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"Professional Solenoid Valve and Flowmeter"

2W Series 2/2 way Direct Acting Solenoid valve

DHG Series 3/2 way Direct Acting Solenoid valve

DHD Series 2/2 way Pilot Solenoid valve

DHGW Series 2/2 way Pilot Solenoid valve High Temperature

DHF Series 2/2 way Anticorrosive Solenoid valve

What's Solenoid Valve and How Do They Work

A solenoid valve operates as an electronically controlled valve, employing a solenoid consisting of an electric coil encompassing a mobile ferromagnetic core, known as the plunger. When the valve is at rest, the plunger obstructs a small orifice, preventing the flow of fluids. By passing an electric current through the coil, a magnetic field is generated, which exerts an upward force on the plunger, causing the orifice to open. This fundamental principle serves as the basis for the functioning of solenoid valves, enabling them to be opened and closed as needed.

Solenoid Valve Fast Facts

  • Solenoid valves are specifically engineered for use with clean liquids and gases, ensuring optimal performance when handling such substances.
  • These valves offer precise flow control, making them well-suited for delicate processes in medical devices and manufacturing, where accuracy is crucial.
  • With their fast response time, solenoid valves facilitate swift opening and closing actions, which are essential for safety applications and rapid responses to potential hazards.
  • Their long service life and dependable performance result in reduced maintenance requirements and the ability to withstand demanding usage conditions effectively.
  • Solenoid valves find a wide range of applications across various industries, including water treatment, automotive, and food processing, thanks to their versatility and adaptability to diverse operational needs.

How does solenoid valve work?

solenoid valve industrial darhorthainald valve components

The functioning of a solenoid valve involves two primary components: the solenoid and the valve body (G), as depicted in Figure. The solenoid comprises an electromagnetically inductive coil (A) wrapped around an iron core known as the plunger (E). When at rest, the valve can be either normally open (NO) or normally closed (NC). In the de-energized state, a normally open valve remains open, and a normally closed valve remains closed.

When an electric current flows through the solenoid, it becomes energized, generating a magnetic field. This magnetic attraction causes the plunger to move, overcoming the force exerted by the spring (D). If the valve is normally closed, the plunger is lifted, allowing the seal (F) to open the orifice and enable the flow of the media through the valve. Conversely, if the valve is normally open, the plunger moves downward, causing the seal (F) to block the orifice and stop the flow of the media through the valve. To prevent vibration and humming in AC coils, a shading ring (C) is used.

Solenoid valves find extensive application in various scenarios, where they encounter different pressures and flow rates, ranging from high to low. These valves utilize distinct operating principles optimized for specific applications. The three most crucial operating principles are explained in this article: direct acting, indirect acting, and semi-direct acting operation. Each principle serves its purpose effectively based on the requirements of the given application.

solenoid valve flowmeter darhor 2W21 Series SS

2/2 way solenoid valve

2/2 way solenoid valve features two ports: an inlet and an outlet. To ensure its correct functioning, the flow direction is crucial, often indicated by an arrow. This type of valve serves the purpose of either opening or closing the orifice. An illustration of a 2/2 way solenoid valve can be seen in Figure




solenoid valve industrial darhorthailand DHG Series DHG31 SS

3/2 way solenoid valve

The 3/2 way solenoid valve is designed with three connection ports, and it generally operates in two distinct states or positions, effectively switching between two different circuits. This versatile valve is employed for various purposes, such as opening, closing, distributing, or mixing media. An example of a 3/2way solenoid valve can be observed in Figure.


Type of Solenoid valve

Normally closed (NC) solenoid valve

In a normally closed solenoid valve configuration, the valve remains closed when it is de-energized, preventing the flow of media through it. However, when an electric current is applied to the coil, an electromagnetic field is generated, pushing the plunger upwards and overcoming the spring force. As a result, the seal is unseated, and the orifice is opened, allowing the media to flow through the valve. Figure illustrates the operating principle of a normally closed solenoid valve in both the de-energized and energized states. For more in-depth information on the differences between normally closed and normally open solenoid valves

solenoid valve industrial darhorthainald normally closed tyle

Normally open (NO) solenoid valve

In a normally open solenoid valve configuration, the valve remains open when it is de-energized, allowing the media to flow through it. However, when an electric current is applied to the coil, it generates an electromagnetic field that pushes the plunger downwards, overcoming the spring force. As a result, the seal is seated in the orifice, effectively closing it and preventing the flow of media through the valve. Figure  illustrates the operating principle of a normally open solenoid valve in both the de-energized and energized states.

A normally open solenoid valve is particularly well-suited for applications requiring the valve to remain open for extended periods as this configuration is more energy-efficient. For more detailed information on the distinctions between normally closed and normally open solenoid valves

solenoid valve industrial darhorthainald normally open type

Frequently asked Questions

A solenoid is a three dimensional coil. In physics , the term solenoid refers to a loop of wire , often warped around a metallic core , which produces a magnetic field when an electric current pass through it.

On a direct operated valve the armature opens the main orifice of the valve.On the lift operated valve the armature open a small pilot valve that reliefs the pressure and the volume above the diaphragm, so that the differential pressure can lift the diaphragm and opens the valve.The assisted lift operated valve similar the servo operated valve, however the armature is connected to the diaphragm and will lift it to open the valve even if there is no differential pressure.

In principle , a servo-operated solenoid valve used the differential pressure to operate the valve. The differential pressure lifts up the diaphragm and opens valve.

Water hammer is a typical result of high liquid velocity, high pressure and high flow velocity through small pipes.It occurs when the valve closes too fast so that the movement of the liquid is stopped to fast and “hammer” in the pipe.

Differential pressure is the pressure loss over the solenoid valve, between inlet and outlet pressure.

You can see it on the armature tube. The NC (normally closed) version is blank while the NO(normally open) version has a groove in the middle of the tube.

The Kv value we mention in product catalogues and technical brochures give the capacity of water with the differential pressure of 1 bar measured in cubic meter per hour.

The NC or NO operation types of the solenoid valve are determined by the valve ,not the coil.The same coil can be used for both NO and NO valves.

It’s possible but only when media is cleaned.Darhor recommends that solenoid valve be installed with coil upwards. This minimises risk of dirt collection in the armature tube.


  1. Type : [ ] 2/2 way  [ ]  3/2 way
  2. Operating mode : [ ] NO    [ ] NC
  3. Coil Class : [ ]  High temp.  [ ] Normally class  [ ] Explosion proof
  4. Coil Voltage : [ ] 220 AC  [ ]  110 AC  [ ] 24 AC  [ ]  12 AC  [ ] 24 DC  [ ] 12DC
  5. Fluid Media : [ ]  Air  [ ] Water  [ ] Light oil  [ ] Steam  [ ] Corrosive [ ] Other ……………
  6. Fluids temp. : [ ] ……… °C
  7. Body Material : [ ] Brass  [ ]  Stainless
  8. Size : Pipe size
  9. Ambient temp : [ ] Indoor [ ] Outdoor [ ] Underwater

Basic faults and solution

Following has to be checked.
– Media can be used for the application.
– Seal material can bu used with the media.
– Differential pressure within the specifications.
– Position of the valve is correct.
– Check the coil input , such as voltage and frequency according to specifications.
– Is the coil burned or disconnected?

– Check if there if dirt in the main orifice.
– Check for outside damage of the valve , e.g. has it been dropped? bent armature tube
– Check if the equalizing orifice connection is blocked because of dirt or deposits.
– Check pilot filter or pilot drillings. Armature is stuck inner tube.
– Check if the diaphragm function is limited because of the wear or swelling. e.g. EPDM seal exposed to oil.
– No voltage on coil.Lift coil slightly and note whether if offers resistance. e.g. Never remove an coil with voltage applied , it might burn out.
– Secure that the valve and the armature are not blocked with dirt
– Coil burnt out , differential pressure to high (valve will not open and thereby consume to much power). Too high ambient or media temperature. Outside of specifications.

The main reason is likely dirt or wear in the actuator system.This applies only for ac voltage systems.

Coils on solenoid valve can be relative hot when energized continuously, without any problems.If the coil over time has a malfunction or even start to melt or burn , there is a technical problem that must be solved.Please check the application condition like ambient , medium temperature and coil enclosure.