Method for leak testing and leak testing appartus

Abstract

For leak testing closed containers ( 9 ) which are filled with a filling product containing at least one liquid component the container is introduced in a test cavity ( 1 ) which is evacuated at least down to vapour pressure of that liquid component. The pressure in the surrounding of the container ( 9 ) and thus within test cavity ( 1 ) is monitored. Monitoring is performed by a vacuum pressure sensor ( 7 ), whereas lowering pressure surrounding the container ( 9 ) is performed by a vacuum pump ( 5 ). Leakage is detected by monitoring a pressure change in the surrounding of the container which is due to evaporation of liquid emerging from a leak and being evaporated in the low pressure surrounding.

1 . A method for producing a closed and filled container comprising the steps of:
 filling a container with a material comprising at least one liquid component;   sealingly closing said container and   leak testing said container by:   applying a pressure difference across at least a part of the wall of the container which part is to be tested by evacuating the surrounding of said container at least along said part of said wall by means of a pumping arrangement at least down to vapor pressure of said liquid component;   sensing the pressure in said surrounding and evaluating said pressure as sensed after having reached said vapor pressure as an indicia for a leak in said container.   
   
   
       2 . The method of  claim 1 , wherein said evacuating lowers said pressure in said surrounding towards a pressure value which is lower than said vapor pressure by a factor of at least two decades (10 −2 ). 
   
   
       3 . The method of  claim 1 , wherein said container is filled with more than one liquid component and said vapor pressure is the higher vapor pressure of the vapor pressures of said at least two components. 
   
   
       4 . The method of  claim 1 , wherein said testing is performed at room temperature. 
   
   
       5 . The method of  claim 1 , wherein said evaluating comprises monitoring said pressure in said surrounding at a first and at a second point in time and utilizing a difference in the results of said monitoring at said first and second points in time as an indicia for a leak in said container. 
   
   
       6 . The method for testing a closed and filled container, filled with a material comprising at least one liquid component and comprising the steps of:
 applying a pressure difference across at least a part of the wall of said container, which part is to be tested by evacuating the surrounding of said container at least along said part by means of a pumping arrangement at least down to vapor pressure of said liquid component;   sensing the pressure in said surrounding and evaluating said pressure as sensed after having reached said vapor pressure as an indicia for a leak in said container.   
   
   
       7 . The method of  claim 6 , wherein said evacuating lowers said pressure in said surrounding towards a pressure value which is lower than said vapor pressure by a factor of at least two decades (10 −2 ). 
   
   
       8 . The method of  claim 6 , wherein said container is filled with more than one liquid component and said vapor pressure is the higher vapor pressure of the vapor pressures of said at least two components. 
   
   
       9 . The method of  claim 6 , wherein said testing is performed at room temperature. 
   
   
       10 . The method of  claim 6 , wherein said exploiting comprises monitoring said pressure in said surrounding at a first and at a second point in time and utilizing a difference in the results of said monitoring at said first and second point in time as an indicia for a leak in said container. 
   
   
       11 . A leak testing apparatus for leak testing at least one closed and filled container, whereby the content of said container comprises at least one liquid component and comprising:
 at least one sealingly closable test cavity;   at least one evacuating pump operationally connected to said test cavity;   at least one pressure sensor operationally connected to said test cavity;   said evacuation pump being selected so as to enable pumping of said test cavity down to at least vapor pressure of said component approximately at room temperature and said pressure sensor being a vacuum pressure sensor;   a timing unit enabling said evacuation pump to operate up to generating a pressure value in said test cavity as low as at least vapor pressure of said component and enabling evaluation of an output signal of said sensor as a leak indicative signal after said vapor pressure of said component is reached.   
   
   
       12 . The apparatus of  claim 11 , wherein said evacuation pump is at least one of a drag vacuum pump, a piston valve vacuum pump, a diffusion pump, a turbo vacuum pump. 
   
   
       13 . The apparatus of  claim 11 , wherein said sensor comprises a Pirani sensor. 
   
   
       14 . The apparatus of  claim 11 , further comprising a storage unit operationally connected to the output of said sensor and a difference forming unit, one input thereof being operationally connected to the output of said storage unit, the second input thereof being operationally connectable to the output of said sensor, a timing unit operationally connecting the output of said sensor at a first point in time to the input of said storage unit and operationally connecting at a second point in time the output of said sensor to said other input of said difference forming unit.