Process for transferring a liquid using a pump

A process for transferring a liquid from a passive tank for storing the liquid to an active tank, using a transfer pump configured to pump the liquid held in the passive tank and transferring the liquid to the active tank, the method comprising:

• commanding the transfer pump to transfer liquid from the passive tank to the active tank when the active tank has a liquid level below a set point level Lsp and when the passive tank contains liquid at a temperature above the freezing point of the liquid, the active tank including a level gauge which is a discontinuous gauge configured to provide at least x+1 level indications of the level of liquid in the active tank as a function of the relative position of a moving part with respect to x set point levels, x being at least equal to 3, x being a positive integer, by:
• reading a level indication L among the level indications from the level gauge, selecting a time constant from time constants stored in a microcontroller on a basis of the level indication L that has been read and loading the selected time constant which depends on a value of the level indication L;
• starting the transfer pump and measuring a time during which the pump transfers liquid;
• and
• stopping the transfer pump when this time is greater than the time constant, and when a next set point level is not reached,
• wherein the time constant is computed based on a time for passing from level n to level n+1 (with 0<=n <=x, and n being 0 or a positive integer) considering a pump flow rate, which is generally constant, and the volume of liquid between two adjacent set points when n is >0, and between an empty state and the first set point when n =0,
• wherein:
• the tanks store a liquid to be injected in exhaust gases of an internal combustion engine;
• the time constants are stored in the microcontroller that controls the transfer pump;
• each time the engine starts after having been turned off, the microcontroller resets values from the sensors to a default value;
• and
• after a reset, the transfer pump is blocked for a given period of time, and
• wherein the microcontroller stores a number of times the pump has run dry and when this number reaches a given value, the microcontroller blocks the transfer pump until a refill event is detected;
• and then unlocks the transfer function by putting the number at zero.