The switching valve (forced valve) is a pneumatic switching valve installed at the hot end of the switching heat exchanger (or cold storage). The switch of the switching valve is controlled by the signal compressed air from the solenoid valve. According to different roles in the process, there are air and nitrogen pollution switching valves, pure nitrogen suppression valves, and nitrogen pollution three-way valves. From the structural type, there are two types: vertical and horizontal. Vertical switching valves can be divided into two types: air-opening and air-closing. The air-opening type means that when the signal compressed air is cut off, the valve disc can automatically open by its own weight; otherwise, it is the air-closing type. The choice of air-opening and air-closing is determined by the safety of the device. Nitrogen switching valves are air-opening, and air switching valves are air-closing.
Since the action of the switching valve is controlled by the solenoid valve, in addition to selecting the air-opening and air-closing types to prevent damage caused by gas source failure, attention should also be paid to the coordination between the state of the solenoid valve and the state of the switching valve so that the power supply The safety of the equipment will not be endangered in the event of failure. Now respectively explain as follows:
1. Pollution nitrogen switching valve. When the four-way solenoid valve is powered, the switching valve is closed. When de-energized, the switching valve opens. And when the power is off, the air source loses pressure, and it can also be opened by its own weight. This ensures that when a failure occurs, the gas in the upper tower can be emptied through the cold accumulator without causing overpressure.
2. Air switching valve. When the four-way solenoid valve is energized, the switching valve is opened. When power is lost, the switching valve is closed. When the control power supply fails and loses power, the switching valve closes; when the control air source fails and loses pressure, the switching valve closes by its own weight to ensure that the raw material air does not enter the air separation tower when a failure occurs.
3. Polluted nitrogen (pure nitrogen) three-way switching valve. When the four-way solenoid valve is powered on, the three-way switching valve is in the discharge position; when the four-way solenoid valve is powered off, the three-way switching valve is in the discharge position. When the power fails and the power is lost, the three-way switching valve is in the emptying position; when the air source fails and the pressure is lost, the three-way switching valve can be in the emptying position by its own weight.
The above content will share with you what is a switching valve and the function and characteristics of the switching valve.