The role of solenoid valve

The role of solenoid valve, the original work of the solenoid valve, the scope of use of the solenoid valve, the structure of the solenoid valve

Solenoid valve is an automatic basic element used to control the direction of the fluid, belonging to the actuator; usually used for mechanical control and industrial valves, to control the direction of the media, so as to achieve the control of the valve switch.

working principle

There are closed chambers in the solenoid valve. There are through holes in different positions. Each hole leads to a different tubing. The valve is in the middle of the chamber. Two electromagnets are on both sides. Which side of the magnet coil energizes the valve body. On which side, by controlling the movement of the valve body to block or leak out different oil discharge holes, and the oil inlet hole is normally open, the hydraulic oil will enter different oil discharge pipes, and then the oil pressure will be used to push the oil tank. Pistons and pistons actuate piston rods, which move the mechanical devices. This controls the mechanical motion by controlling the electromagnet current.

classification

1. The Electromagnetic Valve is divided into three major categories:

1) Direct acting solenoid valve:

Principle: When the power is turned on, the Electromagnetic Coil generates electromagnetic force to lift the closing member from the valve seat and the valve opens. When the power is turned off, the electromagnetic force disappears. The spring presses the closing member against the valve seat and the valve closes.

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

2) Distributed direct acting solenoid valve:

Principle: It is a combination of direct acting 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 part and the valve opens. When the inlet and outlet reach the starting pressure difference, after the power is turned on, 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 decreases, so that the main valve is pushed upwards by utilizing the pressure difference; when the power is off, the pilot valve utilizes the spring. Force or medium pressure pushes the closure and moves it down to close the valve.

Features: It can also operate at zero differential pressure or vacuum and high pressure, but it requires a large amount of power and 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 pressure difference between the lower part and the upper part is formed around the closing part. The fluid pressure pushes the closing part to move upwards and the valve opens; when the power is turned off, the spring force leads the pilot. The hole is closed and the inlet pressure quickly bypasses the chamber to form a lower, upper high pressure differential around the valve closing member. The fluid pressure pushes the closing member downward and closes the valve.

Features: The upper limit of the fluid pressure range is high and can be installed arbitrarily (customization is required) but the fluid pressure difference must be met.

2. The electromagnetic valve is divided into six subcategories by the difference in principle and valve structure and material:

Direct-acting diaphragm structure, step-by-step structure, pilot diaphragm structure, direct-acting piston structure, step-by-step direct-acting piston structure, and pilot piston structure. Solenoid valve in the selection of matters needing attention

One: Applicability

The fluid in the tubing must match that of the media in the selected solenoid valve model.

The temperature of the fluid must be less than the calibrated temperature of the selected solenoid valve.

Solenoid Valves allow the viscosity of liquids to be generally below 20CST, and should be indicated when more than 20CST.

Working pressure difference, the maximum pressure difference in the pipeline is less than 0.04MPa should be used such as ZS, 2W, ZQDF, ZCM series of direct-acting and step-by-step direct-acting; minimum operating pressure difference is greater than 0.04MPa can use the pilot type (pressure Differential type) Solenoid valve; the maximum working pressure difference should be less than the maximum calibration pressure of the solenoid valve; the general electromagnetic valve is one-way operation, so pay attention to whether there is back pressure difference, if there is a check valve installed.

When the fluid cleanliness is not high, the filter should be installed in front of the solenoid valve. Generally, the electromagnetic valve requires better cleanliness of the medium.

Pay attention to the flow aperture and the nozzle diameter; solenoid valve is generally only two-way control switch; conditions allow to install the bypass pipe, easy to repair; have water hammer phenomenon to customize the solenoid valve opening and closing time adjustment.

Pay attention to the influence of ambient temperature on the solenoid valve

The power supply current and power consumption should be selected according to the output capacity. The power supply voltage is generally allowed to be ±10%. It must be noted that the VA value at the time of AC start is high.

Second, reliability

Solenoid valves are classified into two types: normally closed and normally open; Normally selected are normally closed, energized open, and power off; however, normally open type is used when the open time is very long and closed.

Life test, the factory is generally a type test project, to be exact, there is no professional standard for solenoid valves in China, so choose a solenoid valve manufacturer with care.

When the operation time is very short, the direct-acting type is generally selected and the large-caliber selection is used for the fast series.

The role of solenoid valve, the original work of the solenoid valve, the scope of use of the solenoid valve, the structure of the solenoid valve

Third, security

General solenoid valve is not waterproof, please use waterproof type when conditions do not allow, factory can be customized.

The highest rated pressure of the solenoid valve must exceed the maximum pressure in the pipeline, otherwise the service life will be shortened or other unexpected situations will occur.

Corrosive liquids should be made of all-stainless steel type, and strong corrosive fluids should use plastic king (SLF) solenoid valves.

Explosion-proof products must be selected for explosive environments.

Fourth, economy

There are many solenoid valves that can be used universally, but the most economical product should be chosen based on the above three points.

Solenoid valve selection

Solenoid valve selection should first follow the four principles of safety, reliability, applicability, and economy, followed by six field conditions (ie pipeline parameters, fluid parameters, pressure parameters, electrical parameters, and modes of operation). Special requirements to choose).

Selection basis:

First, select the solenoid valve according to the pipeline parameters: diameter specification (ie DN), interface method

1. Determine the DN size according to the size of the inner diameter of the site pipe or the flow requirement.

2. Interface mode, generally> DN50 to select the flange interface, ≤ DN50 can be freely selected according to user needs.

Second, select the solenoid valve according to the fluid parameters: material, temperature group

1. Corrosive fluids: Corrosion-proof solenoid valves and stainless steel should be selected; Ultra-clean fluids should be used: Food grade stainless steel solenoid valves should be used.

2, high-temperature fluid: to choose to use high-temperature electrical materials and sealing materials manufactured by the solenoid valve, but also to choose the type of piston structure.

3, the fluid state: as large as there are gaseous, liquid or mixed state, especially when the caliber is greater than DN25 must be distinguished when ordering.

4, fluid viscosity: usually 50cSt below can be arbitrarily selected, if more than this value, you must use high viscosity solenoid valve.

Third, according to the pressure parameter selection solenoid valve: principle and structure varieties

1. Nominal pressure: This parameter is the same as the meaning of other common valves and is determined according to the nominal pressure of the pipeline.

2, the working pressure: If the working pressure is low, you must use straight-acting or step-by-step direct-acting principle; the minimum operating pressure difference is above 0.04Mpa when the direct-acting, step-by-step direct-acting, pilot-type can be selected.

Fourth, the electrical choice: The voltage specification should try hard to choose AC220V, DC24 more convenient.

Fifth, choose according to the duration of continuous work: normally closed, normally open, or sustainable power

2, if the opening time is short or the opening and closing time is not long, then select the normally closed type.

3, but some of the conditions for safety protection, such as furnace, kiln flame monitoring, can not be selected normally open, should be selected long-term power type.

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

1. Explosive environment: The corresponding explosion-proof electromagnetic valve must be selected (my company's existing: d II BT4, d II CT5, Ex m I/II T4).

2. When the fluid in the pipe has a backflow phenomenon, the OK71-N and OK72-N series electromagnetic valves with non-return function can be selected.

3, when the need for manual operation of the solenoid valve on the spot, I can choose OK71-S, OK72-S series with manual function solenoid valve.

4, open-air installation or dust more occasions should use waterproof, dust-proof varieties (protection level above IP54).

5, for the fountain must use submersible solenoid valve (protection level above IP68).

1, when the solenoid valve requires a long time to open, and the duration of the excess time off should be selected normally open type. Select the characteristics to use when using

The role of solenoid valve, the original work of the solenoid valve, the scope of use of the solenoid valve, the structure of the solenoid valve

First, security:

1. Corrosive medium: The plastic king electromagnetic valve and all stainless steel should be used; for the strongly corrosive medium, the diaphragm type must be selected. Example CD-F. Z3CF. Neutral medium, should also use copper alloy valve shell material for the solenoid valve, otherwise, the valve shell often rust off, especially infrequent occasions. Ammonia valves cannot use copper.

2. Explosive environment: The corresponding explosion-proof grades must be selected. Waterproof and dustproof types should be selected for open-air installation or dusty occasions.

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

Second, applicability:

1. Media characteristics

1. Electromagnetic valves of different types are selected for quality gas, liquid state or mixed state respectively. Example ZQDF is used for air, ZQDF-Y is used for liquid, ZQDF-2 (or -3) is used for steam, otherwise it may cause malfunction. ZDF series multi-function solenoid valve can be connected to gas and liquid. It is best to state the media status at the time of subscription, and it is not necessary to install the user.

1.2 medium temperature products of different specifications, otherwise the coil will burn off, aging of the seal, seriously affecting life expectancy.

1.3 Medium viscosity, usually below 50 cSt. If it exceeds this value, the diameter is larger than 15mm and ZDF series multi-function solenoid valve is used for special orders. Path is less than 15mm high viscosity solenoid valve.

1.4 When the cleanliness of the medium is not high, a backflushing filter valve should be installed in front of the solenoid valve. In the case of low pressure, a direct-acting diaphragm type electromagnetic valve can be used as a CD-P.

1.5 If the medium is directional and does not allow backward flow, ZDF-N and ZQDF-N are required to use two-way flow, please make special requirements.

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

2. Pipeline parameters

2.1 Select the valve port and model according to the medium flow requirements and the pipe connection method. For example, for a switch from one pipe to two pipes, select CA5 and Z3F for small paths, and select ZDF-Z1/2 for medium or large paths. Another example is to control the convergence of two pipelines, please choose ZDF-Z2/1 and so on. 2.2 According to the flow and valve Kv value selected nominal diameter, but also with the pipe diameter. Please note that some manufacturers are not marked with Kv value, often the size of the valve hole is smaller than the interface diameter, must not be coveted and the price is low.

2.3 working pressure difference

The minimum working pressure difference is 0.04Mpa or more is optional indirect pilot; the lowest working pressure difference is close to or less than zero must use direct-acting or step-by-step direct type.

3. Environmental conditions

3.1 The maximum and minimum temperatures of the environment shall be selected within the allowable range. If there is any excess error, special orders shall be made.

3.2 When the relative humidity in the environment is high and there is water and rain and other occasions, the waterproof solenoid valve should be selected

3.3 There are often vibrations in the environment, and bumps and impacts should be selected for special applications, such as marine solenoid valves.

3.4 Use in Corrosive or Explosive Environments

3.5 If the environmental space is limited, please use the multi-function solenoid valve, because it eliminates the bypass and three manual valves and is easy to repair online.

4. Power conditions

4. 1 According to the type of power supply, use AC and DC solenoid valves respectively. In general, AC power is easy to use.

4.2 Voltage specification Use AC220V.DC24V as much as possible.

4.3 Power Supply Voltage Fluctuation Usually, the AC is selected between +% 10% and -15%, and the DC is allowed to be ± 10% or so. If there is an excess error, it is necessary to adopt a voltage regulator or make special order requirements.

4.4 The rated current and power consumption should be selected according to the power supply capacity. It should be noted that the value of VA is higher when the AC is started, and the indirect-conducting solenoid valve should be preferred when the capacity is insufficient.

5. Control accuracy

5.1 ordinary solenoid valve only open and close two positions, in the control of high precision requirements and the parameters required to be stable, please use a number of solenoid valves; Z3CF three normally open solenoid valve, with micro-open, fully open and close the three types of flow;

ZDF-Z1/1 combination multi-function solenoid valve has four kinds of flow: full open, wide open, small open and full open.

5.2 Operation time: refers to the time when the electrical signal is turned on or off to the completion of the main valve action. Only the company's patented product multi-function solenoid valve can adjust the opening and closing time separately, not only meeting the control accuracy requirements, but also preventing water hammer damage.

The role of solenoid valve, the original work of the solenoid valve, the scope of use of the solenoid valve, the structure of the solenoid valve

5.3 leakage

The leakage value given on the sample is a common economic grade. If it is too high, please make a special order.

Third, reliability:

1. Work life: This item is not included in the factory test project and it is a type test project. In order to ensure the quality should be selected from the regular manufacturers of brand-name products.

2, the work system: long-term work system, repeated short-term work and short-term work of three. The company's conventional products are long-term work systems, that is, coils allow long-term power work. For long-term valve opening only short-term closure, you should use normally open solenoid valve. Used in short-term work and batch

When large, special orders can be made to reduce power consumption.

3, working frequency: When the operating frequency is high, the structure should be direct-acting solenoid valve, and the power supply should listen to the preferred communication.

4, movement reliability

Strictly speaking, this test has not been formally included in China's electromagnetic valve professional standards, in order to ensure quality should be selected from the regular manufacturers of brand-name products. In some cases, the number of operations is not large, but the reliability requirements are very high, such as fire protection, emergency protection, etc., must not be taken lightly. Of particular importance, it should also take two consecutive double insurance.

Fourth, economy:

One of the scales it chooses, but it must be an economy that is based on safety, application, and reliability.

Economicality is not only the selling price of a product, but also priority is given to its function and quality, as well as the cost of installation, maintenance and other accessories.

More importantly, the cost of a solenoid valve in the entire automatic control system in the entire automatic control system and even the production line is negligible. If a small amount of money is spent on mistakes, the damage group is huge.