Custom filter solutions for mobile hydraulics
A holistic approach to system analysis, innovative flow optimisation, and the development of cutting-edge filter technology-based systems for mobile machines. As experienced specialists, we develop custom filter solutions that ensure maximum reliability without any compromises, even in highly dynamic load cycles in the field.
In the challenging mobile machine sector, standardised laboratory values often reach their technological limits. Development engineers and designers at OEMs constantly face the challenge that conventional components cannot withstand the extreme real-world conditions on construction sites or in the field. When standardised test methods fail to adequately reflect system performance, customer-specific filter solutions become essential for ensuring long-term system availability. RT-Filtertechnik GmbH combines extensive application expertise with scientifically proven testing methods to ensure highly efficient filtration in real-world operating conditions. Our focus is on optimising all of the machine's functionality, both technically and in economic terms.
System expertise for large-scale mobile production: RT-Filtertechnik as a B2B partner
As an established development partner in the B2B sector, RT-Filtertechnik offers custom systems that are precisely tailored to meet the highly complex requirements of modern mobile hydraulics systems. At our state-of-the-art facilities in Friedrichshafen and Kromsdorf, we combine our extensive expertise in mobile hydraulics and systems to set new standards in technological innovation.
Our engineering approach is distinguished by the fact that we do not merely focus on isolated individual products. Our top priority is always to ensure seamless machine functionality while minimising interfaces as much as possible. By taking a holistic approach to system analysis, we help leading OEMs achieve significant cost reductions while enhancing their competitiveness in the global market. Every mobile application requires unique design approaches – this is where our custom filter solutions come in, seamlessly combining functional excellence with space efficiency.
Dynamic multipass test (HLCT)Reliable filtration in real-world load cycles
Anyone who searches specifically for phrases such as "hydraulic filter testing methods under real conditions in mobile hydraulics" in engineering will find that reliable filtration under real conditions goes far beyond rigid laboratory standards. Standardised testing procedures are commonly used to help consumers compare filter elements more easily, but they only provide limited insight into how these elements perform in real-world applications, such as in excavators, wheel loaders, or other mobile machines. Laboratory standards assume constant conditions. In reality, however, filtration media typically perform significantly better under constant flow rate conditions than they do under dynamic stress.
Why constant test conditions are not realistic
In mobile machines, hydraulic systems are typically filtered in the return line due to the limited space available in the tank. All flows converge at this point, whether they originate from the cylinders of the booms, the excavator buckets, the dozer blades, and other attachments, or from the rotation system and drive system. The continuous valve switching in individual circuits results in varying amounts of oil being pumped back at different times. This means that there is a constant dynamic flow rate at the filter element.
This phenomenon significantly impacts the hydraulic filter's separation efficiency under dynamic flow rate conditions: particles smaller than the actual pores of the filter material typically become trapped within the filter element due to what are known as Van der Waals forces. Under dynamic loads, these forces are often insufficient – the particles become dislodged again and are carried back into the system, resulting in premature wear.
The RT test bench for the Hydraulic Load Cycle Test (HLCT)
The ongoing development of filter technology-based testing methods at RT-Filtertechnik in Kromsdorf led to the groundbreaking HLCT (Hydraulic Load Cycle Test). This unique test bench enables the flexible replication of prevailing load profiles for any type of application. Machine studies have shown that almost all real load profiles can be categorised into four symmetrically distributed main groups:
- Profile B: The positive and negative flow rate ramps have the same rise time.
- Profile C: Shorter rise time of positive flow rate ramp compared to negative flow rate ramp.
- Profile D: Longer rise time of positive flow rate ramp compared to negative flow rate ramp.
- Profile E: Identical rise time of positive and negative flow rate ramps and an especially high repeat rate.
The built-in high-tech test bench operates using a highly efficient two-circuit system. The first circuit is designed for flow rates between 30 and 150 litres per minute, while the second circuit covers flow rates from 120 to 750 litres per minute. This means that it can perform static multipass tests according to ISO 16889 in the range of 30 to 740 l/min as standard. The key advantage for practical use: Both test circuits can be subjected to highly dynamic cycles, allowing for flow rate changes ranging from the minimum to the maximum up to 4 Hz. A dynamic cycle can also be recorded directly from a field test and transferred one-to-one to a test bench control. The evaluation of these challenging results is based on the previously applicable standard for dynamic multipass tests (ISO 23369).
Scientific proof of separation quality
When a filter is exposed to test contamination under these changing real-world conditions, the qualitative differences in filter design become clearly apparent. When evaluating particle size for a defined separation ratio (βx= 200), the following applies: The higher the measured β-value, the worse the actual filtration performance in dynamic operation.
The process for determining this data is precisely defined: In the initial phase, key parameters such as temperature, flow rates, and ramp times are recorded – either provided by the customer or determined through collaborative field tests conducted on the machine. A representative, continuously repeating work cycle is extracted from the recorded load profile and abstracted for test bench programming. The result is custom filter solutions that consistently deliver outstanding performance in demanding real-world applications, without making any compromises.
The direct, cross-manufacturer comparison impressively demonstrates the stability of the RT filter structure under real-world conditions.
Static | Dynamic | |
|---|---|---|
| Competitor (βx(c) = 200) | 8.4 µm | 15.1 µm |
| RT standard (βx(c) = 200) | 7.6 µm | 10.5 µm |
Flow simulation (CFD): Maximum efficiency in tank systems through virtual optimisation
Anyone who specifically searches for terms such as "flow simulation hydraulic tank" or "CFD calculation B2B fluid systems" in engineering will discover an often underestimated potential for optimisation. Historically, hydraulic tanks have often been poorly integrated into the overall system in many mobile machines. In addition to extensive field measurement and testing programmes, RT-Filtertechnik uses state-of-the-art computer-based flow simulations. Every mathematical simulation helps to uncover hidden inefficiencies in the development phase and eliminate them in a targeted manner.
Previous analyses have clearly demonstrated that many conventional tanks contain unused dead spaces where oil does not flow at all. A perfectly optimised tank filter system can reduce the required tank volume by up to 30%. For the end user, this means a significant reduction in installation space and weight, as well as tangible cost savings: Customers can save up to 10% on oil consumption while maintaining consistent system performance. We are happy to support our customers during the early project planning phase so that we can integrate perfectly tailored, customer-specific filter solutions directly into the system architecture.
The four pillars of RT simulation expertise
Basic CFD (Computational Fluid Dynamics) calculation
This method is used to accurately depict the overall flow profile within the tank. It reveals unused areas (dead spaces) and provides the geometric foundation for flow optimisation and a smoother return flow.
Bubble simulation
Air in hydraulic oil is one of the main causes of cavitation and control problems. The bubble simulation visualises the exact behaviour and movement of individual air bubbles within the oil flow. Validations conducted at our in-house testing facility confirm that the simulation aligns very closely with real-world physical measurements.
Multi-phase simulations
This advanced method visualises the actual movement of oil in the tank during dynamic operating cycles. It clearly demonstrates just how much the medium agitates the surface as it flows back into the tank. The more violently the oil churns at the surface, the greater the critical internal air intake into the fluid system. In addition, the virtual model can simulate whether oil can escape through the breather filter during extreme driving conditions, such as an abrupt braking manoeuvre in the mobile machine. Based on these findings, effective countermeasures are developed and implemented immediately, such as the precise installation of a baffle inside the tank.
Each simulation concludes with a detailed analysis of the results and well-founded, constructive recommendations for improving the tank system's design. This is how virtual data can be transformed into a real, measurable competitive advantage for challenging B2B applications.
Application-oriented development of filter technology: realistic field tests for tailor-made fluid systems
Anyone searching for terms like "application-specific filter development in mobile hydraulics" in engineering will quickly realise that sustainable filtration can only be optimised using real data obtained directly from the machine. For RT-Filtertechnik, this means that we validate highly efficient, custom filter solutions directly in the field. We support and guide our clients through their specific projects by conducting tailor-made field tests and comprehensive measurement and testing programmes. Long-term projects carried out collaboratively ensure an optimal maintenance strategy and maximise system availability.
The four focus areas of mobile system analysis As part of its intensive development support, RT-Filtertechnik focuses on four key technological areas:
Analysis and commissioning measurements
Sampling or measuring points are installed directly on mobile machines at strategically selected locations. High-precision measurement sensors capture a wide range of specific performance data in real-world operations.
Definition and measurement of flow rate profiles
The flow rate profile is precisely recorded and analysed during various operating cycles. This precise measurement provides an essential physical data foundation for the application-oriented development of filter technology and subsequent programming in HLCT testing.
Investigation of issues such as "air in oil"
Trapped air in a fluid system can significantly impair its functionality and separation efficiency. Targeted analyses are conducted directly on the machine to study air separation behaviour, effectively preventing cavitation and system malfunctions.
Oil tests for conductivity
A safety factor in the system that is often underestimated. Insufficient oil conductivity poses a risk of electrostatic discharge, which can damage the filter medium or sensitive electronic components.
Field validation – Mobile measurement technology in harsh real-world conditions
Theoretical expertise is reinforced by practical, measurement-based setups right on the vehicle, providing valid data for design purposes:
- Online oil quality measurements on wheel loaders: A FCU 8210 type particle counter is installed directly on a wheel loader to continuously monitor particle concentration. This online particle measurement enables continuous monitoring of the cleanliness class throughout the entire actual work cycle.
- Visual and sensor-based analysis of "air in oil": To understand the exact separation behavior of air bubbles in a construction machine, RT-Filtertechnik relies on the temporary installation of a special acrylic glass tube, combined with advanced measurement technology, among other methods. This makes the physical effects in the return flow directly visible and precisely measurable.
- Conductivity measurement to prevent electrostatic discharge: Field measurements are conducted directly on the system using a portable conductivity meter. This is essential because low oil conductivities of less than 500 pS/m have been shown to cause electrostatic discharges in hydraulic systems.
Through this in-depth, collaborative support and the direct integration of real-world field data with cutting-edge testing methods, we create sustainable, optimised, and custom filter solutions that are perfectly tailored to each B2B application.
