A solenoid valve is an essential component in modern industrial automation, enabling fast and precise fluid control with electrical signals. These valves can start, stop, or change the direction of fluid flow, making them indispensable across sectors like water treatment, packaging, automotive systems, and food processing.
At BLCH, we specialize in delivering high-quality solenoid valves engineered for durability, efficiency, and versatility in demanding industrial environments. This comprehensive guide will help you understand the different types of solenoid valves, how they work, and how to select the right one for your application.
How Does a Solenoid Valve Work?
A solenoid valve functions as an electromechanically operated device used to control the flow of liquids or gases in a system. It essentially acts as a gatekeeper—allowing media to pass through or blocking it based on electrical signals. The two core components of a solenoid valve are the solenoid coil and the valve body.
Inside the solenoid coil is a ferromagnetic plunger (or armature) surrounded by a tightly wound wire. When electrical current is applied to the coil, it generates a magnetic field, pulling the plunger inwards or upwards. This movement either opens or closes the orifice within the valve body, enabling or restricting the media flow accordingly.
In its resting state, the valve can be either normally closed (NC) or normally open (NO). A normally closed valve stays shut when no power is supplied, only opening when current activates the coil. A normally open valve does the opposite, remaining open until energized. This default configuration is essential for system designers to select the correct valve based on fail-safe requirements or energy efficiency.
What makes solenoid valves highly effective in industrial systems is their ability to be controlled remotely and automatically. This eliminates the need for manual intervention, streamlining processes in environments such as production lines, water treatment facilities, or pneumatic systems. Because the response is rapid and repeatable, solenoid valves are ideal for applications where timing and accuracy are critical.
At BLCH, our solenoid valves are engineered for reliability, quick response, and low maintenance. Whether it’s a low-pressure water system or a high-speed pneumatic circuit, our valves respond instantly and precisely—providing engineers and system integrators with dependable performance in even the most demanding environments.
What Are the Main Types of Solenoid Valves?
Solenoid valves can be broadly categorized into three main operational types: direct-acting, indirect-acting (pilot-operated), and semi-direct acting. Each type operates on slightly different principles and is suitable for specific use cases depending on factors like pressure, flow rate, and system design.
1. Direct-Acting Solenoid Valves
In direct-acting valves, the solenoid coil directly moves the plunger to open or close the valve orifice—no pressure difference is required for the valve to operate. This makes them ideal for low-pressure or zero-pressure systems where immediate response is critical, such as in laboratory setups, pilot lines, or simple on/off fluid controls.
Direct-acting valves are known for their fast switching speeds, compact construction, and minimal maintenance. Because they don’t rely on system pressure, they’re perfect for intermittent operations or systems that start from rest. At BLCH, our direct-acting solenoid valves are engineered to deliver consistent performance, even in small-scale or sensitive environments.
2. Indirect-Acting (Pilot-Operated) Solenoid Valves
These valves use the media’s own pressure to aid in operation. The solenoid coil opens a small pilot hole, allowing pressure to move a diaphragm or piston and fully open the main orifice. This design allows a relatively small solenoid coil to control a large flow rate, making indirect-acting valves highly energy-efficient for high-pressure and continuous flow systems.
Commonly used in water systems, compressed air networks, and industrial fluid handling, indirect valves require a minimum pressure differential (typically ≥ 0.5 bar) to function properly. BLCH’s pilot-operated valves are optimized for high-flow, high-efficiency environments and built with durable materials to withstand aggressive or corrosive media.
3. Semi-Direct Acting (Assisted-Lift) Solenoid Valves
Semi-direct acting valves combine the benefits of both direct and indirect types. While they use pressure to assist in operation, the solenoid also provides mechanical force to lift the diaphragm, allowing operation from zero pressure while still managing high flow rates.
These valves are especially useful in systems where startup may begin at low or no pressure but quickly scale up—like in irrigation pumps or certain automated industrial machines. BLCH’s semi-direct solenoid valves are fitted with reinforced coils and precision diaphragms to ensure reliable operation across fluctuating pressures, making them a versatile choice for a broad range of customers.
Understanding these three types is key to selecting the right solenoid valve. Each has its strengths, and at BLCH, we provide a full range of all three, ensuring that your system has the perfect match—whether you need speed, power efficiency, or flexibility under changing operating conditions.
Normally Open vs. Normally Closed Solenoid Valves
When selecting a solenoid valve, one of the most important considerations is its default state when not powered: Normally Closed (NC) or Normally Open (NO). This simple distinction can have major implications for safety, energy usage, and operational reliability.
Normally Closed (NC) Solenoid Valves
A normally closed solenoid valve remains shut when no electrical power is applied. Once energized, the solenoid coil generates a magnetic field that lifts the plunger, allowing fluid or gas to flow through the orifice.
This configuration is the most common choice in industrial systems, especially when:
The valve should remain closed as a fail-safe (e.g., gas shut-off systems, chemical dispensing)
The media should only flow during active operation
Power failures must automatically stop the process
For example, in automated compressed air systems, an NC solenoid valve prevents unwanted pressure buildup when the system is idle. At BLCH, our NC valves are designed with tight sealing and robust coil construction to ensure immediate closure during a power loss, protecting both equipment and operators.
Normally Open (NO) Solenoid Valves
In contrast, a normally open solenoid valve stays open when de-energized, and closes only when the coil is powered. This type is ideal when a system should allow flow in its natural state—such as in cooling circuits, emergency drains, or pressure relief lines.
Some applications also benefit from the energy-saving potential of NO valves. For instance, if the system requires the valve to remain open for long periods, a normally open design avoids the need for continuous power to maintain that state, thereby reducing electricity usage and minimizing heat buildup in the coil.
At BLCH, we offer NO solenoid valves that combine energy efficiency with fast response times, helping engineers build smarter, more sustainable control systems.
What About Bi-Stable (Latching) Valves?
A third option, bi-stable or latching solenoid valves, provides a unique advantage—the valve retains its position (open or closed) even when power is removed. It changes state only when a short pulse of power is sent. These valves are ideal for remote or battery-powered systems where energy consumption must be minimized.
Latching valves from BLCH use precision-balanced magnets and carefully engineered plungers to ensure stable and accurate switching with minimal power. They’re perfect for automated systems with infrequent switching cycles, such as solar-powered irrigation controls or isolated monitoring stations.
Understanding the operating behavior of NO, NC, and latching solenoid valves allows you to tailor your fluid control system precisely to your needs—balancing safety, efficiency, and reliability.
2-Way and 3-Way Solenoid Valves Explained
Solenoid valves are categorized not just by their function (NO/NC), but also by the number of ports and flow paths they manage. Among these, 2-way and 3-way configurations are the most commonly used in industrial applications. Understanding how they work—and when to use each—can help optimize your fluid control system for both performance and cost-efficiency.
2-Way Solenoid Valves
A 2-way solenoid valve has two ports: an inlet and an outlet. When the solenoid is energized, it either allows or blocks the flow of media through these ports. These valves function like a switch—either on or off—for the flow of liquid or gas.
This simplicity makes them perfect for:
On/off control of water, air, or oil in pipelines
Automated systems like water treatment units, HVAC flow control, or bottling lines
Applications requiring tight sealing and fast reaction time
At BLCH, we provide high-performance 2-way valves that feature optimized flow paths, compact footprints, and low power consumption, making them easy to integrate into both small-scale and large industrial systems. Our valves also come in a variety of materials, ensuring compatibility with aggressive media or high-pressure requirements.
3-Way Solenoid Valves
A 3-way solenoid valve includes three ports, offering more flexible fluid routing. The most common port designations are:
P (Pressure or Inlet)
A (Actuator or Outlet)
E or R (Exhaust or Return)
Depending on the valve’s default state (NO or NC), a 3-way valve can either direct media from the pressure port to the actuator, or vent media from the actuator to the exhaust port.
These valves are widely used for:
Controlling single-acting pneumatic cylinders
Switching between two fluid lines
Vented pressure release systems
For instance, in packaging automation, a 3-way solenoid valve can control the motion of a pneumatic gripper—allowing air in to extend it, and venting to retract it. BLCH’s 3-way solenoid valves are engineered for high cycling durability, low internal leakage, and precise response, even in dusty or high-vibration environments.
Whether you’re looking to simply control flow or dynamically switch directions, choosing the correct valve configuration is key. BLCH offers both 2-way and 3-way valves in various operation types (direct, indirect, semi-direct) and materials, ensuring you get the most reliable and efficient performance for your specific system.
Materials Matter: Housing and Sealing
Selecting the correct materials for both the housing and sealing components of a solenoid valve is crucial for ensuring long-term reliability, chemical compatibility, and mechanical strength. Each application environment poses unique challenges—high pressure, aggressive chemicals, extreme temperatures—and the right material combination helps the valve withstand these stresses while maintaining a leak-free operation.
Housing Materials
The valve body, or housing, is the main structure that contains the flow path and interfaces with the system. BLCH offers solenoid valves in several robust materials to meet diverse industrial needs:
| Material | Strengths & Best Uses |
| Brass | Resistant to corrosion in neutral fluids; widely used for water, air, and light oils. It’s cost-effective and easy to machine. Ideal for general-purpose applications. |
| Stainless Steel | Highly durable and chemical-resistant; perfect for aggressive fluids, high temperatures, and food/pharma processing lines. BLCH uses precision-cast stainless steel for superior sealing surfaces. |
| PVC (Polyvinyl Chloride) | Lightweight, affordable, and excellent for corrosive media. Often used in water treatment or chemical dosing systems. Not ideal for high-pressure or high-temperature use. |
| Aluminum | Combines strength with low weight and good heat dissipation. Great for pneumatic systems and mobile equipment. BLCH aluminum-bodied valves are treated with anti-oxidation coatings for extended service life. |
| Cast Iron | Very strong and vibration-resistant. Used in heavy-duty systems like industrial washing, fire suppression, or mining operations. |
BLCH carefully selects housing materials not only based on compatibility, but also on cost-efficiency, ease of maintenance, and lifespan under real industrial conditions.
Sealing Materials
Just as important as the housing is the seal—the material that directly contacts the media and ensures tight shut-off. The seal must be chemically compatible and capable of withstanding the operating temperature and pressure ranges.
| Seal Type | Features & Applications |
| NBR (Nitrile) | Excellent oil and fuel resistance; ideal for petroleum-based fluids and general-purpose pneumatics. |
| EPDM (Ethylene Propylene Diene Monomer) | Great for hot water, steam, and outdoor applications; resists ozone and weathering. |
| FKM (Viton) | High-performance in harsh chemical and high-temperature environments, including acids and solvents. |
| PTFE (Teflon) | Extremely inert and wide temp range; suitable for highly aggressive fluids or media with suspended solids. |
BLCH provides seal customization for special applications. For instance, in food-grade or pharmaceutical systems, seals may need to resist both heat and cleaning agents. In oil refineries, seals must tolerate hydrocarbons and maintain elasticity over long periods.
Choosing the correct combination of housing and seal material not only prevents leaks and downtime but also extends valve life and reduces maintenance frequency. BLCH offers comprehensive support to help engineers select the right materials based on specific working conditions, fluid types, and safety requirements.
Unique Features You Should Consider
While selecting the right solenoid valve type and material is essential, modern industrial systems often demand more than just basic open-and-close functionality. Today’s solenoid valves come with a variety of advanced features that enhance performance, improve safety, and reduce energy consumption. Understanding these optional enhancements can help you fine-tune your system for better efficiency and reliability.
Here are some of the most useful features BLCH offers in our solenoid valve portfolio:
Power Reduction Technology
Many BLCH solenoid valves come equipped with a power-saving coil, designed to deliver a full voltage pulse during activation and then reduce to a lower holding current. This reduces overall power consumption, minimizes coil heat buildup, and prolongs service life—particularly useful in systems with frequent or long-term valve operation.
This feature is often found in building automation, compressed air systems, and process controls, where hundreds of valves may be operating simultaneously.
Manual Override
A manual override allows operators to mechanically open or close the valve without electrical power—ideal for system testing, commissioning, or emergency maintenance. BLCH valves feature user-friendly override designs, offering tactile feedback and clear visual indicators, helping maintenance teams work quickly and safely.
In critical systems such as fire suppression or gas distribution, this function ensures continued access to fluid control even during power failures or electrical faults.
High-Pressure Versions
Some applications—such as hydraulic test rigs, steam systems, or compressed gas cylinders—require valves that can withstand very high pressures. BLCH provides specially designed solenoid valves rated for up to 250 bar, built with reinforced bodies and upgraded sealing systems to maintain performance under extreme loads.
These are commonly deployed in energy production, machine tools, and industrial automation where pressure surges are common.
Media-Separated Design
Certain industries—like medical diagnostics, semiconductor manufacturing, or chemical dosing—need valves that completely isolate the media from the internal actuator components. BLCH offers media-isolated solenoid valves, which prevent contamination of either the fluid or the valve mechanism, preserving precision and hygiene over long-term use.
These valves are often used for controlling aggressive acids, slurries, or sensitive biological fluids.
Vacuum and Low-Leakage Options
When used in vacuum systems or sensitive environments, a valve’s internal leakage rate and sealing capability are critical. BLCH manufactures direct-acting and semi-direct solenoid valves capable of operating in rough vacuum conditions, with specialized designs that maintain sealing integrity even under low pressure.
Optional low-leakage versions are available for applications such as laboratory instrumentation, packaging, or environmental testing chambers.
Adjustable Response Time & Position Feedback
To prevent water hammer or pressure spikes, certain BLCH solenoid valves feature adjustable opening/closing speeds—achieved via external screw adjustment or electronic timing. This provides smoother transitions and protects downstream components in sensitive systems.
Additionally, position feedback options—including electrical signals or NAMUR-compatible sensors—allow real-time valve status monitoring. This is essential for automated process control, enabling early detection of faults or irregularities.
Whether you’re designing a smart factory, building fluid logic systems, or looking to reduce downtime and energy use, BLCH’s enhanced solenoid valve features offer the tools you need to elevate your system’s performance and reliability.
How to Choose the Right Solenoid Valve?
Choosing the right solenoid valve is not just a matter of finding the correct size or voltage—it requires a comprehensive understanding of your application environment, media characteristics, and system performance goals. A well-matched valve ensures smooth operation, extends system lifespan, and reduces maintenance costs over time.
Here are the key selection criteria you should consider when specifying a solenoid valve:
✅ Media Compatibility
The very first step is to identify the type of media the valve will handle. Is it water, air, oil, steam, gas, or an aggressive chemical? Each fluid has its own set of physical and chemical properties—such as viscosity, corrosiveness, and temperature sensitivity—that influence material selection.
For clean water or air, brass or stainless steel with NBR or EPDM seals are often sufficient.
For aggressive chemicals or acids, opt for PTFE seals and corrosion-resistant housings like PVC or stainless steel.
For steam or high-temperature gases, Viton (FKM) seals are recommended due to their thermal stability.
BLCH provides detailed media compatibility charts and technical support to help ensure the right housing and seal materials are selected for your exact conditions.
✅ Operating Pressure and Flow Rate
Determine both the minimum and maximum operating pressure of your system. If your application has very low pressure—or starts from zero pressure—you’ll need a direct-acting or semi-direct acting valve. If the system maintains a steady pressure differential, an indirect (pilot-operated) valve may be more energy-efficient.
Flow rate requirements will affect orifice size, and in turn, the valve body size. BLCH engineers can assist with flow calculations to ensure the valve won’t become a bottleneck or cause turbulence in your system.
✅ Valve Function: NO, NC, or Bi-Stable?
Think about what the valve needs to do in the absence of power. Does the system need to stay closed for safety? Then a normally closed (NC) valve is preferred. For systems that need passive flow until a fault occurs (such as emergency drainage), a normally open (NO) valve might be better. If power-saving is your top priority, a latching (bi-stable) valve could be the answer.
✅ Voltage and Electrical Requirements
BLCH offers solenoid valves compatible with common industrial voltages—12V, 24V, 110V, and 220V, in both AC and DC formats. Select a voltage that aligns with your system’s control logic or existing power source. Also consider if your application needs low inrush current, power-saving coils, or special connectors for moisture or dust protection.
✅ Mounting & Connection Type
Determine your pipeline connection type: threaded (BSP/NPT), flanged, welded, or push-in. Valve mounting orientation (horizontal or vertical) may also matter in gravity-fed or backflow-sensitive systems.
✅ Ambient Conditions
If the valve will operate outdoors or in extreme environments (dust, moisture, heat, or vibration), ensure the valve’s IP rating and material selection reflect those challenges. For example, in humid environments, stainless steel with sealed coils provides long-term resistance to corrosion and electrical failure.
At BLCH, we know that every application is different. That’s why we offer custom configuration options, detailed datasheets, and one-on-one technical consultations. Whether you’re designing a new system or retrofitting an old one, our team is ready to help you choose a solenoid valve that meets both your performance goals and budget constraints—without compromise.
Common Solenoid Valve Applications
Solenoid valves are used in a vast range of systems across multiple industries. Their ability to offer precise control, quick response, and remote actuation makes them ideal for both simple and complex automation needs. Whether you’re handling air, water, oil, gas, or even corrosive chemicals, solenoid valves are often the most reliable choice for fluid management.
Here are some of the most common and impactful application areas:
Water Treatment and Irrigation
In water filtration systems, solenoid valves are used to automatically start and stop the flow of water based on sensor data or programmed schedules. They’re also widely applied in irrigation controllers, allowing precise control over watering cycles for agricultural fields or landscaping systems. BLCH solenoid valves with water-resistant seals and corrosion-resistant housings are often used in these demanding outdoor environments.
HVAC and Refrigeration Systems
Solenoid valves play a vital role in controlling refrigerant flow in air conditioning systems, chillers, and heat pumps. They help manage flow switching between heating and cooling modes, pressure control, and defrost cycles. BLCH offers compact, fast-acting valves for use in high-efficiency HVAC installations where energy management is critical.
Industrial Automation and Pneumatics
In automated manufacturing lines, solenoid valves are used to activate pneumatic cylinders, manage air flow in pick-and-place systems, and control compressed air delivery. BLCH provides both 2-way and 3-way solenoid valves designed for high-frequency cycling and harsh industrial environments—perfect for packaging machines, robotics, or conveyor systems.
Cleaning Equipment and Car Wash Systems
Whether it’s an automated car wash, pressure washer, or industrial parts cleaning system, solenoid valves are essential for controlling detergent, water, and air flow. BLCH valves are often selected for their fast reaction time, anti-corrosion design, and ability to work reliably under fluctuating pressure and temperature conditions.
Medical, Laboratory, and Food Processing
In highly regulated environments like medical devices, lab analyzers, and food production equipment, solenoid valves manage fluid samples, cleaning agents, or food-grade gases. These applications demand precision, hygiene, and zero leakage, which BLCH supports through specialized designs like media-isolated solenoid valves and high-purity sealing materials.
Automotive Systems
From automated lubrication systems to EV battery cooling and fuel vapor control, solenoid valves are increasingly used in modern automotive systems. They help ensure efficient energy use, safe operation, and emission control. BLCH supports this sector with compact, vibration-resistant valves optimized for vehicle environments.
Custom Applications and OEM Integration
In addition to off-the-shelf solutions, BLCH also supports OEM manufacturers with tailored valve solutions for proprietary systems. Whether you’re building a custom dispensing unit, a smart appliance, or an industrial control cabinet, our engineering team can help integrate the ideal solenoid valve into your platform.
Final Thoughts
Choosing the right solenoid valve is about understanding your system’s unique requirements—from pressure and flow to temperature and media compatibility. At BLCH, we provide expertly engineered solutions that keep your systems running reliably and efficiently.
Ready to optimize your automation setup? Get in touch with BLCH to explore our full range of industrial solenoid valves.
