Why Tank Optimisation?

Global pressure and small tanks

Environmental pollution and climate change continue steadily. In response to these dramatic developments, laws have been passed to reduce pollution, such as the Euro standards for exhaust emission. Complying with these pollution limits calls for additional measures, such as installing extra exhaust treatment systems next to the combustion engine. This takes up a lot of space inside the machine, however. In addition, global pressure and the demand for higher energy efficiency rise. This finally results in the hydraulic tanks being given increasingly complex and smaller shapes. These designs significantly limit the amount of air separation that can take place inside the tank, so more free air circulates inside the hydraulic system.

Problems with air in oil

Free air in hydraulic systems still represents a major technical challenge today. As long as the air is dissolved in the oil, it does not change its technical characteristics. Undissolved air, however, i.e. air bubbles, causes the following:

  • Signs of corrosion on pumps and controls,
  • Efficiency loss of pumps and hydraulic motors
  • Increased compressibility and thus possible stuttering movements of the output element,
  • Accelerated oil aging, varnish
  • Noise
  • Component damage (e.g. cavitation)
  • Escaping oil, foam development in the tank
  • Temperature increase
  • Dynamic operation problem
  • Micro-diesel effect
  • Reduced filter capacity
  • Changes to the viscosity

An optimisation of the tank system with improved air separation is essential in order to counteract the problems with air in oil and to remain globally competitive.


HYDAC sees the opportunity of optimisation and reducing the tank in every existing tank system.


The reduction in tank volume not only saves material and oil costs, it also brings the customer additional space on his machine and protects the environment.

HYDAC Tank Optimisation Platform

HYDAC offers its customers a comprehensive platform about the topic of tank optimisation. Our priority target is to provide the customer an optimised filter-tank solution. Two carrying pillars support this target. On the one hand there is technical consulting and engineering with simulations, laboratory and field tests and individual consultation, on the other hand there is our Air-X technology. It encompasses our Air-X filters, our special Air-X elements and complete Plug & Play filter-tank-solutions. 

Consulting and Engineering


We offer different computer-aided simulations for system optimisation. These include simulations of:

  • Flow
  • Deaeration
  • Sloshing

Laboratory and Field Tests

In addition to simulation, we also perform experimental investigations of tank systems in the laboratory or directly on the machine. 

Therefore, a unique air content sensor for quantitative characterisation, validation and optimisation of the tank system is available.

Individual Consultation

In our development center, the HYDAC FluidCareCenter®, we combine filter competence and application knowledge with many years of experience in the field of "air in oil" to provide competent and individual advice regarding tank optimisation.

Air-X Technology

Maximum air separation and thus optimisation of the tank can only be achieved by a combination of an optimised filter and tank. HYDAC has developed a new filter series for this purpose. These special filters offer the best way to protect the system from air and the resulting consequences. 


The innovative filters provide the following features for optimum air separation:


  • Low outlet velocity
  • Minimised turbulences in the tank
  • Smooth oil blending in the tank
  • When flowing from below, outlet above the oil level is possible
  • Coalescence of air bubbles at the integrated deaeration windows and thus faster air separation


  • Reduction of oil volume,
    therefore, cost savings for end user and environmental protection
  • Reduction of tank size, 
    therefore, cost savings for OEM (material) and additional design space
  • Lower complexity,
    therefore, minimal effort with fittings, piping and connections and cost savings for OEM (material, assembly)

The following video shows the comparison of a tank with a conventional return line filter (right) against a smaller tank with optimised filter concept (left). The flow rate fluctuates. It can be clearly seen that the oil in the conventional tank is sloshing around. In the optimised tank the oil level is smooth in spite of a smaller tank.

We provide you:

  • Many years of project experience and know how
  • Extensive system optimisation tools like simulation and testing
  • Application-oriented filter solutions
  • Comprehensive optimisation of filter-tank system



Your benefits at a glance:


  • Professional support during tank system selection
  • Design space optimised tank systems
  • Cost reduction due to lower level of complexity and less material
  • Increase of machine reliablility
  • Environmentally friendly products due to lower oil volume

Application Examples


Filter type RFT
Tank size old 460 Liters
Tank size new 280 Liters
Quantity per year 1,500
Savings per year ~ € 227,000

Fire truck

Filter type RKT
Tank size old 280 Liters
Tank size new 150 Liters
Quantity per year 500
Savings per year ~ € 90,000

Road sweeper

Filter type RFB
Tank size old 150 Liters
Tank size new 80 Liters
Quantity per year 500
Savings per year ~ € 52,000

Wheel loader

Filter type RKB
Tank size old 104 Liters
Tank size new 80 Liters
Quantity per year 5,000
Savings per year ~ € 170,000