What are Solenoid Valves?
Solenoid valves are electrically operated open or closed valves. These valves control the flow of air, gas, or liquids as component of a product or equipment. Solenoid valves operate as normally closed or normally open. In their simplest form, 2-way solenoid valves are on/off valves that when energized either allow the flow or stop the flow through the valve. More complex designs like 3 and 4-way directional or multipurpose valves control or switch the direction of the media, while solenoid valves mounted on a manifold provide limitless options to distribute flow through a system.
A solenoid valve is controlled by an electric current that passes through the solenoid. These electromechanically operated valves come in a broad range of configurations and materials suitable for countless applications. Direct-acting solenoid valves are used to shut off, release, dose, distribute, or mix fluids or gasses and may have two or more ports to accomplish the task. Two-way solenoid valves have one inlet and one outlet port and a single orifice while three-way valves have three port connections and two valve orifices.
Click here to learn more about how solenoid valves and manifolds work
Below are the components of a 2-way Normally Open Solenoid Valve
* Stop material - Magnetic stainless steel
* Stop Port – Present in 3-way and 2-way Normally Open valves
* Coil – When energized produces a magnetic field
* Lead Wires – Electrical connection
* Plunger Guide Tube
* Plunger – Magnetic stainless steel
* Compensating Spring – Used in 3-way and 2-way Normally Open valves
* Body Orifice Seal
* O-Ring Body Seal
* Inlet Port
* Plunger Return Spring – Spring that produces plunger movement regardless of mounting orientation
* Valve Body
How does the 2-way Normally Open solenoid valve work?
De-Energized
1. The valve is controlled by electrical current through the solenoid.
2. When power is off, the plunger is raised, allowing liquid or gas to flow through the valve out of the Stop Port
3. Pressurized liquid or gas goes through the Inlet Port and out the Stop Port
...when energized
4. When the coil is energized, a magnetic field is created, causing the plunger to rise in the valve, sealing the stop orifice and closing the valve
5. The plunger blocks the stop orifice. This does not allow the pressurized liquid or gas to pass the valve
6. This allows the pressurized liquid or gas to pass through the valve
Here is the schematic or flow diagram of the 2-way normally open valve 
2-Way Normally Closed Solenoid Valves
The parts of a 2-way Normally Closed Solenoid Valve are similar to the N.O. valve
* Stop material - Magnetic stainless steel
* Stop Port – Present in 3-way and 2-way Normally Open valves
* Coil – When energized produces a magnetic field
* Lead Wires – Electrical connection
* Plunger Guide Tube
* Plunger – Magnetic stainless steel
* Compensating Seal – Used in 3-way and 2-way Normally Open valves
* Body Orifice Seal
* O-Ring Body Seal
* Valve Body
* Plunger Return Spring – Stainless steel, provides positive plunger return regardless of mounting position
* Inlet Port
* Outlet Port
How does a 2-way Normally Closed Solenoid Valve work?
De-energized
1. The valve is controlled by an electrical current that passes through the solenoid
2. When power is off the plunger is down and seals against the orifice and closes the valve
3. Pressurized liquid or gas goes through the Inlet Port into the valve cavity
...when energized
4. When the coil is energized, a magnetic field is created, causing the plunger to rise up inside the valve, unsealing the orifice and opening the valve
5. The plunger directly opens an orifice inside the valve
6. This allows the pressurized liquid or gas to pass the valve
Here is the schematic or flow diagram of the 2-Way normally closed valve 
Different Types of 3-Way Valves
What is a 3-way Valve? Three-way valves have three pipe connections or ports and two orifices. One is always open, allowing for two flow paths depending on the valve's energized state. This allows the flow or pressure to a load to be applied or stopped when the valve is energized (de-energized), and the flow or pressure to move to a different destination when the valve is de-energized (energized).
There are four common types of 3-way solenoid valves:
* 3-way Normally Closed
* 3-way Normally Open
* 3-way Directional Control
* 3-way Multi-Purpose
What are the different parts of a 3-way Solenoid Valve?
* Stop material - Magnetic stainless steel
* Stop Port – Present in 3-way and 2-way Normally Open valves
* Coil – When energized produces a magnetic field
* Lead Wires – Electrical connection
* Plunger Guide Tube
* Plunger – Magnetic stainless steel
* Compensating Seal – Used in 3-way and 2-way Normally Open valves
* Body Orifice Seal
* O-Ring Body Seal
* Valve Body
* Plunger Return Spring
* Inlet Port
* Body Orifice
* Outlet Port
What are the Basic Functions of a 3-Way Solenoid Valve?
Solenoid valves control the flow of fluids, air, gases, and other media in many types of systems and products.
1. The valve is controlled by an electrical current that passes through the solenoid.
When De-energized
2. When the power is off, the plunger is down which seals off the body orifice and stops the flow of liquid or gas through the valve.
...when energized
3. When the coil is energized the plunger is raised, sealing off the stop orifice and opening the body orifice allowing flow through the body of the valve
The basic function of 3-way valves:
* Normally Closed
* De-energized: Port 1 → Port 2
* Energized: Port 2 → Port 3
* Normally Open
* De-energized: Port 1 → Port 3
* Energized: Port 1 → Port 2
* Directional Control
* De-energized: Port 1 → Port 2
* Energized: Port 1 → Port 3
* Multi-purpose
* De-energized: Port 1 → Port 2
* Energized: Port 2 → Port 3
Things to Consider when Selecting the Right Valve for the Application
Once you understand the operation of the valve, there are a myriad of consideration about the valve’s function, the environment, and requirements needed to begin to select the right solenoid valve for your application. A few examples include the media, capacity, temperature, power, cycles, pressures, and more. The application might need to control the flow of a viscous fluid or nitrous oxide under low or high pressure. The valve might be operating in a harsh freezing environment with limited power availability needing cryogenic rated rings and a low power draw coil for a solar power connection. Below is a list of valve-related considerations.
Valve Functions
As covered above, do you need a 2-way on/off or a multi-port (3-way) valve?
Is it normally closed or normally open?
Will the valve operate on short or long cycle times?
Media Type
What type of gas or liquid is moving through the value?
Air or inert gas systems may have traces of oils or other chemicals that might affect valve components like seals and body alloys.
Flow Rate
What is the approximate desired flow rate of the media?
Calculate the Flow Coefficient (Cv). Formulas are available online. Flow rates can be achieved through the combination of valve components including port and orifice size, applied pressure, and more.
Available Power
Does the valve need to operate at a specific wattage?
Does it run off battery power?
Is energy conservation an imperative?
Conserving energy can be accomplished through a variety methods including the selection of orifice size and pressures as well as using magnetic latching.
Operating Environment
Will the valve operate in a high temperature, a corrosive or high vibration environment, with limited energy availability or limited space, or will it require specific agency approvals?
Environmental issues directly affect the selection of valve’s components.
Connections
What is the inlet size (port) and type?
What type of electrical connection is required... spades, leads, DIN, conduit?
Multiple Lines
Does your system incorporate more than one line?
Are there multiple controls or operations needing valves?
Incorporating a manifold system may be the most efficient solution to controlling multiple lines.
Valve Assembly
Based on the requirements of your system, might it be beneficial to outsource some subassembly operations?
Having your valves ship complete with all its components clocked to precise angles to fit your space, connections sealed and torqued properly, and electrical leads are terminated ready for finished assembly.
Supply Options
Need your valves delivered every two weeks, all at once or to have your inventory managed?
An almost unlimited number of supply options are available to ease your initial investment or maximize your available space. Whatever you need.
Additional Terminology
Here is a list of additional terms you'll need to be familiar with when deciding on the right valve. Being able to address these factors will help the specification process go smoothly.
Ambient Temperature:
Temperature of the media surrounding external surfaces of a valve.
Ampere Rating:
Current drain when the valve is energized.
Bubble Tight:
Sealing capability within the valve which is virtually undetectable during a pressure decay test time period. Approximately equal to 1X10-5 cc/sec using air.
Burst Pressure:
The pressure differential between the internal and external surfaces of a valve will cause the pressure-containing parts to rupture resulting in an external leak.
Cv Factor:
A dimensionless coefficient or value which indicates the relative flow capacity of a valve, defined as the gallons of water per minute (USGPM) at 60° F, which will flow through the valve at a one (1) PSIG pressure drop.
Coil Insulation Class Rating:
Coil magnet wire insulation rating. Exceeding this rating causes premature coil failure.
Class B: 130° C (266° F)
Class F: 155° C (311° F)
Class H: 180° C (356° F)
Coil Voltage:
Voltage at which the coil must be energized if the valve is to perform as stated in the specifications. Normally, the coil voltage tolerance is +10% to -15% of the rated coil voltage.
Continuous Duty:
Coils rated for continuous duty are designed to be energized continuously without overheating or failure. All Solenoid Solutions Inc. standard valves are equipped with coils rated for continuous duty.
Duty Cycle:
The ratio of "on" time to "total cycle" time. If a valve is on for 2 seconds and off for 8 seconds, the total cycle time is 10 seconds and the duty cycle is 20%.
* To get started, here are the items needed to spec a solenoid valve.
Continuous Duty:
Coils rated for continuous duty are designed to be energized continuously without overheating or failure. All Solenoid Solutions Inc. standard valves are equipped with coils rated for continuous duty.
De-energized:
No power is applied to the coil. Typically, this is the "fail-safe" condition. A normally closed valve is closed when the coil is de-energized.
Energized:
Power is applied to the solenoid valve coil causing the valve to change state. A normally closed valve will open when energized.
Differential Pressure (delta P):
The pressure difference between the inlet and outlet of a valve.
Examples:
100 PSIG Inlet Pressure, 50 PSIG Outlet Pressure, Differential Pressure = 50 PSIG
120 PSIG Inlet Pressure, Atmospheric (0 PSIG) Outlet Pressure, Differential Pressure = 120 PSIG
50 PSIG Inlet Pressure, Vacuum Outlet, Differential Pressure = 65 PSIG (Assumes perfect vacuum)
Atmospheric (0 PSIG) Inlet Pressure, Vacuum Outlet, Differential Pressure = 15 PSIG (Assumes perfect vacuum)
Direct Acting:
In direct-acting solenoid valves, the solenoid plunger directly opens or closes the orifice when the coil is energized or de-energized.
Directional Control:
Type of valve whose function is to divert a flow of media from one inlet line to one of two outlet lines.
Filter:
A device whose primary function is to remove contaminants from the flowing media. Solenoid Solutions Inc. recommends that a filter be placed directly before its solenoid valves.
Adapter:
Hex-shaped plated steel or stainless steel part designed to attach the stop port on 2-way normally open and 3-way valves to a piping system using NPT threads. Learn more about connection size.
