Solenoid valves are used to control fluid flow in hydraulic systems using electric currents. Unlike other valves, solenoid valves make operations faster, easier, and automated. It has become easy to manage everything from home appliances like dishwashers to heavy machines such as forklifts using solenoid valves.

Read on to learn about the types of solenoid valves, their component parts, and how they are used. This article will guide you in selecting an optimal valve that best suits your needs.

What is a Solenoid Valve?

A solenoid valve is electrically used to regulate liquid or gas flow. The solenoid, a coil of wire through which an electric current passes, is wound around a plunger. Energizing the solenoid produces a magnetic field that automatically opens and closes the valve.

Operating principles for solenoid valves differ significantly from other types. Solenoid valves use electricity to control the direction of flow. There are numerous types of solenoid valves popularly used in hydraulic systems, considering either their applications or design.

Principal Components of the Solenoid Valve

The components depend on the types of solenoid valves and their operations. The critical four elements of a solenoid valve are listed and described below.

Coil:

The coil is one of the integral parts of a solenoid valve. The coil is wrapped around a tube where the plunger is contained. A magnetic field is generated when electricity flows through it. It is this magnetic pull that controls the flow of liquid by pulling the plunger down or pushing it up. The coil of the valve provides quick motion for controlling the valve.

Plunger:

The plunger is a movable piece fitted inside the coil, typically made from some magnetic material. This makes it easy to respond to the magnetic field which the coil provides. The plunger is adjusted to open or close the valve. It also helps in restricting or assisting with the flow of the fluid depending upon its position.

In solenoid valves, the movement opens the valve by lifting the plunger from the valve to enable the liquid to flow. When the coil is turned off, the plunger returns to how it was. The flow of the current is thereby stopped or changed in direction, helped by the spring.

Valve Body:

The body of the valve houses all the other components and containment for the fluid. It is primarily a hollowed housing that has passages through which the fluid will pass and exit. The body also contains the plungers’ seat, where the plungers will rest when not in use.

The valve body is solid and reliable, considering the operations it conducts on other components that it houses. The durability of the valve body determines the solenoid valve as a whole. It is structured to hold fluid over some time without leakage.

Spring:

It resides in the valve, just next to the plunger. The spring always aids the valve whenever the magnetic field cannot operate the movement of the plunger. It leaves the plunger closed any moment when the coil is without current to block the liquid flow. The spring holds the plunger in position when electric current is flowing.

Types of Solenoid Valves

There are several types of solenoid valves depending on design, flow passages, and actuation modes used in their application. The types of hydraulic solenoid valves with diagram below are used in diverse ways according to the level of control needed.

Direct Acting Solenoid Valves

Direct-acting solenoid valves function using a direct pull from the solenoid coil that is used in closing or opening the valve. After charging the coil, the magnetic field directly pulls the plunger to permit the flow of liquid. Direct-acting solenoid valves shall be used only for low-pressure applications since they function without pressure from within the system.

Common Applications:

• They are used in low-pressure fluid control applications, like water dispensers and dishwashers.
• In medical instruments, oxygen systems use such controls to work on specific on/off devices.
• They are applied in laboratory applications where small quantities of chemicals, liquids, or gases need to be handled.
• Solenoid valves are also used in pneumatic systems due to their simplicity and reliability in handling low-pressure air control.

Pilot Operated Solenoid Valve

Pilot-operated solenoid valves help to open and shut the primary valve using the system pressure. This feature makes them more appropriate for high-pressure use. When the solenoid valve is active, it creates an opening for pressure to be released from one part of the valve. This type operates better than direct acting in terms of higher flow rates.

Typical applications:

• Pilot-operated solenoid valves also function to control heavy pressure in water treatment factories.
• They are used to manage the flow of oil and gas in pipelines, especially those that require a lot of fluid.
• They are fit for hydraulic systems where high flow rates or pressure is needed to power heavy machinery.

Two-Way Solenoid Valves

This type of solenoid valve is the most basic type of solenoid valves and have both an inlet and outlet. These ports control and stop the fluid movement into the valve. If the valve is open, the liquid will flow smoothly based on the connectivity of the two ports. If the valve is closed, then this flow will stop. 

Applications:

• Two-way solenoid valves are helpful in irrigation where you need to put on or off the liquid flow.
• Automobiles also use two-way solenoid valves to regulate the stream of fuel, enabling it to flow freely or stop when required.
• They also function in household appliances like washing machines to control the water flow.
• They are used to push out water or foam in fire stifling systems when needed.

Three-Way Solenoid Valves

Unlike the two-way solenoid valves, this type has three ports and can redirect the liquid flow between two separate pathways. The three-way solenoid valve has an exhaust, outlet, and inlet port. Without electricity, only two out of the three ports will connect. Once energized, fluid is diverted from one outlet path to another, making it easy to switch applications.

The port usually connected regardless of the presence or absence of electric current is called the “common port”.

Applications:

• Three-way solenoid valves are employed to switch air between different pathways in pneumatic control systems to control actuators.
• They function in contactless faucets where the valve can switch between opening and closing based on sensors.
• They are also used to switch between gas and fuel in systems that require both options as required in burners.

Four-Way Solenoid Valves

This type of solenoid valve has four or more ports, two for outlets and two for inlets. They are designed for double-acting motors or cylinders that require directional control to control the liquid flow. An energized solenoid can change the direction of fluid flow from one set of ports to another.

Applications:

• Four-way valves function to direct the movement of hydraulic cylinders, making extending and retracting possible.
• They also serve to control the direction in heavy machinery like mining equipment.
• They are helpful in systems that need a controlled movement of tools or parts for automation.

Proportional Solenoid Valves

Proportional solenoid valves, rather than simply control the flow of fluid, regulate the flow rate. The level of electric current applied to the coil controls the plunger’s position, enabling the valve to open or close gradually. This action gives the proportional valve control over the specific flow rate, depending on the current applied. 

Applications:

• They are used to adjust speed and the amount of pressure required in systems where smooth flow is needed, like robotics.
• They manage the amount of fluid pumped into molds, integral for products with unwavering quality.
• Proportional solenoid valves are used in healthcare equipment like ventilators to regulate airflow based on patient needs.

Factors to Consider When Choosing a Solenoid Valve

There are several factors that you should consider before picking the solenoid valve that will work best for you. Some of them are:

Flow Rate and Pressure Requirements: 

The flow rate refers to the volume of fluid required to go through the valve per time. This rate is calculated in liters or gallons per minute. This factor is important when considering getting a solenoid valve as it determines the valve size and orifice. This size affects the amount of fluid that can go through the valve within a specific period. 

If you have a system that needs a high flow rate, a bigger valve will suit you better. If yours is a low-flow system, then a smaller valve and orifice are suitable to manage the fluid flow effectively.

Material Compatibility: 

The materials used in a solenoid valve must be compatible with the fluid flowing through it. Different types of fluid respond differently to valve materials. Some valves work well with aggressive fluids, while some do not. When fluid not compatible with the valve material is supplied in it, it can lead to several problems.

Some results of using valves with non-compatible materials include swelling, corrosion, or a total breakdown of the valve material over time. Materials like brass are compatible with water, air, or oil. Harsher fluids like chemicals and saltwater have been said to work best with stainless steel.

Response Time: 

This refers to how fast the solenoid valve responds after it is activated. This factor is crucial for systems that require swift responses to actions, as a slow response could negatively impact performance.

Environmental Conditions: 

Factors such as temperature, exposure to water, humidity, and harsh weather conditions can impact how a solenoid valve operates. Varying temperatures can affect the functioning and lastingness of valve materials. It is important to pick a valve that works best with the temperature of the fluid you will be using.

In hazardous environments like mines and oil systems, choose solenoid valve types that can prevent sparks. Taking note of this will prevent inflammation and ensure your safety and the safety of your team members.

Conclusion

Understanding the types of solenoid valves and their functions will improve your hydraulic system operation and enhance efficiency. For more information on solenoid valves, contact Hydraflu.