Wherever automatic controls are needed for fluid flow, solenoid valves are used. Increasingly, they are found in a wide variety of plant and equipment types. There is a wide range of valve designs available that enable a valve to be chosen based on the application.
The solenoid valve manufacturers have made this product for a control system that, when powered up or de-powered, shuts off or allows fluid flow. Electromagnets are used as actuators. Whenever a magnet is energized, it builds a magnetic field that moves a plunger or pivot against a spring’s force. With the spring action, the plunger or pivoted armature returns to its original position when de-energized.
A direct-acting valve may be internally piloted or externally piloted, depending on the method of actuation. Flow paths or the number of port connections are other distinguishing features.
DIRECT ACTING VALVES
The seat seal is attached to the solenoid core of a direct-acting solenoid valve. During the de-energized condition, a seat orifice is closed, which opens when the valve is energized.
DIRECT ACTING 2 WAY VALVES
An example of a two-way valve is a shut-off valve with an inlet port and an outlet port. Under the de-energized condition, the core spring, together with the fluid pressure, holds the valve seal on the valve seat to prevent the flow. By energizing the solenoid coil, the valve is opened and the core and seal are pulled into it. The electromagnetic force exceeds the combined forces of springs, static pressure, and dynamic pressure.
DIRECT ACTING 3 WAY VALVES
A three-way valve has three port connections and two valve seats. One valve seal stays open and the other closes in the de-energized mode. The reverse occurs when the coil is energized. This type of valve has a plunger core. Depending on how the fluid medium is connected to the working ports, various valve operations can be obtained. Under the valve seat, fluid pressure builds up. When the coil is de-energized, a conical spring holds the valve seat tightly against the lower core seal and blocks fluid flow.
For example, In a 3 port valve named A, R, and P. The fluid exhaust from Port A is directed through Port R. During energization of the coil, the core is pulled into the valve seat at Port R. The upper core seal seals off the valve seat at Port R. Fluid now flows from Port P to Port A.
As opposed to plunger-type valves, pivoted-armature valves have all port connections in the valve body. By using an isolating diaphragm, the fluid medium cannot contact the coil chamber. An array of 3-way valves can be constructed using pivot-armature valves. As a standard feature, armature valves are equipped with manual override.
INTERNALLY PILOTED SOLENOID VALVES
The static pressure forces on direct-acting valves increase with increasing orifice diameters, so the magnetic forces required to overcome the pressure forces also increase. By switching higher pressures with larger orifice sizes, internally piloted solenoids are employed. In this case, the differential fluid pressure performs the major function of opening and closing the valve.
INTERNALLY PILOTED 2 WAY VALVES
Two and three-way pilot solenoid valves are fitted with internally piloted solenoid valves. Seals are provided for the main valve seat by a diaphragm or piston. A bleed orifice on both sides of the diaphragm allows the fluid pressure to build up when the pilot valve is closed. By virtue of the larger effective area on the top of the diaphragm, a shut-off force is available as long as there is a pressure differential between the inlet and outlet ports. Upon opening the pilot valve, the pressure on the upper side of the diaphragm is relieved. By means of greater net pressure, the diaphragm is now raised and the valve is opened. To ensure satisfactory opening and closing, internally piloted valves generally require a minimum differential in pressure.
CONCLUSION
This blog post has provided you with some key information on solenoid valves. They are used in a wide range of applications, and there are a number of different designs available. If you would like to find out more about solenoid valves, please contact us at www.airaindia.com
