METHOD FOR FILLING A CONTAINER QUICKLY WITH A MIXTURE OF AIR AND A TRACER GAS

Abstract: A method for tightness testing of a container (8) by using a tracer gas. Air and the tracer gas are supplied separately until each of them has achieved a predetermined overpressure in the container. Before the container is tightness tested by tracer gas detection in a space surrounding the container, the mixture of air and tracer gas is re-circulated by means of a pump (14) from a container outlet (9) to a container inlet (7) in order to secure that the tracer gas is quickly and uniformly distributed in the container.

Description: "Method for filling a container quickly with a mixture of air and a tracer gas" The invention relates to a method for tightness testing of a container by using a tracer gas, wherein, during a filling operation, air and a tracer gas are fed from an inlet opening to an outlet opening situated at a considerable distance from each other to ensure that the entire container is filled uni¬ formly, whereafter the tightness testing is performed ' by tracer gas detection in a space surrounding the container. A possible leakage in the container is indicated by means of a tracer gas detector, e.g. after a predetermined ' measuring time. Should the tracer gas concentration after said measuring time be below a predetermined value, the container is classified as "tight" or else as "leaking" . Such a method is described in the Swedish patent specification 7506284-4. From environmental and economical points of view.it is important to fill the container effectively and uniformly without any risk of unnecessary gas discharge. For this pur¬ pose, according to the known method, the tracer gas is supplied through one or more inlet openings which are situated at a considerable distance from an outlet of the container. In a conduit connected to the outlet, there is a tracer gas detector which reacts as soon as the tracer gas has passed through the container from the inlet " to the outlet. When the detector re¬ acts, the container is considered to be filled with tracer gas, and the tightness testing operation can be effected. Thereafter, the container is rinsed with air fed through the opening previously used as outlet, whereas the opening previous¬ ly used as inlet is connected to a discharge. The method as described above involves a step forward in that the filling time is reduced considerably as compared to pre¬ vious methods. Furthermore, the known method offers a practical way to indicate when the test container is considered to be filled with tracer gas (i.e. as soon as the detector in the outlet conduit reacts) . However, it is desirable to reduce the filling time still more, to reduce the quantity of tracer gas being discharged during the filling operation, to secure, in spite of a shorter filling time, a completely uniform distri¬ bution of the tracer gas in the test container and to achieve exactly the desired mixture relation (tracer gas to air) during the filling operation. This object is achieved by the inventive method, the features of which are defined in the appended claims.. The invention is described more fully below with reference to the attached drawing schematically showing a device for filling a test container with a mixture of air and tracer gas. The device shown in the figure comprises a feed conduit 1 having a branch la for the filling of pressurized air via a pressure regulator 2 and a cut-off valve 3 as well as a branch lb for the supply of tracer gas from a vessel 4 via a pressure regulator 5 and a cut-off valve 6. The feed conduit 1 may preferably be connected by means of ' a quick coupling device (not shown, e.g. of the kind described in the Swedish patent specifications 7704191-1 and 7903650-5) to an inletopening 7 of a test container 8, the tightness of which is to be tested. The tightness testing itself is per¬ formed in a way known per se, wherein the container 8 is surrounded by a closed casing, such as a cover or the like, and possible escaping gas is detected by means of a tracer gas detector (not shown) in the closed space around the test container. The test container is also provided with an opening 9 situ- ated at a considerable distance (as compared to the size of the container) from the inlet 7. During the filling operation the tracer gas and the air, respectively, will flow from the inlet opening 7 to the outlet opening 9 while test container entirely. For containers having a simple geome- try there is no problem to achieve a uniform filling, but if the container is provided with several chambers communi¬ cating with each other or chamber parts having intermediate narrow passages, it may be difficult to establish whether the entire container has been filled uniformly by tracer gas, i.e. whether the tracer gas concentration is equal in every part of the container. By suitable placement of the inlet and outlet openings 7,9, possibly by means of an inserted hose or the like, the possibilities of achieving a uniform gas distribution are improved considerably. The outlet opening of the test container 8 is connectable to an outlet conduit 10, to which two pressure sensors TV1 and TV2 are connected. The outlet conduit 10 is additionally connec¬ ted to a pressurized air source via a cut-off valve 11 and a pressure regulator 12. According to the invention, the outlet conduit 10 is also fed back, via a cut-off valve 13 and a cir¬ culation pump 14, to the inlet opening 7. The latter is also connected to a discharge ' via a cut-off valve 15. The device operates in the following way: After connection of the fed conduit 1 to an inlet opening 7 of a test container 8 and the outlet conduit 10 to an outlet opening 9 of the container, the test container is supposedly filled with air under atmospheric pressure. The valves 3, 6, 11, 13 and 15 are closed. Suppose that the test container is to be filled with 95 volume! air and 5 volume! tracer gas at an overpressure of 1,0 bar for the subsequent tightness test¬ ing of the container. Then, the valve 6 is first opened to let the tracer gas flow from the tracer gas vessel 4 via the pressure regulator 5 and into the container 8 via the in¬ let opening 7, which causes the pressure to rise. However, one of the pressure sensors TV1 is set at 0,1 bar overpres¬ sure and actuates the cut-off valve 6 electrically upon rea¬ ching said overpressure, so that the latter valve closes again. Thereafter, the valve 3 is opened to let the pressurized air flow into the test container, until the second pressure sensor TV2, set at 1,0 bar, causes the valve 3 to close. Since a gi¬ ven pressure increase in the test container corresponds to a certain gas quantity , it can be definitely established that the test container 8 contains 5 voluπε.% tracer gas. Incase some other mixture percentage is desired, the pressure sensors TV1 and TV2 can easily be adjusted correspondingly. However, it is still not certain that the tracer gas quantity is uniformly distributed into all the parts of the test con¬ tainer. Therefore, the valve 13 is opened and the pump 14 is started so as to circulate the gas mixture via the outlet opening 9, the conduit 10, back into the inlet opening 7 un¬ der a heavy flow. Hereby, turbulence and an effective stir- ring will occur in the container 8, whereby the gas mixture is homogenized and distributed uniformly in a very short time, whereupon the pump 14 is stopped. Upon completion of the tighness testing in the above-mentioned way, the valve 13 is closed and the valves 11 and 15 are open¬ ed, so that the container is rinsed with air in the opposite direction to a discharge (at 15) . The tracer gas mixture may, if so desired, be collected and the tracer gas may be en¬ riched for re-use. After the air rinsing operation, the quick connectors at the inlet and the outlet of the test container are released, and a new test container is connected and filled with a mixture of tracer gas and air and is thereafter tight¬ ness tested. The complete filling, testing and rinsing opera¬ tion can be automatically controlled by means of an electric circuit controlling the different valves, the circulating pump as well as the duration of the various working steps. Thus, the important operational features are that the gas mix¬ ture is recirculated by means of the pump 14 and that it is possible to achieve a predetermined mixture relation by means of the pressure sensors TVl and TV2. In other respects, the method can be applied in many ways within the scope of the inventive idea set forth in the appended claims.

Claims: C L A I M S 1. A method for tightness testing of a container (8) by using a tracer gas, wherein, during a filling operation, air and a tracer gas are fed from an inlet opening (7) to an outlet opening (9) situated at a considerable distance from each other to ensure that the entire container is filled uniformly, whereafter the tightness testing is performed by tracer gas detection in a space surrounding the container, c h a r a c- t e r i z e d in that the mixture of air and tracer gas is re¬ circulated (14) from the outlet opening (9) to the inlet opening (7) during the filling operation. 2. A method as set forth in claim 1, c h a r a c t e r i z e d in that, during the filling operation, air and a tracer gas are supplied separately (la,lb) through the inlet opening (7) of the container until a respective predetermined overpressure (TVl, TV2) is achieved, whereupon the gas mixture is re¬ circulated (14) .

Inventors: HOFFMAN S
Applicants: HOFFMAN S, NOLEK SYSTEM AB
Application year: 1980
Main classification: G01M3
IPC codes: G01M3