The solenoid (electromagnetic) valve is remarkable in that it can be controlled by an electrical signal coming through the wires. The response time does not exceed half a second, which makes it possible to use such devices as automated high-speed pipe valves operating from signaling sensors. But first of all, let's talk a little about the composition and principle of action.
The solenoid valve is formed by a bronze body with a channel and a solenoid with a divided core in the form of a fixed rod and a stem, enclosed in a sealed sleeve. The latter is connected to the membrane by means of a plunger. A pair of springs regulates the smoothness of the moving part. The plunger is most often supplied with an axial hole with a side groove. It equalizes the pressure acting on the membrane from both sides. As a result, the solenoid valve switches with minimal effort from the open state to the closed state and vice versa. The solenoid is screwed into the housing with an O-ring around the perimeter. In this case, the membrane rests on a saddle formed by the fluid flow channel. The upper part of the core contains a fixed element and is equipped with a shielding coil. This is necessary to improve the properties of the electromagnetic field in the internal space of the sleeve and to prevent vibrations when the device is powered by alternating current.
Everyone, I think, is familiar with the hum of wires under power lines - this is the result of vibrations caused by alternating voltage. The passage channel is blocked by a membrane with an anchor from the movable part of the solenoid core - a wire coil. In the normal state, the fluid passage may be free, or it may be blocked. Depending on this, the solenoid valve can be:
- normally open;
- normally closed.
The normal state in this case is the initial one, when there is no external voltage. The blocking core is driven by an electric current applied to the outer coil of the solenoid. As soon as a control voltage is applied to the electrodes, a metal rod connected to the diaphragm drives it. The path for the medium to flow through the valve is then blocked or opened. As soon as the external signal disappears, the system returns to its original state.
The solenoid valve, which is based on mixing two inlet streams into one outlet stream or diverting part of the inlet stream, has more than two sockets for connecting pipes.
Depending on the number of inputs and outputsdistinguish models:
- two-way;
- three-way;
- four-way.
If the first variety is designed directly to work as shut-off valves, then more complex modifications allow solving quite specific tasks. When certain conditions occur, part of the flow descends into a branch. Or the two streams are mixed in certain proportions. The three-way solenoid valve can be used to maintain the set temperature in the hot water or heating circuit. If the temperature is too high, the water flow through the boiler will be blocked. Conversely, lowering the temperature below the set point will cause most of the water to heat up.
