A sealing system for sealing a rotational shaft of a centrifugal pump, comprising: a double mechanical seal having a pump-side sealing mechanism (10, 12) and an atmospheric-side sealing mechanism (11, 13); a pump mechanism driven by the rotational shaft, the pump mechanism being located between the pump-side sealing mechanism (10, 12) and the atmospheric-side sealing mechanism (11, 13); a first chamber defined by at least the atmospheric-side sealing mechanism (11, 13) and the pump mechanism; a second chamber defined by at least the pump-side sealing mechanism (10, 12) and the pump mechanism; a medium circulation line for circulating a fluid barrier-and-cooling medium between the first chamber and the second chamber, the medium circulation line being coupled to the first chamber and the second chamber, the fluid barrier-and-cooling medium being different from a fluid handled by the centrifugal pump; a heat exchanger attached to the medium circulation line; a branch line coupled to the medium circulation line; an accumulator coupled to the branch line, the accumulator being configured to pressurize and store a fluid barrier-and-cooling medium; the sealing system being characterised in that it further comprises: J an on-off valve attached to the branch line; an optional pressure detector arranged to measure pressure in the first chamber a pressure detector arranged to measure pressure in the second chamber; and a system controller configured to open the on-off valve when the pressure in the second chamber is lower than a threshold value, the threshold value being higher than discharge pressure of the centrifugal pump. a double mechanical seal having a pump-side sealing mechanism (10, 12) and an atmospheric-side sealing mechanism (11, 13); a pump mechanism driven by the rotational shaft, the pump mechanism being located between the pump-side sealing mechanism (10, 12) and the atmospheric-side sealing mechanism (11, 13); a first chamber defined by at least the atmospheric-side sealing mechanism (11, 13) and the pump mechanism; a second chamber defined by at least the pump-side sealing mechanism (10, 12) and the pump mechanism; a medium circulation line for circulating a fluid barrier-and-cooling medium between the first chamber and the second chamber, the medium circulation line being coupled to the first chamber and the second chamber, the fluid barrier-and-cooling medium being different from a fluid handled by the centrifugal pump; a heat exchanger attached to the medium circulation line; a branch line coupled to the medium circulation line; an accumulator coupled to the branch line, the accumulator being configured to pressurize and store a fluid barrier-and-cooling medium; the sealing system being characterised in that it further comprises: J an on-off valve attached to the branch line; an optional pressure detector arranged to measure pressure in the first chamber a pressure detector arranged to measure pressure in the second chamber; and a system controller configured to open the on-off valve when the pressure in the second chamber is lower than a threshold value, the threshold value being higher than discharge pressure of the centrifugal pump. J an on-off valve attached to the branch line; an optional pressure detector arranged to measure pressure in the first chamber a pressure detector arranged to measure pressure in the second chamber; and a system controller configured to open the on-off valve when the pressure in the second chamber is lower than a threshold value, the threshold value being higher than discharge pressure of the centrifugal pump.