Solenoid valve is the industrial equipment with electromagnetic control, is used to control the fluid automation of the basic components, is not limited to hydraulic, pneumatic. Adjust the direction, flow rate, speed, and other parameters of the medium in the industrial control system.

1. Solenoid valve are divided into three categories in principle:

1) Direct-motion solenoid valve:

Principle: When electrified, the solenoid coil generates an electromagnetic force to lift the closing part from the valve seat, and the valve opens; when the power is cut off, the electromagnetic force disappears, the spring presses the closing part on the valve seat, and the valve closes.

Features: in vacuum, negative pressure, zero pressure, but the diameter generally does not exceed 25mm.

2) Distributional direct-motion solenoid valve:

Principle: it is a combination of direct movement and pilot principle, when there is no pressure difference between the entrance and outlet, after electricity, the electromagnetic force directly pilot small valve and the main valve closing parts in turn up, the valve opens. When the inlet and outlet reach the starting pressure difference, after the start-up, the main valve lower chamber pressure rises and the upper chamber pressure drops to push the main valve up, the pilot valve uses the spring force or medium pressure to move down to close the valve.

Features: in zero pressure difference or vacuum, high pressure can also be * action, but the power is large, must be installed horizontally.

3) Pilot-type solenoid valve:

Principle: When energized, the electromagnetic force opens the pilot hole, the upper chamber pressure drops rapidly, around the closing parts form high pressure difference, fluid pressure pushes the closing parts upward, the valve open; when power off, the spring force closes the pilot hole, the inlet pressure through the bypass hole around the valve difference, fluid pressure pushes the closing parts down, close the valve.

Features: High upper fluid pressure range, can be installed (to be customized) but must meet the fluid pressure difference conditions.

2. Solenoid valve is divided into six branch subcategories from the differences in valve structure and material:

Straight diaphragm structure, step heavy diaphragm structure, pilot membrane structure, direct piston structure, step direct piston structure, pilot piston structure.

Precautions for the solenoid valve during type selection

First, applicability

The fluid in the pipeline must be the same with that calibrated in the solenoid valve series model selected. The temperature of the fluid must be less than the calibration temperature of the selected solenoid valve. The allowable liquid viscosity of solenoid valve is generally below 20CST and 20 greater than C S T should be indicated.

When the fluid cleanliness is not high, the filter should be installed in front of the solenoid valve, and the general solenoid valve requires good cleanliness of the medium. Pay attention to the flow aperture and the diameter of the pipe; the solenoid valve is generally only two switch control; install the bypass pipe for easy maintenance; customize the solenoid valve during the water hammer. Note the effect of the ambient temperature on the solenoid valve. Power supply current and power consumption should be selected according to the output capacity. The power supply voltage generally allows about 10% of ±. Attention must be paid to the high VA value during AC start

Two, reliability

Solenoid valve is divided into normal closed and normal open two kinds; generally choose normal closed type, power open, power closed; but in a very short time to choose normal open type. Life test, the factory generally belongs to the type test project, to be exact, China has no professional standard of solenoid valve, so the selection of solenoid valve manufacturers carefully. The action time is very short when the frequency is high, generally choose direct motion type, large caliber choose fast series.

Three, safety

General solenoid valve is not waterproof, in the conditions do not allow, please choose waterproof type, the factory can be customized. Corrosive liquid should be selected with all stainless steel type, strong corrosive fluid should choose plastic king solenoid valve. Explosive environment must choose the corresponding explosion-proof products.

Four, economy

First, the four principles of safety, reliability, applicability and economy should be followed successively. Secondly, choose according to the six field conditions (namely, pipeline parameters, fluid parameters, pressure parameters, electrical parameters, action mode and special requirements).

Selection basis:

1. Select the solenoid valve according to the pipeline parameters: diameter specification (i. e., DN) and interface mode

1. Determine the diameter (DN) size according to the field pipe inner diameter size or flow requirements.

2. Interface mode, generally> DN50 should choose the flange interface, and DN50 can be selected freely, according to the user needs.

Two, according to the fluid parameters of the solenoid valve selection: material, temperature group

1. Corrosive fluid: should choose corrosion-resistant solenoid valve and all stainless steel; eat ultra-clean fluid: should choose food-grade stainless steel material solenoid valve.

2. High temperature fluid: to choose the high temperature resistant electrical materials and sealing materials made of the electromagnetic valve, and to choose the piston structure type.

3. Fluid state: large to gaseous, liquid or mixed state, especially when the diameter is greater than DN25 order must be distinguished.

4. Fluid viscosity: usually below 50cSt, if this value is exceeded, a high viscosity solenoid valve should be selected.

Three, according to the pressure parameters to choose the solenoid valve: the principle and structure varieties

1. Nominal pressure: This parameter has the same meaning as other general valves, and is determined according to the pipe nominal pressure.

2. Work pressure: If the working pressure is low, the principle of direct motion or step by step type must be selected. When the working pressure difference is above 0.04Mpa, the direct motion type, step by step type and pilot type can be selected.

Four, electrical selection: voltage specifications should be as far as possible to choose AC220V, DC24 is more convenient.

Five, according to the duration of continuous working time to choose: often closed, often open, or sustainable power

If the open time is short or the open and close time is not much, then choose the often closed type.

However, some working conditions used for safety protection, such as furnace, kiln flame monitoring, can not be selected to often open, should be selected for a long-term power type.

Six, according to the environmental requirements to choose auxiliary functions: explosion-proof, check back, manual, waterproof fog, water shower, diving

1. Explosive environment: the solenoid valve with the corresponding explosion-proof grade must be selected

2. When the fluid in the pipe has a backflow phenomenon, the solenoid valve with a check function can be selected.

3. When the field manual operation of the solenoid valve is required, the manual function solenoid valve can be selected.

4. Water-proof and dust proof should be selected for open installation or dust (the protection level is above IP54).

5. Diving solenoid valve must be used for the fountain (the protection level is above IP68).

6. When the solenoid valve needs to open for a long time, and the duration of the excess closing time should be selected.