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.