Proportional Solenoid Valves: Types, Uses, Features and Benefits

27 Dec.,2022

 

Proportional Solenoid Valves

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Introduction

This article takes an in depth look at proportional solenoid valves.

You will learn more about topics such as:

  • What is a Proportional Solenoid Valve
  • Uses for a Proportional Solenoid Valves
  • How Proportional Solenoid Valves are Made
  • Types of Proportional Solenoid Valves
  • And much more…

Chapter One – What is a Proportional Solenoid Valve?

A proportional solenoid valve is a mechanism for controlling fluid flow through the use of a restrictor. In many applications, the flow rate regulation affects process systems regarding level, pressure, temperature, weight, thickness, humidity, density, color, and viscosity. The actuator for a proportional solenoid valve is its solenoid that is used for variable valve positioning.

A traditional solenoid valve is a two way valve that can be open or closed. A proportional solenoid valve provides the same functions as a traditional solenoid but with greater control over the positioning of the plunger and spool. They have a wide range of positions to meet the needs of any flow control application.


To regulate flow rate, proportional solenoid valves vary the position of the valve plunger. The positioning of the plunger is controlled by a magnetic field that is created by power supplied to the solenoid coil using the input it receives from the driver. The two positions of a proportional solenoid valve are open and closed, both of which are held in position without a source of power.

Chapter Two – Uses for Proportional Solenoid Valves

The unique nature of proportional solenoid valves allows them to be activated remotely to control the flow of air, gas, or fluids. A common use for proportional solenoid valves is to control fluid flow in engines and hydraulically operated machinery. Their more specialized functions include controlling the flow of power and compressed air in marine applications, construction, food processing, woodworking, material handling, and metalworking industries.

The defining factors for proportional solenoid valves are their linearity, frequency response, and hysteresis, how much the valve lags. These three factors determine how accurately the valve will control flow.

Proportional Solenoid Valves Uses

Solenoid Valves in Irrigation

The purpose of a proportional solenoid valve in irrigation is to control water flow and automatically operate sprinkling systems. Initially, the valve is adjusted in accordance with how much it will open and close. Once set, proportional solenoid valves operate automatically if the upstream pressure is greater than the downstream pressure.

They can be set to be open or closed before being actuated.


Valves and Coolant

A coolant proportional solenoid valve controls the flow of antifreeze and cleaning solutions in a coolant system. They have an adjustment screw or knob used to set how much the valve will open when actuated. When installed, all coolant proportional solenoid valves remain closed until actuated.

An electronically activated coolant proportional solenoid valve changes the directional flow of coolant, adjusts the flow rate, and proportionally distributes coolant volume.


Braking Systems

Brake proportional solenoid valves limit the pressure that reaches the rear brakes to prevent rear wheel lock up. The control of the valve allows a vehicle to stop safely and smoothly. The rear brakes of a vehicle require less pressure than front brakes and are the reason for using proportional solenoid valves.

The types of brake proportional solenoid valves vary according to the type of braking system and are normally custom designed to fit the system.


Applications in Medicine

Proportional solenoid valves are widely used in the medical field to control the flow of liquids. Medical applications require precise control and exceptional accuracy. For these reasons, proportional solenoid valves are used since they are known for their excellent control and safety.

The use of proportional solenoid valves in medicine includes providing doses and controlling the release of liquids.


Hydraulic Equipment

There are several different types of proportional solenoid valves for use with hydraulic equipment, including flow, directional, and pressure relief valves. The reason proportional solenoid valves are used with hydraulics is their many positions. They can hold any position along with the proportional solenoid rated stroke. Proportional solenoid valves have a more sophisticated design than a traditional on and off solenoid.

In a hydraulic system, proportional solenoid valves are part of a closed loop system requiring precision and accurate control. Common types of proportional solenoid valves for hydraulics are bolt, screw, and three pin. Regardless of the type, they control the flow, pressure, and direction of the hydraulic media.


Solenoid Valves in a Furnace

The gas supply to a furnace must be precisely controlled to avoid overheating the furnace and maintain a controlled temperature in a residence or business. Proportional solenoid valves regulate the gas supply to ensure proper temperature control. A differential temperature signal gives feedback regarding the gas flow when the desired temperature is reached. The proportional solenoid valve shuts off gas flow at that time.


Ventilation Machine

The purpose of a ventilation machine is to send and receive respiratory air for the lungs. They are used when a patient is unable, incapable, or having problems breathing during treatment or due to an injury. The air must be transferred to the patient at the correct pressure, flow, and oxygen ratio. Precision flow control is exceptionally important for the life of the patient.

Using precision calculations, proportional solenoid valves are designed and engineered with the correct voltage to provide the type of control a ventilation machine requires.


Leak Detection

Leak detection is a necessity in a wide range of applications. From water to gas usage, leaks can cause major problems and be dangerous. Proportional solenoid valves are designed to apply increasing pressure at a defined profile to test a system. In some configurations, the proportional solenoid valve is attached directly to the control panel and turns off the supply when a leak is detected.


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Chapter Three – Types of Proportional Solenoid Valves

The position of a proportional solenoid valve is adjusted according to the voltage that crosses the coil. The higher the voltage, the greater will be the magnetic current and the more the valve spindle moves. The difference between a proportional solenoid and a regular solenoid is the ability to control the position of the spool using a regulating magnet.

When a proportional solenoid valve is used in a system, it is referred to as proportional technology. They are designed to regulate load build up in modern fluid technology systems. Their varying positions soften the change in forces directed against the actuator.

Proportional Solenoid Valves Types

3-Way Reducing Valve

The 3-way proportional pressure reducing valve is used for pressure control by converting a single input into a proportional pressure signal. It is connected with a subplate and has exceptional precision and sensitivity. As the flow demands vary, the opening of the valve will change to maintain proper circuit pressure. They are designed to vent a load when there is a pressure spike.

There are many applications that use a 3-way proportional solenoid reducing pressure valve, which includes hydraulics, turbochargers, transmissions, oil pumps, and brake systems.


Canister Proportional Solenoid Valve

A canister proportional solenoid valve is used to control the purge or flow of vapors from the canister to the engine manifold. The proportional solenoid valve provides precision control of fluid flow and simplifies the operation of the system. It can be used for canister diaphragm flow control and vacuum regulation, providing a multifunctional unit for improved performance and cost savings.


Directional Control

Proportional directional control valves are mainly used in hydraulic systems. They can be direct or pilot operated and can operate in a closed loop application. Directional proportional solenoid control valves direct the flow of fluids to an available cylinder. They are the solution to the problem of opening multiple valves with multiple solenoids. Since they have an infinite number of positions, they can easily adjust to differences in flow volume.


Flow Control

Proportional solenoid flow control valves control the flow rate by varying the position of the valve plunger. It is a method for controlling pressure, level, and temperature. The plunger on a proportional solenoid flow control valve is changed by the power sent to the solenoid coil, which changes the stroke positions. The power for the valve is controlled by a pulse width modulator (PWM).


Pressure Reducing

A proportional solenoid pressure reducing valve keeps pressure constant and regulated on the secondary side of a system regardless of the pressure fluctuations on the primary side. They eliminate the need for an additional pressure relief valve. They reduce pressure in relation to the solenoid current and work independently of the inlet pressure. When inactive, they leave the connection to the tank fully open with a minimum of pressure.


Pressure Relief

Pressure relief proportional solenoid valves are a remote method for increasing or decreasing pressure. They are used to limit the amount of pressure in a system using electronically transmitted signals. Proportional solenoid pressure relief valves are designed to operate at various pressure ranges to increase controllability. They can be used for PTO, transmission, pressure, and hydraulic control.


Chapter Four – How Proportional Solenoid Valves Are Made

A proportional solenoid valve aims to control variations in flow and pressure in accordance with electrical input. They are found in places where the pressure and flow continuously change and replace fixed flow or pressure valves. A proportional solenoid valve increases the accuracy and efficiency of a system and reduces the number of components.

A common place where proportional solenoid valves are found is in conditions where precision control is required for acceleration and deceleration. They can reduce flow variations that cause changes in inlet and outlet pressure.

Making Proportional Solenoid Valves

Proportional Solenoid Valve Spool

A proportional solenoid valve spool has "V" notches to provide control over fluid flow, the actuator’s speed, and the fluid’s direction. This allows a single valve to control direction and actuator speed. The fact that the spool does not shift completely at one time is what makes a proportional solenoid valve unique.


Driver Card

A proportional solenoid valve receives its instructions from a programmable logic controller (PLC) or a computer. The driver card is a pulse width modulator (PWM) that can control other devices. The input from the PLC sends current to the valve’s solenoid. The spool shifts due to the electromechanical force. The driver uses a comparator with hysteresis to pulse a switch, which results in a constant amplitude PWM current signal.


Solenoid Coil

The solenoid coil is the central part of a proportional solenoid valve. It is made up of a coil, tube, and armature. Copper wire is used to make a solenoid coil and is divided into Classes F, H, and N. Each of the three classes can withstand varying temperatures from 155°C up to 200°C. When the proportional solenoid valve is electrified, the solenoid coil creates a magnetic field that forces the plunger to move proportionally.


Plunger

The plunger is the part of the proportional solenoid valve that is connected to the device being controlled and opens or closes a valve. Plungers can take various shapes, including square or rectangular bars and round piston like. When the proportional solenoid valve is electromagnetically activated, the plunger is positioned by the directions from the PLC and moves proportionally to actuate the valve.


Feedback Transducer

When the spool shifts, its motion is measured by a position feedback transducer. The purpose of the feedback transducer is to check the position of the spool. Its data is sent to the driver card. The signal the driver card receives will be compared to the input from the PLC. If the two sets of data do not match, the driver will reset the position of the spool until its signal matches the input data.


Chapter Five – How a Proportional Solenoid Valve Works

The typical solenoid valve has the simple function of opening or closing a valve or activating a switch. They are electromagnetically driven and have little controllability. A proportional solenoid valve has controllability and can regulate and monitor the positioning of a valve. They monitor load build up to reduce the load on mechanical components.

The operations of a proportional solenoid valve can be performed by a servo motor, which is more expensive than a proportional solenoid valve. Since a PLC or computer can easily control proportional solenoid valves, they are a less expensive method for process control.

Operation of a Proportional Solenoid Valve

The foundational principle upon which a proportional solenoid valve operates is that it is possible to control the positioning of a solenoid plunger by varying the DC current. In order to control the static friction of the plunger, the inlet signal is transformed into a PWM signal using controlling electronics.

A PMW is a method for controlling the power supplied to electrical instruments and devices. The voltage to the plunger is rapidly turned on and off, which puts the plunger into a fast weak amplitude oscillation. The oscillation puts the plunger in a balanced condition to ensure constant sliding friction.

The operation of a proportional solenoid valve is similar to that of a normal on and off solenoid. When the solenoid coil is electrified, it produces an electromagnetic field that moves the armature of the coil. In the case of a proportional solenoid valve, voltage enters at both ends of the solenoid coil, which drives it to open. Eventually, the electromagnetic field and the spring force balance on the spool, causing the position of the valve to remain unchanged.

When the input from the control source changes, a change occurs in the valve opening to meet the demands of the required parameters.

The system of a proportional solenoid valve has these functions.

  • Temperature control: a current change occurs when the solenoid valve is heated.
  • Start time control: a start time switch provides control to prevent damage to an operation during start up.
  • Signal control: if the input signal is less than the predetermined value, the valve closes.
  • Extremes control: the values of the coil can be set for an operation’s extremes.
  • Remote control: the remote control function is one of the major advantages of a proportional solenoid valve.
  • Parameter control: the parameters for the proportional solenoid valve can be set on a PLC or computer.
  • Safety: if the power to the application is cut off, the valve closes.

A process control system is expensive and has a high failure rate. A proportional solenoid control valve, combined with an intelligent controller and sensors, provides precision control that costs far less than traditional methods.

The main benefit of proportional solenoid valves is providing users with exceptional control over flow rates with heightened precision and accuracy for a wide variety of machine cycles at variable speeds with greater safety. The use of a proportional solenoid valve is dependent on pressure variations, back pressure range, the type of fluid to be controlled, the temperature range of the process, and the ambient temperature.

Conclusion

  • A proportional solenoid valve is a method for controlling fluid flow through the use of a restrictor. In certain operations, the regulation of the flow rate affects process systems in regard to level, pressure, temperature, weight, thickness, humidity, density, color, and viscosity.
  • To regulate flow rate, proportional solenoid valves vary the position of the valve plunger. The positioning of the plunger is controlled by a magnetic field that is created by power supplied to the solenoid coil.
  • A common use for proportional solenoid valves is to control fluid flow in engines and hydraulically operated machinery. In more specialized functions, they control the flow of power and compressed air in the marine, construction, food processing, woodworking, material handling and metalworking industries.
  • The position of a proportional solenoid valve is adjusted according to the voltage that crosses the coil. The higher the voltage, the greater will be the magnetic current and the more the valve spindle moves.
  • A proportional solenoid valve has controllability and has the ability to regulate and monitor the positioning of a valve.

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