A solenoid valve is an electromechanical device where the solenoid uses an electric current to create a magnetic field and thereby operate a system which regulates the starting of fluid movement in a valve.
Solenoid valves differ in the characteristics of the electric energy they use, the effectiveness of the magnetic field they generate, the mechanism they use to regulate the liquid, and the type and features of liquid they control. The system varies from linear action, plunger-type actuators to pivoted-armature actuators and rocker actuators. The valve can use a two-port style to modify a flow or use a three or even more port style to switch flows between ports. Multiple solenoid valves can be placed together on a manifold.
Solenoid valves will be the most regularly used control components in fluidics. Their duties are to shut down, release, dosage, distribute or blend liquids. They are found in many software areas. Solenoids present fast and secure switching, high dependability, long service lifestyle, good moderate compatibility of the materials utilized, low control power and compact design.
There are numerous valve design variations. Normal valves can possess many ports and fluid paths. A 2-method valve, for instance, provides 2 ports; if the valve is open, then your two ports are linked and liquid may movement between the ports; if the valve is closed, then ports are isolated. If the valve is open when the solenoid isn’t energized, then the valve is certainly termed normally open (N.O.). Likewise, if the valve is certainly shut when the solenoid isn’t energized, then your valve is definitely termed normally closed. There are also 3-way and more complicated designs. A 3-method valve has 3 ports; it links one interface to either of the two other ports (typically a Pulley supply interface and an exhaust slot).
Solenoid valves are also characterized by how they operate. A small solenoid can generate a limited pressure. If that push is enough to open up and close the valve, then a direct acting solenoid valve is possible. An approximate relationship between your required solenoid power Fs, the liquid pressure P, and the orifice area A for a primary performing solenoid valve is normally:
\displaystyle F_s=PA=P\pi d^2/4 F_s=PA=P\pi d^2/4
Where d may be the orifice size. A typical solenoid force might be 15 N (3.4 lbf). A credit card applicatoin might become a low pressure (e.g., 10 psi (69 kPa)) gas with a little orifice diameter (e.g., 3⁄8 in (9.5 mm) for an orifice area of 0.11 in2 (7.1×10−5 m2) and approximate force of 1 1.1 lbf (4.9 N)).
The solenoid valve (small black box at the top of the photo) with input air line (small green tube) used to actuate a larger rack and pinion actuator (gray box) which controls the water pipe valve.
When high pressures and large orifices are encountered, after that high forces are needed. To generate those forces, an internally piloted solenoid valve style may be feasible. In such a design, the range pressure is used to create the high valve forces; a little solenoid controls how the line pressure is used. Internally piloted valves are found in dishwashers and irrigation systems where the fluid is drinking water, the pressure might be 80 psi (550 kPa) and the orifice size could be 3⁄4 in (19 mm).
In a few solenoid valves the solenoid acts on the primary valve. Others use a small, full solenoid valve, referred to as a pilot, to actuate a more substantial valve. While the second type is truly a solenoid valve combined with a pneumatically actuated valve, they can be purchased and packaged as a single unit known as a solenoid valve. Piloted valves need significantly less capacity to control, but they are noticeably slower. Piloted solenoids usually need full power at all times to open and stay open, where a direct performing solenoid may just need complete power for a short period of time to open it, and only low capacity to hold it.
A direct acting solenoid valve typically operates in 5 to 10 milliseconds. The procedure period of a piloted valve depends on its size; common values are 15 to 150 milliseconds.
Power usage and supply requirements of the solenoid vary with application, being primarily dependant on liquid pressure and line diameter. For example, a popular 3/4″ 150 psi sprinkler valve, designed for 24 VAC (50 – 60 Hz) residential systems, includes a momentary inrush of 7.2 VA, and a keeping power requirement of 4.6 VA. Comparatively, an industrial 1/2″ 10000 psi valve, intended for 12, 24, or 120 VAC systems in high pressure fluid and cryogenic applications, comes with an inrush of 300 VA and a holding power of 22 VA. Neither valve lists a minimum pressure required to remain shut in the un-powered state.
While right now there are multiple design variants, the following is a detailed breakdown of an average solenoid valve design.
A solenoid valve has two primary parts: the solenoid and the valve. The solenoid converts electricity into mechanical energy which, subsequently, opens or closes the valve mechanically. A direct acting valve offers only a little flow circuit, proven within section E of the diagram (this section is usually pointed out below as a pilot valve). In this example, a diaphragm piloted valve multiplies this little pilot stream, by using it to regulate the stream through a much larger orifice.
Solenoid valves might use metallic seals or rubber seals, and could also have electric interfaces to permit for easy control. A spring enable you to hold the valve opened (normally open) or closed (normally closed) while the valve is not activated.
A- Input side
C- Pressure chamber
D- Pressure alleviation passage
E- Electro Mechanical Solenoid
F- Output side
The diagram to the proper shows the look of a simple valve, controlling the flow of water in this example. At the top figure is the valve in its closed state. The drinking water under great pressure enters at A. B can be an elastic diaphragm and above it really is a poor springtime pressing it down. The diaphragm includes a pinhole through its center that allows a very small amount of drinking water to stream through it. This water fills the cavity C on the other side of the diaphragm so that pressure is certainly equal on both sides of the diaphragm, however the compressed springtime supplies a net downward power. The springtime is fragile and is able to close the inlet because drinking water pressure is normally equalized on both sides of the diaphragm.
Once the diaphragm closes the valve, the strain on the outlet side of its bottom level is reduced, and the higher pressure above keeps it even more firmly closed. Thus, the spring can be irrelevant to keeping the valve closed.
The above all works since the small drain passage D was blocked simply by a pin which is the armature of the solenoid E and which is pushed down by a spring. If current is certainly approved through the solenoid, the pin is certainly withdrawn via magnetic power, and the drinking water in chamber C drains out the passage D quicker compared to the pinhole can refill it. The pressure in chamber C drops and the incoming pressure lifts the diaphragm, hence opening the main valve. Water right now flows straight from A to F.
When the solenoid is once again deactivated and the passage D is closed once again, the springtime needs hardly any force to push the diaphragm down once again and the main valve closes. In practice there is frequently no separate springtime; the elastomer diaphragm is molded to ensure that it features as its spring, preferring to maintain the closed form.
Out of this explanation it could be seen that this type of valve relies on a differential of pressure between input and output as the pressure at the input must always be greater than the pressure at the output for it to work. If the pressure at the output, for just about any reason, rise above that of the insight then your valve would open up whatever the condition of the solenoid and pilot valve.
Solenoid valve designs have many variations and challenges.
Common components of a solenoid valve:
Retaining clip (a.k.a. coil clip)
Solenoid coil (with magnetic return path)
Core tube (a.k.a. armature tube, plunger tube, solenoid valve tube, sleeve, guideline assembly)
Plugnut (a.k.a. fixed primary)
Shading coil (a.k.a. shading band)
Core springtime (a.k.a. counter spring)
Core (a.k.a. plunger, armature)
Core tube-bonnet seal
Bonnet (a.k.a. cover)
The core or plunger is the magnetic component that techniques when the solenoid is energized. The primary can be coaxial with the solenoid. The core’s movement will make or break the seals that control the movement of the fluid. When the coil is not energized, springs will contain the primary in its regular position.
The plugnut is also coaxial.
The core tube contains and guides the core. It also retains the plugnut and may seal the fluid. To optimize the motion of the primary, the primary tube needs to be non-magnetic. If the primary tube had been magnetic, then it would offer a shunt route for the field lines. In some styles, the core tube can be an enclosed metal shell produced by deep drawing. Such a style simplifies the sealing problems because the fluid cannot get away from the enclosure, but the design also increases the magnetic path resistance since the magnetic route must traverse the thickness of the core tube twice: once close to the plugnut as soon as near the core. In a few other designs, the primary tube isn’t closed but rather an open tube that slips over one end of the plugnut. To retain the plugnut, the tube could be crimped to the plugnut. An O-ring seal between the tube and the plugnut will prevent the liquid from escaping.
The solenoid coil consists of many turns of copper wire that surround the core tube and induce the movement of the core. The coil is frequently encapsulated in epoxy. The coil also offers an iron framework that provides a minimal magnetic path level of resistance.
The valve body must be appropriate for the fluid; common components are brass, stainless, aluminum, and plastic.
The seals should be compatible with the fluid.
To simplify the sealing problems, the plugnut, core, springs, shading band, and other elements are often subjected to the liquid, so they must be compatible as well. The requirements present some unique problems. The core tube needs to be nonmagnetic to pass the solenoid’s field through to the plugnut and the primary. The plugnut and primary need a materials with good magnetic properties such as iron, but iron is definitely prone to corrosion. Stainless steels can be utilized because they come in both magnetic and nonmagnetic types. For example, a solenoid valve might use 304 stainless for the body, 305 stainless steel for the primary tube, 302 stainless for the springs, and 430 F stainless steel (a magnetic stainless steel) for the core and plugnut.
Many variations are feasible on the basic, one-way, one-solenoid valve described over:
one- or two-solenoid valves;
immediate current or alternating current powered;
different number of ways and positions;
Solenoid valves are used in fluid power pneumatic and hydraulic systems, to control cylinders, fluid power motors or bigger industrial valves. Automatic irrigation sprinkler systems also use solenoid valves with an automatic controller. Domestic washers and dishwashers make use of solenoid valves to control water entry into the machine. Also, they are often found in paintball gun triggers to actuate the CO2 hammer valve. Solenoid valves are often described simply as “solenoids.”
Solenoid valves can be utilized for several commercial applications, including general on-away control, calibration and test stands, pilot plant control loops, process control systems, and various original equipment manufacturer applications.