The working process of nitrogen generator is controlled by three two position five way pilot solenoid valves controlled by PLC, and then the solenoid valves respectively control the opening and closing of eight pneumatic pipeline valves. Three two position five way pilot solenoid valves respectively control the status of left suction, equalizing pressure and right suction. The time flow of left suction, pressure equalization and right suction has been stored in the PLC. In the power-off state, the pilot gas of three two position five way pilot solenoid valves is connected to the closing port of the pneumatic pipeline valve.

When the process is in the left suction state, the solenoid valve controlling the left suction is energized, and the pilot gas is connected to the openings of the left suction valve, the left suction valve and the right exhaust valve to open the three valves to complete the left suction process and desorb in the right adsorption tower.

When the process is in the equalizing state, the solenoid valve controlling the pressure equalizing is energized, and the other valves are closed; the pilot gas is connected to the openings of the upper equalizing valve and the lower equalizing valve, thus opening the two valves and completing the equalizing process.

When the process is in the right suction state, the solenoid valve controlling the right suction is energized, and the pilot gas is connected to the openings of the right suction valve, the right suction production valve and the left exhaust valve, so that these three valves are opened to complete the right suction process and desorb in the left adsorption tower at the same time.

In each stage of flow, except for the valve that should be opened, all other valves should be closed.