Patent ID: 8615986

Claim:
A process for transferring liquid from a passive tank for storing the liquid to an active tank, using a transfer pump intended for pumping the liquid held in the passive tank and transferring said liquid to the active tank, wherein the pump is commanded so as to transfer the liquid from the passive tank to the active tank when said active tank has a liquid level L below a set point level Lsp and when the passive tank contains liquid at a temperature above a freezing point of the liquid, wherein said process comprising: measuring a temperature Text outside of the active tank and the passive tank; checking whether or not the liquid in the passive tank is frozen using the measured temperature Text, former values of Text, and a time constant that corresponds to the liquid in the passive tank changing from a solid state to a liquid state or vice versa; comparing the liquid level L in the active tank to the set point level Lsp; activating the transfer pump if the liquid in the passive tank is not frozen and L<Lsp, so as to pump the liquid in the passive tank and transfer the liquid into the active tank until a target level Lt is reached, where Lt>=Lsp, and the transfer pump is stopped; and not activating the transfer pump if the liquid in the passive tank is frozen or if L>=Lsp.