Solenoid valve from the principle is divided into three categories.
1. Direct-acting solenoid valve.
Normally closed type direct-acting solenoid valve when the coil is powered off, the oxygen concentrator electromagnetic force disappears, the dynamic core under the action of spring force reset, the solenoid valve closed, and the media cut off.
Energized, the electromagnetic coil generates electromagnetic force so that the core to overcome the spring force is lifted, the solenoid valve open, the media flow. Normally open type and the opposite.
Features: In the vacuum, negative pressure, and zero pressure can work normally, but the diameter of the pipe is generally not more than 25mm.
2. Step-by-step direct-acting solenoid valve.
It is a combination of direct-acting and piloting principle, when the inlet and outlet pressure is the same.
After energized, the electromagnetic force directly to the pilot small valve and the main valve closed parts in turn upward lift, the valve open. When the inlet and outlet reach the start pressure difference, after energizing, the electromagnetic force pilot small valve, the main valve lower chamber pressure rises and the upper chamber pressure falls, thus using the pressure difference to push the main valve upward.
When the power is off, the pilot valve uses spring force or medium pressure to push the closing member and move downward to close the valve.
Features: In the zero differential pressure or vacuum, high pressure can also act, but the power is larger, requiring horizontal installation.
3. The pilot solenoid valve.
When energized, electromagnetic force to open the pilot hole, the chamber pressure drops rapidly, forming a low pressure differential around the closing piece, fluid pressure to push the closing piece upward, the valve open; power off, the spring force to close the pilot hole, the inlet pressure through the bypass hole quickly chamber around the closing piece to form a low pressure differential, fluid pressure to push the closing piece downward, closing the valve.
Features: The upper limit of the fluid pressure range is high, can be installed at will (need to customize) but must meet the fluid pressure differential conditions.
Solenoid valve selection should follow the four principles of safety, applicability, reliability and economy in order of choice.
- Corrosive media should be used plastic or stainless steel solenoid valve, for the strong corrosive media must be used isolated sealed structure solenoid valve.
- Explosive environment must be used in the corresponding explosion-proof grade products, open-air installation or dusty occasions should be selected waterproof, dustproof varieties.
- The nominal pressure of the solenoid valve should exceed the highest working pressure in the pipe.
1. Media characteristics.
- The medium temperature and pressure state should be selected in line with the parameters of the solenoid valve, the medium temperature should be selected within the allowable range of the solenoid valve, otherwise the coil will burn off, the seal aging, seriously affecting the life.
- Viscosity is usually below 20cSt. If more than this value, the solenoid valve for special orders. Cleanliness should be equipped with a filter in front of the solenoid valve.
- The medium is generally directional flow, and does not allow backflow, if the reverse pressure difference, should be installed check valve to protect the normal work of the solenoid valve.
2. Pipeline parameters.
- To select the valve diameter and model according to the media flow requirements and pipeline connection, but also according to the flow rate and valve Kv value selected nominal diameter, can also be selected with the internal diameter of the pipeline.
- The minimum working pressure difference in 0.04Mpa or more is the pilot operated solenoid valve; the minimum working pressure difference is close to or less than zero must be selected direct-acting or step-by-step direct-acting solenoid valve.
3. Environmental conditions.
- The maximum and minimum temperature of the environment should be selected within the allowable range of the selected product.
- High relative humidity in the environment and water dripping rain, etc., should be selected waterproof solenoid valve.
- In a corrosive or explosive environment should be used in accordance with the safety requirements of the selection of solenoid valve.
4. Power conditions.
- Power supply voltage fluctuations usually AC selection +%10%-15%, DC allows ± 10% or so.
- Should be based on the power supply capacity to choose the rated current and power consumption.
- It should be noted that the AV value is higher when starting AC, and the pilot-operated solenoid valve should be preferred when the capacity is insufficient.
- Working life: to ensure the quality and life of the solenoid valve should be selected from the regular manufacturers of products.
- Some occasions are not many actions, but the reliability requirements are very high, such as fire, emergency protection, etc., more to choose high-quality and reliable products.
Economy is one of the selection of solenoid valve scale, but must be in the safety, application, and reliability of the basis of choice. Economy is not only the selling price of the product, but also to give priority to its function and quality, as well as the cost of installation and maintenance and other accessories required. In short, the economy does not only refer to the price of the product, but the product’s performance to price ratio, comprehensive cost to price ratio.