Automatic pressure supplementing device and method

The invention discloses an automatic pressure supplementing device and method, and belongs to the technical field of mechanical seal flushing fluid. The automatic pressure supplementing device comprises a flushing fluid storage tank, a power part, a pressure transmitter and a first automatic valve, wherein flushing fluid is arranged inside the flushing fluid storage tank; the power part has an opening position and a closing position, when the power part is located at the opening position, one end of the power part communicates with the flushing fluid storage tank, and the other end of the power part communicates with an inlet of a pump skid; the pressure transmitter is arranged at the inlet of the pump skid, the pressure transmitter has a set high value and a set low value, when the actual pressure of the pressure transmitter is higher than the set high value, the power part is switched from the opening position to the closing position, and when the actual pressure of the pressure transmitter is lower than th