Leak testing of a pressure vessel

Abstract

An end cap for a pressure vessel has at least one part for connecting the end cap to a housing. The at least one part comprises a number of recesses. The recesses are arranged to form at least one fluid passage between an inside and an outside of the end cap when the end cap is plugged on the housing. A housing for a pressure vessel has at least one counterpart for connecting an end cap to the housing by engaging a part of the end cap. The at least one counterpart comprises a number of recesses. The recesses are arranged to form at least one fluid passage between an inside and an outside of the housing when the end cap is plugged on the housing. A method for leak testing a pressure vessel and a method for checking a connection between at least one end cap and a housing of a pressure vessel for leak tightness are also described.

Claims

1. In combination, an end cap and a housing having an open end, the end cap to close the open end of the housing, one of the end cap and housing comprising a slot and the other of the end cap and housing comprising a key, the key and slot together forming a key and slot joint when the end cap and housing are assembled, n first recesses, n an integer, the n first recesses arranged with an angular spacing of about 360°/n to each other around the slot of the end cap, and n second recesses arranged with an angular spacing of about 360°/n to each other around the slot, each second recess being arranged adjacent, but offset perimetrally of the housing and end cap from a respective first recess to provide a respective fluid passage which extends at least partially perimetrally of the housing and end cap between an inside and an outside of the assembled end cap and housing, wherein n is an integer greater than 1.

2. The apparatus of claim 1 wherein each of the first recesses are arranged at a first side wall of the slot and each of the second recesses are arranged at an opposing second side wall of the slot in a radial plane angularly spaced from a radial plane containing the respective first recesses with the portion of the slot between each first recess and a respective second recess spanning the perimetral offset and forming a portion of a respective permanent fluid passage.

3. The apparatus of claim 1 wherein the slot is formed on the end cap and the key is formed on the housing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a schematic cross-sectional side view of an end cap according to the state of the art;

(2) FIG. 2 shows a partially cross-sectional side-view of an embodiment of an diffusion and/or filtration devices comprising an end cap according to the present description;

(3) FIG. 3 shows a top view of one embodiment of an end cap according to the present description;

(4) FIG. 4 shows a schematic cross-sectional side view of an embodiment of a pressure vessel according to the present description;

(5) FIG. 5 shows a schematic cross-sectional side view of another embodiment of a pressure vessel according to the present description;

(6) FIG. 6 shows a schematic cross-sectional side view of another embodiment of a pressure vessel according to the present description, wherein the housing comprises two leg portions;

(7) FIG. 7 shows a schematic cross-sectional side view of yet a further embodiment of a pressure vessel according to the present description;

(8) FIG. 8 shows a schematic cross-sectional side view of still another embodiment of a pressure vessel according to the present description;

(9) FIG. 9 shows a schematic cross-sectional side view of another embodiment of a pressure vessel according to the present description;

DETAILED DESCRIPTION

(10) FIG. 1 shows an end cap 10 according to the state of the art for diffusion and/or filtration devices. As shown in FIG. 1, the end cap 10 comprises an inlet or outlet 12, respectively, for a liquid, arranged axially (axis I-I) in the center of the end cap 10. A two-start thread fitting a standard blood-line connector is provided round the inlet or outlet, as the case may be.

(11) The end cap 10 is configured to be plugged on an opening of a housing (not shown) for assembly of the respective diffusion and/or filtration device. For this purpose, the end cap 10 comprises a slot 11, which is part of a circular key and slot joint, which surrounds an edge of the end cap 10. Generally, a respective key of the key and slot joint is integrated in the housing (not shown) for engaging the slot 11 integrated in the end cap 10.

(12) However, even if the end cap 10 according to the state of the art is just plugged on a housing, the device can provide certain tightness and thus, passes usual leak tests. So it is not possible to identify devices which are already welded and devices which are just plugged together.

(13) FIG. 2 shows a side, partially cross-sectional view of an embodiment of an assembled diffusion and/or filtration device 28 according to the present disclosure. The device 28 comprises an end cap 20 according to the present description and a housing 27 which are configured for being connected to each other by means of a key and slot joint. The device 28 further comprises a supporting structure 25 for supporting a bundle of hollow fiber membranes (not shown) inside the housing 27.

(14) The end cap 20 comprises a slot 21 which is part of the key and slot joint and which can be engaged by a key 22 integrally formed at one end of the housing 27. The key 22 represents the second part of the key and slot joint and surrounds an opening of the housing 27. As shown in FIG. 2, the key and slot joint is not engaged yet. When the end cap 20 is plugged on the housing 27 the key 22 enters the slot 21 and the legs 26 are spread outwardly. In order to ensure tightness and rigidity of the device 28, the end cap 20 is to be welded to the housing 27.

(15) In order to identify devices being improperly or even unwelded, volitional leaks are provided in the key and slot joint. According to one embodiment as shown in FIG. 2, the slot 21 comprises a number of recesses 23, 24. A first recess 23 is arranged at an inner side wall and a second recess 24 is arranged at an outer side wall of the slot 21. Thus, the recesses 23, 24 are arranged to form at least one fluid passage between an inside and an outside of the device 28 in case the end cap 20 is plugged on the housing 27 by locally enlarging a cross-section of the slot 21. Further, they are extended in an axial direction of the end cap 20 (as defined in FIG. 1: I-I). Thus, the fluid passage represents the volitional leak and is defined by the recesses 23, 24, a surface of the key 22 and the slot 21.

(16) The recesses 23, 24 are just formed at local spots of the slot. Thus, when the key 22 engages the slot 21, only the proper slot 21 is closed by the key 22. However, the recesses 23, 24 remain open with respect to the inside and the outside of the device 28.

(17) In order to ensure access to the first recess 23 of the slot, also the supporting structure 25 can comprise at least one notch 29 to provide a channel for the fluid to be guided from an internal space inside of the housing 27 towards the first recess 23. As the supporting structure 25 is inserted mechanically into the housing 27, it does not provide a sealing effect preventing the fluid flow towards the first recess 23. Thus, the at least one notch 29 of the supporting structure 25 is provided optionally to improve the fluid flow, but it is not mandatory.

(18) FIG. 3 shows a top view of one embodiment of an end cap 20 according to the present description.

(19) According to the depicted embodiment, three first recesses 23a, b, c and three second recesses 24a, b, c are arranged at the slot 21 of the end cap 20. The first recesses 23a, b, c are arranged with an angular distance of about 120° to each other. The same applies to the second recesses 24a, b, c. Each first recess 23a, b, c and each corresponding second recess 24a, b, c being arranged next to the respective first recess 23a, b, c are arranged with an offset Δu to each other with respect to the at least one slot 21, thus forming at least one fluid passage between an inside and an outside of the end cap 20, in case the end cap is plugged on said housing. According to the embodiment, the end cap 20 comprises three fluid passages. However, any number of fluid passages is possible. On the one hand, a high number of fluid passages might improve a quality test for ensuring that a circular welding was successful, if desired. On the other hand the high number of fluid passages might reduce the rigidity of the end cap 20. Thus, an optimal number has to be defined according to respective requirements.

(20) For way of example only, the first recess 23a is arranged at a first side wall of the slot 21 and the second recess 24a is arranged at an opposing second side wall of the slot 21. However, the first and the second recesses are not arranged in a common radial plane but in planes P1, P2 being spaced apart from each other. Each plane represents one radial cross section of the slot.

(21) Thus, when the key 22 of the housing 27 engages the slot 21, the fluid can also pass from the first recesses 23a, b, c into the slot 21 and from the slot 21 into the second recesses 24a, b, c or vice versa, according to the present description. In case of the offset Δu, the fluid has to pass along the slot 21 to get from one plane P1, P2 to the other and overcome the offset Δu.

(22) For way of example only, the recesses 23a, b, c, 24a, b, c can have a length 1 of about 1 mm along the extension of the slot (circumferential direction) and a width w between 0.03 mm to 0.1 mm in a direction being perpendicular to the slot, for example in a radial direction of a circular end cap. It will be understood, that also any other suitable values are possible.

(23) Furthermore, it is possible to form an additional recess (not shown) along the slot 21 between both planes P1, P2 to improve the flow of the fluid by locally increasing a depth of the slot 21.

(24) FIG. 4 shows a schematic cross-sectional view of a pressure vessel, wherein the end cap 30 comprises two annular leg portions 32, 35 forming an annular slot in between, wherein the two leg portions define a contacting surface between the end cap 30 and the counterpart on the housing 31. By means of the key and slot joint the end cap can be plugged on the housing of the device so as to close an opening of the housing. Here, the slot is engaged by an annular single-legged key counterpart 38 of the housing, so that the slot formed by the two leg portions of the end cap is closed by the key. Specifically, the two side walls of the annular leg portions of the end cap facing the slot, i.e. the outer side wall 36 of the inner leg 35 and the inner side wall 34 of the outer leg 32, overlap with both side walls of the annular leg portion 38 of the housing. In such an embodiment, the side walls of the annular leg portions of the end cap facing the counterpart of the housing comprise recesses as to provide at least one fluid passage which extends from the inside of the pressure vessel to the outside of the pressure vessel, in case the end cap is plugged on the housing. Thus, artificial leaks, i.e. volitional leaks, defined by the fluid passages are generated and a fluid is able to flow through the fluid passages from the inside to the outside or vice versa.

(25) In case the end cap is plugged on the housing, the key of the key and slot joint which is integrated in the housing engages the slot of the end cap and substantially seals the slot. However, the recesses locally enlarge a cross-section of the slot and therefore are not sealed by the key. In fact, the walls of the fluid passage are formed by both, walls of the recesses and a surface of the key, in case the end cap is plugged on the housing.

(26) FIG. 5 shows a similar embodiment as described in FIG. 4. Here, the end cap described above is engaged by a counterpart of the housing comprising two annular leg portions 39, 42 analogue to the leg portions of the connecting joint of the end cap. More specifically, the outer leg portion 39 of the housing form the key of the key and slot joint, wherein the side walls 34, 36 of the annular leg portions facing the inner of the slot of the end cap overlap the inner and outer side walls 41, 40 of the outer leg portion 39 of the housing, respectively, and the inner side wall 37 of the inner leg portion 35 of the end cap overlaps the outer side wall 43 of the inner leg portion 42 of the housing.

(27) In such an embodiment, both side walls of the inner leg portion 35 and the inner side wall 34 of the outer leg portion 32 of the end cap comprise recesses as to provide at least one fluid passage between an inside and an outside of the pressure vessel, when the end cap is plugged on said housing.

(28) FIG. 6 shows a similar embodiment as displayed in FIG. 5. Here, the inner leg portion 42 of the housing forms the key of the key and slot joint, wherein the side walls of the annular leg portions facing the slot of the end cap overlap the inner and outer side wall 44, 43 of the inner leg portion 42 of the housing and the outer side wall 33 of the outer leg portion 32 of the end cap overlaps the inner side wall 41 of the outer leg portion 39 of the housing.

(29) In such an embodiment, both side walls of the outer leg portion 32 and the outer side wall 36 of the inner leg portion 35 of the end cap comprise recesses as to provide at least one fluid passage between an inside and an outside of the pressure vessel, when the end cap is plugged on said housing.

(30) FIG. 7 shows a further embodiment, where the slot on the end cap is engaged by three leg portions 45, 48, 51 of the housing, i.e. both inner and outer side walls of the two annular leg portions 32, 35 of the connecting joint of the end cap are engaged by three annular leg portions of the counterpart of the housing. More specifically, the inner side wall 47 of the outer leg portion 45 of the housing overlaps the outer side wall 33 of the outer leg portion 32 of the end cap, the inner and outer side wall 50, 49 of the middle leg portion 48 of the housing overlaps the side walls 34, 36 of the two leg portions facing the slot on the end cap, and the outer side wall 52 of the inner leg portion 51 of the housing overlaps the inner side wall 37 of the inner leg portion 35 of the end cap.

(31) In the above-mentioned embodiments, every side wall of the two annular leg portions of the end cap engaging one side wall of the annular leg portions of the counterpart of the housing comprises recesses as to provide at least one fluid passage between an inside and an outside of the pressure vessel, when the end cap is plugged on said housing.

(32) FIG. 8 shows a schematic cross-sectional view of a further embodiment, where the at least one connecting part of the connecting joint of the end cap is designed to overlap the counterpart of a housing or to be overlapped by the same. Here, the at least one connecting part of the connecting joint is an annular leg portion 54 defining a front side wall 55 and a rear side wall 56, wherein the leg portion extends from the connecting joint to the exterior of the end cap and is perpendicular to the axial direction of the end cap. The axial direction is usually defined by an axis of symmetry or by a direction of extraction, when the end cap is extracted from a casting mold. In both cases, the axial direction is aligned in parallel with a longitudinal axis of the housing or the pressure vessel, respectively, in case the end cap is plugged on the housing. The overlapping surface on the front side wall 55 is defined by the length of the leg portion and comprises at least one recess as to provide a fluid passage between an inside and an outside of the pressure vessel, when the end cap is plugged on said housing.

(33) FIG. 9 shows a similar embodiment as described in FIG. 8, wherein the annular leg portion 54 of the end cap has an angle α of 270°>α>90° to the axial direction, defining a outer side wall 57 and an inner side wall 58. Again, the overlapping surface on the outer side wall 57 is defined by the length of the leg portion and comprises at least one recess as to provide a fluid passage between an inside and an outside of the pressure vessel, in case the end cap is plugged on the housing.

(34) In an analogue embodiment, the inner side wall 58 of the annular leg portion 54 overlaps the counterpart of the housing (not shown), wherein the overlapping surface of the end cap provides said recesses.