Whether in excavators, presses or production lines: Hydraulic drives are part of the foundation of modern machine architecture. Their technical potential to transmit high forces in a targeted manner and convert them into precise movements has made them an indispensable key technology in fluid technology. This article provides you with a technically sound introduction to the world of hydraulics: from physical principles and central fields of application to future-oriented system developments.

The physical basis: How hydraulics transform pressure into movement

Hydraulic drives are based on clear, fundamental physical principles. They use pressurized fluids (usually hydraulic oil) to convert hydraulic energy into mechanical movement. This can be a linear movement in a cylinder or a rotating movement via a hydraulic motor.

The basis are three elementary laws of fluid mechanics:

• Pascal's law
• Bernoulli's equation
• the continuity equation

Pascal's law states that pressure exerted on an enclosed fluid (i.e. a liquid or gas) in a closed system spreads evenly and unchanged in all directions. This means that a change in pressure at one point in the fluid has the same effect immediately and everywhere in the system - regardless of the shape of the container. One example of this is the hydraulic jack: a large load can be moved with little force.

Bernoulli's equation describes the relationship between pressure, velocity and height in a flowing medium. It is based on the principle of conservation of energy: the sum of the static pressure, the dynamic pressure and the hydrostatic pressure along a flow line remains constant. In practice, this means that if a fluid flows faster, the pressure decreases.

The continuity equation describes the principle of mass conservation in a flowing fluid. It states that the volume flow in a closed system remains constant, regardless of changes in the cross-section of the pipe, only the flow velocity changes. This means that the amount of fluid entering a system is equal to the amount leaving the system.

The interaction of these physical principles forms the basis for the function of hydraulic systems.

The main elements of hydraulic drives are the pump, motor and cylinder:

A pump converts mechanical energy into hydraulic energy and pressurizes the fluid. Cylinders and motors convert the energy back into movement in a targeted manner. The resulting work output can be calculated using the following formula:

W = P × Q × η

• W stands for the power of the drive in watts,
• P for the pressure in the system in Pascal,
• Q for the volume flow in cubic meters per second and
• η for the overall efficiency of the drive

This equation can be applied for everyday use:

(l/min × bar) / 600 = kW

Hydraulic drives are characterized by

• high power density
• stepless controllability
• remarkable robustness
• comparatively simple design

What are the advantages of hydraulic drive technology?

One of the key advantages of hydraulic drive technology is its exceptionally high energy density. Compared to electric or pneumatic systems, hydraulic power units enable the implementation of large forces with comparatively small sizes.

Hydraulic drives also impress with their infinitely variable controllability. Both pressure and volume flow can be precisely and dynamically adapted to changing load requirements. This means that hydraulic drives are not only powerful, but can also be controlled sensitively.

The components used - pump, valves, cylinders and motors - are technically mature, modular and designed for harsh environmental conditions. Their robust design makes them resistant to thermal, mechanical and chemical loads.

Added to this is the inherent energy efficiency of the system. Losses can be minimized thanks to the ability to provide power as required and to buffer load peaks in a targeted manner. At the same time, the simple and service-friendly design reduces maintenance costs. This combination of power, control, durability and efficiency gives hydraulic drives their outstanding position in industrial practice.

What are typical areas of application for hydraulic drives?

Wherever high forces are required in a confined space, hydraulic drives are in play. Their versatility, coupled with their power density, makes them the first choice in numerous industries.

Whether on construction sites, in agricultural machinery or in automated production lines: Hydraulic systems show their strength where mechanical solutions reach their limits. In mobile machinery, they control lifting, turning and swivel movements. They make it possible to move loads weighing several tons - precisely and in a controlled manner, even with sensitive operation.

Hydraulic drives are also used across the board in industry - especially where high process forces, precise motion sequences or repeatable positioning are required. In pressing plants, they ensure uniform force transmission, in plastic injection molding systems for millimeter-precise control, in machine tools for fast and precise axis adjustment.

Thanks to their compact design, hydraulic actuators can also be used where space is limited. At the same time, the closed circuit reduces the risk of leaks and minimizes maintenance costs. The combination of power, precision, efficiency and durability makes hydraulic systems a mainstay of modern machine concepts. This applies not only today, but also with a view to future requirements.

Technology with vision: What do modern hydraulic drives have to achieve?

Hydraulic drive technology is constantly evolving. New requirements for efficiency, connectivity and environmental compatibility are constantly driving development forward. Speed-controlled drives are a key topic here. They make it possible to regulate the flow rate according to demand. The system only supplies as much energy as is actually needed. This reduces energy consumption, protects the components and improves the eco-balance of the overall machine.

With increasing digitalization, standardized interfaces are coming to the fore. Modern hydraulic drives can now be easily integrated into complex automation architectures. IoT-enabled sensors, control units and cloud platforms are used to permanently monitor the condition of the system. Predictive maintenance replaces traditional maintenance and prevents unplanned downtime. Industry 4.0 has long since arrived in hydraulics and ensures greater transparency, availability and efficiency.

At the same time, the design of drive units is changing. Electrified and hybrid systems are increasingly being used - especially in mobile machines. Lighter components, compact designs and modular concepts offer new degrees of freedom in design.

Sustainability is increasingly becoming an integral part of development. Efficient use of resources, reduced emissions and long product life cycles are no longer a side effect, but a technological objective. Anyone developing hydraulic drives today must not only guarantee performance, but also take responsibility.

Hydraulic drives from ARGO-HYTOS: Get advice now

ARGO-HYTOS offers you sustainable, economical and convincingly powerful solutions in the field of hydraulic drives. Our teams of experts support you in the selection, design and integration of your systems - regardless of whether you are modernizing existing systems or developing new machines.

Visit our contact page and let our experts advise you without obligation. Together, we can create efficient, robust and innovative hydraulic drive solutions that meet your requirements.