Scope of use of gas solenoid valve:

The product is suitable for automation pipeline control systems for flammable and explosive media in petrochemical, chemical, gas pipeline networks, industrial kilns, and pipelines.

Characteristics of gas solenoid valve:

Piston structure; Stable performance; Autocratic coil, long-term power supply, not easy to burn out;

Working principle of rapid shut-off valve:

A: When the valve needs to be opened, first power on the valve, unscrew the protective cover (there is a threaded hole in the middle of the protective cover, which can be used as a handle on the linkage rod), pull the handle firmly, and the valve will open.

B: When the valve needs to be closed, the coil loses power and the valve quickly closes.

Special function of rapid shut-off valve:

◆ Signal feedback: When the valve is opened, the signal common line and the open signal line are connected; When the valve is closed, the signal common line and the closing signal line are connected.

Manual function: When the safety valve needs to be closed, unscrew the manual protective cover and press the manual handle firmly to close the valve.

Generally used in conjunction with gas alarms

Scope of use of gas solenoid valve:

The product is suitable for automation pipeline control systems for flammable and explosive media in petrochemical, chemical, gas pipeline networks, industrial kilns, and pipelines.

Characteristics of gas solenoid valve:

Exquisite appearance; Piston structure; Stable performance; Autocratic coil, not easy to burn out;

Working principle of rapid shut-off valve:

A: When the valve needs to be opened, unscrew the protective cover (there is a threaded hole in the middle of the protective cover, which can be used as a handle on the linkage rod), pull the handle firmly, and the valve will open.

B: When the valve needs to be closed, the coil should be energized for no more than 2 seconds and the valve should quickly close.

Special function of rapid shut-off valve:

◆ Signal feedback: When the valve is opened, the signal common line and the open signal line are connected; When the valve is closed, the signal common line and the closing signal line are connected.

Manual function: When the safety valve needs to be closed, unscrew the manual protective cover and press the manual handle firmly to close the valve.

As an actuator of automation instruments, solenoid valves have seen a sharp increase in usage in recent years. This article provides a brief overview of the development trends of mature technologies in China, examining the directions of simplification, intelligence, generalization, and specialization. It also briefly discusses the social factors that affect the development of solenoid valve technology.

The development of the direction of refinement and simplification is essential, and only simplicity can be passed down for a long time. This is also the eternal pursuit of scientists and engineers.

(1) Simplify the control circuit. Previous actuators extensively used pneumatic and electric control circuits, which increased the complexity of the system. Pilot operated solenoid valves, on the other hand, form a control circuit inside the valve that utilizes the working medium itself, with a very simple structure. In the past, multiple technical parameters of solenoid valves at home and abroad were still limited, but now the diameter of solenoid valves in China has been expanded to 300000 mm; The medium temperature ranges from -200 ℃ to 450 ℃; The working pressure ranges from vacuum to 25MPa. The action time ranges from tens of seconds to a few milliseconds. The new development of these technologies can completely replace the bulky and expensive two position control quick shut-off valves, pneumatic switch valves, electric switch valves, and partially replace continuous adjustment pneumatic and electric control valves. (How to better meet the requirements of adjustment accuracy, which will be discussed in the following text). Foreign industries such as textiles, light industry, and urban construction have extensively adopted solenoid valves, while metallurgical and chemical industries have taken the lead in using more and more solenoid valves in auxiliary systems.

Domestic automation professionals are increasingly paying attention to solenoid valves.

(2) When simplifying the operation of the automatic control valve in the pipeline system, some auxiliary valves and fittings must also be equipped on the pipeline. For example, isolating the bypass is a typical installation method that requires three manual valves, with manual valve 1 being the bypass valve and manual backup. And manual valves 2 and 3 are isolation valves, ensuring online maintenance of automatic control valve 5. Of course, two tees 4 and a flexible connector 6 are also required. This piping system takes up a large amount of space, is time-consuming to install, and is prone to leakage. The ZDF series multifunctional solenoid valve cleverly eliminates these additional accessories and still has the function of isolating bypass, thus winning the Geneva International New Technology Gold Award. A filter needs to be installed in front of the automatic control valve. When multiple self-control valves are used in combination, it is often necessary to install one-way valves to prevent interference between pipelines. Now, one-way solenoid valves, combination solenoid valves, and filtered solenoid valves have all played a role in simplifying pipelines.

1、 Working principle of solenoid valve - Introduction

Electromagnetic valve, also known as Electromagnetic value in English, is an automated basic component used to control fluids. It is commonly used in industrial control systems to adjust parameters such as direction, flow rate, and velocity of media. Electromagnetic valves have the characteristics of high precision, good flexibility, multiple models, and wide applications. Electromagnetic valves can be divided into various types, and different electromagnetic valves can play their roles in different positions of the control system.

2、 Working principle of solenoid valve

There is a sealed chamber inside the solenoid valve, with a piston in the middle and two electromagnets on both sides of the chamber. Once the electromagnetic coil is energized, the valve body is attracted to the direction of the energized electromagnet by force; And there are through holes at different positions in the chamber, connecting different oil pipes, so the part of the oil discharge hole can be selected to be opened by controlling the movement of the valve body; Due to the oil inlet being in a normally open state, the movement of the valve body allows hydraulic oil to enter different oil discharge pipes. The pressure of the oil pushes the piston of the cylinder, which in turn pushes the piston rod, thereby driving the mechanical device. By utilizing this principle, it is possible to achieve the function of controlling mechanical motion by controlling the on/off of electromagnetic current.

3、 Working principle of solenoid valve - classification

Electromagnetic valves can be classified into various types based on their functions, such as water solenoid valves, high-pressure solenoid valves, fire solenoid valves, etc. They can also be classified into six types based on valve structure, materials, etc.: direct acting diaphragm structure, pilot diaphragm structure, distributed direct acting piston structure, etc. However, the most important classification method for solenoid valves is based on their principles, which can be divided into three types: direct acting solenoid valves, step-by-step direct acting solenoid valves, and pilot operated solenoid valves. Next, let's take a look at the differences in the principles of these three types of solenoid valves?

4、 Working principle of solenoid valve - direct acting solenoid valve

When the direct acting solenoid valve is powered on, it generates magnetic force through the electromagnetic coil to lift the closing member from the valve seat and open the valve, controlling the movement of the mechanical device; When the power is cut off, the electromagnetic force disappears, and the closing member is re pressed against the valve seat by the spring, causing the valve to close.

5、 Working principle of solenoid valve - pilot operated solenoid valve

When the pilot operated solenoid valve is powered on, the electromagnetic coil generates electromagnetic force to open the pilot hole, causing a sharp drop in pressure in the upper chamber and creating a high pressure difference between the upper and lower parts at the closing part. As a result, the closing part is pushed upward by pressure, and the valve is opened; When the power is cut off, the electromagnetic force disappears, and the pilot hole closes under the action of the spring, forming a pressure difference of high and low at the closing part, which then pushes the closing part downwards and closes the valve.

6、 Working principle of solenoid valve - step-by-step direct acting solenoid valve

The step-by-step direct acting solenoid valve combines the working principles of direct acting and pilot operated solenoid valve switches. When there is no pressure difference at the inlet and outlet or the pressure difference is small enough to push the valve to move, the valve is opened by the action of electromagnetic force (similar to the direct acting solenoid valve); When the pressure difference between the inlet and outlet can push the valve to move, use the pressure to open the valve (similar to a pilot operated solenoid valve); After power failure, when there is no pressure difference or electromagnetic force, the valve closes under the action of the spring.

In summary, the working principle of solenoid valves is to control the valve opening and closing by controlling the power on and off of the solenoid coil, thereby controlling the movement of the mechanical device. The difference in the working principle of the three types of solenoid valves lies in the different ways in which the solenoid coil opens and closes the valve.

There are many factors that affect the service life of solenoid valve products, and corrosion of solenoid valves is one of the important influencing factors. Extending the service life of solenoid valves, improving project safety, and anti-corrosion of solenoid valves are important considerations. How to effectively protect solenoid valve products, and what are the precautions in purchasing? You need to know the following methods.

Select corrosion-resistant materials based on the type of medium

In practical production applications, solenoid valves face a variety of media types, and even for the same medium, the corrosion rate of materials varies under different pressures, temperatures, and concentrations. For example, aluminum is highly corrosive in concentrated nitric acid with a concentration of over 80%, but its corrosion is not severe in medium to low concentrations of nitric acid. Carbon steel is most severely corroded in sulfuric acid with a concentration of 50%, and when the concentration reaches over 90%, the corrosion sharply decreases. So, when purchasing solenoid valve products, you can analyze the type of medium and the degree of corrosion of materials by different concentrations of media, or consult the manufacturer directly.

Select corrosion-resistant solenoid valves

Corrosion resistant solenoid valves are solutions specifically designed for corrosive media. Many corrosion-resistant solenoid valves use non-metallic materials as the contact surface between the solenoid valve cavity and the media. Materials such as natural rubber and polytetrafluoroethylene not only have good corrosion resistance, but also play a role in saving precious metals as long as the pressure and temperature of the project environment meet the characteristics of the materials.

Surface treatment of solenoid valve

The surface treatment of solenoid valves can be divided into thermal spraying and spray coating. Thermal spraying is one of the techniques for adding a protective layer to the surface of equipment. Thermal spraying is the use of high energy density heat sources, such as gas combustion flames, electric arcs, plasma arcs, electric heating, gas explosions, etc., to heat and melt metal or non-metal materials, and then spray them onto the pre treated basic surface in the form of atomization to form a spray coating. Thermal spraying can improve the corrosion resistance, wear resistance, high temperature resistance and other characteristics of the surface of solenoid valves, extending the service life of products.

Spray coating is a common method, which belongs to non-metallic materials. When applied to metal surfaces or cavities, it can effectively isolate the medium and atmosphere, achieving the purpose of corrosion prevention.

Control corrosive environment

Controlling the corrosive environment is mainly aimed at the working environment where the solenoid valve is located, such as effectively controlling dust, water vapor, smoke, and toxic gases in the environment to maintain cleanliness and dryness.

Electromagnetic valves are widely used in our production. Let's first have a preliminary understanding of electromagnetic valves. Electromagnetic valves are composed of electromagnetic coils and magnetic cores, and are valve bodies containing one or several holes. When the coil is powered on or off, the operation of the magnetic core will cause the fluid to pass through the valve body or be cut off, in order to change the direction of the fluid. The electromagnetic components of the solenoid valve consist of a fixed iron core, a moving iron core, coils, and other components; The valve body is composed of slide valve core, slide valve sleeve, spring base, etc. The electromagnetic coil is directly installed on the valve body, which is enclosed in a sealed tube, forming a simple and compact combination. The solenoid valves we commonly use in production include two position three-way, two position four-way, two position five way, etc. Let's first talk about the meanings of the two: for solenoid valves, it means being energized or de energized, and for the valves being controlled, it means being open or closed.

It consists of valve body, valve cover, electromagnetic components, spring, and sealing structure. The sealing block at the bottom of the moving iron core closes the valve body inlet with the pressure of the spring. After being powered on, the electromagnet is attracted, and the sealing block with a spring on the upper part of the moving iron core closes the exhaust port. The airflow enters the membrane head from the intake port, playing a controlling role. When the power is lost, the electromagnetic force disappears, and the moving iron core leaves the fixed iron core under the action of the spring force, moves downward, opens the exhaust port, blocks the intake port, and the diaphragm head air flows through the exhaust port to be discharged, and the diaphragm returns to its original position. In our oxygen production equipment, there are applications such as emergency shut-off of the membrane regulating valve at the inlet of the turbine expander

When current passes through the coil, excitation is generated, and the fixed iron core attracts the moving iron core. The moving iron core drives the slide valve core and compresses the spring, changing the position of the slide valve core and thus changing the direction of the fluid. When the coil loses power, the slide valve core is pushed by the elastic force of the spring, pushing the iron core back and forth, causing the fluid to flow in the original direction. In our oxygen production, the switch of the forced valve of the molecular sieve switching system is controlled by a two position four-way solenoid valve, and the airflow is supplied to both ends of the piston of the forced valve. So as to control the opening and closing of the forced valve.

As an actuator of automation instruments, solenoid valves have seen a sharp increase in usage in recent years. This article analyzes the main characteristics of solenoid valves and provides a brief overview of the development trends of mature technologies in China from an application perspective. It examines the directions of simplification, intelligence, generalization, and specialization, and briefly discusses the social factors that affect the development of solenoid valve technology.

1、 The main characteristics of solenoid valves

(1) The system is simple, easy to connect to a computer, and the price is affordable. The solenoid valve itself has a simple structure and low price, making it easier to install and maintain compared to other types of actuators such as regulating valves. More significantly, the composed self-control system is much simpler and priced much lower. Due to the fact that the solenoid valve is controlled by switch signals, it is very convenient to connect with industrial control computers. In today's era of widespread computer use and significant price reductions, the advantages of solenoid valves are even more apparent.

(2) External leakage is blocked, internal leakage is easy to control, and safe to use. Internal and external leakage is a factor that endangers safety. Other self-control valves usually extend the valve stem and control the rotation or movement of the valve core through electric, pneumatic, or hydraulic actuators. All of this needs to solve the problem of long-term leakage of valve stem seals; Only solenoid valves use electromagnetic force to seal the iron core inside the magnetic isolation sleeve, without dynamic sealing, so external leakage is easily blocked. Electric valve torque control is not easy, which can easily cause internal leakage and even break the valve stem head; The structural type of solenoid valve is easy to control internal leakage until it is reduced to zero. So, the use of solenoid valves is particularly safe, especially suitable for corrosive, toxic, or high and low temperature media.

(3) Action express, with minimal power and lightweight appearance. The response time of solenoid valves can be as short as a few milliseconds, and even pilot operated solenoid valves can be controlled within tens of milliseconds. Due to its self-contained circuit, it responds more sensitively than other self-control valves. A well-designed solenoid valve coil has low power consumption and is considered an energy-saving product; It can also automatically maintain the valve position by triggering the action, without consuming any electricity during normal operation. The electromagnetic valve has a small external size, which saves space and is lightweight and beautiful.

(4) Diverse models and versatile applications. Although solenoid valves have inherent shortcomings, their advantages are still very prominent, so they are designed into a variety of products to meet different needs and have a wide range of applications. The progress of solenoid valve technology also revolves around how to overcome inherent shortcomings and better leverage inherent advantages.

(5) The adjustment accuracy is limited and the applicable medium is restricted. Electromagnetic valves usually have only two states: on/off, and the valve core can only be in two extreme positions, which cannot be continuously adjusted. (There are many new ideas trying to break through, but they are still in the experimental stage) Therefore, the adjustment accuracy is still limited to a certain extent. Electromagnetic valves have high requirements for the cleanliness of the medium, and are not suitable for media containing particles. If impurities are present, they must be filtered out first. In addition, viscous media are not suitable, and the viscosity range of media suitable for specific products is relatively narrow.

2、 Introduction to the Development of Electromagnetic Valve Technology More Electromagnetic Valve Technology

The development of the direction of refinement and simplification is essential, and only simplicity can be passed down for a long time. This is also the eternal pursuit of scientists and engineers.

(1) Simplify the control circuit. Previous actuators extensively used pneumatic and electric control circuits, which increased the complexity of the system. Pilot operated solenoid valves, on the other hand, form a control circuit inside the valve that utilizes the working medium itself, with a very simple structure. In the past, multiple technical parameters of solenoid valves at home and abroad were still limited, but now the diameter of solenoid valves in China has been expanded to 300000 mm; The medium temperature ranges from -200 ℃ to 450 ℃; The working pressure ranges from vacuum to 25MPa. The action time ranges from tens of seconds to a few milliseconds. The new development of these technologies can completely replace the bulky and expensive two position control quick shut-off valves, pneumatic switch valves, electric switch valves, and partially replace continuous adjustment pneumatic and electric control valves. (How to better meet the requirements of adjustment accuracy, which will be discussed in the following text). Foreign industries such as textiles, light industry, and urban construction have extensively adopted solenoid valves, while metallurgical and chemical industries have taken the lead in using more and more solenoid valves in auxiliary systems.

Domestic automation professionals are increasingly paying attention to solenoid valves.

(2) When simplifying the operation of the automatic control valve in the pipeline system, some auxiliary valves and fittings must also be equipped on the pipeline. This piping system takes up a large amount of space, is time-consuming to install, and is prone to leakage. The ZDF series multifunctional solenoid valve cleverly eliminates these additional accessories and still has the function of isolating bypass, thus winning the Geneva International New Technology Gold Award. A filter needs to be installed in front of the automatic control valve. When multiple self-control valves are used in combination, it is often necessary to install one-way valves to prevent interference between pipelines. Now, one-way solenoid valves, combination solenoid valves, and filtered solenoid valves have all played a role in simplifying pipelines.

1、 Characteristics of solenoid valve

1. Choose different types of solenoid valves for gas, liquid or mixed states, such as ZQDF for air, ZQDF-Y for liquid, ZQDF-2 (or -3) for steam, otherwise it may cause misoperation. The ZDF series multifunctional solenoid valve can be connected to air Liquid. It is best to inform the media status when booking, so that the installation user does not need to adjust it again.

2. Products with different specifications and medium temperatures may cause the coil to burn out and the seals to age, seriously affecting their lifespan.

3. The viscosity of the medium is usually below 50cSt. If the diameter exceeds 15mm, use the ZDF series multifunctional solenoid valve for special ordering. High viscosity solenoid valve with a diameter less than 15mm.

4. When the cleanliness of the medium is not high, a backwash filter valve should be installed in front of the solenoid valve. When the pressure is low, a direct acting diaphragm solenoid valve such as CD-P can be used.

5. If the medium flows in a directional manner and does not allow reverse flow, ZDF-N and ZQDF-N need to flow in both directions. Please make special requirements. The temperature of the medium should be selected within the allowable range of the solenoid valve.

2、 Pipeline parameters

1. Select valve ports and models based on the requirements of medium flow direction and pipeline connection method. For example, for switching from one pipeline to two pipelines, CA5 and Z3F are selected for small diameters, and ZDF-Z1/2 is selected for medium or large diameters. For controlling the convergence of two pipelines, please choose ZDF-Z2/1, etc.

2. Select the nominal diameter based on the flow rate and valve Kv value, or choose the same pipe inner diameter. Please note that some manufacturers do not indicate the Kv value, and the valve hole size is often smaller than the interface pipe diameter. Do not be tempted by low prices and make mistakes.

3. Work pressure difference. Indirect pilot type can be used when the minimum working pressure difference is above 0.04Mpa; For those with a minimum working pressure difference close to or less than zero, direct acting or step-by-step direct acting must be selected.

3、 Environmental conditions

1. The maximum and minimum temperatures of the environment should be selected within the allowable range. If there is any deviation, special orders should be made.

2. In environments with high relative humidity and water droplets and rain, waterproof solenoid valves should be selected.

3. Special types such as marine solenoid valves should be selected for situations where there are frequent vibrations, bumps, and impacts in the environment.

4. When used in corrosive or explosive environments, priority should be given to selecting corrosion-resistant materials based on safety requirements.

5. If the environmental space is limited, please choose a multifunctional solenoid valve as it eliminates the need for a bypass and three manual valves, and is easy to maintain online.

1. Switch form:

The solenoid valve is driven by a coil and can only be turned on or off, with a short action time when turned on or off.

The driving of electric valves is usually done by motors, and the opening or closing action requires a certain amount of time for analog measurement, which can be adjusted.

2. Job nature:

Electromagnetic valves generally have a small flow coefficient and a small working pressure difference. For example, the flow coefficient of a typical 25 caliber solenoid valve is much smaller than that of a 15 caliber electric ball valve. The drive of solenoid valves is through electromagnetic coils, which are relatively easy to be damaged by voltage surges. Equivalent to the function of a switch, it has two functions: on and off.

Electric valves are generally driven by motors, which are more resistant to voltage surges. Electromagnetic valves are quick opening and quick closing, generally used in places with low flow and low pressure, requiring high switching frequency. Electric valves are the opposite. The opening of the electric valve can be controlled, with states including open, closed, and half open/half closed, which can control the flow rate of the medium in the pipeline. However, the solenoid valve cannot meet this requirement.

Electromagnetic valves can generally reset when powered off, while electric valves require a reset device for this function.

3. Applicable process:

Electromagnetic valves are suitable for some special process requirements, such as leakage, special fluid media, etc., and are relatively expensive.

Electric valves are generally used for regulation, and there are also switch quantities, such as at the end of fan coil units.

There are many types of solenoid valves, and different solenoid valves play a role in different positions of the control system. The most commonly used ones are one-way valves, safety valves, directional control valves, speed regulating valves, etc.

Working principle

The solenoid valve has a sealed chamber with through holes at different positions, each connected to a different oil pipe. The middle of the chamber is a piston, and there are two electromagnets on both sides. The valve body will be attracted to which side when the magnet coil on the other side is energized. By controlling the movement of the valve body, different oil discharge holes can be opened or closed. The oil inlet hole is normally open, and hydraulic oil will enter different oil discharge pipes. Then, the pressure of the oil will push the piston of the oil cylinder, which in turn drives the piston rod, which drives the mechanical device. In this way, the mechanical motion is controlled by controlling the current on and off of the electromagnet.

Main classification

1. Electromagnetic valves can be classified into three main categories based on their principles:

Direct acting solenoid valve

Principle: When powered on, the electromagnetic coil generates electromagnetic force to lift the closing member from the valve seat, and the valve opens; When the power is cut off, the electromagnetic force disappears, and the spring presses the closing member against the valve seat, causing the valve to close.

Characteristics: It can work normally under vacuum, negative pressure, and zero pressure, but the diameter generally does not exceed 25mm.

Step by step direct acting solenoid valve

Principle: It is a combination of direct action and pilot operated principle. When there is no pressure difference between the inlet and outlet, after being energized, the electromagnetic force directly lifts the pilot small valve and the main valve closing member upward in sequence, and the valve opens. When the inlet and outlet reach the starting pressure difference, after being energized, the electromagnetic force pilot small valve, the lower chamber pressure of the main valve rises, and the upper chamber pressure drops, thereby using the pressure difference to push the main valve upwards; When the power is cut off, the pilot valve uses spring force or medium pressure to push the closing member downwards, causing the valve to close.

Features: It can also operate under zero pressure difference, vacuum, and high pressure, but with high power, it must be installed horizontally.

Pilot operated solenoid valve

Principle: When powered on, the electromagnetic force opens the pilot hole, causing the pressure in the upper chamber to rapidly decrease, creating a pressure difference of high and low around the closing element. The fluid pressure pushes the closing element to move upward, and the valve opens; When the power is cut off, the spring force closes the pilot hole, and the inlet pressure quickly forms a lower and higher pressure difference around the closing valve through the bypass hole. The fluid pressure pushes the closing valve to move downward and close the valve.

Features: The upper limit of the fluid pressure range is relatively high, and it can be installed freely (customized), but it must meet the fluid pressure difference conditions.

2. Electromagnetic valves are divided into six sub categories based on differences in valve structure, materials, and principles: direct acting diaphragm structure, step-by-step direct acting diaphragm structure, pilot diaphragm structure, direct acting piston structure, step-by-step direct acting piston structure, and pilot piston structure.

3. Electromagnetic valves are classified according to their functions: water solenoid valves, steam solenoid valves, refrigeration solenoid valves, low-temperature solenoid valves, gas solenoid valves, fire solenoid valves, ammonia solenoid valves, gas solenoid valves, liquid solenoid valves, miniature solenoid valves, pulse solenoid valves, hydraulic solenoid valves, normally open solenoid valves, oil solenoid valves, DC solenoid valves, high-voltage solenoid valves, explosion-proof solenoid valves, etc.

The steam solenoid valves we come into contact with in our daily lives are often divided into two types:

1. Boiler steam - saturated steam

2. Steam from thermal power plants - superheated steam

1. Saturated steam: relatively stable temperature and pressure, temperature below 250 ℃, working pressure below 1.6Mpa

2. Overheated steam: with a large base of temperature and pressure changes, the highest temperature can reach over 400 ℃, and the working pressure is below 4.0Mpa

Classification of steam solenoid valves

For the first type of steam, we usually choose soft sealed steam solenoid valves.

Structural characteristics

This valve is a pilot operated secondary opening solenoid valve composed of two main components: the auxiliary valve and the main valve

advantage

Heat resistance: Special high-temperature resistant electrical and sealing materials are used for the electromagnetic and sealing parts, and various insulation measures are applied

Wear resistant: Reasonable material selection, valve cup and guide sleeve cleverly utilize the lubrication effect of fluid to reduce wear and improve service life

Condensation resistance: The condensation water in the steam pipeline is an important factor affecting the operation of the steam solenoid valve, while this valve is not affected by condensation water

Soft sealed solenoid valve

This series of solenoid valves can also be widely used in textile, printing, chemical, plastic, rubber, pharmaceutical, food, building materials, machinery, electrical, surface treatment steam solenoid valves, scientific research departments, as well as automatic control systems for bathrooms, canteens, air conditioning, etc.

Classification of steam solenoid valves

For the second type of steam, we usually choose hard sealed steam solenoid valves

Structural characteristics

Adopting metal hard sealing improves the product's operating temperature and service life

Reasonable material selection, cleverly utilizing the lubrication effect of fluid in the valve cup and guide sleeve to reduce wear

Hard sealed solenoid valve

This product has a wide range of universal media and can be used for fluids such as water, light oil, heavy oil, non corrosive gases, and steam.

In the drainage system of power station exhaust pipelines and the exhaust system of evaporators, the main function is to perform dual position automatic regulation and remote control of the medium in the pipelines.

working condition

Normally closed - powered on to open, powered off to close

Normally open - power off to open, power on to close

The steam solenoid valves we come into contact with in our daily lives are often divided into two types:

1. Boiler steam - saturated steam

2. Steam from thermal power plants - superheated steam

1. Saturated steam: relatively stable temperature and pressure, temperature below 250 ℃, working pressure below 1.6Mpa

2. Overheated steam: with a large base of temperature and pressure changes, the highest temperature can reach over 400 ℃, and the working pressure is below 4.0Mpa

Classification of steam solenoid valves

For the first type of steam, we usually choose soft sealed steam solenoid valves.

Structural characteristics

This valve is a pilot operated secondary opening solenoid valve composed of two main components: the auxiliary valve and the main valve

advantage

Heat resistance: Special high-temperature resistant electrical and sealing materials are used for the electromagnetic and sealing parts, and various insulation measures are applied

Wear resistant: Reasonable material selection, valve cup and guide sleeve cleverly utilize the lubrication effect of fluid to reduce wear and improve service life

Condensation resistance: The condensation water in the steam pipeline is an important factor affecting the operation of the steam solenoid valve, while this valve is not affected by condensation water

Soft sealed solenoid valve

This series of solenoid valves can also be widely used in textile, printing, chemical, plastic, rubber, pharmaceutical, food, building materials, machinery, electrical, surface treatment steam solenoid valves, scientific research departments, as well as automatic control systems for bathrooms, canteens, air conditioning, etc.

Classification of steam solenoid valves

For the second type of steam, we usually choose hard sealed steam solenoid valves

Structural characteristics

Adopting metal hard sealing improves the product's operating temperature and service life

Reasonable material selection, cleverly utilizing the lubrication effect of fluid in the valve cup and guide sleeve to reduce wear

Hard sealed solenoid valve

This product has a wide range of universal media and can be used for fluids such as water, light oil, heavy oil, non corrosive gases, and steam.

In the drainage system of power station exhaust pipelines and the exhaust system of evaporators, the main function is to perform dual position automatic regulation and remote control of the medium in the pipelines.

working condition

Normally closed - powered on to open, powered off to close

Normally open - power off to open, power on to close

1. Ensure the quality of the solenoid valve

The selection of solenoid valves must undergo strict calculations; The type, caliber, and various performance must meet the requirements; The materials for various components of solenoid valves must be strictly selected, with sufficient strength and stiffness, and must pass pressure tests, air tightness tests, and other tests in accordance with national standards. The manufacturing technology and testing methods of the manufacturer must comply with the standards and be approved by the competent department. It is strictly prohibited for small factories without production conditions to carry out production.

2. Ensure reliable operability

This not only refers to the manufacturing quality of the solenoid valve itself, but also includes the training and improvement of the quality of the operators. To prevent misoperation, process personnel must pay attention to the precautions indicated on the nameplate. According to China's standards for pneumatic solenoid valves. The nameplate of the pneumatic actuator should at least indicate the manufacturer's name, product model, rated flow coefficient, design tag number, product number, and manufacturing year and month. Arrows indicating the direction of medium flow, DN values, and PN letters and values should be cast or punched out on the valve body. Important valves should have sufficient accessories, such as positioners, limit switches, etc. There should be sufficient installation and operation space, adequate lighting, and strict operating procedures.

To solve the reliability and maintainability issues of solenoid valves, in addition to giving sufficient consideration in design, strict control of key processes should also be implemented during the manufacturing process. The key manufacturing technologies and implementation methods for high reliability and maintainability solenoid valves include welding, processing, verification testing, and functional testing.

1. Welding

The welding parts of solenoid valves include sleeve, piston, valve head sealing surface welding, piston outer surface welding, and shield sleeve component self welding. Conduct full inspection before, during, and after welding to ensure that the welding quality meets the specified requirements.

2. Mechanical processing

The key technology for mechanical processing of solenoid valves lies in the precision machining of the sealing surfaces of the sleeve, piston, and valve head, as well as the precision machining of the inner hole of the sleeve, the inner and outer surfaces of the piston, and the outer circle of the valve head. These parts have high surface hardness and high dimensional accuracy, making them difficult to process. Firstly, these processing procedures should be identified as critical processes, and process capability assessment must be conducted before manufacturing. Only after passing the assessment can processing be carried out. During the machining process of parts, a control program with designated personnel, equipment, and processes is adopted to ensure the machining quality of the parts.

Principles for selecting specifications and models of solenoid valves

3. Grinding of sealing surface

In order to ensure the sealing performance of its valve seat, the sealing surface must be ground to achieve the required roughness. The contact surfaces between the piston and the sleeve, as well as between the piston and the valve head, should adopt a mating process to ensure that the sealing meets the specified requirements.

Self operated regulating valve (self operated control valve) relies on the pressure and temperature of the medium flowing through the valve as energy to drive the valve disc to change the valve opening, achieving automatic operation of regulating pressure, flow rate, and temperature, without the need for external power supply and secondary instruments. Self operated regulating valves are often used to control the pressure behind the valve. Refrigeration solenoid valves

The difference between pneumatic control valve and self operated control valve:

Self regulating valves can not only control the pressure behind the valve, but also control the pressure in front of the valve in many situations. The self regulating valve is actually a pure proportional control system, which may result in residual errors. The regulating valve controls pressure regardless of the flow rate. But for any type of regulating valve, the direct control is the flow rate. The biggest difference between these two types of valves is that the control valve requires both external energy sources (such as power or gas) as driving energy and external control instrument signals to change the relative position of the valve's shut-off component, thereby achieving a change in fluid flow rate. Self regulating valves, on the other hand, do not require external energy sources or signals from external control instruments. They can achieve pressure regulation solely based on the pressure signal of the regulated medium. The characteristic of self operated pressure regulating valve is that it does not have external driving energy, so the operating force of this product is relatively small.

Refrigeration solenoid valve

1. In terms of regulation: Regulating valves have higher regulation accuracy than self operated valves. The regulation accuracy of self operated regulating valves mainly depends on the accuracy of the spring and diaphragm of the self operated valve. Generally, the final regulation accuracy will not be better than 5%, with a guarantee of 10%. However, the final adjustment accuracy of ordinary regulating valves depends on the accuracy of the meter transmitter and the accuracy of the regulator, and the accuracy of the regulator is very high, and its impact is generally ignored. So the regulation accuracy of self operated valves is definitely much worse than that of ordinary regulation circuits. When the regulation accuracy requirements are high, it is not recommended to use self operated valves.

2. Application: One on-site, one remote transmission, one using medium pressure regulation, and one using instrument air. If the regulating valve is led to DCS control, it can be easily changed to the given value, and can be manually quickly closed or opened, with various related trend records. The self regulating valve cannot be adjusted and can only be operated on site. The degree of intelligence will be greatly reduced. Self operated regulating valves are difficult to adjust the set value, so they are used in situations where the setting does not need to be changed frequently, such as supplying lubricating oil to equipment. Self operated regulating valves require pressure from the process medium, so they are not suitable for use in relatively clean environments where the medium has corrosion, particles, etc.

3. Installation and design: Self operated regulating valves have pre valve pressure control and post valve pressure control. During design, proper spacing should be left for the installation of pressure points. During installation, the self regulating valve actuator on the steam pipeline should be installed downwards, and the pressure point should be connected to the condenser from the bottom of the main pipe. The condenser should be higher than the actuator and lower than the steam main pipe to avoid steam overheating and damage to the valve body. In addition, the actuator should be installed upwards. As self regulating valves are commonly used in gas pipes, the pressure point should be opened from the top of the main pipe at this time.

Selection criteria:

1. Select the solenoid valve based on pipeline parameters: diameter specification (i.e. DN), interface method

1) Determine the diameter (DN) size according to the on-site pipeline inner diameter size or flow requirements;

2) Interface method, generally>DN50 requires flange interface, ≤ DN50 can be freely selected according to user needs.

2. Select the material and temperature group of the solenoid valve based on fluid parameters

1) Corrosive fluids: corrosion-resistant solenoid valves and all stainless steel should be selected; Edible ultra clean fluid: It is recommended to use food grade stainless steel solenoid valves;

2) High temperature fluid: It is necessary to choose electromagnetic valves made of high-temperature resistant electrical materials and sealing materials, and to choose piston type structures;

3) Fluid state: up to gaseous, liquid, or mixed state, especially when the diameter is greater than DN25, it must be distinguished;

4) Fluid viscosity: Usually below 50cSt, it can be freely selected. If it exceeds this value, a high viscosity solenoid valve should be used.

3. Selecting solenoid valves based on pressure parameters: principles and structural types

1) Nominal pressure: This parameter has the same meaning as other general valves and is determined based on the nominal pressure of the pipeline;

2) Work pressure: If the work pressure is low, the principle of direct action or step-by-step direct action must be selected; When the minimum working pressure difference is above 0.04Mpa, direct acting, step-by-step direct acting, and pilot operated can all be selected.

4. Electrical selection: The voltage specifications should preferably be AC220V or DC24, which are more convenient.

5. Choose based on the duration of continuous work: normally closed, normally open, or continuously powered on

1) When the solenoid valve needs to be opened for a long time and the duration exceeds the closing time, the normally open type should be selected;

2) If the opening time is short or the opening and closing time is not long, choose the normally closed type;

3) However, for some working conditions used for safety protection, such as furnace and kiln flame monitoring, the normally open type cannot be selected, and the long-term electrified type should be selected.

6. Select auxiliary functions according to environmental requirements: explosion-proof, check, manual, waterproof fog, water shower, and diving.

Selection principle

Security:

1. Corrosive media: Plastic king solenoid valves and all stainless steel should be selected; For strongly corrosive media, isolation membrane type must be selected. Neutral media, it is also advisable to use copper alloy as the valve shell material for solenoid valves, otherwise rust debris often falls off from the valve shell, especially in situations where the action is not frequent. Ammonia valves cannot use copper materials.

2. Explosive environment: Corresponding explosion-proof products must be selected, and waterproof and dustproof varieties should be selected for outdoor installation or in dusty environments.

3. The nominal pressure of the solenoid valve should exceed the maximum working pressure inside the pipe.

Applicability:

1. Medium characteristics

1) Select different types of solenoid valves for gas, liquid, or mixed states;

2) Products with different specifications and medium temperatures may cause the coil to burn out and the sealing components to age, seriously affecting their service life;

3) The viscosity of the medium is usually below 50cSt. If it exceeds this value and the diameter is greater than 15mm, use a multifunctional solenoid valve; When the diameter is less than 15mm, use a high viscosity solenoid valve.

4) When the cleanliness of the medium is not high, a backwash filter valve should be installed in front of the solenoid valve. When the pressure is low, a direct acting diaphragm solenoid valve can be selected;

5) If the medium flows in a directional manner and backflow is not allowed, it needs to flow in both directions;

6) The medium temperature should be selected within the allowable range of the solenoid valve.

2. Pipeline parameters

1) Select valve ports and models based on the requirements of medium flow direction and pipeline connection method;

2) Select the nominal diameter based on the flow rate and valve Kv value, or choose the same pipe inner diameter;

3) Working pressure difference: Indirect pilot type can be used when the minimum working pressure difference is above 0.04Mpa; For those with a minimum working pressure difference close to or less than zero, direct acting or step-by-step direct acting must be selected.

3. Environmental conditions

1) The maximum and minimum temperatures of the environment should be selected within the allowable range;

2) In environments with high relative humidity and water droplets and rain, waterproof solenoid valves should be selected;

3) Special varieties should be selected for situations where there are frequent vibrations, bumps, and impacts in the environment, such as marine solenoid valves;

4) When used in corrosive or explosive environments, priority should be given to selecting corrosion-resistant types according to safety requirements;

5) If the environmental space is limited, a multifunctional solenoid valve should be selected because it eliminates the need for a bypass and three manual valves, and is easy to maintain online.

4. Power supply conditions

1) Select AC and DC solenoid valves according to the type of power supply. Generally speaking, AC power supply is easy to access;

2) Voltage specifications should prioritize AC220V and DC24V as much as possible;

3) The fluctuation of power supply voltage is usually selected as% -15% for AC, and ± for DC. If it exceeds the tolerance, voltage stabilization measures must be taken;

4) The rated current and power consumption should be selected based on the power capacity. Attention should be paid to the high VA value during communication start-up, and indirect induction solenoid valves should be preferred when the capacity is insufficient.

5. Control accuracy

1) Ordinary solenoid valves only have two positions, on and off. When high control accuracy and stable parameter requirements are needed, multi position solenoid valves should be selected;

2) Action time: refers to the time from when the electrical signal is turned on or off to when the main valve action is completed;

3) Leakage rate: The leakage rate values given on the sample are commonly used economic levels.

Reliability:

1. The working life is not included in the factory test items, but belongs to the type test items. To ensure quality, branded products from reputable manufacturers should be selected.

2. Work system: divided into three types: long-term work system, repeated short-term work system, and short-term work system. For situations where the valve is open for a long time but only closed for a short time, it is advisable to use a normally open solenoid valve.

3. Working frequency: When the operating frequency requirement is high, the structure should preferably use a direct acting solenoid valve, and the power supply should preferably use AC.

4. Action reliability

Strictly speaking, this test has not yet been officially included in the professional standards of Chinese solenoid valves. To ensure quality, branded products from reputable manufacturers should be selected. In some situations where the number of actions is not high, but the reliability requirements are very high, such as fire protection, emergency protection, etc., we must not take it lightly. It is particularly important to adopt dual insurance for two consecutive uses.

Economy:

It is one of the selected scales, but it must be economical based on safety, applicability, and reliability.

Economy is not only about the price of the product, but also about prioritizing its functionality and quality, as well as the cost of installation, maintenance, and other accessories.

More importantly, the cost of a single solenoid valve in the entire control system and even in the production line is negligible. If one chooses the wrong one for the sake of small gains, it can cause huge damage to the group.

Firstly, the expression of listening to sound;

1. The action speed of the solenoid valve is the fastest among all valves, at the millisecond level. Under normal circumstances, when powered on, a "bang" sound is heard instantly, crisp and clear. If the coil burns out, there will definitely be no sound;

2. There is also a situation where there is a continuous "bang" sound after being powered on, which is usually due to insufficient suction, insufficient voltage, or impurities in the valve chamber causing the valve core to get stuck;

3. After the communication solenoid valve is powered on, there will also be a sound, but this continuous and stable current sound is normal;

4. If the solenoid valve is activated, the flow sound of the pipeline medium should be heard at this time;

Stainless steel solenoid valve

Secondly, observe external performance;

1. Check if the coil has bulged or cracked,

2. Check if the wiring is damaged;

3. Whether the valve body is cracked, especially for some plastic or iron valve bodies that are prone to aging at low or high temperatures, this problem may occur;

Thirdly, test the intrinsic performance;

1. If the coil is good, there will be a magnetic field outside the coil, just try it with an iron nail;

2. Touch the temperature of the coil. Except for high-temperature and low-temperature solenoid valves, a typical solenoid valve will feel warm after being powered on for about half an hour. If it is cold, it can be judged that the wiring is broken. If it is particularly hot (except for high-temperature steam media), it can be judged that there is a short circuit;

3. If you can still hear the sound of water or air flow at the outlet of the pipeline after it is closed, but you can clearly feel that the sound is loud when there is no valve open - what are the manifestations of a broken solenoid valve? This is a very obvious one, which means that the valve is not tightly closed and there is a problem with the sealing position.

solenoid valve

By following the above steps on site, it is easy to determine whether the solenoid valve is broken, whether there is a malfunction, and what are the general manifestations of a broken solenoid valve. The above three methods can be used to easily determine. Electromagnetic valves belong to precision components and are the most widely used type in all valve fields. They are very practical for water, gas, and oil with low viscosity. However, there are also many working conditions that are not suitable for using electromagnetic valves, such as mud, powder, grease, particles, and other media. Therefore, when determining whether to choose an electromagnetic valve and which one is more suitable,

High temperature solenoid valves are widely used in shipbuilding industry, testing equipment, heating equipment, hydraulic equipment and other fields, with working temperatures above 300 ℃ in thermal conductivity systems. Heating devices, industrial kilns, high-temperature soot blowing, drying equipment, steel mills, thermal power plants, textile printing and dyeing, petrochemicals, chemical equipment, HVAC, coating equipment, pharmaceutical machinery, electroplating and coating control systems, such as power plant exhaust pipe drainage system and exhaust steam system. In industrial production, automatic control of steam and heat transfer oil is not only necessary for the production process, but also a necessary condition for energy conservation. For many years, high-temperature solenoid valves such as steam and thermal oil have caused serious economic losses and hindered production due to such quality issues. Therefore, improvements and optimizations were made to the valves, and an analysis was conducted on how to apply and select them to meet the requirements of various production lines.

process control

In order to solve the reliability and maintainability issues of high-temperature and high-pressure solenoid valves, in addition to considering reasonable structure and suitable materials in the design, it is also necessary to control the production process of their key components during the manufacturing and testing processes. The key and special processes for processing high-temperature and high-pressure solenoid valves include surface treatment, welding, and precision machining.

1) The fine machining of nuts, valve plugs, and valve bodies is a key component of solenoid valves. The key points are the size of the inner hole of the screw cap, the outer ring of the valve plug, and the roughness of the sealing surface. Identify surface treatment of valve plugs as a critical process. Valve plugs have the characteristics of high hardness, high dimensional accuracy, and easy deformation, so it is necessary to screen the surface treatment of valve plugs. Conduct process capability analysis on key components to ensure the machining quality of the parts. Personnel, equipment, designated locations, regular inspections, data collection for statistical analysis.

2) The valve cover of the solenoid valve is welded to the magnetic insulation tube, and the magnetic insulation tube is welded to the fixed iron core. The original self fusion welding was changed to wire filling welding, which improved the welding strength and prevented fatigue cracking. Conduct compressive strength test and air tightness test after welding to ensure welding quality.

3) High temperature solenoid valves generally use hard seals for sealing. In order to ensure that the sealing performance meets the requirements, the sealing surface of the valve seat and the sealing of the valve core must be grounded. The sealing surface of the valve plug and valve seat adopts matching grinding technology to make the roughness of the sealing surface greater than 0.2 microns.

Production process control and maintenance of high-temperature solenoid valves

maintenance

When using high-temperature steam solenoid valve products, it is also necessary to pay attention to the installation and working environment conditions of the solenoid valve, such as temperature and pressure. The maintenance of steam solenoid valve products during normal use is also an important part to ensure their normal operation.

1) Please read the product manual carefully before installation and check if the installed product fully meets the usage requirements. Suggest that users send someone to be responsible for maintenance.

2) Before installation, the pipeline and accessories must be thoroughly cleaned to remove metal dust, residual raw material bands, rust and other impurities inside the pipeline. For unclean media, install a filter in front of the valve.

3) During installation, prevent condensation and impurities from depositing inside the valve. Do not install the valve at the lowest point of the pipeline to avoid affecting operation.

4) In order to ensure the normal use of the solenoid valve, multiple tests are required after installation before it can be officially used.

5) When working, pay attention to the working pressure of the front and rear valves. The maximum working pressure should not exceed the nominal pressure. The difference in the required minimum working pressure is that the difference in pipeline working pressure must be greater than the minimum pressure difference to prevent the solenoid valve from failing to operate. When the working pressure exceeds the rated pressure or maximum working pressure, the system should stop using or reduce the working pressure.

6) During normal valve maintenance, the dirt inside the valve should be cleaned regularly. For example, between the mating surfaces of the screw cap and valve plug, and between the static core and the dynamic core, be careful not to damage the sealing surfaces.

7) When the medium of the high-temperature solenoid valve is thermal oil, when removing it from the pipeline, the valve internals should be cleaned with CCL4 and compressed air should be blown clean for storage. When disassembling and cleaning, all components should be arranged neatly and restored to their original state.

8) The high-temperature solenoid valve should be cleaned of condensed water and gas first, and then tried several times until it operates normally before being put into use. When the electromagnetic valve for thermal oil is not in use for a long time, the manual valve should be closed at the same time.

Conduct research, analysis, and improvement through design, manufacturing, and maintenance. Effectively solved the problem of insensitive operation, jamming, and closing of high-temperature solenoid valves. The clever design and treatment between the valve core and the guide rail improve the smoothness effect, reduce wear, extend service life, adapt to medium temperature changes and frequent work. Enable valves to have higher reliability and safety throughout the entire system.

Electromagnetic valve is one of the earliest valve products, and there are many types derived from it. Among them, the development of high-temperature solenoid valves is relatively early due to various reasons such as applicability. Under normal circumstances, early developed varieties will gradually fall behind with the development of technology and be completely eliminated. However, high-temperature solenoid valves are becoming increasingly popular in the market, and their sales have remained at a high level without any downward trend.

The reason for this situation is actually quite simple and easy to understand. The main reason is that although solenoid valves appeared earlier, when their development gave rise to high-temperature solenoid valves, their technology and other aspects were already relatively mature, and the subsequent changes needed were very few, and there were not many areas that could be improved.

In addition, with the development of technology, there are increasingly more high-temperature environments in modern industry. Among valve products in these environments, high-temperature solenoid valves that can function normally under high temperature conditions are naturally popular, and their demand is further increasing.