Where are proportional valves used?

Proportional valves are commonly used to control pressure to a cylinder or hydraulic motor. They provide infinite spool positioning and thus infinitely adjustable flow volumes. The resulting flow or pressure output is proportional to the input change, i.e. triple the input produces triple the output.

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They are controlled electronically either by sending a voltage (10V to 10V) or current signal (420mA) to the valve depending on model of valve. The electrical signal supplied to the solenoid coils creates a variable force that overcomes a spring force and shifts the main spool enough to allow supply pressure (P) to flow to port A or B.

Example proportional valve

For example, if solenoid B receives a signal, it shifts the main spool to the left, allowing oil to flow to and increase pressure in port A. Radial drillings in the main spool allow some oil to go to the left side of piston sensor 1. Oil in this area and in port A combine to work against the force of solenoid B until equilibrium is reached. If port A increases more than solenoid B’s force, the main spool will shift to the right and allow some of port A’s oil go to the tank.

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Why use a proportional valve?

A proportional valve provides a change in output pressure or flow in the same ratio as the change in the input; for example, if the input doubles then the output will also double.

What are the key features?

Proportional Valves are suited to applications where output pressure will vary - either in steps or continuously. Stepped output pressure means the pressure is held at one value before the pressure is increased to another value. Continuous output pressure is where pressure is continually increased at a set rate.

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Proportional Valves can be interconnected, for example, the output from one being used as an input to another. Many are programmable, with onboard diagnostics, making them highly suited to Industry 4.0 system design.

They are dependable, cost-effective (particularly air-pilot operated), give fast response and consistent control.".

What are the benefits?

Proportional Valves can help reduce cycle times, by quickly achieving a stable pressure. They have a fast, precise response, which will improve efficiency. They also give repeatable control and pressure output, giving an expected response each time.

What are the key considerations for selection?

There are some basic parameters to consider. Firstly, what is being controlled? Pressure, flow or some other characteristic. What input and output pressure range will be required, and at what range of flow rates? What is the likely operating temperature that the Proportional Valve will experience? Are there other environmental considerations, such as a wet and dirty application.

It is important to consider if the process is a static, a step-by-step, or dynamic one. This may very well dictate the response time required and hysteresis performance.

Cost may be a consideration and, as stated, air pilot operated valves are particularly cost-effective.

What are the typical applications?

Proportional Valves are suited to analytical and test instrumentation, process applications such as tensioning, spraying and blow molding. They are also found in medical and foundry applications. However, they can also be used in many other applications. Please contact us with any specific enquiries.

Visit our Proportional Valves section to find out more.

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