Common Types and Classifications of Solenoid Valves

As a key executive component in industrial automation control systems, solenoid valves control the on-off or direction change of fluids through electromagnetic force. They feature a compact structure and rapid response, making them an indispensable part of many pneumatic and hydraulic systems. This article will sort out the common types and classification methods of solenoid valves, and finally provide references for your selection in combination with specific models of the AirTAC brand.

1. Working Principle of Solenoid Valves

The basic working principle of a solenoid valve is to use the electromagnetic force generated by an energized electromagnetic coil to drive the valve core to move, thereby changing the on-off state or flow direction of the flow channel in the valve body. According to different structural principles, solenoid valves can be divided into three major categories: direct-acting type, step-by-step direct-acting type (also known as backflush type), and pilot-operated type.

2. Classification by Operating Principle

Type Working Principle Characteristics Application Scenarios
Direct-acting When energized, the electromagnetic coil generates electromagnetic force to directly lift the valve core and open the valve; when de-energized, the spring force resets the valve core and closes the valve. Can work under vacuum, negative pressure, and zero pressure difference, but usually has a small passage diameter (generally not exceeding 25mm) and a large electromagnetic head volume. Occasions with small flow and requiring zero-pressure start-up.
Step-by-step direct-acting / Backflush A combination principle of direct-acting and pilot-operated. When there is no pressure difference, the electromagnetic force directly lifts the main valve closure member; when there is a pressure difference, the main valve is opened by the combined action of the pressure difference and electromagnetic force. Can work reliably under zero pressure difference or high pressure, but has large power and volume, and usually requires vertical installation. Occasions that need to work under a certain pressure and have high requirements for reliability.
Pilot-operated When energized, the electromagnetic force opens the pilot hole, and the pressure difference pushes the main valve core to open; when de-energized, the pilot hole closes, and the medium pressure pushes the main valve core to close. Small volume and low power, but requires a minimum working pressure difference to operate and has requirements for medium cleanliness. Occasions with large flow, low pressure, or requirements for power consumption and volume (must meet the pressure difference condition).

3. Classification by Structure and Material

Solenoid valves can be further subdivided into multiple categories based on the structure and material of the valve disc:


  • Direct-acting diaphragm structure, step-by-step direct-acting diaphragm structure, pilot-operated diaphragm structure: Diaphragm valves are sensitive to pressure changes and have good sealing performance, so they are often used for gas media.
  • Direct-acting piston structure, step-by-step direct-acting piston structure, pilot-operated piston structure: Piston valves have a robust structure, high pressure resistance, and long service life, making them suitable for occasions with higher pressure or frequent operations.


The selection of valve seat and sealing material is also crucial, which is mainly divided into soft sealing (such as NBR nitrile rubber, FKM fluororubber, etc., with good sealing performance), rigid sealing (metal sealing, high temperature and high pressure resistance), and semi-rigid sealing.

4. Classification by Function and Application

Solenoid valves are widely used in various fields. According to the medium they control and their special functions, they can be divided into multiple types:


  • General type: Controls common media such as air, water, and oil.
  • Specialized type:
    • Pneumatic solenoid valves: Designed specifically for controlling gases such as compressed air, like many series of products from AirTAC.
    • Water solenoid valves, steam solenoid valves, gas solenoid valves, oil solenoid valves, refrigeration solenoid valves, fire-fighting dedicated solenoid valves, etc.
  • Special working condition type:
    • High-temperature solenoid valves, high-pressure solenoid valves, low-temperature solenoid valves, vacuum solenoid valves.
    • Anti-corrosion solenoid valves (made of corrosion-resistant materials such as stainless steel).
    • Explosion-proof solenoid valves: Used in flammable and explosive hazardous environments.

5. Classification by Number of Ports and Positions

This is one of the most intuitive ways for us to distinguish solenoid valves:


  • "Number of positions" refers to the number of working positions of the valve core. Common ones are two-position (on/off) and three-position (such as closed center, exhausted center, and pressurized center).
  • "Number of ports" refers to the number of ports on the valve body, such as two-way (one inlet and one outlet), three-way (one inlet, one outlet, and one exhaust or one inlet and two outlets), four-way, and five-way (often used to drive double-acting cylinders).


Examples:


  • 2/2 Way (Two-position Two-way): Normally open or normally closed, the most basic on-off function.
  • 2/3 Way (Two-position Three-way): Can be used to control single-acting cylinders or switch the channel of one air source.
  • 2/5 Way (Two-position Five-way): Most commonly used to control the two air inlets and two exhaust ports of double-acting cylinders.
  • 3/5 Way (Three-position Five-way): In addition to two working positions, there is a neutral position (such as closed center, exhausted center, and pressurized center), which is used to control the cylinder to stop or hold at the middle position.

6. Classification by Other Methods

Solenoid valves can also be classified according to the following methods:


  • Medium pressure in the pipeline: Vacuum type, low-pressure type, medium-pressure type, high-pressure type, ultra-high-pressure type.
  • Medium temperature: Normal temperature type, medium temperature type, high-temperature type, ultra-high-temperature type, low-temperature type, ultra-low-temperature type.
  • Working voltage:
    • Alternating Current (AC): Common voltages include AC220V, AC110V, and AC24V.
    • Direct Current (DC): Common voltages include DC24V and DC12V.
      It is recommended to prioritize common voltages (such as AC220V and DC24V), as the delivery cycle for special voltages may be longer.
  • Protection level: Such as IP65 (dustproof and waterproof), explosion-proof type, etc.

7. AirTAC Solenoid Valve Recommendations

AirTAC is a world-renowned manufacturer of pneumatic components, and its solenoid valve products are known for high reliability, stable performance, and complete specifications. The following are several common series of AirTAC solenoid valves for your reference:


Series/Model Example Type Characteristics Application Scenarios
4V210-08 (e.g., DC24V, AC220V) 2/5 Way Pilot-operated Double electric control design, supports forward and reverse switching, fast response, and high reliability. Controlling double-acting cylinders in industrial automation, such as handling equipment and packaging machinery.
4V310-10 (e.g., DC24V, AC220V) 2/5 Way Pilot-operated Double electric control design, supports forward and reverse switching, stable performance, and good durability. Air circuit control in industrial environments such as injection molding machines and punching machines.
3V1 Series (e.g., 3V1-M5) 2/3 Way Direct-acting Direct-acting normally closed type, sensitive commutation, no need for oil lubrication, multi-valve integration to save space, with manual device. Small automation equipment, simple air circuit on-off control.
4V400 Series (e.g., 4V410-15) 2/5 Way / 3/5 Way Pilot-operated Spool structure, good sealing performance, sensitive response; three-position solenoid valves have three central function options; double-head two-position solenoid valves have memory function; long service life. Control of double-acting cylinders that require complex functions such as neutral stop or holding.

Selection Suggestions:

  • Voltage matching: Select AC or DC voltage according to the on-site power supply, and ensure the voltage value matches.
  • Threaded port: Pay attention to whether it is PT (BSPP) thread or NPT thread to ensure matching with the pipeline.
  • Medium and pressure: Confirm that the solenoid valve is suitable for air and works within the rated pressure range (e.g., 0.15-0.8MPa).
  • Functional requirements: Select 2/3 way, 2/5 way, or 3/5 way according to the cylinder type (single-acting / double-acting) and functional requirements (simple commutation / neutral stop).
  • Installation space: For compact spaces, consider compact series or multi-valve integrated valve islands.


Note: The above recommendations are based on public information. Before final selection, be sure to refer to AirTAC's official latest product catalog or consult its technical personnel to confirm whether all parameter details meet your specific application requirements, especially the port size, pressure level, and voltage specifications.

Summary

Understanding the types and classifications of solenoid valves is the first step to selecting and using them correctly. Solenoid valves are mainly divided into direct-acting, step-by-step direct-acting, and pilot-operated types according to their operating principles; they can be divided into diaphragm type and piston type according to their structural materials; they should correspond to different media and working conditions according to their functions and applications; and the "number of positions and ports" directly determines their control functions.


As a leading brand in the industry, AirTAC provides a rich and diverse range of solenoid valve products (such as the 4V210, 4V310, and 3V1 series), which can meet various needs from simple on-off control to complex control. It is hoped that this article can provide clear guidance for you in the complex world of solenoid valves.


It is hoped that this article can help you better understand solenoid valves. If you have more specific needs, consulting professionals or suppliers is always a good idea.
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