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How to Select Solenoid Valve and Considerations

How to Select Solenoid Valve and Considerations

     Principle: normally closed direct-acting solenoid valve energized, the electromagnetic coil generates electromagnetic suction to lift the spool, so that the spool seals away from the valve seat port, the valve is open; power failure, the electromagnetic force disappeared, relying on the spring force on the spool seals on the seat port, the valve is closed. (Normally open type is the opposite of this)

     Characteristics: in a vacuum, negative pressure, zero differential pressure can work properly, the larger the valve caliber, the larger the volume and power of the electromagnetic head. For example, the direct-acting solenoid valve produced by our company can be used in 1.33×10-4 Mpa vacuum.

Direct-acting solenoid valve

      Principle: its principle is a combination of direct-acting and pilot, when energized, the solenoid valve will first open the auxiliary valve, the main valve cavity pressure is greater than the upper cavity pressure and the use of differential pressure and electromagnetic force at the same time the role of the valve is open; power failure, the auxiliary valve using spring force or medium pressure to promote the closure of the sealing member, downward movement to close the valve port.

     Characteristics: in zero differential pressure or about a certain pressure can also work reliably, the general working differential pressure does not exceed 0.6MPa, but the electromagnetic head power and volume is larger, requires vertical installation.

     Principle: when energized, electromagnetic force drive pilot valve to open the pilot valve, the main valve upper cavity pressure drops rapidly, in the main valve upper and lower cavities to form a pressure difference, relying on the medium pressure to push the main valve closure upward, the valve opens; power failure, the spring force to the pilot valve closure, the inlet medium pressure through the throttle hole into the main valve upper cavity quickly in the upper cavity to form a pressure difference, so that the main valve closure.

      Features: small size, low power, but the range of media differential pressure is limited to meet the differential pressure conditions (0.01MPa).

     Solenoid valve is an industrial device controlled by electromagnetism, used to control the fluid automation infrastructure components, belongs to the actuator, and is not limited to hydraulic, pneumatic. Solenoid valves are used in many products because of their precision and flexibility of control. Solenoid valve as a circuit safety gatekeeper, its choice of application to be safe and reliable. Solenoid valve in different control systems, the need for solenoid valve model function will be different, therefore, based on the reality of the requirements to choose the right solenoid valve.

Pilot operated solenoid valve

Four selection principles

Ⅰ. Safety.

  1. Corrosive media: it is appropriate to use plastic king solenoid valve and all stainless steel (316); for strong corrosive media selection of isolated diaphragm type. Neutral media, can also choose copper alloy for the valve body material solenoid valve. Ammonia valve can not be used copper.          
  2. High temperature steam media: it is appropriate to use stainless steel or cast steel valve body, and PTFE seals. Ordinary high temperature (below 180 degrees) can also be used copper alloy valve body. High temperature (350 degrees) of thermal oil and steam using hard seal, and increase the heat sink.
  3. Explosive environment: the corresponding explosion-proof grade products, open-air installation or dusty occasions should be selected waterproof, dust proof
  4. The working pressure of the solenoid valve should exceed the high working pressure in the pipe.

Ⅱ. Applicability.

  1. The medium temperature of different products, solenoid coil selection will be different (such as high-temperature solenoid valve shall be equipped with high-temperature coil), otherwise the coil will burn out, seriously affecting the life of life.
  2. Working differential pressure: low working differential pressure of 0.03Mpa or more can be selected pilot solenoid valve; low working differential pressure close to or less than zero selection of direct-acting or step-by-step direct-acting solenoid valve.
  3. According to the flow and valve Kv value selected nominal diameter (DN), can also be selected with the pipe diameter.
  4. The environment of high relative humidity and water dripping rain and other occasions, should choose waterproof solenoid valve.
  5. Voltage specifications with as much as possible to prioritize the selection of AC220V or DC24V.

Ⅲ. Reliability.

  1. Work regimes: permanent work regimes, short-term repetitive work regimes and short-term work regimes. For a long time the valve is open only a short time to close the case, it is appropriate to use normally open solenoid valve.
  2.  Working frequency: high frequency requirements, the structure should be preferred direct-acting solenoid valve, power supply priority selection of alternating current (AC).

Ⅳ. Economy.

  1. Economy is one of the scales of choice, but in the safe, suitable, reliable basis of economy, do not be greedy, choose to sound low price, but the quality of the coil and material is very poor.
  2. Economy is also a single product selling price, but also to prioritize its function and quality, as well as installation and maintenance and other accessories required for the cost.

Points to note for installation

  1. When installing, the arrow on the valve body should be consistent with the medium flow direction. It should not be installed in the place where there is direct water dripping or splashing. Solenoid valve should be installed vertically;
  2. After the installation of the solenoid valve, there shall be no reverse differential pressure in the pipeline. And need to be energized a few times, so that the appropriate temperature before being officially put into use.
  3. Solenoid valve should be cleaned before installation. Passing medium should be free from impurities. Valve before the installation of filters.
  4. When the solenoid valve failure or cleaning, in order to ensure that the system continues to operate, should be installed bypass device (especially steam piping).

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