
Solenoid Valve
Explore All Types of Solenoid Valves We Offer
A solenoid valve is an electromagnetically operated device that controls the flow of liquids or gases by opening or closing when an electric current is applied. Finding the right solenoid valve for your application is crucial for efficient fluid control. At KUHNWAY, we provide a wide range of high-quality water solenoid valves and specialized options designed for various pressure, temperature, and fluid types. Here’s an overview of our key sol valve series:
-
MD Series – Direct-Acting Diaphragm Solenoid Valves
Designed for air, water, and light oil, these valves offer fast opening and closing speeds and can operate at zero pressure differential with larger flow openings. Available with maximum pressure ratings of 10, 15, or 20 kgf/cm², they suit various pressure conditions. The diaphragm options include NBR, EPDM, and VITON, while the body materials are bronze, SUS304, and SUS316, ensuring compatibility with different fluid media.
-
MT Series – Pilot-Operated Piston Solenoid Valves
Engineered for steam and heavy oil applications, these valves feature a dual-piston ring and guide rod design for enhanced durability and precise operation. The stainless steel guide seat ensures smooth performance while minimizing flow restrictions. They withstand temperatures up to 200°C and are available with maximum pressure options of 10, 16 (for steam), and 20 kgf/cm², making them ideal for high-temperature and high-pressure systems.
-
BMF Series – Large-Diameter Pilot-Operated Solenoid Valves
Built for high-flow applications, these valves include a manual override knob, allowing operation without power when needed. The valve body is available in threaded or flanged connections, with flange sizes ranging from 2" to 16" to accommodate different pipe diameters. Material choices include cast iron, bronze, graphite cast iron, SUS304, and SUS316, making them suitable for a wide range of fluid media and industrial applications.
Our solenoid valve products are also available in normally closed, normally open, and explosion-proof options, catering to a broad range of applications. Whether you need a water solenoid valve, steam control, or a high-flow system, we have the perfect solution for you. Contact us today to find the right solenoid valve for your needs!
.
A normally closed solenoid valve stays closed when de-energized, blocking the flow. When energized, the coil creates a magnetic field, lifting the plunger to open the valve and allow flow. When power is cut, the spring returns it to the closed position, stopping the flow automatically.
.
A normally open solenoid valve allows flow when de-energized and closes when energized. It’s ideal for continuous flow applications like cooling and drainage systems and ensures fail-safe operation by opening during power loss.
.
An explosion-proof solenoid valve is built for flammable and hazardous environments, such as petrochemicals, natural gas, and pharmaceuticals. Its sealed housing prevents sparks or heat from igniting explosive gases or dust. Designed to meet strict safety standards, it ensures safe operation in high-risk areas by eliminating ignition risks.
What is a Solenoid Valve and Its Functions?
A solenoid valve is an electromechanical valve that uses an electromagnetic actuator (solenoid) to control fluid flow. The solenoid converts electrical energy into mechanical motion, using a magnetic field to move a plunger or core, which either opens or closes the valve. In simple terms, when the solenoid is energized, the valve changes its state—either allowing fluid to pass through or stopping it. These valves function in a binary manner, fully open or fully closed without intermediate positions.
Solenoid valves are widely used in various applications, such as controlling water flow in dishwashers, managing air in pneumatic systems, and regulating fuel in engines. Their ability to provide quick, remote, and precise control makes them essential components in many automated systems.
Solenoid valves and motor valves both use electrical energy, but solenoid valves rely on electromagnetic coils for rapid open/close switching with digital (DO) control. They suit small pipelines (≤DN50), offering fast action, low power use, and good sealing. However, they only provide on/off control, require clean fluids, allow one-way flow, and need a minimum pressure difference.
As for motor valves, they use reversible motors for analog (AI) control and precise flow adjustment, ideal for larger pipelines. They handle impure fluids, support bidirectional flow, and stay powered safely, though slower operation and reset needs are trade-offs. To sum up, solenoid valves are best for quick-switching, low-pressure applications, while motor valves excel in large-scale flow regulation where precise control is needed.
Components of Solenoid Valve
A solenoid valve has two primary components: the solenoid and the valve body. The solenoid is an actuator that uses an electromagnetic coil, while the valve body contains the parts that come into contact with the fluid. The specific parts of the solenoid may vary, but the valve body components are generally consistent, although their design and material may differ.
The following are the general components of a solenoid valve and their functions:
-
Coil (A)
The coil is made of insulated copper wire wound around the outer part of the magnetic core tube. When energized, the coil generates a magnetic field that drives the movement of the plunger, thereby controlling the opening and closing of the solenoid valve. -
Spring (B) and Plunger (C)
The plunger (or piston) is the core actuating component of the solenoid valve. It is typically cylindrical and made of ferromagnetic material, located inside the solenoid tube. The spring provides initial preload force. In a normally closed valve, the spring pushes the plunger downward to close the orifice; in a normally open valve, it supports the plunger upward, keeping the valve open when de-energized. -
Diaphragm Return Spring (D)
The diaphragm return spring connects the diaphragm to the plunger. It helps return the diaphragm to its original position and stabilizes the valve’s operation. -
Valve Cover and Body (E)
The valve cover protects the upper internal components. The valve body is the main pressure-bearing part, housing the diaphragm, inlet and outlet ports, and flow passages. It is the core structure for controlling fluid flow. -
Solenoid Tube (F)
The solenoid tube is a hollow guiding component that directs the up-and-down motion of the plunger. Any defects or accumulation of debris inside the tube may cause the plunger to stick, overheat, or lead to valve failure. -
Shading Ring (G)
The shading ring is a single or a few turns of a conductive material (such as copper or aluminum). It creates a phase shift in the magnetic field, reducing noise and vibration during AC operation and allowing for smoother valve performance. -
Seal (H)
The seal is responsible for closing or opening the orifice, preventing medium leakage. In normally closed valves, when energized, the plunger moves upward, lifting the seal and opening the orifice. In normally open valves, the plunger moves downward to close the orifice. -
Diaphragm and Pilot Hole (I)
In diaphragm-type solenoid valves, the diaphragm isolates the electromagnetic components from the fluid. The pilot hole provides pressure balancing, reducing the force required to open the diaphragm. This is a key design feature in pilot-operated solenoid valves. -
Orifice (J)
The orifice connects the inlet and outlet ports. The plunger opens or closes this orifice to regulate the flow of fluid through the valve. Depending on the valve design, there may be one or more orifices to suit its operating mechanism.

How Does a Solenoid Valve Operate?
Solenoid valves come in various types, each designed for specific functions and configurations. These valves are essential in pneumatic and hydraulic systems. Let’s take a closer look at how solenoid valves work in these applications.
-
Pneumatics
Pneumatic solenoid valves control the flow of compressed air in a system, which is used to actuate cylinders, drive machinery, or regulate vacuum applications.
3/2-Way Valves: These valves have three ports—one for the inlet, one for the outlet, and one for the exhaust. They are commonly used in single-acting pneumatic cylinders and vacuum applications. The valve works by directing compressed air into the cylinder, extending it, and then venting the air to allow the cylinder to return to its original position.
5/2-Way Valves: These valves feature five ports—two inlets, two outlets, and one exhaust. Their primary function is to control double-acting cylinders, where air needs to be alternated between two ports to extend and retract the actuator. The exhaust port allows for smooth operation by venting used air. These valves are widely used in automation, robotics, and packaging machinery, where precise motion control is required.
5/3-Way Valves: Similar to 5/2-way valves, these also have five ports but include three positions, offering greater control over the actuator’s movement. These valves are useful for applications that require intermediate stops or controlled holding positions in motion control systems. The center position can be configured in different ways:
-
All ports blocked: Holds the actuator in position.
-
All ports open: Allows free movement of the actuator.
-
Pressure applied to both outlets: Ensures equalized pressure on both sides, keeping the actuator balanced.
-
Hydraulic
Hydraulic solenoid valves regulate the flow of pressurized oil or fluid in hydraulic systems, which operate under high pressure to drive actuators and motors.
4/2-Way Valves: These valves have four ports—two inlets and two outlets—allowing control of the flow direction in hydraulic systems. They are used for double-acting hydraulic cylinders, where shifting the valve redirects fluid to extend or retract the actuator. When the solenoid is energized, it changes the valve’s position, altering the fluid path and controlling movement.
4/3-Way Valves: Like 4/2-way valves, these also have four ports, but they include three positions to provide additional control. The neutral (center) position allows for different configurations:
-
Closed-center position: All ports are blocked, stopping fluid movement and maintaining pressure in the system.
-
Float-center position: The actuator is left free to move, allowing it to return to its original state.
-
Pressure-relieved position: The system pressure is reduced to prevent overloading.
These valves are useful in systems that require intermediate holding positions, precise fluid control, or pressure relief functions.
For a 2/2-way valve, the way it works depends on its internal design. Let’s break down how the three main types—direct-acting, semi-direct-acting, and pilot-operated—function in detail.
-
Direct-acting
In a direct-acting 2/2-way valve, the plunger (core) directly blocks or opens the valve orifice. When no power is applied, a spring holds the plunger down, sealing the orifice and stopping flow. When the coil is energized, the magnetic field pulls the plunger upward, overcoming the spring and lifting the seal, allowing fluid to pass through. There's no need for a pressure differential—this valve type operates independently of system pressure.

-
Semi-direct-acting
A semi-direct-acting valve combines both direct and pilot principles. It has a diaphragm or piston with a small pilot orifice and a plunger connected to the diaphragm. When energized, the plunger lifts and opens both the pilot hole and assists the diaphragm to rise. This allows the line pressure to help open the valve fully, enabling high flow rates even at zero pressure differential.

-
Pilot-operated
Pilot-operated solenoid valves are designed for high-pressure and high-flow systems, but they require a minimum pressure differential to function. When de-energized, the pressure above the diaphragm keeps the valve closed. Energizing the coil opens a small pilot hole, releasing pressure above the diaphragm to the outlet side. This pressure drop allows higher inlet pressure to push the diaphragm up, opening the valve. Once de-energized, pressure equalizes again, and the spring forces the diaphragm closed.

Another key distinction is whether a valve is normally closed or normally open, determining its default state when not powered. Here are the working principles of these solenoid valves:
A normally closed (NC) solenoid valve stays closed when de-energized, preventing any fluid or gas from passing through. When an electrical current is applied to the coil, it generates a magnetic field that pulls the plunger upward, overcoming the spring force. This action lifts the seal and opens the orifice, allowing media to flow through the valve. When power is cut off, the spring pushes the plunger back down, sealing the orifice and stopping the flow.
NC solenoid valves are commonly used in safety systems, fuel control, and industrial automation, where the valve needs to remain closed for extended periods, ensuring energy efficiency and secure operation.
A normally open (NO) solenoid valve remains open when de-energized, allowing uninterrupted flow. When electrical current is supplied, the coil produces a magnetic field that forces the plunger downward, overcoming the spring force. This movement closes the orifice and prevents media from passing through. Once the power is turned off, the spring returns the plunger to its open position, restoring flow.
NO solenoid valves are ideal for applications that require continuous flow, such as cooling systems, ventilation, and pressure relief systems. They enhance energy efficiency and safety by preventing overpressure or overheating in critical processes.
Types of Solenoid Valve
Solenoid valves can be classified based on their mode of operation, which determines how they control fluid flow. The main types include direct-acting, semi-direct-acting, and pilot-operated (internally and externally piloted) solenoid valves. Each type functions differently, offering unique benefits depending on system requirements.
-
Direct-acting
Direct-acting solenoid valves operate without relying on external pressure. When the coil is energized, the electromagnetic force lifts the plunger, opening the valve to allow fluid or gas to flow. Once de-energized, a spring forces the plunger back into place, closing the valve.
This type of solenoid valve is ideal for low-pressure systems and applications requiring instant response and fast operation, as there is no pressure delay. They are commonly used in fuel injection systems, refrigeration units, and medical devices where precise and immediate flow control is necessary. Direct-acting solenoid valves have the fastest operation, are reliable, and have a compact design.
-
Semi-direct-acting
Semi-direct acting solenoid valves, also known as assisted-lift solenoid valves, combine the advantages of direct acting and indirect acting designs. Unlike pure direct acting valves, the solenoid plunger is directly connected to the diaphragm, allowing the valve to operate at zero pressure while using system pressure to handle higher flows.
When the solenoid is energized, the plunger lifts, opening both the primary and secondary orifices. This action creates a pressure drop, further lifting the diaphragm, allowing fluid to flow smoothly. This design makes the semi-direct acting valve highly efficient over a wide pressure range, providing faster response times and higher flow capabilities than standard direct acting valves.
The ability to operate without minimum pressure requirements while still accommodating high flow rates makes it ideal for steam systems, compressed air networks and HVAC applications. These features allow it to bridge the gap between low pressure precision control and high flow industrial applications, making it a versatile choice in automated fluid control systems.
-
Piston-Type vs. Diaphragm-Type
The semi-direct-acting solenoid valves can be further classified into piston-type (like our MK10~25 series) and diaphragm-type (like our MA, MD series). Here’s a comparison of their differences:
-
Piston-Type: These use a piston mechanism to control fluid flow, offering high-pressure resistance and longer durability. They are commonly used in industrial applications requiring high operating pressures and heavy-duty performance.
-
Diaphragm-Type: These use a flexible diaphragm to open and close the valve. They are ideal for low to medium-pressure applications and work well with clean or slightly contaminated fluids. These valves are often used in water systems, gas control, and HVAC applications due to their smooth operation and lower maintenance requirements.
Note that diaphragm materials can vary in chemical resistance, temperature tolerance, and application suitability. Let’s look at some common options:
-
NBR (Nitrile Rubber): Best for oils, fuels, and water but has limited heat and chemical resistance.
-
EPDM: Excels in hot water, steam, and mild chemicals, making it ideal for HVAC and food processing, though it is not compatible with oils.
-
VITON (FKM): Offers superior resistance to acids, fuels, and high temperatures, making it perfect for chemical applications, but it performs poorly in hot water and steam.
-
Teflon (PTFE): With exceptional chemical and temperature resistance, suitable for corrosive fluids, though it is less flexible than rubber-based diaphragms.
-
Pilot-operated (Internally and externally)
Pilot-operated solenoid valves, also known as indirect-acting or servo-assisted valves, rely on a pressure differential rather than the solenoid’s electromagnetic force alone to control fluid flow. It normally needs a minimum of 0.5 bar. Instead of directly opening or closing the main valve, the solenoid controls a smaller pilot valve, which in turn regulates the pressure in the main chamber. This design significantly reduces the energy needed to actuate large valves, making it particularly effective for high-pressure applications where a direct-acting solenoid valve would require an impractically large and powerful coil.
There are 2 subtypes: internally-piloted and externally-piloted.
Internally-piloted solenoid valves utilize the system’s fluid pressure to control the main valve. In the closed position, pressure builds up on both sides of a diaphragm through a bleed orifice, keeping the valve shut due to the larger surface area on top. When the solenoid is energized, the pilot valve opens, releasing pressure from the upper chamber and creating an imbalance that forces the diaphragm upward, opening the main valve for fluid flow.
Externally piloted solenoid valves operate similarly but rely on an external pressure source instead of system pressure. These valves include an additional port that connects to a separate fluid circuit, which actuates the diaphragm or piston. This setup allows them to function even in low-pressure or vacuum environments, where system pressure alone wouldn’t be sufficient for actuation.
Both internally and externally piloted solenoid valves are designed to handle high-flow and high-pressure applications efficiently. Since the main actuating force comes from the pressure differential rather than the solenoid coil itself, these valves can control large fluid volumes using relatively small solenoids. This feature makes them energy-efficient, cost-effective, and reliable for process automation, HVAC systems, chemical processing, and water distribution networks. Their ability to control large flows with minimal energy input makes them a preferred choice for large-scale industrial and commercial applications.
Benefits of Solenoid Valve
Solenoid valves offer a range of benefits that make them ideal for various uses. Their automation-friendly design, fast response times, and energy efficiency make them a top choice for fluid control. Let’s break down why they’re so effective.
-
Remote Operation
One of the biggest advantages of solenoid valves is that they can be controlled remotely. This makes them perfect for hard-to-reach or hazardous environments, such as handling toxic, high-temperature, or high-pressure fluids. Instead of manual adjustments, operators can control flow with a simple electrical signal.
-
Fast Response Times
Speed is critical in many industrial applications, and solenoid valves excel in this area. They can open and close in milliseconds, ensuring instant fluid control. This is especially important in automated manufacturing, emergency shut-off systems, and pneumatic operations where every second counts.
-
Low Energy Consumption
Solenoid valves are designed to be energy-efficient. Some models can hold their position with minimal power consumption, reducing operating costs and making them ideal for long-term industrial use. This is beneficial for battery-operated devices, energy-conscious manufacturing plants, and HVAC systems.
-
Versatility
Solenoid valves come in a variety of configurations, making them highly adaptable. They support both AC and DC voltages, meaning they can be integrated into different electrical systems with ease. Whether you need a valve for water systems, gas pipelines, or high-pressure applications, there’s a solenoid valve that fits the job.
-
Enhanced Safety
Safety is a priority in industries dealing with corrosive, toxic, or high-pressure substances. Solenoid valves use an electromagnetic seal, eliminating the need for dynamic sealing, which reduces leak risks. Their precise control also makes them ideal for high-risk environments like chemical plants and refineries.










