What Is a Proportional Valve?

What Is a Proportional Valve?

The output pressure or flow rate provided by the proportional valve is the same as the input change. For example, if the input is doubled, the output will also be doubled. Proportional valves can be connected to the output, from one being used as input to another. Many are programmable with on-board diagnostics, making them very suitable for Industry 4.0 system design.

They are also called...

The terms I/P and E/P valves are also used. This relates to current, I (4 to 20 mA) or voltage, and E (0 to 5V or 0 to 10V) is used as the input supply for the coil to control the output pressure. They are sometimes called electronic regulators.

How does the proportional valve work?

We may remember an experiment done in school, where an electric current passes through a coil to generate a magnetic field, which in turn attracts (or repels) magnetic materials.

Increasing the current will increase the strength of the magnetic field, and conversely, the attractive (or repulsive) force of the magnetic material will increase. The proportional valve has a geometric shape to ensure a constant magnetic field strength that exceeds the stroke of the magnet at a given current.

At the same time, a spring is introduced to counteract the force of the magnet; when the spring is compressed by the movement of the magnet, the reaction force of the spring increases until it balances with the magnetic force and the movement stops. If the current increases, the magnet (solenoid) will move further against the spring until the forces are balanced again. Considering that the magnet is attached to a spool, the pressure or flow can be controlled according to the ratio of the current applied to the solenoid.

How to choose a proportional valve?

Proportional Valve

Here are some basic parameters to consider:

What is controlled? Pressure, flow or other characteristics?

What flow rate range is required?

What is the operating temperature that the proportional valve may experience?

Are there other environmental considerations, such as wet, dirty or explosive applications?

Is this process static, gradual or dynamic? This determines the response time and hysteresis performance well.

Finally, cost may be a consideration.

Typical application of proportional valve

Proportional valves are particularly suitable for applications where the output pressure or flow needs to be changed, whether in one process or from one process to the next. They are reliable, cost-effective, and provide quick response and consistent control. Proportional valves can help reduce the number of cycles and quickly achieve stable pressure or flow.

Examples of typical applications are:

Bottle filling-the proportional valve maintains a constant pressure in the filling reservoir regardless of the liquid level. The pressure sensor in the reservoir provides feedback to the proportional valve, ensuring that a constant volume of liquid is delivered to the bottle within a given time.

Furnace control-the gas supply is regulated by a proportional valve; when the required temperature is reached, the differential temperature signal is used as feedback to shut off the air flow.

Leak test-proportional valve can apply increasing pressure on a given test piece on a specified profile.

Do I need anything else to make the proportional valve work?

Depending on the type of proportional valve, an electric, or pilot air, supply will be required, with proper control. Air may need to be supplied at a given quality and needs to be properly filtered.

Feedback sensors are necessary for the valve to control any specific process, such as the pressure and temperature mentioned above. The proportional valve will need to be connected to the system, so fittings and tubing are essential.

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