2. According to the pressure maintaining method of the positive pressure chamber, it can be divided into two ways: positive pressure with dilution airflow and positive pressure with leakage compensation.
3. Positive pressure with dilution air flow means that the protective gas continuously flows through the positive pressure cavity and keeps a certain flow rate, so that the pressure of the positive pressure cavity is kept within the working pressure range, and the gas in the positive pressure cavity can be continuously cleaned and replaced. Because the protective gas continuously flows through the positive pressure cavity, it can not only meet the explosion-proof requirements, but also take away the heat generated by the operation of internal components, so it is more suitable to install some electrical components or equipment with high calorific value, such as frequency converters, soft starters, high-power thyristors, motors, etc. The disadvantage is that the required gas flow is large, and the user's on-site gas source needs to provide sufficient flow and pressure.
4. Positive pressure with leakage compensation means that the control system detects the pressure in the positive pressure chamber in real time and controls the inflow and outflow of protective gas through the solenoid valve. When the pressure in the positive pressure chamber is too low, open the air intake solenoid valve to replenish air, so that the pressure rises to the working pressure range; When the pressure in the positive pressure chamber is too high, open the exhaust solenoid valve to exhaust, so as to reduce the pressure to the working pressure range. Because the protective gas does not flow continuously, the positive pressure enclosure with leakage compensation is suitable for installing low-voltage electrical components with low calorific value, such as various electrical control systems.
5. According to the requirements of national standards, the positive pressure explosion-proof control cabinet must also have interlocking and alarm functions. That is, when the ventilation process of the positive pressure chamber is not completed or the pressure in the positive pressure chamber does not reach the working pressure range, the positive pressure chamber cannot be electrified to ensure safety. When the pressure of the positive pressure chamber in operation is lower than the lower limit or upper limit of the set alarm pressure, the control system takes adjustment measures and sends out an audible and visual alarm to remind users. When the adjustment measures taken by the control system are invalid and the pressure continues to decrease or increase to the lower limit or upper limit of the set power-off pressure, the system should cut off the power supply of the positive pressure cavity in time and stop running.