What Are Solenoid Valves and Their Major Types?
Within the realm of piping systems and fluid transportation, solenoid valves prove to be an indispensable piece of equipment with their various capabilities. As an electrically controlled valve, solenoids utilize magnetic fields to open and close orifices. As such, they serve a large variety of applications such as vacuums, irrigation systems, car washes, heating systems, compressed air systems, and much more. Due to their wide use for the transportation of clean liquids and gases, understanding their functionality and types can be useful for procuring parts and maintenance endeavors.
While the exact operations and design of a solenoid valve may differ by type, most share two basic components which are the valve body and the solenoid component. The solenoid is attached to the valve body, and an electromagnetic coil is wound around an iron core which serves as the plunger. Depending on the solenoid and its use, the solenoid may naturally remain open or closed while there is no power being provided. To initiate operation of the solenoid valve, an electrical current may be induced to the solenoid, causing the coil to become energized. With its construction and energy, the solenoid forms a magnetic field which has magnetic attraction to the plunger of the valve. With enough force, the plunger can be lifted or closed depending on the natural state of the valve, allowing for fluids to either flow freely through the component or be impeded by a seal.
With their means of operation, solenoid valves are highly useful for closing, opening, dosing, distributing, or mixing fluids within a piping system. With their ability to be remotely activated, they are also highly beneficial for hard to reach areas or those that are unsafe for individuals to be in for manual operation. Additionally, a variety of solenoid valves exist to accommodate various pressure values and flow rates of fluids. Depending on the need of the system and the circuit function, a solenoid valve will often either be a 2-way or 3-way valve.
With the 2-way valve, two ports exist to serve as an inlet and an outlet. To ensure that such components are installed correctly, manufacturers will typically place an arrow that indicates the direction of flow. With 2-way valves, operations are often more simpler, typically consisting of the opening and closing of the orifice for controlling flow and pressure. With a 3-way solenoid valve, however, three connection ports allow for two positions during operation. As such, 3-way solenoid valves can allow for opening, closing, distributing, and mixing fluids on two different circuits.
Regardless of how many ports the solenoid valve contains, the principles of operation are determined through the means of powering and additional components. With a direct acting solenoid valve, a spring is used to maintain the open or closed positioning of the valve seal, and a plunger overcomes the spring’s force through the magnetic field provided by the solenoid. By adjusting the diameter of the opening and the magnetic force of the solenoid, the flow rate of fluids and pressure can be directly influenced. In general, direct acting solenoid valves are used for smaller flow rates, and they do not follow a minimum operating pressure.
With an indirect acting valve, also known as a servo operated valve, the pressure difference between the inlet and outlet of the valve can be used to open and close the seal. As such, indirect acting valves have a minimum pressure differential in order to prevent easy opening and closing. With a rubber diaphragm separating the inlet and outlet of the valve, pressure and a spring keep the seal in place. When an electrical current is induced, the solenoid causes the pilot orifice to open, and thus the pressure located above the diaphragm drops. As a result, the diaphragm moves in order to allow for fluids to either flow freely or be impeded by a seal. Due to their construction and means of operation, such solenoid valve types often are used for fluids that are flowing in a single direction.
With the semi-direct acting solenoid valve type, elements of the direct and indirect acting types are mixed. Because of this, such solenoid valves can operate at zero bars of pressure and are more capable of accommodating higher flow rates as compared to the direct acting type. The semi-direct solenoid valve also features a membrane that is placed within the solenoid valve case, and it is directly connected to the plunger. With energization of the solenoid component, the plunger can directly affect the positioning of the diaphragm. As there is also a second orifice that may be opened by the plunger during operation, the pressure difference may be changed alongside the flow rate. To ensure such operations are carried out, semi-direct solenoid valves require more powerful coils so that they can consistently handle larger flow rates and varying pressures.
Last but not least, the 3-way direct acting valve is one in which operations differ depending on whether one wants to mix or divert fluids within a system. As only two ports can be connected at a time, one port must be open and another closed. As such, 3-way solenoid valves may act for diverting, mixing, or universal applications depending on the internal part configuration of the valve. In all types, energization is still required for the actuation of the plunger for changing seal positioning.
When deciding on which type of solenoid valve is best for your particular operation, there are various considerations that should be made. Depending on the fluids that are transported and the environment that the system is operating in, one should carefully choose materials that can ensure efficient operation and resist any heat, chemicals, pressures, or other stressors that valves may face. Additionally, solenoid valves may be powered by DC or AC power, and thus the correct version should be chosen. Alongside factors such as desired response times, ratings, pressure capabilities, and seal materials, choosing the right fit for your needs can be made easier.
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