The solenoid valve and the principles of its operation

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 allows the use of such devices as an automated high-speed pipe shut-off valve, which operates from signaling sensors. But first of all, little about the composition and the principle of action.
The solenoid valve forms a bronze body with a channel and a solenoid with a separated core in the form of a fixed rod and a rod enclosed in a sealed sleeve. The latter is connected to the membrane by means of a plunger. A pair of springs adjusts the smooth running of the moving part. The plunger is most often provided with an axial hole with a lateral protector. It equalizes the pressure acting on the membrane on both sides. As a result, the solenoid valve is switched by a minimum force from the open state to the closed state and vice versa. The solenoid is screwed into the body with a sealing ring around the perimeter. The membrane then lies on the 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 inner space of the sleeve and to prevent vibrations when the device is powered by alternating current.

Everyone, I think, is familiar with the buzz of wires under power lines - this is the consequence of vibrations caused by alternating voltage. The passageway is covered by a membrane with an anchor from the movable part of the core of the solenoid-a wire coil. In the normal state, the fluid passage may be free, or may be blocked. Depending on this, the solenoid valve can be:

• Normally open;

• Normally closed.

The normal state in this case is the initial state when there is no external voltage. The blocking core is driven by an electric current applied to the outer coil of the solenoid. Once the control voltage is applied to the electrodes, the metal rod connected to the diaphragm drives it. Then the path for the flow of the medium through the valve is blocked or opened. Only the external signal disappears, the system returns to its original state.

The solenoid valve, the principle of operation of which is based on the mixing of two input streams into one output or the withdrawal of a part of the input stream, has more than two funnels for connecting the pipes.

Depending on the number of inputs and outputs, the following models are distinguished:

• Two-way;

• Three-way;

• Four-way.

If the first version is intended directly for operation as a stop valve, then more sophisticated modifications allow solving quite specific tasks. If certain conditions arise, some of the flow descends into a branch. Alternatively, two streams are mixed in certain proportions. The solenoid valve three-way valve can be used to maintain the set temperature in the hot water circuit or heating. If the temperature is too high, the water traffic through the boiler will be blocked. Conversely, lowering the temperature below the set point will cause the main part of the water to be heated.