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A solenoid valve is an electromechanical valve for use with liquid or gas controlled by running or stopping an electric current through a solenoid, which is a coil of wire, thus changing the state of the valve. The operation of a solenoid valve is similar to that of a light switch, but typically controls the flow of air or water, whereas a light switch typically controls the flow of electricity. Solenoid valves may have two or more ports: in the case of a two-port valve the flow is switched on or off; in the case of a three-port valve, the outflow is switched between the two outlet ports. Multiple solenoid valves can be placed together on a manifold. Solenoid valves are the most frequently used control elements in fluidics. Their tasks are to shut off, release, dose, distribute or mix fluids. They are found in many application areas. Solenoids offer fast and safe switching, high reliability, long service life, good medium compatibility of the materials used, low control power and compact design. Besides the plunger-type actuator which is used most frequently, pivoted-armature actuators and rocker actuators are also used.
Principle
A solenoid valve has two main parts: the solenoid and the valve body. The solenoid converts electrical energy into mechanical energy which, in turn, opens or closes the valve mechanically. A Direct Acting valve has only a small flow circuit, This Diaphragm Piloted Valve multiplies this small flow by using it to control the flow through a much larger orifice. Solenoid valves may use metal seals or rubber seals, and may also have electrical interfaces to allow for easy control. A spring may be used to hold the valve opened or closed while the valve is not activated.
Common uses
The most common uses of solenoid valves are in pneumatic systems - controlling cylinders or larger industrial valves. Some examples of solenoid valves are general-purpose, combustion, and dust collector; there are many others. The use of two-way solenoid valves in central heating systems is not generally recomended due to the high closing speeds, causing water hammering (in the case of direct operated valves), or insufficient pressure drop to operate the pilot system in pilot-operated solenoid valves.
Danfoss Solenoid valves
Danfoss solenoid valve bodies and electrical coils are normally supplied separately and then combined.
They are assembled quickly and simply without tools, providing optimum product flexibility and availibility. If a coil does need to be replaced, it can be done without stopping or draining any system.
The solenoid valves are also available as assembled units if required.
Danfoss produces four kinds of solenoid valves:
Direct-operated valves (or pilot valves) are relatively simple valves. Ideal for autoclaves, boilers, compressors, printing machines, and water treatment, these valves are available in limited sizes and capacities and operate from zero bar differential pressure.
Direct servo-operated valves are used for larger capacities such as commercial dish washers, dry cleaning machines, and high pressure cleaners. They consist of a main servo part with a diaphragm and pilot part. The valves require a minimum differential pressure for the diaphragm to open and close correctly; pressure above and below the diaphragm is equalised by a hole in the diaphragm. Direct servo-operated valves with assisted lift are ideal for conditions where there is a risk of zero, low or unknown differential pressures. The armature is connected to the diaphragm by a spring that allows the valve to operate like a direct valve for low differential pressures and a servo valve for higher differential pressures. This valve type is suitable for closed water/heating systems, and safety fuel shut-offs. Indirect servo-operated valves are for larger capacities than direct operated and direct servo-operated valves and most suited where damping water hammer is required. The pressure above and below the diaphragm is equalised by a separate channel unit with filter protection. This valve is typically used for commercial dish washers, compressors and water treatment.
To make sure you choose the right valve for your needs, you must also consider:
• Media characteristics and temperature
• Risk of water hammer
• Coil supply (voltage, frequency, power)
• Ambient temperature
• Valve cycles and frequency of opening and closing
EV210A, Direct-operated 2/2-way compact solenoid valves
EV210A covers a wide range of small, direct-operated 2/2-way solenoid valves for use in industrial machinery.
The compact design together with the broad range of coils means that EV210A covers a broad variety of industrial applications.
EV220A, Servo-operated 2/2-way solenoid valves
EV220A is a compact indirect servo-operated 2/2-way solenoid valve program, especially designed for use in machines and equipment with limited space.
EV220A w/ filter, Servo-operated 2/2-way solenoid valves
EV220A is a compact indirect servo-operated 2/2-way solenoid valve program, especially designed for use in machines and equipment with limited space.
The built-in and interchangeable filter ensures long-lasting problem free operation, even when used with water, oil and air with impurities.
EV310A, Direct-operated 3/2-way compact solenoid valves
EV310A covers a wide range of small competitive, direct-operated 3/2-way solenoid valves for use within industrial applications, for example pilot valve applications.
EV210B, Direct-operated 2/2-way solenoid valves
EV210B covers a wide range of direct-operated 2/2-way solenoid valves for universal use. EV210B is a real robust valve program with high performance and can be used in all kind of tough working conditions.
EV220B (6-22 series), Servo-operated 2/2-way solenoid valves
EV220B 6-22 is a direct servo-operated 2/2-way solenoid valve program with connections from 1/4" to 1".
This program is especially for OEM applications demanding a robust solution and moderate flow rates.
EV220B (15-50 series), Servo-operated 2/2-way solenoid valves
EV220B 15-50 is a universal indirect servo-operated 2/2-way solenoid valve program.
Valve body in brass, dezincification resistant brass and stainless steel ensures that a broad variety of application can be covered.
Built-in pilot filter as standard, adjustable closing time and enclosures up to IP67 ensures optimal performance even under critical working conditions.
EV220B (65-100 series), Servo-operated 2/2-way solenoid valves
EV220B 65-100 is a 2/2-way solenoid valve program for use in robust industrial applications, demanding high flow rates. The valve is designed with cast iron valve bodies and flanged connection.
Water-hammer damped design and built-in pilot filter ensures a reliable operational period.
EV222B, Servo-operated 2/2-way solenoid valves with isolating diaphragm
EV222B is an indirect servo-operated solenoid valve program for use in connection with contaminated or aggressive media.
Valve body in stainless steel, isolating diaphragm protecting the solenoid system against impurities, build in pilot filter, adjustable closing time, enclosures up to IP67 ensure a reliable and satisfaction function.
EV250B Assisted Lift Operated 2/2 Way Solenoid Valve
Danfoss solenoid valve EV250B with assisted lift can operate from zero and up to 16 bar differential pressure.
This 2/2-way valve program is especially to use in closed circuits with low differential pressure, but demanding moderate flow rates. Valve body in dezincification resistant brass for ensuring a long life even in connection with aggressive steam media.
EV310A Direct-Operated 3/2 Way solenoid valve
EV310A covers a wide range of small competitive, direct-operated 3/2-way valves for use within industrial applications, for example pilot valve applications.
EV310B Direct-Operated 3/2 Way solenoid valve
EV310B covers a wide range of direct-operated 3/2-way valves for universal use.
EV310B is a real robust valve program with high performance and can be used in all kind of tough working conditions. Clip-on coils can not be used on EV310B.
Further details on Danfoss solenoid valves.
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