Process for starting a pump

Abstract

Process for starting a pump intended to pump a liquid contained in a tank and to produce a substantially constant outlet pressure (setpoint pressure), according to which: 1/ the temperature (T 1 ) of the liquid held in the tank is determined and compared to a setpoint temperature (T 0 ); 2/ if the temperature (T 1 ) is greater than the setpoint temperature (T 0 ), the pump is actuated; 3/ if the temperature (T 1 ) is less than or equal to the setpoint temperature (T 0 ), the tank is heated for a time t 1 ; then 4/ the pump is actuated for a time t 2 during which the pump outlet pressure is measured; 5/ if this pressure is stable and in an acceptable margin of the setpoint pressure, the pump is kept going; and 6/ if this pressure is not stable and/or is not in the acceptable margin of the setpoint pressure, the pump is stopped and the tank is heated for a time t 3 , at the end of which steps 4 to 6 are repeated.

1 . A process for starting a pump intended to pump a liquid contained in a tank and to produce a substantially constant outlet pressure (setpoint pressure), wherein:
 1. the temperature (T 1 ) of the liquid held in the tank is determined and compared to a setpoint temperature (T 0 );   2. if the temperature (T 1 ) is greater than the setpoint temperature (T 0 ), the pump is actuated;   3. if the temperature (T 1 ) is less than or equal to the setpoint temperature (T 0 ), the tank is heated for a time t 1 ; then   4. the pump is actuated for a time t 2  during which the pump outlet pressure is measured;   5. if this pressure is stable and in an acceptable margin of the setpoint pressure, the pump is kept going; and   6. if this pressure is not stable and/or is not in the acceptable margin of the setpoint pressure, the pump is stopped and the tank is heated for a time t 3 , at the end of which steps 4 to 6 are repeated.   
   
   
       2 . The process according to  claim 1 , wherein the pump is driven by a motor and is controlled by a controller, and wherein an ECM (Electronic Control Module) sends, to the controller, a PWM (Pulse Width Modulation) control signal having a duty cycle that varies as a function of the desired operating conditions for the pump, the controller acting on the motor to apply said operating conditions to the pump. 
   
   
       3 . The process according to  claim 1 , wherein the liquid is an aqueous urea solution. 
   
   
       4 . The process according to  claim 1 , wherein the pump is integrated into a base plate submerged in the tank which also integrates other active components of the tank. 
   
   
       5 . The process according to  claim 4 , wherein the base plate integrates a heating element. 
   
   
       6 . The process according to  claim 5 , wherein a liquid feed line comes out of the tank and a liquid return line arrives at the tank, and wherein these lines are also equipped with a heating element. 
   
   
       7 . The process according to  claim 6 , wherein the pump is a rotary pump, and wherein the lines are purged after each use of the pump just before the is stopped by reversing its direction of rotation for the time necessary to convey the liquid contained in the feed and return lines back to the tank. 
   
   
       8 . The process according to  claim 6 , wherein the time t 1  is the minimum time required to obtain a volume of liquid equal to the volume of the injection line, the return line and the components in these lines. 
   
   
       9 . The process according to  claim 2 , wherein the controller is connected to a pressure sensor, and wherein the controller compares, in a loop, the pressure setpoint value with the value measured by the sensor and consequently acts on the rotational speed of the motor in order to attempt to stabilize the pressure at the setpoint value. 
   
   
       10 . The process according to  claim 9 , wherein during the period t 2 , the pressure is measured periodically, and wherein a mathematical criterion based on the variance is applied to the pressure measurements and to the setpoint pressure. 
   
   
       11 . The process according to  claim 10 , wherein, if the pressure is not stable and/or is not in an acceptable margin with respect to the setpoint pressure at the end of several iterations (of steps 4 to 6), the controller stops the pump and sends information to the ECM, according to which information the pump has not been able to be started. 
   
   
       12 . The process according to  claim 1 , it which has been tested in a MATLAB/SIMULINK® simulation environment and/or which has been concretely applied to an SCR (Selective Catalytic Reduction) system.