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Proportional valve – Precision and versatility in fluid technology
Proportional valves are used to control pressure, flow rate or temperature with a high degree of accuracy. They are deployed in a wide range of applications, from medical technology for ventilators to flame control in metal cutting.
Bürkert offers various electromagnetic and electromotive proportional valves that are known for their reliability.
What is a proportional valve?
Proportional valves can be used to control liquids and gases precisely and continuously. They are also known as control valves or continuous valves. They work in closed control loops and enable the design of compact systems that require little space. This is why they are often used in fluid technology and pneumatics.
Types of proportional valves
There are different types of proportional valves that are suitable for different media and requirements. Here is a selection of possible variants and their characteristics:
The valve opening is actuated directly by the solenoid actuator. These valves react quickly and are suitable for small volume flows.
These use a small, directly controlled pilot valve to control larger forces or currents in the main valve. They are suitable for higher flow rates.
In the idle state, the valve remains closed and no medium flows. This variant is preferentially used in safety-critical applications to prevent unwanted flow or overpressure in the event of a power failure.
In the idle state, the valve is open so that the medium can flow unhindered. This variant is suitable for applications where a constant flow rate is required even without a power supply.
The medium exerts pressure on the valve seat from below and assists with the opening of the valve. This type of flow enables a particularly high setting range and makes the valve less sensitive to higher output pressures.
The medium exerts pressure on the valve seat surface from above. As a result, the operating pressure assists with the safe closing of the valve. This can be an advantage in safety-critical applications. As a rule, the setting range is smaller with this type of flow.
Functionality of proportional valves
A proportional valve reacts quickly and precisely, whilst also offering exceptional repeatability. Unlike traditional shut-off valves, which can only be open or closed, a proportional valve controls the flow value continuously. The seat opening of the valve opens and closes in proportion to the electrical control signal. This means, for example, that when controlling a proportional valve with current, a higher current at the valve inlet leads to a greater volume flow at the valve outlet.
Proportional valves are therefore ideal for applications in which mass or volume flows can change. They can be found in electronic devices as well as in mechanical and plant engineering.
Various actuator types
Electromagnetic
Electromotive
Piezoelectric
Pneumatic
Bürkert provides electromagnetic and electromotive proportional valves for the most compact closed-loop control and fluid technology solutions possible.
Electromagnetic proportional valve
In general, electromagnetic proportional valves are direct-acting plunger valves. The spring force and the magnetic force act against each other here. When the power is off, the spring presses the lifting armature onto the valve seat, keeping the valve closed. When an electric current passes through the coil, it generates magnetism that lifts the lifting armature and opens the valve.
Special design features in proportional valves ensure that a balance of magnetic force to spring force is achieved for each adjustable current. This allows different core positions to be set over the entire current range without having to measure them. The possible current range is set via control electronics and depends, among other things, on the pressure conditions.
What characterises Bürkert’s electromagnetic proportional valves?
✓ Large setting range with flat characteristic curve and high repeat accuracy. ✓ Insensitive to high back pressures. ✓ The seat valves have an integrated seat seal. This means that the valve can also be used for shutting off.
Electromotive proportional valves
Electromotive-controlled proportional valves provide very precise control thanks to integrated stepper motors. These stepper motors generate their force in a linear or rotary motion, which is utilised by a seat valve or disk valve. The valves can remain in a defined position without consuming electricity and are therefore very efficient. In contrast to electromagnetic proportional valves, electromotive proportional valves are also used in open control loops. An integrated position sensor enables precise position control.
What quality features make Bürkert’s electromotive proportional valves unique?
✓ Very fast actuating time compared to electromotive proportional valves from other manufacturers. ✓ Position sensor that enables a targeted approach to certain positions. ✓ Electromotive proportional valves from Bürkert have an integrated positioner. ✓ They are also optionally available with an integrated process controller, which saves space and interfaces.
What is the difference between proportional valves and control valves?
Control valves are designed to keep a set-point value for a measured quantity, such as the volume flow, constant. They operate in a closed control loop, with sensors recording the actual value and comparing it with the set-point value. A controller then adjusts the opening position of the valve to compensate for deviations.
Proportional valves, on the other hand, do not have an integrated controller as standard. However, Bürkert offers external process controllers that can be connected directly to electromagnetic proportional valves. In addition, electromotive proportional valves from Bürkert are also available with an optional integrated process controller.
Proportional valves from Bürkert: solutions that set standards
Bürkert stands for quality and innovation. With decades of experience in fluid technology, we offer a wide range of proportional valves that comply with market-specific standards. Our proportional valves are not only extremely compact and robust, but also very powerful. Visit our eShop and order the right valve for you.
