What Are Proportional Valves Used For?
A proportional valve, also referred to as an electro-proportional valve, produces an output direction, pressure, or flow proportional to an electronic control input. What this means is a setting is entered and the valve keeps the flow at that number. They are used in applications and machines that require precise position, velocity, or force. They are well suited for mobile, medical, and industrial applications. Proportional valves are beneficial for circuits that need to vary either flow or pressure to reduce lunge, fluctuations, and shock. What are proportional valves used for? We will get in-depth on how they operate and what they do here.
Before Proportional Control Valves
Not too long ago, there were only two types of electrically operated valves—solenoid and servo valves. Solenoid valves are also referred to as “bang-bang” solenoids, and they are either actuated or unactuated. They are either ON or OFF. The spool in a standard 2-position, solenoid-operated valve shifts all the way to its new position at high speed. Since they have no intermediate position, they facilitate very little control. This rapid, full shift can cause an actuator to jump or lunge on startup and produce excessive shock when stopping, which may cause machine damage or adversely affect piping, causing leakage.
Servo valves are continuously controlled, high-frequency response devices that receive commands through their electronic control systems. They provide a high degree of control over position, velocity, and acceleration. They can accept and accurately respond to command signals at frequencies exceeding 100 Hz. Their continuous feedback from electronic transducers ensures high accuracy all the time.
Proportional Control Valves
The features and benefits of proportional valves are positioned between those of solenoid and servo valves. A proportional valve is more closely related to a low-cost, low-performance servo valve. Proportional valves are operated by proportional solenoids, but servo valves are operated by servo motors. The main difference between them is proportional control valves only work with electronic controllers. A combination of a proportional valve and an electronic controller can be had for a few hundred dollars, which is more than a lever valve, but it still provides variable flow control. Inexpensive electro-proportional valve and controller systems are not made for high-performance systems. Their coil strength is often lower, and they have higher hysteresis and a lower frequency response. They are also susceptible to performance variances due to changes in inlet pressure and actual pressure drop. All that said, they serve their purpose based on performance, control, and cost. Keep these factors in mind when you are trying to choose a proportional valve for your application.
- Amethyst Jamiro