Working Principle and Main Categories of Plastic Solenoid Valve

Solenoid valve is the industrial equipment with electromagnetic control, is used to control the fluid automation basic element, belongs to the actuator, is not limited to hydraulic, pneumatic. Adjust the direction, flow rate, speed, and other parameters of the medium in the industrial control system. The solenoid valve can cooperate with different circuits to achieve the desired control, and the control accuracy and flexibility can be guaranteed. There are many kinds of solenoid valves, different solenoid valves in the different positions of the control system to play a role, the most commonly used is the one-way valve, safety valve, direction control valve, speed control valve, etc.

Working principle: the solenoid valve has closed cavity, open hole in different positions, each hole connects different pipe, cavity in the middle of the piston, two sides are two pieces of solenoid magnet, which magnet coil power body will be attracted to which side, through the control valve body movement to open or close different oil holes, and oil hole is often open, hydraulic oil will enter different oil pipe, and then through the oil pressure to push the cylinder piston, piston and drive piston rod, piston rod drive mechanical device. This controls the mechanical motion by controlling the electrical flow break of the electromagnet.

Main categories: (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) Step-by-step direct-motion solenoid valve: Principle: it is a kind of direct movement and pilot type combination principle, when there is no pressure difference between the entrance and outlet, after the electricity, the electromagnetic force directly to the 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 power supply, 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, formed around the closing parts on the low on high pressure difference, fluid pressure pushes the closing parts upward movement, the valve open; when power off, the spring force closes the pilot hole, the inlet pressure through the bypass hole quickly forms a low on high pressure difference around the closing valve parts, 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.

Solenoid valve from the valve structure and material difference and principle difference, divided into six branch sub-categories: direct diaphragm structure, step by step direct diaphragm structure, pilot diaphragm structure, direct piston structure, step direct piston structure, pilot piston structure.

Solenoid valve, according to the function classification: water solenoid, steam solenoid, refrigeration, cold, gas, fire solenoid, ammonia, gas, liquid solenoid, micro, pulse, hydraulic, often open, oil, dc, high pressure solenoid valve, explosion-proof solenoid valve, etc.

1. According to the material points:

 1) Stainless steel solenoid valve: is the most common solenoid valve products, stainless steel material because of good quality, stable work, the most popular with users. This series of products are widely used in textile, printing, chemical, plastic, rubber, pharmaceutical, food, building materials, machinery, electrical appliances, surface treatment and other production and scientific research departments, as well as bathroom, canteen, air conditioning and other people's daily life facilities.

2) Brass solenoid valve: some users with low requirements, will choose the brass solenoid valve products, the price of such solenoid valve products is relatively low, suitable for the ordinary working environment. This series of products are generally adapted to liquid, water, gas, hot water, oil, gas and other media.

3) Plastic solenoid valve: in some special workplace, and used in special media solenoid valve, such as acid and alkaline medium working environment, brass and stainless steel solenoid valve products are easy to corrosion, so with special material (engineering plastics PVC, CPVC, UPVC, ABS or polytetrafluoride, etc.) made of plastic solenoid valve in corrosion resistance is particularly excellent, This series of products are suitable for suitable drinking water, all kinds of untreated sewage, rainwater, seawater and various acid and alkali salt solutions, organic solvents, etc

2. According to the function points:

1) Switch type solenoid valve, that is, play the switch role, when there is a current flow, the solenoid valve control line or oil road pass off.

2) Proportion solenoid valve, that is, according to the size of the input current is different, the output pressure is different, when the input current is changed, the output pressure of the solenoid valve can be changed, mostly used in the hydraulic system. Selection basis: solenoid valve selection should first follow the safety, reliability, applicability, economy four principles, followed by according to the six aspects of the field conditions (i. e., pipeline parameters, fluid parameters, pressure parameters, electrical parameters, action mode, special requirements).

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

1）Determine the channel diameter (DN) size according to the field pipe internal diameter size or flow requirements;

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

4、Select the solenoid valve according to the fluid parameters: material, temperature group

1）Corrosive fluid: should choose corrosion-resistant solenoid valve and all stainless steel; edible 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 state, liquid or mixed state, especially when the diameter is greater than DN25, must be distinguished;

4) Fluid viscosity: usually choose below 50cSt is optional, if this value is exceeded, then want to choose a high viscosity solenoid valve.

5、Select the solenoid valve according to the pressure parameters: the principle and the structure variety :

1) Nominal pressure: this parameter means the same as other general valves and is determined according to the nominal pipe nominal pressure;

2) Working pressure: if the working pressure is low, the principle of direct pressure or step by step must be adopted; the direct pressure is above 0.04Mpa when the minimum working pressure difference is above 0.04 M p a.

6、Electrical selection: voltage specifications should be preferred AC220V, DC24 is more convenient.

7. Choose according to the length of continuous working time: often close, often open, or sustainable power supply；

1) When the solenoid valve needs to open for a long time and lasts more than the closing time, choose the regular open type;

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

3) However, some working conditions used for safety protection, such as furnace and kiln flame monitoring, but can not be often opened, should be selected for a long-term power-on type.

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