Field of the Invention

The present invention is directed to an apparatus for leak testing of joints between tubes and tube sheets. The invention also discloses a method for carrying out a testing proce dure using such an apparatus.

Background of the Invention

In the art, there is a number of situations where it is necessary to test the tightness be tween a pipe penetrating a plate, particularly in applications where it is desirable to have for example a liquid on one side of the plate and air or other liquid/media on the other side of the plate. Leaking in the connection between the pipe and the plate is undesira ble. Naturally, it will be possible to introduce a liquid on one side of the plate and then optically detect whether or not there is a leak, after which the leak may be repaired. However, for industrial purposes, this is a very cumbersome and impractical manner of testing such connections. Further, a problem arises when there is a large number of pipes penetrating a plate member in a very small area, such that the distance between adjacent pipes is very limited. In such situations it may be very difficult to detect which pipe is leaking, and furthermore the repair may also be rather cumbersome.

US 4602500 A discloses one solution for a leak testing apparatus, for testing connec tions between tubes penetrating a plate material.

Object of the Invention

Consequently, it is an object of the present invention to provide a leak testing apparatus which is easy to use, easy to apply, and may be applied in a very quick and safe manner in order to reliably detect potential leaks for pipes penetrating plates. Description of the Invention

The invention addresses this by providing a leak testing apparatus, for testing connec tions between tubes penetrating a plate material, wherein the apparatus comprises:

- a housing having a central cylindrical longitudinal hollow, said housing having a first end, in use adapted to engage the plate material surrounding the tube, and a second end opposite said first end, where a first seal is arranged projecting from said first end; a piston arranged inside said housing, said piston having a longitudinal axis parallel to the longitudinal extend of the hollow, where a distal end of the piston in use is inserted into the tube; a second seal arranged circumferentially on the piston, such that in use said second seal may be brought into sealing engagement with the tube; where the second end of the housing is closed by an endcap where at least one channel is provided longitudinally in said piston and a con- nection to said channel allowing connection to a source of pressurized medium is pro vided, connecting the pressurized medium to a space, in use limited by the first seal, the plate material, the tube and the second seal, and optionally part of the piston and part of the housing.

Particularly, when manufacturing and quality-testing heat exchangers or large cooling installations, a number of pipe penetrations through plates is necessary in order to pro vide sufficient heat exchange area in a heat exchanger. In these constructions, the pipes will typically be very close to each other and as such, there is not much space to operate on. With the present invention, all the extra space required adjacent to a pipe penetration is sufficient space in order for the first seal to come into sealing engagement with the surrounding plate. As the piston operates inside the pipe’s diameter, accommodation of the first seal is all the space needed adjacent the pipe. Once this connection is estab lished, the piston, together with the housing, will create a very small but efficient pres- sure chamber surrounding the interface between the tube and the plate. When applying an air pressure or a liquid pressure to this confined pressure chamber, it is relatively easy to register whether there is a drop in pressure due to a leak or that the pressure is maintained. At the same time, the entire testing only involves the area immediately sur rounding the interface between the plate and the pipe, and as such, the involvement of the remaining part of the structure, for example a heat exchanger, is very, very limited. Furthermore, due to the very limited space required by the first seal surrounding the pipe, it is possible to apply a plurality of leak testing apparatuses close to each other, for example on every second or every third pipe, and in this manner carry out the testing in an expedient and rational manner. If the pressurised medium for example is air, there is furthermore no “pollution” connected with the test, whereas if water or oil is used, it will be necessary to clean the plate after the testing procedure. Also, if the air molecules are too large, it may be possible to test with for example a gas having smaller molecules, in order to be able to detect even minute leaks.

In a further advantageous embodiment of the invention, the housing has an outer sur- face, where on said outer surface engagement means are provided, said engagement means adapted to connect the leak testing apparatus to a robot, which robot is program mable to execute a leak testing routine. As for example a heat exchanging unit has a large number of tubes penetrating a plate where said pipes/tubes are arranged in a well- defined geometrical relationship, it is desirable to carry out the testing in an automated manner, for example by applying a robot to handle the leak testing apparatus, the testing may be carried out very efficiently. The robot will either, based on pre-programmed coordinates, be able to insert the leak testing apparatus in the pipes correctly or, by means of for example a vision system, recognise where the leak testing apparatus shall be applied. At the same time, it is relatively easy to program the robot to identify the exact pipe which is being tested and at the same time to store the test results.

In a further advantageous embodiment of the invention, means are provided inside said housing for urging the piston away from said end cap, thereby bringing the second seal into sealing engagement with the tube.

Furthermore, in order to achieve this movement of the piston relative to the housing, the leak testing apparatus in a further advantageous embodiment provides that the means may be:

A helical spring arranged between the endcap and the end of the piston, or; Pressurized gas introduced into the housing between the endcap and the end of the piston, or;

A threaded member arranged in the endcap, such that a thread is provided in the endcap into which the threaded member is screwed, where a distal end of the threaded member engages the end of the piston.

These means are all rather conventional, but they assure that a safe and tight connection may be achieved. Particularly, the use of the pressurised gas in instances where the actual leak testing is also carried out with a gas is very convenient, however it requires that the gas conduits inside the housing are split into two, such that the gas supplied to the testing chamber is completely separated from the gas urging the piston and thereby the second seal against the end of the tube.

In a further advantageous embodiment, the second seal is rotationally symmetric around the pistons’ longitudinal axis and has a conical shape, such that the narrower part of the conical shape is arranged towards the end of the piston which in use is inserted into the tube. Due to the conical shape, it is assured that the piston will fit to the pipe diameter. Usually, the leak testing apparatus is elected for a standard type of pipe diameter, such that various leak testing apparatuses are necessary in order to be able to test various pipes/tubes (with different diameters). However, the pipes even having the same nomi nal diameter will have variations in the diameter after they have been deformed in order to press-fit against the plate during the manufacturing process. Therefore, there will be (slight) variations in the diameter of the pipes/tubes which the conical- shaped second seal will compensate for, and in this manner create a tight seal sufficient for carrying out the pressure test of the connection.

In an alternative embodiment, a further advantageous aspect of the invention discloses that the piston comprises two elements: a first element being an outer piston cylinder, where a part of the outer piston cylinder in use is inserted into the tube, where concen trically inside said outer piston cylinder is arranged a plunger, where said plunger ex tends outside a first end of the outer piston cylinder, and where the distal end of the part of the plunger extending outside the outer piston cylinder is provided with an enlarge ment, and where the second seal is arranged between the enlargement and the end of the outer piston cylinder, such that when the plunger is moved along the longitudinal axis, bringing the enlargement closer to the end of the outer piston cylinder, the second seal will expand radially outwards, in use against the inner wall of the tube. With this embodiment, the expansion of the second seal inside the tube will establish the seal and thereby establish the pressure chamber.

The embodiment discussed above is designed to create a seal by engaging the end rim of the pipe, whereas in this embodiment, the seal is carried out inside the tube.

In a further improvement of this embodiment, the surfaces of the enlargement and the outer piston cylinder, facing the seal will have oblique surfaces such that the distance between the enlargements surface and the outer piston surface is larger at the periphery than closer to the stem, whereby in use as the plunger is moved closer to the end of the outer piston cylinder the oblique surfaces will urge the seal into sealing contact with the tubes inner wall.

With this configuration of the surfaces, the seal will be urged radially outwards as the two surfaces are brought closer to each other. Thereby, the forces needed to create the deformation of the seal, such that it creates a sealing engagement with the inner side of the tube, may be lessened and a better contact may be achieved.

One common technique of creating tight connections between a pipe penetrating a thin plate is by so-called tube expansion process, where the aperture in the plate is slightly larger than the tube, and once the tube has been installed/penetrated through the plate, a tool is arranged inside the tube in order to expand the outer diameter of the tube, such that it will come into mechanical engagement with the surrounding plate material. The present invention is specifically advantageous for use in connection with testing of this type of connections, but also other types, for example welded, soldered, adhesive or other types of connections may be tested using the apparatus described above. The invention is also directed to a method of using, such a leak testing apparatus as described above, and obviously such a method will in an expedient manner obtain the advantages as already explained. Furthermore, by installing a robot adapted to ar range/insert the leak-testing apparatuses, the process of testing a large number of con nections between tubes and plates may be carried out in a rational, expedient and cheap manner. This is all facilitated by the inventive apparatus and as such, the overall com bination of the leak testing apparatus with an automatic means, such as for example a robot, brings great advantages to the quality control testing and overall performance of the device.

Description of the Drawing

The invention will now be described with reference to the drawing in which

Figure 1 illustrates a first embodiment of the invention where the leak-testing apparatus 1 has been inserted in a tube 2.

Figure 2 illustrates a cross-section through an embodiment of the invention,

Figure 3 illustrates another embodiment of the invention, where the leak-test ing apparatus 1 is inserted into a pipe 2.

Detailed Description of the Invention

In Figure 1 is illustrated a first embodiment of the invention, where the leak-testing apparatus 1 has been inserted in a tube 2. The tube has been installed in a plate material 3 in such a manner that a mechanical tightening has been established between a rim of an aperture 4, through which the tube is inserted, and the outside of the tube 2. The object of the present invention is to test the tightness of the connection between the tube 2 and the rim 4 of the aperture in the plate material 3. The plate material may have many thicknesses, but typically, the material thickness in the actual direction indicated by the dashed line 100 (see fig.2) is often between 0.4 mm up to 50 mm when this apparatus is used for example with heat-exchangers for industrial applications the plate thickness is typically between 5mm and 50 mm. Likewise, just for an example, the diameter of the tube may be 10 mm and the distance between adjacent tube openings 10 may for example be 1 to 50 mm.

As is evident from Figure 1, the pipe ends 2 penetrating the plate 3 are arranged in very close proximity to each other and in a rational and determined manner (geometrical pattern) across the entire plate 3.

Turning to Figure 2, a cross-section through an embodiment of the invention is illus trated, where the leak-testing apparatus 1 has been inserted in a tube 2. The tube 2 is arranged, as illustrated in Figure 1, penetrating a plate 3. In this embodiment, the apparatus 1 comprises a housing 10, inside which housing a piston 12 is arranged. A front part 14 of the piston 12 is inserted inside the tube 2. During the insertion of the piston 12 inside the tube 2, a first seal 16 is arranged pro- jecting from a first end 18 of the housing 10. On the piston 12 is arranged a second seal 20 which, during the insertion of the piston 12 inside the tube 2, comes into contact with the rim 22 of the pipe 2. As illustrated in Figure 1, the rim 22 of the pipe 2 may extend above the plate material 3 or be substantially flush or sunk relative to the plate material as illustrated with reference to the pipe endings 2’. In the embodiment illustrated in Figure 2, the rim 22 of the pipe 2 extends slightly above the surface of the plate material 3. As the piston 12 is inserted into the pipe 2, the second seal 20 will engage the rim 22 of the pipe, and thereby establish a tight connection. At the same time, the first seal 16 has engaged a surface of the plate 4, also establishing a tight seal. Therefore, a small space 24 is created, where the space is limited by the housing 10, including the first seal 16, the plate material 4 and the second seal 20.

The housing 10 is furthermore provided with an end cap 30, where in this embodiment the end cap 30 is provided with a connection 32 to a source of pressurised gas. Inside the housing, in a longitudinal direction indicated by the dash line 100, an air channel 33 is provided on the inside wall of the housing 10, such that the pressurised gas provided through the connection 32 may pass the piston and enter the space 24, such that the space 24 may be pressurised in order to test the connection between the plate material 3 and the pipe 2. In order to maintain the piston 12 in tight connection both with the housing and the inner diameter of the pipe 2, a helical spring 35 is arranged inside the housing in order to urge the piston 12 away from the end cap 30.

In other embodiments of the invention, the pressurised gas supplied through the end cap 30 may be used to urge the piston 12 and the second seal 20 against the inner side of the rim 22 of the pipe 2.

The housing 10 is furthermore provided with apertures 34 arranged circumferentially on the outside of the housing 10, such that engagement means, for example from a robot, may be inserted in the apertures in order to guide the leak-testing apparatus 1 to desired test positions.

In Figure 3 is illustrated another embodiment of the invention, where the leak-testing apparatus 1 is inserted into a pipe 2. The pipe penetrates a plate 3, where it is desirable to test the tightness of the connection between the plate 3 and the pipe 2.

The leak-testing apparatus comprises a housing 10. Inside the housing is provided an arrangement comprising an outer piston cylinder 40, and inside the outer piston cylinder 40 is arranged a plunger 42 concentrically with the outer piston cylinder 40. The plunger

42 is movable relative to the outer piston cylinder and may be manipulated from the outside due to the fact that and end 44 of the plunger extends outside the housing 10 of the leak-testing apparatus 1. The plunger is furthermore provided with an enlargement 46 in a distal end which in use will be inserted into the tube 2. Between the enlargement 46 and the free end 48 of the outer piston cylinder 40 is arranged a second seal 50. By moving the plunger relative to the outer piston cylinder 40, thereby reducing the distance between the enlargement 46 and the free end 48 of the outer piston cylinder 40, the second seal 50 will be com- pressed and deformed and thereby create a tight seal between the inner wall of the tube 2 and the housing 10. The housing 10 is, as it was the case with the embodiment of the invention discussed above with reference to Figure 2, provided with a first seal 16 such that a space 54 is created. The space 54 is limited by the housing 10, the first seal 16, the outer piston cylinder 40, the second seal 50 and an end seal 56 arranged between the housing 10 and the outer piston cylinder 40.

Furthermore, the leak-testing apparatus 1 is provided with a connection for a pressurised medium, such as for example air, where the connection 32 is connected to the space 54 as described above. In this manner, by applying a pressurised gas such as for example air to the space, testing of the tightness of the connection between the plate 3 and the tube 2 may be carried out. Once the test has been completed, the plunger 42 is moved relative to the outer piston cylinder 40 such that the second seal 50 will move back to its original shape (be released), whereby the leak-testing apparatus 1 may be removed from the tube 2.