What is a Solenoid Valve?
Solenoid valves are electrically controlled valves consisting of a solenoid and a valve body. They work by the rotary or linear action of a mechanical plunger when an electrical signal is applied to the solenoid.
Solenoid valves are used in a wide variety of products from fighter jets to washing machines to autonomously control the flow of fluid in a system.
In solenoid valves, mechanical valves work in conjunction with a solenoid. Therefore to understand the working of Solenoid valves, firstly we need to understand what is a solenoid and mechanical valve?
What is a Solenoid and How does it Work?
A solenoid consists of an electric coil and a movable ferromagnetic plunger. When an electric current passes through the coil, a magnetic field is created. This generated magnetic field exerts force and moves the plunger. When the electrical circuit is closed. Spring pushes the plunger to its initial position.
What is a Valve?
Valves are mechanical devices used to regulate the flow and pressure of a fluid. Various types of valves are used in the piping system to control the flow. Click this Link!! to know the various types of valves.
Types of Solenoid Valve
According to, How does a solenoid valve work? they can be classified into three types.
- Normally Open Solenoid Valves.
- Normally Closed solenoid valves.
- Bi Stable Solenoid Valve.
Normally Open Solenoid Valves
Normally open valves are designed in such a way that the flow of liquid or gases occurs when valves are not energized.
In other words, when the solenoid is energized. Plunger blocks the path of the flow of liquid. Normally open valves have applications where most of the time flow of fluid is open.
Normally Closed Solenoid Valve
Normally closed valves are designed in such a way that the flow of liquid or gases is restricted when valves are not energized.
In other words, when the solenoid is energized, the plunger opens the path of the flow of liquid. Normally closed valves have applications where most of the time flow of fluid is closed.
Bistable / Latching Solenoid Valves
Latching Solenoid valves stay in their current position until power is applied. Therefore they can be either normally open or normally closed types of valve.
For example, if a Bi-stable solenoid valve is open. When power is applied, it will switch its position and will get closed. As a result, they do not require a continuous power supply.
Types of Solenoid Valves According to their Working Principle
A wide variety of solenoid valves are available depending on their working principle, type of application, type of fluid they can handle, and pressure requirements. Our focus will be on understanding the working of various types of solenoid valves according to their working principle.
- Direct Operating
- In-Direct Operating
- 3 Way Direct Acting
1. Working of Direct Operating Solenoid Valve
Direct operating valves can be a normally closed or normally open type of solenoid valves. They are used for relatively small flow rate applications with no minimum pressure difference requirements. In other words, they can operate without any pressure difference as well.
Direct Operating Normally Closed Solenoid Valve Working Principle
In direct operating normally closed solenoid valves, when the solenoid is not energized, spring pushes the plunger and closes the valve. In this way when electrical current is not passed flow of fluid is restricted.
Whereas when the solenoid is energized, a magnetic field is generated. This magnetic field attracts the plunger and the valve gets opened. In this way when electrical current is passed through the solenoid coil fluid starts flowing through the valve.
Direct Operating Normally Open Solenoid Valve Working Principle
Direct-Operating-normally-open solenoid valves work just the opposite way. In this when the solenoid is not activated spring pushes the plunger upward. That results in the flow of liquid. Whereas when the solenoid is energized, it pushes the plunger in the downward direction. That results in the closing of the valve.
2. Working of Indirect Acting Solenoid Valve
Indirect acting solenoid valves control a larger amount of flow of liquid just by controlling a smaller amount of liquid flow through pilot orifice using solenoid valves.
As shown in the above image, In the valve closed position pilot orifice is closed and the spring pushes the membrane to close the flow.
When the solenoid is energized, the pilot orifice is opened and liquid starts flowing to the outlet. This results in the reduction of pressure on the top of the membrane. Due to the pressure difference, the liquid at the inlet pushed the membrane upward. As a result, the liquid starts following the outlet.
In this way, in indirect acting solenoid valves, even a small solenoid can control a very large amount of liquid flow.
Applications of Solenoid Valves
Solenoid valves are used in products from fighter jets to washing machines to autonomously control the flow of fluid in the system. These fluids can be liquid compounds, water, air, gas, oil, steam, refrigerant, or sculleries. Following are the application examples of Solenoid valves.
- Automatic Washing machines and water filters utilize solenoid valves to control the flow of water.
- Smart irrigation system utilizes solenoid valves to control the flow of water.
- Solenoid valves are used in automated machines where two different liquids have to be mixed.
- They are used in refrigeration and cooling systems to control the flow and direction of refrigerant flow.
- Control the Flow of heated water for space heating.
We will keep adding more information on different types of solenoid valves and how they work. Please add your suggestions, comments, or questions in the comment box.
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