System and method for testing fuel tank integrity

Abstract

The invention relates generally to a system and method for testing fuel evaporative systems, and more particularly to a stand-alone tank tester system (and method) for testing vehicle fuel tank integrity. Furthermore, a self-contained calibration tank with switchable leak sizes for calibrating the tank tester to multiple leak sizes is provided. Constant flow and vacuum methods for testing fuel tank integrity are also provided.

1 . A method for testing the integrity of a fuel tank, comprising:
 applying a constant flow of gas to a fuel tank at a predetermined flow rate;   measuring a tank pressurization rate at which pressure in the fuel tank increases; and   calculating the size of a leak in the fuel tank by:
 (i) storing an uncompromised pressurization rate at which an uncompromised fuel tank would pressurize under the predetermined flow rate; and 
 (ii) comparing the tank pressurization rate to the uncompromised pressurization rate, wherein the size of a leak is proportional to the difference between the uncompromised pressurization rate and the tank pressurization rate. 
   
     
     
         2 . A method of testing the integrity of a fuel tank, comprising:
 reducing pressure in a fuel tank to a predetermined pressure below an ambient pressure;   measuring a pressure ascension rate over a predetermined period of time; and   calculating the size of a leak within the fuel tank by:
 (i) storing an uncompromised pressure ascension rate at which an uncompromised fuel tank would ascend in pressure when pressurized to the predetermined pressure level below ambient pressure; and 
 (ii) comparing the uncompromised pressure ascension rate to the pressure ascension rate, wherein the size of a leak is proportional to the difference between the uncompromised pressure ascension rate and the pressure ascension rate. 
   
     
     
         3 . A method for testing the integrity of a fuel tank, comprising:
 applying a constant reduction of pressure below an ambient pressure to a fuel tank at a predetermined rate;   measuring a tank pressure reduction rate at which a pressure in the fuel tank decreases;   calculating the size of a leak in the fuel tank by:
 (i) storing an uncompromised pressure reduction rate at which an uncompromised fuel tank would pressurize under the predetermined flow rate; and 
 (ii) comparing the tank pressure reduction rate to the uncompromised pressure reduction rate, wherein the size of a leak is proportional to the difference between the uncompromised pressure reduction rate and the tank pressure reduction rate. 
   
     
     
         4 . A method for testing the integrity of a fuel tank, comprising:
 pressurizing a fuel tank that is connected to a cylinder by applying a first predetermined force to a piston disposed within the cylinder;   ceasing movement of the piston in the cylinder when pressure in the fuel tank exerts a second force equal to that of the first force; and   calculating a leak size in the fuel tank by:
 (i) measuring movement of the piston in the cylinder over a predetermined interval, wherein the movement of the piston in the cylinder is proportional to the size of a leak in the fuel tank.