Mixed control solenoid valves n.c. minimum operating pressure 0 bar

2-way solenoid valves normally closed with mixed control

Main components: body with main orifice, cover, membrane assembly (or piston),

quill assembly + moving core assembly, coil.


The normally closed 2-way solenoid valves with mixed control have an inlet and outlet fitting

a fitting of use.

The opening of the main port, present in the

body, occurs due to an imbalance of pressure between the upper face and the lower face of

a membrane (or a piston) together with

direct action of the mobile core which is bound

to the membrane. In essence, the operation is similar to that of the solenoid valves servo-controlled for

regarding the displacement of the membrane,

with the difference that, even with small differences

pressure between supply and use, operation is guaranteed by the direct action exerted by the mobile core on the membrane. Then,

also in this case, when the coil is not powered, in the chamber above the membrane there is

fluid under pressure, while under the membrane there is pressure only in the area outside the main orifice: therefore the resultant of the forces

on the membrane it is such as to push the membrane to close the main orifice. When the

coil is powered, the movement of the mobile core on which a gasket is mounted,

causes the opening of an orifice present on the membrane assembly (pilot orifice) and discharges the

chamber above the membrane; at the same time the nucleus exerts a direct force on the

membrane helping it to open. The sum of

this force and the imbalance of pressure on the two

sides of the membrane causes the displacement of the membrane itself which opens the main orifice. Note:

In this family of solenoid valves, unlike

those servo-controlled, a minimum pressure difference between the supply and the use fitting is not necessary to ensure correct

operation of the solenoid valve itself. However, an excessive pressure difference between the supply

and the use, as on the normally closed 2-way solenoid valves with direct control, causes an increase

of the force required to open the pilot orifice, so if this pressure difference is greater than the maximum value for which the solenoid valve has been designed, the latter may not open

also with powered coil. For the correct operation of the solenoid valve and to avoid the rapid deterioration of the membrane, it is desirable that, when you start to close the valve, the flow rate value does not exceed Kv, i.e. the value of flow rate guaranteed with pressure drop across

the solenoid valve equal to 1 bar. For this reason, if the supply pressure with the valve open is greater than 1 bar, the use of the free-mouth valve is not recommended, i.e. without an appropriate restriction

on the discharge port which reports the pressure drop on the solenoid valve to the value of 1 bar

pay particular attention in the hydraulic circuit design, to the water hammer problem,

which can cause overpressures that could tear the membrane or damage other parts of the solenoid valve.

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