Hydraulic valves in construction machinery

The efficiency and performance of hydraulic systems in construction machinery depends largely on the valve technology used. Valves regulate and control the fluid flow, thereby ensuring the functionality and controllability of hydraulic circuits. Three valve types that are particularly relevant in this context are in-line valves, cartridge valves and CETOP valves.

In-line valves perform basic control functions directly in the hydraulic pipework system. They are integrated into the pipework and do not require any additional housing or base plates. This not only reduces the space required, but also the number of potential leakage points in the system.

In construction machinery, for example, they are used in the hydraulic control circuits of excavator arms. There they regulate the volume flow or act as lowering brake valves to ensure precise and safe movement of the hydraulic cylinders. The simple installation and robust design of these valves are decisive advantages for use in mobile machines that are exposed to high loads and changing environmental conditions.

Cartridge valves, also known as screw-in valves, are installed directly in valve blocks or housings. Their modular design allows flexible adaptation of the control functions within a compact hydraulic block.

A key advantage of cartridge valves is the ability to realise complex control systems in the smallest of spaces. In modern wheel loaders or mobile cranes, for example, they control the finely tuned interaction of main and auxiliary consumers. Their high tightness and low leakage contribute to energy efficiency, which is particularly important in mobile applications with limited energy sources.

The use of standardised bores means that valves with identical functions can be flexibly replaced or extended without having to replace entire valve blocks. This facilitates maintenance and repair, minimising downtimes of construction machinery.

CETOP valves are characterised by their standardised connection profiles, which make them highly interchangeable and offer a wide range of combinations. They are used in particular for control systems with several actuators and can be expanded into complex hydraulic control systems using intermediate plate valves.

One example of their practical use in construction machinery is the control of attachments on hydraulic excavators. With the help of CETOP directional control valves, the driver can switch flexibly between different tools such as grabs, hammers or buckets without having to carry out mechanical conversion work. The integration of proportional valves within the CETOP standard also enables infinitely variable control of the volume flow, which is crucial for precise machine operation.

Hydraulic valves are categorised into different types depending on their function and intended use:

• Directional valves control the volume flow and regulate the direction of movement of hydraulic cylinders and motors. They are essential for controlling the movement of excavator arms or loading shovels.
• Pressure valves such as pressure limiting or pressure reducing valves ensure a stable operating pressure and prevent damage caused by excess pressure in the hydraulic systems of construction machinery.
• Flow control valves, including throttle and throttle check valves, regulate the volume flow and thus influence the speed of hydraulic movements, for example in telescopic booms.
• Shut-off and shuttle valves prevent unwanted movements and secure hydraulic loads. They are used in load holding systems for cranes and aerial work platforms, for example.
• Overcentre valves are responsible for the safe and controlled lowering movement of loads by preventing uncontrolled sagging, as is required for crane booms or the lifting arms of concrete pumps, for example.

Not all specific valve types are available in every model as an in-line valve, CETOP valve or cartridge valve. While directional control valves are available as both CETOP valves and cartridge valves, they are less commonly used as in-line valves. Pressure valves, on the other hand, are widely used in all three designs, as they can be flexibly adapted to different control concepts and space conditions.

Flow control valves also exist in various designs, particularly as inline and cartridge valves, to enable precise volume flow control in compact systems. Shut-off and shuttle valves are often designed as in-line or cartridge valves, while CETOP valves are used less frequently for these applications. Check valves are predominantly realised as cartridge valves, as this design allows integration into compact valve blocks and offers a high level of functional reliability.

Construction machinery is exposed to extreme environmental and operating conditions, which places special demands on hydraulic valves. These include high pressure and temperature resistance, as machines often work under heavy loads and in different climate zones. The valves must also be highly resistant to vibration and impact, as construction machinery is often used on uneven terrain and in harsh conditions.

Another important criterion is the tightness of the valves, as leaks not only reduce the efficiency of hydraulic systems but also cause environmental damage. Ease of maintenance is also a key factor, as repairs on construction sites often must be carried out quickly and with limited resources.

In addition, the trend towards automation and digitalisation in the construction industry requires hydraulic valves to be compatible with modern control systems. This includes the use of sensor technology and electronic control to enable more precise and energy-efficient control.

Choosing the right valve type is essential for the efficiency and longevity of a hydraulic system. In-line valves offer a space-saving solution for simple control functions, while cartridge valves enable complex control systems thanks to their modular design. CETOP valves, on the other hand, guarantee a high degree of flexibility and easy expandability thanks to their standardisation.

In construction machinery applications, well thought-out valve technology pays off through improved controllability, reduced downtime and an overall increase in operating efficiency. With the right combination of these valve types, hydraulic systems can be optimally customised to the specific requirements of the respective application.