A hydraulic tank performs key tasks in hydraulic systems. It stores the oil, ensures a stable operating circuit, and supports the functional reliability of the entire system. The design of the tank determines

• how reliably hydraulic systems operate,
• how clean the medium remains.

In the design of modern machines and systems, the tank is not considered in isolation, but as part of an overall system. Factors such as space availability, weight, oil volume, and ease of maintenance play just as important a role as requirements for efficiency and durability. Even small differences in design can have a noticeable impact on system performance.

This means that developers are focusing more closely on the hydraulic tank. It is no longer viewed as a simple container, but rather as a complex component that influences energy consumption, service intervals, and operating costs. The following article shows which design principles, technologies, and details determine this influence.

Injection Molded Tank or Hybrid Tank: Differences in the Manufacturing Concept

In hydraulic systems, tank design is increasingly decisive for efficiency and operational safety. The tank is not only an oil reservoir, but also has a direct effect on flow behavior, air separation, and the cleanliness of the medium. Two design principles have become established for mobile applications:

• the fully injection-molded tank
• the Hybrid Integrated Tank (HIT)

Both are based on high-performance plastics such as polyamide, but differ in terms of manufacturing process, functional integration, and area of application.

Injection-molded tanks are made from glass fiber-reinforced plastic, which is processed into a homogeneous housing in molds. The process delivers high dimensional accuracy and repeatable quality, which is a major advantage, especially in series production with large quantities. At the same time, injection molding allows for very precise integration of various functions such as filter housings, oil baffles, connections, and mounting points.

This design is particularly suitable for compact systems with medium volumes and clearly defined interfaces. Due to the necessary injection molding tools and the associated investment costs, it is particularly economical for larger quantities.

The hybrid tank combines rotational molding technology with injection molded parts. The rotationally molded base body provides high volume capacities and mechanical stability, while strategically placed injection molded modules perform functions such as filter housings, quick-connect fittings, or oil level gauges.

This combination opens up design freedom, as modules can be positioned or added variably without the need for new basic tools. The number of external interfaces is significantly reduced, which minimizes the risk of leaks and simplifies assembly. Thanks to the choice of materials (high-performance plastics), the tank remains dimensionally stable even at temperatures up to 100 °C. This makes it suitable for heavy-duty mobile machines.

This means that two solutions are available to meet different requirements:

• Injection molding for standardized series with high-cost pressure for larger quantities
• Hybrid for larger tank volumes, higher thermal loads, and diverse machine platforms, even for smaller annual quantities.

In both cases, the tank is transformed from a static reservoir into an integral system component that makes a decisive contribution to overall performance.

How does air separation affect the size of the hydraulic tank?

The air content in hydraulic oil has a direct impact on the stability and efficiency of the entire system. Air bubbles alter the compressibility of the medium, lead to pressure fluctuations, and impair the response behavior of pumps and actuators. At the same time, noise levels increase and there is a higher risk of cavitation.

In addition, oxygen ingress, among other things, accelerates the aging of the oil, which shortens its service life and increases operating costs. In classic designs, this problem is mitigated by large tanks. A higher oil volume ensures longer dwell times, allowing air bubbles to rise and escape. However, this method is space- and resource-intensive: large containers mean more installation space, higher weight, greater oil requirements, and ultimately higher costs.

This is where ARGO-HYTOS' AirEX system comes in. A special flow guide in the return filter combines individual air bubbles into larger bubbles, which separate from the oil more quickly. In addition, targeted flow calming reduces turbulence when entering the tank. In practice, this significantly reduces the air content, and degassing is up to 70% faster than with conventional return filters.

As a result, the required tank volume can be reduced by up to 50% without compromising operational safety. This saves oil, weight, and installation space, and creates design freedom for other assemblies. AirEX modules are available in both top-entry and bottom-entry versions and can be integrated into ARGO-HYTOS tank systems.

What role does functional integration play in hydraulic tanks?

The classic tank with separate attachments for filters, filler necks, ventilation, and oil level control is hardly competitive anymore. Modern systems rely on complete functional integration within the tank module. The direct integration of return filters, ventilators, filling strainers, oil drain valves, and suction strainers not only saves space. It also drastically reduces the number of potential leakage points.

For example, the filter system is housed directly in the tank body, eliminating the need for external sealing surfaces. This is complemented by an internal baffle plate that calms oil movements and further promotes degassing. Integrated oil level gauges provide reliable information on the filling status without the need for external sensors. Optionally, electronic or optical contamination indicators can be added for filter monitoring, allowing condition-based maintenance. Optional electronic or optical clogging indicators can be added for filter monitoring, allowing condition-based maintenance.

What are the benefits of Quick-Connect for hose assembly?

When installing hydraulic hose lines, screw connections are still a frequent source of errors – whether due to insufficient tightening torque, tensioning, or leakage after vibration. Quick-connect couplings circumvent this problem with a tool-free, releasable connection technology that is easy to visually inspect. A retaining clip ensures that the connection is locked in place, while at the same time allowing the connection to rotate and facilitating tension-free installation.

The system really comes into its own in confined installation conditions. The connections can be reliably closed even in areas that are difficult to access. The material is robust, temperature-resistant up to +120°C, and suitable for both mineral oil-based and biodegradable hydraulic fluids. Electrically conductive variants are available if required to prevent electrostatic discharge in the system.

How do material selection and temperature behavior affect system performance?

ARGO-HYTOS uses high-performance plastics with high thermal stability for its tanks. Variants such as PA6GF30 offer a wide operating temperature range from -30°C to +100°C, and even up to +120°C for short periods. This property allows operation even under demanding thermal conditions – for example, in mobile machines with high power density and harsh operating conditions.

Compared to metal tanks, the low specific weight of plastics also reduces the system weight. This offers advantages in terms of emissions and payload, especially in mobile applications. Chemical resistance to biodegradable hydraulic oils (HEES, HETG) is also ensured. Complemented by precisely manufactured O-ring seals, the system remains permanently leak-tight even under changing temperatures.

Important system advantages at a glance

 

• Ready-to-install complete modules with integrated functions
• Reduced tank volume thanks to AirEX filter technology with improved air separation
• Minimized risk of leakage due to elimination of external sealing surfaces
• Efficient hose installation thanks to tool-free quick-connect system
• Lower system weight with high thermal load capacity
• Optional functions: clogging indicators for filters, oil drain valves, dipsticks, temperature sensors

 

 

How does the hydraulic tank affect the overall performance of a system?

An efficiently designed tank acts as a system component, not as a passive container. It ensures continuous deaeration of the oil, thereby protecting the pump from cavitation. Thanks to integrated filtration, the oil is cleaned directly as it enters the tank. This extends the service life of downstream filter units.

Flow simulations during tank development ensure optimized inflow and distribution of the oil in the tank and prevent dead zones.

Developing customized tank solutions

growing — and with them the importance of well-designed tanks. If you want to increase performance, ease of maintenance, and system reliability, modular plastic tanks with AirEX and Quick-Connect offer a scalable solution. ARGO-HYTOS has the experience, technology, and system expertise to implement precisely these solutions for your specific project.

If you want to optimize your machine platforms, talk to us. Together, we will develop tanks that are precisely tailored to your hydraulic systems. Get in touch with us now!