What Is a Valve? Importance of Valves for Industrial Use

A valve is a device that regulates the flow of fluid through a pipe or channel. Valves are used in many applications, from controlling water flow in your home to industrial processes that use high-pressure steam to generate energy or create products. They are essential to many systems because they help prevent damages, overpressure situations, or other fluid control incidents. Valves ensure that all components are working within the pre-set conditions. 

What is a Solenoid Valve? 

A solenoid valve is a type of control valve that uses an electromagnet to open or close a passage between the inlet and outlet ports. A solenoid valve is similar to a regular valve in that it controls the fluid flow, but it uses electricity rather than mechanical means. This makes them far more precise than manual valves because there’s no human error involved in operating them. They can also be controlled remotely, which means you don’t have to be physically present for these devices to do their job properly.

How Solenoid Valves Work 

The working principle of a solenoid valve is pretty straightforward. But before diving deep into how these devices work, it’s essential to understand the various parts of a solenoid valve. Typically, a solenoid valve has two main parts: a valve body and a solenoid. The solenoid contains an inductive coil, a shading ring, a plunger, and a spring. 

Figure 1: (A) Coil; (B) Armature; (C) Shading Ring; (D) Spring; (E) Plunger; (F) Seal; (G) Valve Body.

Solenoid valves are essential components in various systems, operating based on the principles of electromagnetic force and the control of valve trim. When an electric current is applied to the coil of a solenoid valve, it generates an electromagnetic field that exerts a force on the plunger, enabling the valve to either open or close. Conversely, when the power supply is interrupted, the plunger returns to its original position, causing the valve to close or allow fluid to pass through it, depending on its design.

Integral to the operation of solenoid valves is the valve trim, which includes seals that play a critical role in regulating the orifice. These seals open or close, thereby permitting or restricting the flow of fluid. Additionally, in AC coils, a shading ring is often employed to prevent undesirable humming and vibration, enhancing the valve’s performance.

Solenoid valves are available in two primary configurations: normally open and normally closed. A normally open solenoid valve remains in an open state unless an electrical current is applied to the inductive coil surrounding its metal core, causing it to close. Conversely, a normally closed solenoid valve remains closed until energized by an electrical current, at which point it opens to allow fluid flow.

Manufactured using materials such as stainless steel or bronze, solenoid valves are designed to withstand the challenges of their operating environments, including resistance to corrosion caused by exposure to heat, chemicals, and moisture. These features make solenoid valves versatile components, serving critical roles in a wide range of applications across various industries.

Solenoid Valves Circuit Function 

Solenoid valves can help open, close, distribute or mix the flow of liquid or gas in a pipe. The circuit function determines a solenoid valve’s specific use case or purpose. In terms of circuit functions, the most common types of solenoid valves are 2-way and 3-way solenoid valves. A 2-way solenoid valve comes with two ports and is commonly used to open/close an orifice allowing or restricting fluid flow. A 3-way solenoid valve comes with three ports. This valve can switch between two circuits and is commonly used to open, close, mix or distribute fluid media. 

Different Working Principles of Solenoid Valves 

Now that you know the simple working principle and the two main types of solenoid valves, it’s time to explore the different working principles in detail. Below are the main types of solenoid valves based on their working principles.

• Direct-acting valves. With the solenoid valves, the fluid-flow rate and maximum fluid pressure/operating pressure are proportional to the orifice diameter/size and the valve’s magnetic force. That means these valves are ideal for relatively small flow rates. Direct-acting solenoid valves do not require minimum operating pressure and can be used from zero bar up to maximum allowable pressure.

• Indirect-acting/ pilot-operated solenoid valve. These solenoid valves work on pressure differential (a minimum of 0.5-bar). Pilot-operated solenoid valves only control fluid flow in one direction. They are commonly used in systems with high flow rates but with a sufficient pressure differential.
• Semi-direct acting solenoid valve. This type combines the qualities of direct and indirect solenoid valves. For this reason, the valve can work without a pressure differential while still handling a high-flow rate. 

Choosing a Solenoid Valve for Your Industrial Applications 

Solenoid valves are a great way to control fluid flow in your industrial system. They’re also relatively simple to use and maintain. But there are many options out there—each one has its own features and uses. So how do you pick the right one for your application?

Ideally, you want to choose the right solenoid valve that meets your system requirements. That means focusing on the circuit function, housing material, seal material, voltage specifications, pressure and temperature rating, and operating type. Other factors to consider are the valve’s response time, industry approvals, and the degree of protection from dust and liquid damage. If you are new to solenoid valves, you should work with a seasoned professional to ensure you pick the right product and get value for your money.