multi-layered mat structure. A typical high-performance filter mat from RT Filtertechnik is strategically composed of the following:

Upstream side: A sturdy wire or elastomer mesh is used for initial rough stabilisation.
Pre-filtration: An integrated protective layer and a dedicated pre-filter material help to reduce the load on the main filter stage.
Fine filtration: The main fine filtration material ensures a precisely defined separation rate.
Downstream side: Optional protective layers and integrated drainage layers are supported by a final fabric layer designed to withstand hydraulic forces.

Application-specific filtration and patented protection against imitation

RT Filtertechnik offers flexibility in application-specific designs through a modular system of approximately 4,000 standard filter elements, as well as custom material combinations tailored to customer needs. Classic protective filters and police filters are made using robust wire mesh bellows with fineness levels ranging from 10 to 650 µm. High-performance suction filter elements utilise state-of-the-art synthetic filter media, ensuring long-term stability with filtration capabilities ranging from 10 µm nominal to 40 µm absolute.

The largest category is return line filtration, where specially optimised manufacturing techniques, in addition to traditional glass fibre materials, ensure excellent pulsation stability. The portfolio includes absolute filtration ratings of 3 µm, 5 µm, 10 µm, and 20 µm, which are designed either for flow rate optimisation or an extended service life.

Maximum market advantage thanks to pleat structure

A major concern for OEMs is the unauthorised replacement of components in the aftermarket. Using patented manufacturing processes, RT Filtertechnik creates complex structures – such as the Helios pleat design – from a continuous pleated star structure. These provide reliable protection against imitations. High-precision folding machines also make it possible to enhance the service life of lightweight, flow-optimised materials or manufacture heavier, pulsation-stable filter elements with a significantly reduced pressure drop.

Energy-efficient filtration to minimise differential pressure

Reducing flow resistance in mobile hydraulics is a key factor in lowering fuel costs and CO₂ emissions. RT Filtertechnik uses real-world test field simulations to precisely match the production process and material to the customer’s specific requirements, ensuring the perfect combination. Our energy-efficient materials are available across our entire product range, either as a self-supporting option or as filter elements without support cylinders in our E-Line series.

Filter medium type	Technological features & advantages
Micro glass fibre media	Optimised for flow, this product offers excellent an excellent contamination retention capacity with minimal resistance.
Melt-blown materials	High-tech nonwoven materials with versatile processing capabilities and a differentiated pore structure.
Glass fibre composite media	High-end, wet laid structures designed for extreme mechanical stress.

This advanced filtration technology allows for a significantly higher volume of oil to flow through compared to standard glass fibre systems, while maintaining the same pressure drop. Alternatively, it enables a significant reduction in installation space while maintaining the same differential pressure, without compromising on long-term pulsation resistance during dynamic operation.

Sustainable filtration and pioneering resource expertise

At RT Filtertechnik, true sustainability in fluid technology is based on a fundamental design principle: the main flow direction is from the inside to the outside. While conventional components that are flowed through from the outside to the inside can often be built smaller, internal-to-external filtration offers the unbeatable advantage during element replacement that the oil can drain cleanly without accumulated contamination getting back into the tank or the clean system.

To protect downstream fine filter media, high-efficiency magnetic cores can be installed on the upstream side using a bayonet lock, enabling preliminary separation of ferromagnetic particles as small as < 10 µm. Studies have shown that in systems with transmission or clutch supply, the proportion of metallic contaminants ranges from 25 to 35 percent by weight, placing a significant burden on the fine filter medium.

SFREE filtration – absolute protection against electrostatic dischargees

A major issue in modern hydraulic systems is the use of highly refined, zinc-free and ash-free hydraulic oils. These materials have excellent durability, but their manufacturing process results in extremely low electrical conductivity. When oil flows through conventional filter media, a significant electrostatic charge builds up between the oil and the fibre structure due to triboelectric effects. If the voltage becomes too high, it can cause sudden, uncontrolled discharges within the system.

The consequences are devastating for the operator:

Material destruction: Sparks burn holes in the filter layers, causing the cleanliness class to collapse.
Electronic damage: Any electromagnetic waves emitted can interfere with or damage sensitive measuring sensors.
System wear: Accelerated oil degradation leads to dangerous oil sludge buildup in valve seats and crevices.
Safety risk: In the worst-case scenario, there is a risk of combustion and explosions in the tank.

RT Filtertechnik solves this problem with the innovative filtration technology in their Stat-Free (SFREE) filter elements. In this process, the media used are electrically tuned to each other with such precision that they exhibit minimal potential differences among themselves. Very few charge carriers are released, which completely prevents discharges in both the element and the system. SFREE technology is available for all filtration ratings ranging from 3 µm to 20 µm, including combined 2-stage filter elements, ensuring the maximum service life for your electronic and hydraulic components.