Pressure valves perform a central control and protection function in hydraulic systems. They regulate the pressure of the hydraulic oil and ensure that machines work reliably, safely and efficiently. This applies to mobile applications such as excavators or stationary industrial systems.

Pressure valves regulate and limit the pressure in a hydraulic system. The specific task depends on the requirements of the respective area of application. The choice of valves is decisive for the stability and durability of a system.

ARGO-HYTOS develops and manufactures a wide range of pressure valves - direct or pilot operated, in poppet or spool design, modular or as a screw-in valve. The range is supplemented by variants with PED certification for applications with pressure reservoirs or pressure accumulators.

In the following, you will find out about the various pressure valves available, how they work and what is important when using them in practice.

What types of pressure valves are there?

Pressure valves can functionally be divided into these three categories:

• Pressure relief valves
• Pressure reducing valves
• Pressure control valves

Each of these types fulfills a specific task in the pressure control of hydraulic systems and must be selected according to the operational requirements.

Pressure relief valves protect hydraulic systems from dangerous overpressure. They react directly to the inlet pressure and open as soon as this exceeds the set target value. The excess hydraulic fluid is drained into the tank via the valve, which immediately reduces the pressure in the system.

In the case of directly controlled versions, the valve is triggered directly via the pressure force on a spring-loaded valve element. Pilot operated versions work with a pilot stage that controls the main stage. This is ideal for higher flow rates or sensitive systems. Due to their design, pressure relief valves deliberately generate a significant pressure drop and are therefore not suitable for pressure control.

Pressure reducing valves reduce a high inlet pressure to a defined, constant level at the outlet. This is particularly necessary if individual consumers in the system require a lower operating pressure than others.

In the case of pressure reducing valves with secondary protection, the inlet is throttled if the pressure in the outlet is exceeded and the return to the tank is opened at the same time. This ensures stable pressure ratio control - regardless of pressure fluctuations in the supply.

Pressure control valves ensure continuous regulation of the pressure within a system or sub-circuit. They react to changing loads and volume flows in order to keep a defined operating pressure constant even under dynamic conditions. This not only stabilizes the process, but also reduces energy consumption, wear and noise levels in the system.

Pressure valve technology from ARGO-HYTOS

The demands placed on modern hydraulic systems are as varied as the applications themselves. Whether in mobile hydraulics, in industrial systems or in safety-critical systems with pressure accumulators: Every application requires precisely coordinated pressure control.

ARGO-HYTOS offers a comprehensive portfolio of pressure valves covering a wide range of designs, control principles and approvals. The combination of many years of development experience and practice-oriented system expertise enables individual solutions with maximum reliability, power density and energy efficiency.

Poppet and spool type design

Pressure valves in poppet design are characterized by excellent tightness and a short response time. The conical valve body closes positively and non-positively on the poppet. This ensures reliable sealing without leakage oil even at high pressure. Pressure valves in poppet design are particularly suitable for safety-critical applications or systems with frequent load changes.

Spool valves offer a softer opening characteristic and are more resistant to contamination. Their uniform control characteristics make them ideal for applications with variable volume flows and stable pressure control with a high flow rate.

Installation and modular designs

Built-in valves - designed as screw-in cartridges - offer a compact solution for confined installation spaces and integrated control blocks. They can be installed directly in customer-specific housings, which saves weight, space and costs.

Modular valves, on the other hand, are mounted on standardized sub-bases (e.g. CETOP) and allow easy expansion or modification of existing systems. They offer maximum flexibility, particularly in mechanical and plant engineering, for example for integrating additional safety functions such as secondary or shock valves.

Direct-acting and pilot-operated versions

Direct operated pressure valves react immediately to changes in pressure. They have a simpler design and offer a fast, direct response. This makes them ideal for applications with low to medium flow rates.

Pilot operated valves are used for higher flow rates or when particularly sensitive pressure control is required. They use a pilot stage to control the main spool. This enables flatter pressure curves and precise pressure control even with fluctuating load behavior.

Proportional pressure valves

Proportional pressure valves enable infinitely variable pressure control via an electrical control signal. This is ideal for applications with changing load situations or automated pressure adjustment. ARGO-HYTOS offers proportionally actuated pressure relief, pressure control and pressure reducing valves in CETOP, modular and screw-in versions. Variants with integrated electronics or spool position sensor are optionally available.

Valves with certification in accordance with the Pressure Equipment Directive 2014/68/EU (PED)

Special safety requirements apply to systems with pressure reservoirs or accumulators. For this area, ARGO-HYTOS offers special pressure valves with PED certification in accordance with Directive 2014/68/EU. These valves, such as the SR1A-B2 or the VPP-R-16, guarantee a defined opening characteristic and prevent impermissible pressure peaks.

The certified variants are available with a fixed or adjustable pressure characteristic and are equipped with a secured adjustment screw for tamper-proof configuration. This makes them an indispensable component in safety-critical hydraulic circuits.

How do pressure valves work?

Pressure valves intervene specifically in the hydraulic circuit to control, limit or keep the pressure constant.

Pressure relief valves work as safety components. They open as soon as the pressure in the system exceeds a preset limit value. The excess hydraulic fluid is drained directly to the tank, reducing the pressure. They are opened either by the pressure force on a valve element or via a pre-controlled pilot stage. The valve automatically returns to the closed position as soon as the pressure falls below the limit value again.

Pressure reducing valves regulate the pressure of downstream components. The inlet pressure is reduced to a lower, constant outlet pressure by a control valve. If the outlet pressure rises, the valve closes partially or completely and opens the relief channel to the tank if required. The special feature is the 3-way function, which both regulates the inlet and discharges excess pressure.

Pressure control valves keep the system pressure at a constant level - regardless of load or volume flow fluctuations. They react continuously to changes and adjust the flow rate so that the set operating pressure is permanently maintained. This ensures stable processes, reduces wear and optimizes energy efficiency.

Why are pressure valves indispensable in many areas?

Pressure relief valves safeguard the operation of hydraulic systems and thus protect machines and people from damage. Pressure relief valves perform a protective function. They prevent overpressure in line systems and cylinders, for example in the event of blocked loads or load peaks in mobile machinery, and protect the components from overload and damage.

They also protect the structure of the system in presses and hoists and prevent process interruptions.

Pressure reducing valves enable the supply of different consumers in a complex hydraulic circuit with an adapted pressure level in each case. In agricultural machinery, for example, steering, lifting gear and auxiliary control units require different pressure ranges. The valve regulates the higher system pressure down to a precise, low level and protects sensitive components such as control valves or sensors from overload.

In machine tools, the pressure reducing valve ensures that clamping systems or coolant circuits are not damaged by excessive pressure.

Pressure control valves stabilize the pressure in dynamic systems - regardless of whether the inlet pressure or the volume flow changes. In municipal commercial vehicles, the valve ensures constant pressure at consumers with changing loads. In industry, it keeps the pressure in production plants at the desired level and ensures consistent quality and process reliability.

Would you like to find out more about ARGO-HYTOS solutions in the field of pressure valves? Then get in touch with our team of experts.