The principle and function of pneumatic valve solenoid valve

Pneumatic valves are the most common fluid control equipment in industrial pipelines. They are mainly composed of pneumatic actuators and valves. The valves are driven by compressed clean air to control the flow and shut-off of pipeline media. The execution speed is very fast, and it is usually used for quick cut-off. Pneumatic valves are usually equipped with various accessories, such as solenoid valves, air source treatment triplex, limit switches, positioners, control boxes, etc., to achieve local control and remote centralized control. For a two-position valve that only needs to be on and off, a solenoid valve is a necessary configuration. The solenoid valve controls the on/off of the pneumatic valve through excitation/demagnetization.

In terms of the air circuit (or liquid circuit), the two-position three-way solenoid valve has 1 air inlet (connected to the air source), 1 air outlet (provided to the target equipment air source), 1 exhaust hole (generally install a muffler, if you are not afraid of noise, you can not install it. The 2-position 5-way solenoid valve has 1 air inlet (connected to the air source), 1 forward action air outlet and 1 reverse action air outlet (provided respectively for the target equipment. Reverse action exhaust hole (muffler installed). For small control equipment, the air pipe generally uses 8~12mm industrial rubber air pipe.

Electrically speaking, the two-position three-way solenoid valve is generally a single solenoid (that is, a single coil), and the two-position five-way solenoid valve is generally a double electric control (that is, a double coil). Coil voltage level generally adopts DC24V, AC220V and so on. The two-position three-way solenoid valve is divided into two types: normally closed type and normally open type. The normally closed type means that the air circuit is broken when the coil is not energized, and the normally open type means that the air path is open when the coil is not energized.

(1) The action principle of the normally closed two-position three-way solenoid valve: the coil is energized, the gas circuit is connected, and once the coil is powered off, the gas circuit will be disconnected, which is equivalent to jogging.

(2) The action principle of the normally open two-position three-way single solenoid valve: when the coil is energized, the gas circuit is disconnected. Once the coil is powered off, the gas circuit will be connected, which is also inching.

The action principle of the two-position five-way double solenoid valve: when the positive action coil is energized, the positive action air circuit is connected (the positive action air hole has air), even after the positive action coil is powered off, the positive action air circuit is still connected, and it will be maintained until the reverse action coil is energized. When the reverse action coil is energized, the reverse action air circuit is connected (there is air in the air hole of the reverse action), even after the reverse action coil is powered off, the reverse action air circuit is still connected, and it will remain until the positive action coil is energized. This is equivalent to self-locking (the so-called memory function). Based on the characteristics of the two-position five-way dual-electric control solenoid valve, when designing the electromechanical control circuit or programming the PLC program, it is enough to let the solenoid valve coil operate for 1~2 seconds, which can protect the solenoid valve coil from being easily damaged.