In addition, viscous media can not be applied, and the applicable viscosity range of specific products is relatively narrow
.
All of these need to solve the problem of leakage of long-term action stem dynamic seal; only the electromagnetic valve is completed by the electromagnetic force acting on the iron core sealed in the magnetic insulating sleeve, there is no dynamic seal, so the leakage is easy to be blocked
.
At this time, the main valve is closed under the action of spring return and pressure, and the medium is cut off
.
Electric valve torque control is not easy, easy to produce internal leakage, or even pull off the head of the valve stem; the structure of the solenoid valve is easy to control internal leakage until it is reduced to zero
.
Air inlet 3
.
At this time, the pressure of the upper chamber of the main valve is unloaded through the pilot valve port, and the main valve core moves upward under the simultaneous action of the pressure difference and the electromagnetic force, so as to open the main valve medium circulation
.
Principle: it is a combination of direct acting and pilot type
.
The solenoid valve usually has only two states of on-off, the spool can only be in two limit positions, and can not be adjusted continuously
.
At this time, the medium flows in from the balance hole, and the pressure in the upper chamber of the main valve core increases, and moves downward under the action of spring force, and the main valve port is closed
.
Features: it can also operate under zero pressure difference or vacuum or high pressure, but it has high power and must be installed horizontally
.
In today’s era of computer popularization and price drop, the advantage of solenoid valve is more obvious
.
Valve body 2
.
The external leakage is blocked, the internal leakage is easy to control, the use is safe, and the internal and external leakage is the key factor endangering the safety
.
Features: small volume, low power, high upper limit of fluid pressure range, can be installed arbitrarily (need to be customized), but must meet the conditions of fluid pressure difference
.
As the solenoid valve is controlled by switch signal, it is very convenient to connect with industrial control computer
.
According to the characteristics of solenoid valve, how to select the type of solenoid valve? In order to extend the service life of solenoid valve, how to maintain it? Structure principle of solenoid valve (1
.
Introduction of direct acting solenoid valve: there are two types: normally closed type and normally open type
.
Step by step direct acting solenoid valve introduction: this kind of valve is connected with primary opening valve and secondary opening valve
.
Plunger) after looking at the dynamic diagram, do you find that the working principle of solenoid valve is very simple! When the solenoid valve is not powered on, the valve needle under the action of the spring will bet the channel of the valve body, and the solenoid valve is in the cut-off state
.
The normally open principle is the opposite
.
What is more remarkable is that the automatic control system is much simpler and the price is much lower
.
Five models are diverse and widely used
.
Principle: when the normally closed type is electrified, the electromagnetic coil generates electromagnetic force to lift the open part from the valve seat and open the valve; when the power is off, the electromagnetic force disappears and the spring presses the open part on the valve seat and the valve is open
.
When the coil is powered off, the electromagnetic force disappears
.
The medium containing particles cannot be used
.
When the coil is electrified, the electromagnetic force is generated to make the moving iron core and the static iron core close, the pilot valve port is opened, and the pilot valve port is set on the main valve port, and the moving iron core is connected with the main valve core
.
When the coil is connected to the power supply, the coil generates magnetic force, the valve core is lifted up against the spring force, the channel in the valve is opened, and the solenoid valve is in the conduction state
.
The electromagnetic valve is small in size, saving space, light and beautiful
.
Introduction of indirect pilot solenoid valve: this kind of solenoid valve is formed by connecting the pilot valve and the main valve core to form a channel combination; normally closed type is closed when it is not powered on
.
At this time, the pressure of the upper chamber of the main valve core is reduced, which is lower than the pressure of the inlet side, forming a pressure difference, overcoming the spring resistance and then moving upward, so as to achieve the purpose of opening the main valve port, and the medium flows
.
When the coil is electrified, the magnetic force generated makes the moving iron core and the static iron core close, the pilot valve port is opened, and the medium flows to the outlet
.
At this time, the moving iron core closes the pilot valve hole under the action of self weight and spring force
.
The progress of solenoid valve technology is also around how to overcome the inherent shortcomings and how to better play the inherent advantages
.
Now from the introduction, principle, characteristics of three aspects to do a summary
.
When the coil is powered off, the magnetic force disappears, the moving iron core resets under the action of spring force, and the pilot port is closed
.
Solenoid valve is electromagnetic controlled industrial equipment, in the industrial control system to adjust the direction of the medium, flow, speed and other parameters
.
The electromagnetic valve has high requirements on the cleanliness of the medium
.
Therefore, the use of solenoid valve is particularly safe, especially suitable for corrosive, toxic or high and low temperature medium
.
It has the advantages of simple structure, reliable operation and normal operation under zero differential pressure and micro vacuum
.
When the inlet and outlet reach the start-up pressure difference, after power on, the electromagnetic force will pilot the small valve, the pressure in the lower chamber of the main valve will rise, and the pressure in the upper chamber will drop, so as to use the pressure difference to push the main valve upward; when the power is off, the pilot valve will use the spring force or medium pressure to push the closing part downward to close the valve
.
Wire 5
.
Classification of solenoid valves: solenoid valves at home and abroad can be divided into three categories in principle (direct acting, step-by-step direct acting and pilot operated), and six sub categories in principle (direct acting diaphragm structure, step-by-step diaphragm structure, pilot operated diaphragm structure, step-by-step piston structure, and pilot operated piston structure) in terms of disc structure and material
.
The solenoid valve has simple structure and low price
.
(normally open type is opposite to this) features: it can work normally in vacuum, negative pressure and zero pressure, but the diameter is generally not more than 25 mm
.
The response time of the solenoid valve can be as short as several milliseconds, even the pilot solenoid valve can be controlled in tens of milliseconds
.
If it is a impurity, it must be filtered first
.
When there is no pressure difference between the inlet and outlet, the electromagnetic force will lift the small pilot valve and the main valve closing parts up one by one and open the valve
.
Such as solenoid valve with flow diameter less than 6
.
Air outlet 4
.
It is easier to install and maintain than other kinds of actuators such as control valve
.
Economy [uneconomic is a waste of capital, energy and even life] there are many solenoid valves that can be used in general
.
Because of its own loop, it is more sensitive than other automatic control valves
.
It can also automatically maintain the valve position by only triggering action, without power consumption at ordinary times
.
The structure is reasonable, the action is reliable, and the operation is also reliable when the pressure difference is zero
.
In the process of selection, the most economical product should be selected, but it must be based on the economy of safety, applicability and reliability.
.
Although the solenoid valve has inherent shortcomings, its advantages are still very prominent, so it is designed into a variety of products to meet various needs and has a wide range of uses
.
Such as ZQDF, ZS, 2W, etc
.
The normally open type is just the opposite
.
(there are many new ideas trying to break through, but they are still in the trial stage), so the adjustment accuracy is still limited
.
Solenoid valve selection 1
.
The solenoid valve features: 1
.
When the coil is powered on, the electromagnetic force is generated, which makes the moving iron core overcome the spring force to pull in with the static iron core and directly open the valve, and the medium is a channel; when the coil is powered off, the electromagnetic force disappears, the moving iron core is reset under the action of the spring force, and directly close the valve port, and the medium is blocked
.
Principle: when the power is on, the electromagnetic force opens the pilot hole, and the pressure of the upper chamber drops rapidly, forming a high and low pressure difference around the open parts, and the fluid pressure pushes the open parts to move upward, and the valve opens; when the power is off, the spring force opens the pilot hole, and the inlet pressure quickly forms a low and high pressure difference around the closed parts through the bypass hole, and the fluid pressure pushes the opening Move the valve downward and open the valve
.
Other automatic control valves usually extend the valve stem, and the electric, pneumatic and hydraulic actuators control the rotation or movement of the valve core
.
The main valve and pilot valve make the electromagnetic force and pressure difference directly open the main valve port step by step
.
At this time, the medium enters the upper chamber of the main valve core in the balance hole, which increases the pressure in the upper chamber
.
The power consumption of properly designed solenoid valve coil is very low, which is an energy-saving product
.
