Patent ID: 8393144

Claim:
A method for purging an SCR system comprising a line that feeds a urea solution into exhaust gases and a pump that both feeds the urea solution into said exhaust gases and purges at least one part of the line by sucking a gas therethrough by a suction device, according to which the operation of the pump and the operation of the suction device are activated and/or deactivated in a sequential manner in the course of one and a same purge procedure, wherein the purge procedure comprises, successively and in order, the following steps: detecting a shut-off of an engine; checking whether or not the pump has operated while the engine was running; if the pump was not operated, stopping the purge procedure; if the pump was operated, continuing the purge procedure carrying out, successively and in order, the following steps: measuring the pressure at the pump outlet and when this pressure is below a reference value, starting a timer that sets the time to zero (t=0); when the timer detects the end of a predetermined time interval (t 1 ), making the pump rotate in purge mode; when the timer detects the end of a predetermined time interval (t 1 +t 2 ), opening the suction device; when the timer detects the end of a predetermined time interval (t 1 +t 2 +t 3 ), stopping the pump; when the timer detects the end of a predetermined time interval (t 1 +t 2 +t 3 +t 4 ), closing the suction device.