Solenoid valves may be small, but they have a big impact on how fluids and gases are controlled in modern systems. Whether used in automation, water flow regulation, or pneumatic control, a solenoid valve offers fast, precise switching that keeps processes running smoothly. In this guide, we’ll explore what solenoid valves are, how they work, where they’re used, and what to consider when choosing one for your setup.
What is a Solenoid Valve?
A solenoid valve is an electrically controlled valve used to manage the flow of gases or liquids in a wide range of systems, from pneumatic automation to water treatment and beyond. It serves as an essential element in controlling on/off or directional flow with precision, responsiveness, and minimal manual intervention.
Basic Operating Concept
At its core, a solenoid valve consists of two main elements: a valve body and a solenoid coil. The coil is an electromagnet that, when energized, generates a magnetic field. This field activates a movable plunger or armature within the valve, which opens or closes the fluid passage. This simple yet powerful mechanism allows remote and automatic flow control based on electrical signals.
Key Functions in Industrial Systems
Solenoid valves are commonly used to:
Start or stop fluid flow in automated systems
Switch flow direction between ports
Enable timed or sensor-based control of pneumatic or hydraulic functions
Because they are electrically operated, solenoid valves are highly adaptable to digital control systems and programmable logic controllers (PLCs), making them ideal for modern industrial automation setups.
Single vs. Multi-Way Valves
Solenoid valves are available in various flow path configurations:
2/2-way valves for simple on/off control
3/2-way, 5/2-way, and 5/3-way valves for controlling actuators and cylinders in pneumatic systems
This versatility makes them integral to systems where quick actuation, reliability, and precision are required under varying operating conditions.
What Does a Solenoid Valve Look Like?
Solenoid valves may be compact in size, but their structure reflects a high degree of engineering precision. From the outside, they often appear as cylindrical or rectangular bodies with protruding coil sections, electrical connectors, and fluid ports. Internally, each component plays a specific role in regulating fluid flow.
Main External Features
A typical solenoid valve includes:
Valve body with input and output ports, often threaded for secure pipe connections
Solenoid coil housing, usually a black or metallic casing enclosing the electromagnetic coil
DIN connectors or wire leads for electrical input
Mounting holes or brackets for fixed installation
Depending on the model, valves can be modular (stackable) or standalone, with their appearance varying slightly depending on application (pneumatic vs. liquid vs. steam).
Internal Components at a Glance
Internally, most solenoid valves share these essential parts:
Plunger: A movable ferromagnetic core that opens or closes the flow path
Spring: Helps reset the plunger when power is off
Seals and gaskets: Prevent leaks and ensure pressure tightness
Orifice and seat: Define how fluid passes through the valve
For instance, a 5/2-way pilot-operated pneumatic solenoid valve often includes additional chambers for internal pilot pressure, which are less visible from the outside but crucial for operation.
BLCH-Compatible Appearance
If you’re familiar with common models such as the 4V210-08, they represent a rectangular body design with top-mounted coils, side flow ports, and modular manifold compatibility—offering both visual simplicity and engineering efficiency. For 4v series products, please refer to the following figure.
What are Solenoid Valves Made of?
The performance and durability of a solenoid valve are deeply influenced by the materials used in its construction. These materials must withstand specific temperatures, pressures, and chemical environments, making material selection a critical factor in valve reliability and longevity.
Valve Body Materials
The valve body houses the internal components and provides structural support. Depending on the medium (air, water, oil, etc.) and the working environment, manufacturers use different materials such as:
Brass: Offers excellent corrosion resistance and mechanical strength, making it ideal for air, water, and inert gases.
Aluminum: Lightweight and thermally efficient, commonly used in pneumatic systems where portability and quick thermal dissipation are important.
Stainless Steel: Resistant to aggressive media and high temperatures, suitable for corrosive environments and critical applications such as chemical handling or high-temperature steam.
Engineering Plastics (e.g., PBT, PA66): Used in solenoid valves for light-duty tasks, these materials are chemically resistant, electrically insulating, and cost-effective.
These are all materials consistent with BLCH valve product designs, which focus on ruggedness, weight efficiency, and compatibility with clean compressed air and industrial fluids.
Coil and Enclosure Materials
The solenoid coil is typically wound with copper wire due to its excellent conductivity. The coil housing—which can be sealed in epoxy or encased in plastic or metal—is designed to resist heat and moisture, ensuring reliable operation even in challenging industrial environments.
Encapsulated coils improve resistance to vibration and moisture.
Metal housings offer improved mechanical protection in high-impact areas.
DIN coil connectors are often included for easy installation and secure electrical connections.
Seal and Gasket Materials
To prevent leaks and maintain pressure, valves use seals made from various elastomers:
NBR (Nitrile): Good for general-purpose sealing with oils and air.
EPDM: Suitable for water and steam applications.
FKM (Viton): Excellent for chemical resistance and high-temperature performance.
PTFE (Teflon): Used in more chemically aggressive or high-heat situations.
The choice of seal material must always be matched to the fluid type and the system’s pressure-temperature conditions.
Solenoid Valve Applications
Solenoid valves are foundational components in automated control systems, valued for their reliability, rapid actuation, and ability to be electrically integrated into various industrial and commercial processes. Their broad adaptability enables them to serve diverse industries, from manufacturing and utilities to agriculture and building systems.
Industrial Automation and Pneumatic Systems
One of the most common uses of solenoid valves is in pneumatic automation, where they serve as control elements for cylinders, actuators, and other equipment. These valves regulate the compressed air that powers machines, conveyors, packaging systems, and robotic arms.
For example, a 5/2-way solenoid valve is often used to control a double-acting pneumatic cylinder, allowing forward and backward movement based on electrical signals. In production lines, these valves ensure smooth motion control and high-speed switching.
Water and Fluid Handling Systems
Solenoid valves are integral to water flow regulation, both in industrial and residential contexts. In water treatment plants, they control inflow, backwash, and chemical dosing processes. In HVAC systems, they manage chilled or heated water circulation based on thermostat commands.
Additionally, in irrigation systems, solenoid valves are used to automate watering schedules for agricultural fields or landscaping, ensuring efficient and targeted water usage with minimal manual intervention.
Oil and Lubrication Systems
In hydraulic and lubrication systems, solenoid valves regulate the distribution of oil to different machine components. These systems benefit from the valves’ ability to handle varying viscosities and temperatures while ensuring precise flow control.
In heavy machinery or automotive assembly lines, solenoid valves may also be responsible for managing transmission fluid routing, brake actuation, or differential control.
Steam and High-Temperature Applications
Certain solenoid valve models are specially built for high-temperature steam or vapor, often incorporating stainless steel bodies and heat-resistant seals. They are used in sterilizers, autoclaves, and commercial laundry equipment, where dependable flow control under pressure is crucial.
Compressed Air Management
Compressed air is widely used in industrial environments, and solenoid valves enable centralized control of air distribution. Valves are commonly used to:
Start/stop air supply to individual machines
Control air purge systems
Automate air drying and filtration cycles
These functions are especially important in cleanroom environments or manufacturing lines where process stability depends on consistent air pressure and quality.
Special Applications: Refrigeration, Fuel, and More
Solenoid valves also appear in niche systems, such as:
Refrigeration units, where they manage refrigerant flow during cooling and defrost cycles.
Fuel systems, to control the flow of gasoline, diesel, or gas in burners or engines.
Medical equipment, where precise gas or fluid flow is required in ventilators, nebulizers, or dialysis machines.
While these use cases demand more specialized materials or valve formats, the operating principles remain consistent.
Summary of Typical Media Controlled by Solenoid Valves
| Media Type | Common Applications |
| Compressed Air | Pneumatics, air tools, automated machinery |
| Water | Irrigation, HVAC, purification, cleaning systems |
| Oils/Lubricants | Hydraulic circuits, machinery lubrication |
| Steam | Sterilization, heating, industrial cleaning |
| Gases (e.g., Nitrogen, Natural Gas) | Burner control, gas chromatography, welding |
How Does a Solenoid Valve Work?
Understanding how a solenoid valve functions is key to selecting and maintaining the right system for your application. Despite their compact design, solenoid valves are capable of precisely regulating the flow of fluids or gases by transforming electrical energy into mechanical motion.
Basic Working Principle
At the heart of a solenoid valve is the electromagnetic coil, which, when energized, generates a magnetic field. This magnetic force acts on a movable plunger or armature housed inside the valve. When the coil is energized:
In a normally closed valve, the plunger is lifted, opening the orifice and allowing fluid to pass through.
In a normally open valve, the magnetic field pulls the plunger downward to block the orifice, stopping flow.
Once the electrical current stops, a spring mechanism returns the plunger to its original position, either blocking or allowing the flow depending on the valve’s default state.
Direct-Acting vs. Pilot-Operated Valves
There are two major functional types of solenoid valves:
Direct-Acting Solenoid Valves
These valves directly use electromagnetic force to move the plunger, opening or closing the flow path without relying on system pressure. They are ideal for low-flow or zero-pressure systems, commonly used in small pneumatic or water circuits.
Pilot-Operated Solenoid Valves
In these valves, the solenoid controls a small pilot orifice, and the pressure of the fluid itself assists in moving the main diaphragm or piston. This design is efficient for higher flow rates and systems with stable pressure differentials. Pilot-operated valves are common in industrial compressed air systems and water networks.
2-Way, 3-Way, and 5-Way Configurations
Different valve designs control fluid paths in specific ways:
2/2-Way Valve: Two ports (inlet and outlet), opens or closes the flow completely.
3/2-Way Valve: Three ports and two positions, often used to divert flow or exhaust air in pneumatic circuits.
5/2-Way Valve: Used for directional control in double-acting pneumatic cylinders, with five ports for inlet, outlet, and exhaust.
These configurations, combined with variations in electrical control (AC or DC), coil voltage, and actuation time, make solenoid valves versatile components adaptable to diverse engineering needs.
Response Time and Energy Efficiency
Solenoid valves respond quickly—often within milliseconds. Advanced models are designed for continuous duty cycles, with low power consumption and minimal heat generation. This makes them suitable for automated processes requiring rapid, frequent switching.
Key Considerations for Selecting a Solenoid Valve
Selecting the right solenoid valve is essential to ensure smooth operation, long service life, and compatibility with your system’s requirements. With so many valve types, materials, and configurations available, choosing the appropriate model requires careful evaluation of both technical and environmental factors.
1. Fluid Type and Media Compatibility
Different solenoid valves are designed to handle different media, such as compressed air, water, oil, steam, or inert gases. The materials used for the valve body and seals must be compatible with the fluid to:
Prevent corrosion or chemical degradation
Avoid contamination or unwanted reactions
Ensure safe operation over time
For example:
NBR seals are well-suited for air and oil
EPDM is preferred for hot water and steam
Viton (FKM) handles aggressive chemicals and high temperatures
2. Operating Pressure and Flow Rate
Every valve has a specific pressure range and flow capacity (Cv or Kv value):
For low-pressure systems, a direct-acting valve is typically sufficient.
For high-pressure or large-volume systems, a pilot-operated valve is more efficient.
It’s also important to match the valve’s orifice size and internal construction to the desired flow rate to avoid issues like pressure drops, sluggish performance, or leakage under load.
3. Temperature Conditions
Consider both the fluid temperature and the ambient temperature where the valve will be used. High or low temperatures may affect:
Coil durability and insulation
Seal elasticity and leakage resistance
Valve body material integrity
Choose components rated for your operating range to ensure long-term reliability.
4. Electrical Requirements
Solenoid coils are available in multiple voltages (12V DC, 24V DC, 110V AC, 220V AC) and must match the available power source. Additionally, look at:
Coil power consumption (wattage)
Response time
Protection class (IP rating for dust/water)
Low-power coils are preferred in energy-conscious systems, while higher-wattage versions are often used for faster actuation or in critical safety circuits.
5. Mounting and Port Configuration
Consider how the valve will be installed in your system. Check:
Thread types and sizes (e.g., G1/8″, G1/4″, G3/8″)
Manifold compatibility if using modular installations
Mounting orientation requirements
Some valves must be mounted upright for pilot function, while others are more flexible in layout.
6. Cycle Frequency and Duty Cycle
If your application requires frequent switching (e.g., multiple times per second), you’ll need a valve with fast actuation, thermal stability, and continuous duty rating. Evaluate:
Switching speed (opening/closing in milliseconds)
Coil insulation class
Maximum cycles per minute/hour
High-cycle solenoid valves are common in packaging, sorting, and robotic automation systems.
7. Environmental Factors
Your valve might be exposed to:
Dust, oil, or moisture
Vibration or mechanical shock
Corrosive gases or outdoor weather
In these cases, look for:
Encapsulated coils with high IP ratings
Corrosion-resistant valve bodies (aluminum, stainless steel)
Sealed or explosion-proof designs, if required by local safety regulations
Conclusion
Solenoid valves play a vital role in a wide range of systems where fluid or gas flow needs to be managed with precision and speed. From their compact structure and fast response to the flexibility of application across different media and pressures, these components are indispensable in automation and control setups.
Understanding how a solenoid valve works, what it’s made of, and how to select the right one can help you avoid common issues like leakage, sluggish performance, or premature failure. Whether you’re working with compressed air in a pneumatic circuit or managing water flow in a treatment system, choosing the proper valve configuration, material, and electrical specifications is key to long-term reliability.
If you’re exploring dependable options for your setup, BLCH offers a wide range of solenoid valves—such as 2/2-way, 3/2-way, and 5/2-way models—designed for clean air systems, automation lines, and integrated manifolds. Their product line reflects a balance of performance, durability, and cost-efficiency for industrial needs.
