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Basic knowledge of solenoid valve
Solenoid valve is a kind of automatic instrument actuator that we are familiar with. As an important industrial product directly related to enterprise safety production, it has an indispensable and pivotal position in many fields. Due to its simple structure, safe use, reliable work, small power, and good performance consistency among batches of products, solenoid valves have been widely used in many aspects such as automobiles, construction machinery, and agricultural machinery abroad.
Compared with foreign countries, solenoid valves in my country started late, but with the advent of reform and opening up and the rise of private enterprises, the production capacity of solenoid valves is increasing, and products are gradually entering foreign markets. With the rapid growth of my country's economy, the demand for solenoid valves in hydropower, construction, machinery and other industries continues to surge, and there are further requirements for their quality and specifications.
This article gives an introduction to the structure, performance characteristics and working principles of solenoid valves, a brief overview of the future development direction of solenoid valves, and detailed solenoid valve selection and application related matters, hoping to be beneficial to your selection and use of solenoid valves.
1. Approach the solenoid valve
Since the solenoid valve was invented, it has been more and more widely used in various fields, playing an irreplaceable role.
Although the solenoid valve is small, it is an indispensable component in many professional fields. The solenoid valve is regarded as a hand and foot in the hydraulic and pneumatic automation system, which is enough to show that the function of the solenoid valve cannot be underestimated.
2. (1) Introduction to the general concept of solenoid valve
Solenoid valve is used to control fluid automation basic components, belonging to the actuator; and not limited to hydraulic, pneumatic. The solenoid valve is composed of a solenoid coil, a magnetic core, and a valve body containing one or more holes. When the coil is energized or de-energized, the movement of the magnetic core will cause the fluid to pass or be cut off to achieve the purpose of changing the direction of the fluid. The electromagnetic part of the solenoid valve is composed of fixed iron core, moving iron core, guide sleeve coil and other parts; the valve body part is composed of valve core, valve sleeve, spring, valve seat, etc. The electromagnetic components are directly installed on the valve body to form a simple and compact combination. Solenoid valves commonly used in production include two-position two-way, two-position three-way, two-position four-way, two-position five-way, three-position five-way, etc. The meaning of two positions is for the solenoid valve to be electrified and de-energized, and for the valve to be controlled, it is open and closed.
As an industrial equipment controlled by electromagnetic, electromagnetic valves are used in industrial control systems to adjust the direction, flow, speed and other parameters of the medium. There are many types of solenoid valves. Different solenoid valves play a role in different positions of the control system. The most commonly used ones are check valves, safety valves, directional control valves, speed control valves, etc. The solenoid valve is controlled by electromagnetic effect, and the main control methods are relay control, computer program control, etc. In this way, the solenoid valve can cooperate with different circuits to achieve the desired control, and the accuracy and flexibility of the control can be guaranteed.
(2) Working principle of solenoid valve
The solenoid valve includes an electromagnetic part and a valve body part. When the power is turned on or off, the moving iron core of the electromagnetic part will move, thereby driving the on or off of the valve part or the switching of the flow direction.
Of course, the characteristics and principles of each type of solenoid valve are still different. Tracing the development history of solenoid valves, so far, solenoid valves at home and abroad are divided into three categories according to the action mode: direct-acting, recoil (stepwise coincidence), pilot-operated, and from the structure and material of the disc The difference in the above and the difference in principle are divided into six sub-categories (direct-acting diaphragm structure, step-by-step structure, pilot diaphragm structure, direct-acting piston structure, step-by-step direct-acting piston structure, pilot piston structure) . We will make a more detailed discussion on the three types of solenoid valves with slightly different action modes:
1. Direct-acting solenoid valve:
Principle: When energized, the solenoid generates electromagnetic force to lift the closing member from the valve seat, and the valve opens; when the power is off, the electromagnetic force disappears, and the spring presses the closing member on the valve seat, and the valve closes.
Features: It can work normally under vacuum, negative pressure and low pressure, but the diameter generally does not exceed 25mm.
2. Step-by-step reclosing type (recoil type) solenoid valve:
Principle: It is a combination of direct action and pilot type. When there is no pressure difference between the inlet and the outlet, the electromagnetic force directly lifts the pilot small valve and the main valve closing member upwards in turn, and the valve opens. When the inlet and outlet reach the start-up pressure difference, after energization, the electromagnetic force pilots the small valve, the pressure in the lower chamber of the main valve rises, and the pressure in the upper chamber drops, so that the pressure difference pushes the main valve upward; when the power is off, the pilot valve uses a spring The force or medium pressure pushes the closing piece and moves downward to close the valve.
Features: It can operate reliably even under zero pressure difference or under vacuum or high pressure, but the power is large, and it must be installed horizontally.
3. Pilot solenoid valve:
Principle: When the power is turned on, the electromagnetic force opens the pilot hole, the pressure in the upper chamber drops rapidly, and a high pressure difference is formed around the closing part. The fluid pressure pushes the closing part to move upward and the valve opens; when the power is off, the spring force controls the pilot The hole is closed, and the inlet pressure quickly reaches the upper chamber through the bypass hole, forming a lower and upper pressure difference around the valve closing member, and the fluid pressure pushes the closing member to move downward to close the valve.
Features: The upper limit of the fluid pressure range is high, and it can be installed arbitrarily (customization is required) but must meet the fluid pressure difference condition
Three) Performance characteristics of solenoid valve
Although the solenoid valve family is large and complex, people have basic settings for their performance at the beginning of the solenoid valve production. On the whole, all types of solenoid valves have 4 obvious performance characteristics: safety, applicability, reliability, and economy. This is also the primary consideration when people choose solenoid valves.
The safety is mainly designed based on the properties of the medium, the application environment, and the nominal pressure; the applicability is mainly designed based on the characteristics of the medium, pipeline parameters, environmental conditions, power supply conditions, and control accuracy; reliability refers to the working life of the solenoid valve In terms of working system and working frequency, there are also action reliability and economy. Here, economy does not only refer to the product price, but the performance-price ratio and the comprehensive cost-price ratio of the product.
Since the selection of solenoid valve is extremely closely related to the performance of solenoid valve, this article will introduce how to choose solenoid valve in the third part of this article, and at the same time show the performance characteristics of solenoid valve in detail-in order to make the selection of solenoid valve Clearer reference.
2. Development direction of solenoid valve technology
Everything is changing and developing, and solenoid valves are no exception. We know that solenoid valves usually have only two states on and off. The spool can only be in two extreme positions and cannot be adjusted continuously. Therefore, the adjustment accuracy of the solenoid valve is still subject to certain restrictions; the solenoid valve also has higher requirements for the cleanliness of the medium, including particles. The medium cannot be applied, if it is an impurity, it must be filtered out first. In addition, viscous media cannot be applied, and the viscosity range of the media for specific products is relatively narrow.
The characteristics of the solenoid valve itself determine its own limitations. Breaking through limitations is an important proposition in the development of solenoid valve technology.
The integration of traditional fluid power transmission technology with automation and IT technology also puts forward higher requirements for solenoid valves. At present, solenoid valves are developing in the direction of long life, miniaturization, intelligence, energy saving, environmental protection, and high integration.
(1) Development in the direction of intelligence
The intelligentization of solenoid valves mainly refers to how solenoid valves can better cooperate with smart instruments to improve the control accuracy and reliability of the system.
It is generally believed that positional adjustment is difficult to achieve very high accuracy, but in many occasions, using appropriate methods can achieve the required high accuracy, which greatly saves costs.
It is reported that solenoid valves that can completely change the traditional analog control method have appeared in our country, and can be controlled remotely through fieldbus or PC. Some products can be used in traditional production occasions with large flow requirements or control the pressure proportional valve completely through the feedback of digital signals to achieve precise control; even some product designs can meet the high flow and response requirements of customers for solenoid valve islands Fast speed, accurate repeatability and other requirements.
Fieldbus technology has been successfully applied to industrial process control. The important reason that cannot be ignored is the development of solenoid valves that output valve position signals, and its switching value directly enters the remote IO control box. The analog signal is also locally converted into a digital quantity through the AD module, and transmitted to the PLC through the fieldbus cable. It realizes the visualization of the work process, which is convenient for monitoring, and can automatically alarm when abnormalities are found. Moreover, in terms of pipeline configuration, there are combined solenoid valves, double solenoid valves, multiple solenoid valves, and three-position solenoid valves. This enables intelligent control to be executed conveniently and effectively. In terms of maintenance and repair, the multifunctional solenoid valve can isolate itself and perform online maintenance on the solenoid valve under the normal operation of the entire production system, which greatly improves the operating efficiency of the equipment.
(2) Miniaturization and longevity
"Miniaturization" is a trend in the development of solenoid valve technology, which is also an inevitable requirement for solenoid valves to be lightweight. The miniaturization of solenoid valves can not only reduce unnecessary waste of resources, but also help reduce equipment investment.
The miniaturization of solenoid valves does not mean that at the expense of flow. The development of the miniaturization of solenoid valves is based on the premise that the flow rate remains unchanged-this puts forward a further topic for the research of solenoid valves. This involves the scientificization of electromagnetic head technology and flow channels. Under the condition that the thrust of the moving iron core remains unchanged, the large-scale reduction of the volume of the solenoid head provides the possibility of miniaturization and energy saving of the solenoid valve. It is worth mentioning that the development of modern microelectronics technology has become a factor that cannot be ignored in the improvement of "electromagnetic head" technology.
The extension of the service life of solenoid valves is not a new issue. Industries that have a demand for solenoid valves have never stopped seeking to extend their service life. In recent years, the continuous introduction of new materials and manufacturing processes has made it possible to greatly increase the life of solenoid valves, and can improve the friction between the valve core and the valve sleeve in the main valve to the greatest extent.
(3) Ultra-cleanliness and low temperature rise are another important issue facing solenoid valve technology
In today's great social development, the standards of each industry have been improved to varying degrees, including cleanliness and temperature requirements. These two requirements must be implemented in certain industries. For example, in industries closely related to human health, such as micro-processing industry and hemodialysis, biological preparations, and pharmaceuticals, "dust" must not be allowed to appear. Obviously, as a component used in these industries, solenoid valves must consider the elements of cleanliness and temperature when they are designed and produced.
The solenoid valve uses a moving spool to switch the flow channel or change the effective area of the flow channel to control the direction, flow and pressure of the fluid. The friction and impact of the spool in the movement process will inevitably produce particles; recently, in order to improve the solenoid valve Life, the friction pair between the valve core and the valve sleeve often needs grease to be lubricated, and this undoubtedly brings another source of particle generation: grease.
It is reported that ultra-clean solenoid valves have appeared. It can successfully avoid the pollution of the controlled fluid, and at the same time, the temperature rise is only 1℃, which effectively avoids the influence on the constant temperature environment and the performance of special fluids.
(4) Energy saving and environmental protection are continuous challenges
With the continuous deepening of environmental awareness, energy saving and green environmental protection also pose new challenges to the solenoid valve industry. Moreover, the recent entry of the EU's R0HS directive into China is tantamount to setting environmental protection thresholds for various industries.
In the solenoid valve industry, some pioneers have taken their own steps: some solenoid valve manufacturers have begun to set management goals in accordance with the EU's R0HS regulations to prevent the generation of pollutants, and carry out structural improvements and the development of new magnetic materials. Greatly reduce the power of the solenoid valve and effectively reduce the heat generated by the original solenoid coil.
In addition, the automatic holding solenoid valve has appeared. According to reports, this kind of valve is only energized at the moment of opening or closing, and is usually maintained by a permanent magnet, which has a good energy-saving effect.
In fact, the selection of solenoid valve materials, the design of the magnetic circuit, the configuration of the circuit, the manufacture of the valve core, etc. are all related to energy consumption.
From the perspective of environmental protection, materials containing heavy metals such as Pb, Hg, Cd, Cr5+ and PBB and PBDE that are difficult to degrade are harmful to the global environment and human health.
Relevant information shows that Germany is developing miniature valves (or miniature silicon material valves) with piezoelectric drives. When its nominal diameter is 0.25mm and the working pressure is 1-11bar, its power consumption is only 400μW, and the response time is 20μs.
(5) Brief introduction of the development of solenoid valves in my country
In terms of the development of solenoid valves, only domestically, many gratifying changes have been made.
Compared with large foreign professional companies, domestic solenoid valve companies started late, and there is a clear gap in technical and economic strength.
After the reform and opening up, private technology companies have risen and have patents approved in the United States, Japan, and Europe. Products have gradually entered the markets of developed countries, and their economic strength has continued to increase, even surpassing foreign counterparts in small and medium-sized enterprises. In recent years, the satellite launch base, the Daya Bay Nuclear Power Plant, and the Shanghai Baosteel Maintenance Project have won bids for domestic solenoid valves. This reflects that our domestic solenoid valve industry is gradually forming its own production strength.
In the past, unfair competition in the solenoid valve industry was very serious in China. There were unlicensed production, unlicensed sales, counterfeit patents, counterfeit trademarks, fake factory names, fake advertisements and fake products, and consumers suffered greatly. In recent years, with the gradual implementation of IS09000 quality system certification in our country, consumers have more and more easy access to high-quality products. Everyone is gradually consciously choosing certified companies.
It is understood that domestic solenoid valves are also paying more and more attention to localization factors. Now many people of insight have realized the importance of starting from localization. To achieve true localization of solenoid valves, it is necessary to start from technical standards and technical requirements, and truly solve the quality problems of solenoid valves. In terms of standardization, we should move closer to international standards; in terms of technical conditions, we should formulate more scientific and reasonable technical standards; and in terms of price, it must be compatible with high performance.
Three, solenoid valve selection and application
Although solenoid valves have inherent deficiencies, their advantages are still outstanding, so they are designed into a variety of products to meet various needs. And as solenoid valve technology continues to develop toward intelligence and simplicity, the use of solenoid valves is currently Very extensive. It also belongs to solenoid valves, but the situation when different types of solenoid valves are used is very different. Moreover, according to surveys, the sales of solenoid valves have soared in recent years, of which various special solenoid valves occupy an important proportion, which undoubtedly requires a professional eye to select suitable solenoid valves.
(1) The essentials of solenoid valve selection
When choosing a solenoid valve to meet different needs, the first thing you should pay attention to is the inherent characteristics of the solenoid valve itself. The following is a reference to the characteristics of the solenoid valve itself, to introduce several essentials for selecting the solenoid valve.
1. Security:
(1) Corrosive medium: Plastic solenoid valve and all stainless steel should be used; for strong corrosive medium, the isolation diaphragm type must be selected. Examples CD-F, Z3CF. For neutral media, a solenoid valve with a copper alloy as the valve housing material should also be used, otherwise, rust debris will often fall off the valve housing, especially in occasions where the action is infrequent. The valve for ammonia cannot be made of copper.
(2) Explosive environment: corresponding explosion-proof products must be selected, and waterproof and dust-proof products should be selected for outdoor installation or dusty places.
(3) The nominal pressure of the solenoid valve should exceed the highest working pressure in the pipe.
2. Applicability:
(1) Medium characteristics
① Choose different types of solenoid valves for gas, liquid or mixed states, otherwise it is easy to cause malfunction. If you don't know the model, please ask the manufacturer to choose it on your behalf. But it is best to know the state of the medium when ordering.
②The temperature of the medium is different, and the product specifications are also different. You must choose the right one, otherwise the coil will burn out and the dense
Compared with foreign countries, solenoid valves in my country started late, but with the advent of reform and opening up and the rise of private enterprises, the production capacity of solenoid valves is increasing, and products are gradually entering foreign markets. With the rapid growth of my country's economy, the demand for solenoid valves in hydropower, construction, machinery and other industries continues to surge, and there are further requirements for their quality and specifications.
This article gives an introduction to the structure, performance characteristics and working principles of solenoid valves, a brief overview of the future development direction of solenoid valves, and detailed solenoid valve selection and application related matters, hoping to be beneficial to your selection and use of solenoid valves.
1. Approach the solenoid valve
Since the solenoid valve was invented, it has been more and more widely used in various fields, playing an irreplaceable role.
Although the solenoid valve is small, it is an indispensable component in many professional fields. The solenoid valve is regarded as a hand and foot in the hydraulic and pneumatic automation system, which is enough to show that the function of the solenoid valve cannot be underestimated.
2. (1) Introduction to the general concept of solenoid valve
Solenoid valve is used to control fluid automation basic components, belonging to the actuator; and not limited to hydraulic, pneumatic. The solenoid valve is composed of a solenoid coil, a magnetic core, and a valve body containing one or more holes. When the coil is energized or de-energized, the movement of the magnetic core will cause the fluid to pass or be cut off to achieve the purpose of changing the direction of the fluid. The electromagnetic part of the solenoid valve is composed of fixed iron core, moving iron core, guide sleeve coil and other parts; the valve body part is composed of valve core, valve sleeve, spring, valve seat, etc. The electromagnetic components are directly installed on the valve body to form a simple and compact combination. Solenoid valves commonly used in production include two-position two-way, two-position three-way, two-position four-way, two-position five-way, three-position five-way, etc. The meaning of two positions is for the solenoid valve to be electrified and de-energized, and for the valve to be controlled, it is open and closed.
As an industrial equipment controlled by electromagnetic, electromagnetic valves are used in industrial control systems to adjust the direction, flow, speed and other parameters of the medium. There are many types of solenoid valves. Different solenoid valves play a role in different positions of the control system. The most commonly used ones are check valves, safety valves, directional control valves, speed control valves, etc. The solenoid valve is controlled by electromagnetic effect, and the main control methods are relay control, computer program control, etc. In this way, the solenoid valve can cooperate with different circuits to achieve the desired control, and the accuracy and flexibility of the control can be guaranteed.
(2) Working principle of solenoid valve
The solenoid valve includes an electromagnetic part and a valve body part. When the power is turned on or off, the moving iron core of the electromagnetic part will move, thereby driving the on or off of the valve part or the switching of the flow direction.
Of course, the characteristics and principles of each type of solenoid valve are still different. Tracing the development history of solenoid valves, so far, solenoid valves at home and abroad are divided into three categories according to the action mode: direct-acting, recoil (stepwise coincidence), pilot-operated, and from the structure and material of the disc The difference in the above and the difference in principle are divided into six sub-categories (direct-acting diaphragm structure, step-by-step structure, pilot diaphragm structure, direct-acting piston structure, step-by-step direct-acting piston structure, pilot piston structure) . We will make a more detailed discussion on the three types of solenoid valves with slightly different action modes:
1. Direct-acting solenoid valve:
Principle: When energized, the solenoid generates electromagnetic force to lift the closing member from the valve seat, and the valve opens; when the power is off, the electromagnetic force disappears, and the spring presses the closing member on the valve seat, and the valve closes.
Features: It can work normally under vacuum, negative pressure and low pressure, but the diameter generally does not exceed 25mm.
2. Step-by-step reclosing type (recoil type) solenoid valve:
Principle: It is a combination of direct action and pilot type. When there is no pressure difference between the inlet and the outlet, the electromagnetic force directly lifts the pilot small valve and the main valve closing member upwards in turn, and the valve opens. When the inlet and outlet reach the start-up pressure difference, after energization, the electromagnetic force pilots the small valve, the pressure in the lower chamber of the main valve rises, and the pressure in the upper chamber drops, so that the pressure difference pushes the main valve upward; when the power is off, the pilot valve uses a spring The force or medium pressure pushes the closing piece and moves downward to close the valve.
Features: It can operate reliably even under zero pressure difference or under vacuum or high pressure, but the power is large, and it must be installed horizontally.
3. Pilot solenoid valve:
Principle: When the power is turned on, the electromagnetic force opens the pilot hole, the pressure in the upper chamber drops rapidly, and a high pressure difference is formed around the closing part. The fluid pressure pushes the closing part to move upward and the valve opens; when the power is off, the spring force controls the pilot The hole is closed, and the inlet pressure quickly reaches the upper chamber through the bypass hole, forming a lower and upper pressure difference around the valve closing member, and the fluid pressure pushes the closing member to move downward to close the valve.
Features: The upper limit of the fluid pressure range is high, and it can be installed arbitrarily (customization is required) but must meet the fluid pressure difference condition
Three) Performance characteristics of solenoid valve
Although the solenoid valve family is large and complex, people have basic settings for their performance at the beginning of the solenoid valve production. On the whole, all types of solenoid valves have 4 obvious performance characteristics: safety, applicability, reliability, and economy. This is also the primary consideration when people choose solenoid valves.
The safety is mainly designed based on the properties of the medium, the application environment, and the nominal pressure; the applicability is mainly designed based on the characteristics of the medium, pipeline parameters, environmental conditions, power supply conditions, and control accuracy; reliability refers to the working life of the solenoid valve In terms of working system and working frequency, there are also action reliability and economy. Here, economy does not only refer to the product price, but the performance-price ratio and the comprehensive cost-price ratio of the product.
Since the selection of solenoid valve is extremely closely related to the performance of solenoid valve, this article will introduce how to choose solenoid valve in the third part of this article, and at the same time show the performance characteristics of solenoid valve in detail-in order to make the selection of solenoid valve Clearer reference.
2. Development direction of solenoid valve technology
Everything is changing and developing, and solenoid valves are no exception. We know that solenoid valves usually have only two states on and off. The spool can only be in two extreme positions and cannot be adjusted continuously. Therefore, the adjustment accuracy of the solenoid valve is still subject to certain restrictions; the solenoid valve also has higher requirements for the cleanliness of the medium, including particles. The medium cannot be applied, if it is an impurity, it must be filtered out first. In addition, viscous media cannot be applied, and the viscosity range of the media for specific products is relatively narrow.
The characteristics of the solenoid valve itself determine its own limitations. Breaking through limitations is an important proposition in the development of solenoid valve technology.
The integration of traditional fluid power transmission technology with automation and IT technology also puts forward higher requirements for solenoid valves. At present, solenoid valves are developing in the direction of long life, miniaturization, intelligence, energy saving, environmental protection, and high integration.
(1) Development in the direction of intelligence
The intelligentization of solenoid valves mainly refers to how solenoid valves can better cooperate with smart instruments to improve the control accuracy and reliability of the system.
It is generally believed that positional adjustment is difficult to achieve very high accuracy, but in many occasions, using appropriate methods can achieve the required high accuracy, which greatly saves costs.
It is reported that solenoid valves that can completely change the traditional analog control method have appeared in our country, and can be controlled remotely through fieldbus or PC. Some products can be used in traditional production occasions with large flow requirements or control the pressure proportional valve completely through the feedback of digital signals to achieve precise control; even some product designs can meet the high flow and response requirements of customers for solenoid valve islands Fast speed, accurate repeatability and other requirements.
Fieldbus technology has been successfully applied to industrial process control. The important reason that cannot be ignored is the development of solenoid valves that output valve position signals, and its switching value directly enters the remote IO control box. The analog signal is also locally converted into a digital quantity through the AD module, and transmitted to the PLC through the fieldbus cable. It realizes the visualization of the work process, which is convenient for monitoring, and can automatically alarm when abnormalities are found. Moreover, in terms of pipeline configuration, there are combined solenoid valves, double solenoid valves, multiple solenoid valves, and three-position solenoid valves. This enables intelligent control to be executed conveniently and effectively. In terms of maintenance and repair, the multifunctional solenoid valve can isolate itself and perform online maintenance on the solenoid valve under the normal operation of the entire production system, which greatly improves the operating efficiency of the equipment.
(2) Miniaturization and longevity
"Miniaturization" is a trend in the development of solenoid valve technology, which is also an inevitable requirement for solenoid valves to be lightweight. The miniaturization of solenoid valves can not only reduce unnecessary waste of resources, but also help reduce equipment investment.
The miniaturization of solenoid valves does not mean that at the expense of flow. The development of the miniaturization of solenoid valves is based on the premise that the flow rate remains unchanged-this puts forward a further topic for the research of solenoid valves. This involves the scientificization of electromagnetic head technology and flow channels. Under the condition that the thrust of the moving iron core remains unchanged, the large-scale reduction of the volume of the solenoid head provides the possibility of miniaturization and energy saving of the solenoid valve. It is worth mentioning that the development of modern microelectronics technology has become a factor that cannot be ignored in the improvement of "electromagnetic head" technology.
The extension of the service life of solenoid valves is not a new issue. Industries that have a demand for solenoid valves have never stopped seeking to extend their service life. In recent years, the continuous introduction of new materials and manufacturing processes has made it possible to greatly increase the life of solenoid valves, and can improve the friction between the valve core and the valve sleeve in the main valve to the greatest extent.
(3) Ultra-cleanliness and low temperature rise are another important issue facing solenoid valve technology
In today's great social development, the standards of each industry have been improved to varying degrees, including cleanliness and temperature requirements. These two requirements must be implemented in certain industries. For example, in industries closely related to human health, such as micro-processing industry and hemodialysis, biological preparations, and pharmaceuticals, "dust" must not be allowed to appear. Obviously, as a component used in these industries, solenoid valves must consider the elements of cleanliness and temperature when they are designed and produced.
The solenoid valve uses a moving spool to switch the flow channel or change the effective area of the flow channel to control the direction, flow and pressure of the fluid. The friction and impact of the spool in the movement process will inevitably produce particles; recently, in order to improve the solenoid valve Life, the friction pair between the valve core and the valve sleeve often needs grease to be lubricated, and this undoubtedly brings another source of particle generation: grease.
It is reported that ultra-clean solenoid valves have appeared. It can successfully avoid the pollution of the controlled fluid, and at the same time, the temperature rise is only 1℃, which effectively avoids the influence on the constant temperature environment and the performance of special fluids.
(4) Energy saving and environmental protection are continuous challenges
With the continuous deepening of environmental awareness, energy saving and green environmental protection also pose new challenges to the solenoid valve industry. Moreover, the recent entry of the EU's R0HS directive into China is tantamount to setting environmental protection thresholds for various industries.
In the solenoid valve industry, some pioneers have taken their own steps: some solenoid valve manufacturers have begun to set management goals in accordance with the EU's R0HS regulations to prevent the generation of pollutants, and carry out structural improvements and the development of new magnetic materials. Greatly reduce the power of the solenoid valve and effectively reduce the heat generated by the original solenoid coil.
In addition, the automatic holding solenoid valve has appeared. According to reports, this kind of valve is only energized at the moment of opening or closing, and is usually maintained by a permanent magnet, which has a good energy-saving effect.
In fact, the selection of solenoid valve materials, the design of the magnetic circuit, the configuration of the circuit, the manufacture of the valve core, etc. are all related to energy consumption.
From the perspective of environmental protection, materials containing heavy metals such as Pb, Hg, Cd, Cr5+ and PBB and PBDE that are difficult to degrade are harmful to the global environment and human health.
Relevant information shows that Germany is developing miniature valves (or miniature silicon material valves) with piezoelectric drives. When its nominal diameter is 0.25mm and the working pressure is 1-11bar, its power consumption is only 400μW, and the response time is 20μs.
(5) Brief introduction of the development of solenoid valves in my country
In terms of the development of solenoid valves, only domestically, many gratifying changes have been made.
Compared with large foreign professional companies, domestic solenoid valve companies started late, and there is a clear gap in technical and economic strength.
After the reform and opening up, private technology companies have risen and have patents approved in the United States, Japan, and Europe. Products have gradually entered the markets of developed countries, and their economic strength has continued to increase, even surpassing foreign counterparts in small and medium-sized enterprises. In recent years, the satellite launch base, the Daya Bay Nuclear Power Plant, and the Shanghai Baosteel Maintenance Project have won bids for domestic solenoid valves. This reflects that our domestic solenoid valve industry is gradually forming its own production strength.
In the past, unfair competition in the solenoid valve industry was very serious in China. There were unlicensed production, unlicensed sales, counterfeit patents, counterfeit trademarks, fake factory names, fake advertisements and fake products, and consumers suffered greatly. In recent years, with the gradual implementation of IS09000 quality system certification in our country, consumers have more and more easy access to high-quality products. Everyone is gradually consciously choosing certified companies.
It is understood that domestic solenoid valves are also paying more and more attention to localization factors. Now many people of insight have realized the importance of starting from localization. To achieve true localization of solenoid valves, it is necessary to start from technical standards and technical requirements, and truly solve the quality problems of solenoid valves. In terms of standardization, we should move closer to international standards; in terms of technical conditions, we should formulate more scientific and reasonable technical standards; and in terms of price, it must be compatible with high performance.
Three, solenoid valve selection and application
Although solenoid valves have inherent deficiencies, their advantages are still outstanding, so they are designed into a variety of products to meet various needs. And as solenoid valve technology continues to develop toward intelligence and simplicity, the use of solenoid valves is currently Very extensive. It also belongs to solenoid valves, but the situation when different types of solenoid valves are used is very different. Moreover, according to surveys, the sales of solenoid valves have soared in recent years, of which various special solenoid valves occupy an important proportion, which undoubtedly requires a professional eye to select suitable solenoid valves.
(1) The essentials of solenoid valve selection
When choosing a solenoid valve to meet different needs, the first thing you should pay attention to is the inherent characteristics of the solenoid valve itself. The following is a reference to the characteristics of the solenoid valve itself, to introduce several essentials for selecting the solenoid valve.
1. Security:
(1) Corrosive medium: Plastic solenoid valve and all stainless steel should be used; for strong corrosive medium, the isolation diaphragm type must be selected. Examples CD-F, Z3CF. For neutral media, a solenoid valve with a copper alloy as the valve housing material should also be used, otherwise, rust debris will often fall off the valve housing, especially in occasions where the action is infrequent. The valve for ammonia cannot be made of copper.
(2) Explosive environment: corresponding explosion-proof products must be selected, and waterproof and dust-proof products should be selected for outdoor installation or dusty places.
(3) The nominal pressure of the solenoid valve should exceed the highest working pressure in the pipe.
2. Applicability:
(1) Medium characteristics
① Choose different types of solenoid valves for gas, liquid or mixed states, otherwise it is easy to cause malfunction. If you don't know the model, please ask the manufacturer to choose it on your behalf. But it is best to know the state of the medium when ordering.
②The temperature of the medium is different, and the product specifications are also different. You must choose the right one, otherwise the coil will burn out and the dense
