One of the devices that is widely used today in industry and in the installation sector is the solenoid valve.
The solenoid valve or solenoid valve is an electromechanically controlled valve.
The valve consists of an electric coil with a ferromagnetic core inside which it is removable, and in fact the assembly acts as a solenoid or coil.
The core of this coil is called a piston. In the rest position, this piston closes a small hole.
By applying an electric current to the solenoid, this current creates a magnetic field that forces the piston into the solenoid and displaces it.
In this way, the duct opens or closes as the nucleus moves.
In fact, a hydraulic solenoid valve is a valve that operates by applying an electric force and cuts off or adjusts the amount of fluid flow in a hydraulic system.
A hydraulic solenoid valve consists of a solenoid valve that is connected to a solenoid mechanism that is capable of shutting off or controlling the flow of fluid.
This change is based on a command received from the control system.
In two-way valves, the fluid at the outlet is disconnected or connected. (Valve is full closed or full open).
In three-way valves, the inlet fluid is directed to one of the two outlet paths.
Solenoids have advantages such as speed of work, high reliability, fast and reliable disconnection, long service life, integrated design, and low power consumption.
A solenoid valve is composed of two main parts of the body (valve (main valve)) and solenoid (coil).
Solenoid components though
These valves consist of two parts, the solenoid and the body (valve).
The solenoid part itself includes the coil, iron rod, spring, control valve and control cable.
The main valve also consists of inlet, outlet, flow blocking part and diaphragm and spring.
When the solenoid is active, a very weak current of fluid always passes through the duct and the control valve.
Solenoid valves are made of rubber or metal seals for sealing different places.
In valves that use a diaphragm, a spring is used to keep the diaphragm open when the valve is inactive.
Assume a simple design of the solenoid valve in the inactive state and closed path and the fluid used is water.
Water flows from the inlet of the valve and fills the top and bottom of the holes in the diaphragm, creating a constant pressure and the diaphragm does not move and the valve remains closed.
But when the current in the solenoid is established, the magnetic force of the solenoid is pulled upwards and the control valve opens.
By opening this part of the valve, the pressure balance is lost and it pushes the diaphragm upwards and the valve opens.
Always a very small current passes through the control part of the valve, which constantly upsets this balance and the valve remains open.
When the solenoid is deactivated again, the control part closes again, the upper and lower part of the diaphragm reaches the pressure balance again and closes the valve (figure below).
Application of these valves in high-powered wind and hydraulic systems, industrial and automatic sprinkler systems, household machines such as dishwashers and washing machines, oil, gas and petrochemical industries, refrigeration and air conditioning systems, etc.
Functional solenoid valve though
The solenoid is used to open, close and control the flow of liquid or gas through the tube.
How these valves work is quite understandable through their circuit.
A 2/2 valve has two valves (inlet and outlet) and two positions.
These valves can be Normally open or Normally close.
In the Normally open type, when no current is flowing in the coils (de-energized state), even if it is open, the fluid can pass through the valve;
But in the Normally close type, when a current does not pass through the coils, even if it is closed, it prevents the fluid from passing through the valve.
A 2/3 valve has 3 ducts and 2 positions and can disconnect and connect two circuits.
In the figure below, you can see how the circuit of this valve works. The arrows in the figures indicate the direction of flow between the ducts.
Solenoid valves have a variety of functions:
- Direct performance
- Indirect performance
- Semi-direct function
Valve solenoid with direct function
These types of solenoid valves have the simplest mode of operation.
A small spring holds the piston down to close the valve.
The piston is made of ferromagnetic material.
An electric coil is placed around the piston.
When the coil is excited by an electric current, a magnetic field is formed which moves the piston upwards, which causes the valve to open and the fluid to flow.
This valve is called a Normally Close valve. Even normally open has the opposite function of what was said;
In this way, when the coil is not stimulated by electric current, the valve is open.
As electricity flows through the coil, the piston moves down and the valve closes.
Operating pressure and flow rate are directly proportional to the valve diameter and solenoid magnetic force.
This method of operation is used for low current values.
Direct-acting solenoid valves have the ability to operate at pressures from zero to maximum pressure.
The following figure shows how a 2/2 valve works with direct operation.
Solenoid though indirect function
In servo valves with indirect operation (servo operated) or (pilot operated), the difference in fluid pressure between the valve ducts is used to open and close.
Usually these types of valves require a minimum pressure difference of 0.5 bar.
The inputs and outputs are separated by a rubber interface called the diaphragm.
This rubber interface has a hole through which fluid can flow to the upper part.
The amount of pressure as well as the spring above the diaphragm ensures that the valve stays closed.
The upper chamber of the diaphragm is connected to the low pressure duct through a small path.
This connection is closed by the valve in the closed state.
The diameter of this pilot cavity is larger than the diameter of the diaphragm cavity.
When the selenoid is stimulated, the pilot cavity opens, causing the diaphragm pressure to drop.
Due to the pressure difference between the two sides of the diaphragm, the diaphragm rises and fluid can flow from the inlet to the outlet.
Indirect valve selenoids can only be used for one direction of flow.
This type of solenoid is used even in applications with sufficient pressure difference and high current intensity; For example in irrigation and car wash systems.
Valve solenoid with semi-direct function
Semi-direct valve valves have the characteristics of the previous two types.
These valves can operate at zero pressure while controlling high current intensity.
This type of valve is somewhat similar in some respects to the indirect valve and has a diaphragm and a small cavity on both sides.
The difference is that the piston is connected directly to the diaphragm.
When the piston moves upwards, move the diaphragm directly to open the valve.
Simultaneously, another hole is opened by the piston, which has a larger diameter than the first hole in the diaphragm.
This will cause a pressure drop in the upper chamber of the diaphragm.
As a result, the diaphragm will move up not only by the piston, but also by the pressure difference.
This combination allows the valve to operate at zero pressure while controlling high current.
Often, the selenoids of semi-straight valves have stronger coils than indirect ones.
These types of valves are also known as assisted-lift valves.
They are divided into different types such as multi-way, type of power consumption (AC and DC) or its status in OFF and حالت mode.
In some solenoid valves, the solenoid commands the valve directly.
Some solenoids themselves are used as an auxiliary and control valve to start a larger valve.
These types of valves are actually a solenoid valve combined with a larger valve and they will be packaged and sold as a single product.
Valve solenoid application
Control of a larger industrial valve
Control of cylinders in high-powered pneumatic and hydraulic systems
Control of cylinders and fluid entering the engine
Industrial and automatic sprinkler systems
Household machines such as dishwashers and washing machines to control the water entering the machine
Oil, gas and petrochemical industries
Refrigeration and air conditioning systems and…
The benefits of a solenoid though
Solenoid valves have many benefits, including the following:
- High speed
- High reliability
- Quick disconnect and reconnect
- Long service
- Integrated design
- Low power consumption
Types of solenoid valves
- Hydraulic solenoid valve
- Pneumatic solenoid valve
Types of hydraulic and pneumatic valves
- Control hydraulic valve
- Pilot distributor hydraulic valve
- Hydraulic pressure control valve
- Proportional balancing pneumatic valve
- Pneumatic modular valve
- Manual pneumatic valve
Application of hydraulic valves
Hydraulic machine production lines
Application of pneumatic valves
Food industry automation
Tile and ceramic industries
To choose the right solenoid valve, you should pay attention to the following factors
Maximum and minimum linear pressure at which the solenoid valve is located
Maximum and minimum pressure difference between solenoid inlet and outlet
Maximum and minimum flow through solenoid valve
Specific gravity, viscosity and type of fluid in terms of corrosion and…
Ambient and fluid temperature
Electrical specifications and power supply of the coil
Explosive or non-explosive solenoid valve environment
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