Hydraulic Valves – The Synapses of the Hydraulic System

Hydraulic valves are indispensable components in hydraulic systems that control and regulate the flow and characteristics of hydraulic fluid. They act as the “synapses” of the hydraulic circuit and are crucial for its precise and reliable operation. Without valves, starting, stopping, directional changes as well as pressure or flow control would not be possible.

The two main types of hydraulic valves are:

• Spool valves: Use a control spool that opens or closes connections between channels. Frequently used as directional control valves.
• Poppet valves: Operate with a ball, cone or disc pressed onto a valve seat. They are especially tight and suitable for leak-free shut-off.

• Line-mounted valves: Installed directly in hydraulic lines, usually with threaded connections.
• Subplate-mounted valves (CETOP): With standardized mounting patterns (ISO 4401), space-saving, often solenoid operated.
• Sandwich plate valves: Mounted between base and stack valves, used to control flow.
• Monoblock valves: A cast block with integrated passages, fewer sealing surfaces, but in case of failure the entire block must be replaced.
• Cartridge valves: Screwed directly into manifolds, very space-saving.
• Modular stack valves: Flexible combination of individual valve plates, particularly suitable for mobile applications.

• Control flow direction: Direct fluid to different areas of the system.
• Regulate flow: Define the amount and speed of hydraulic fluid.
• Pressure relief: Prevent overpressure by releasing excess pressure.
• Maintain constant pressure: Ensure system stability regardless of load changes.
• Safety functions: Provide protection in case of failure, e.g. load-holding functions.

CETOP valves are standardized (ISO 4401), which means valves from different manufacturers are usually interchangeable. However, an identical flow schematic is essential. Special designs such as negative overlap or higher pressure resistance must be taken into account when replacing.

Yes, hydraulic valves can often be repaired. Examples include replacing solenoid coils or seals. However, for inexpensive valves, a complete overhaul is often not economically viable.

• Solenoid valves CETOP2, CETOP3, CETOP5
• Flange-mounted valves for hydraulic motors
• Flow control and pressure relief valves
• Proportional valves
• Cartridge valves
• Manual control valves
• Counterbalance valves
• Throttle check valves
• Valve and control manifolds for multiple consumers

Mobile applications place special demands on hydraulic valves: robustness, compact design, energy efficiency, and the ability to handle variable loads and environmental conditions. An example is counterbalance valves, which are used as safety elements to hold loads securely and lower them in a controlled manner.