Filter Candle

Abstract

To provide a filter candle 10, 50 for a novel gaseous fluid, especially for hot gas filtration, comprising one or more filter elements 12, 52 of hollow cylindrical shape, a support element 16, and two or more annular sealing disks 34, 36, 54.SOLUTION: A filter candle comprises: a filter element made of porous material, the filter element having identical inner and outer diameters and are disposed coaxially with each other; a support element comprising a metal tube 16 disposed within the filter element, the metal tube having an outer diameter smaller than an inner diameter of the filter element, and the metal tube having a wall 24 with a plurality of perforations 26; and sealing disks having an outer diameter equal to or larger than that of the filter element and an inner diameter smaller than that of the filter element, where first and second terminal sealing disks are disposed at axial end faces of both sides of the filter element disposed in line, and where the filter element is compressed between the terminal sealing disks.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to filter candles for gaseous fluids, particularly for the filtration of hot gases. A typical use of such filter candles is the purification of industrial flue gases or exhaust gases by particle removal.

Background Art

[0002] Filter candles for hot gas applications according to the prior art are often based on a porous filter element in the shape of a hollow cylinder with one end closed. The gaseous fluid to be purified usually passes through the wall of the filter element substantially radially from the outside and exits the filter element through one axial opening. A plurality of such filter candles may be arranged parallel to each other to form a filtration assembly.

[0003] This type of filter candle can also operate as a blowback filter, and the filter element is cleaned by a high-pressure gas flow flowing in the opposite direction to the normal filtration process.

[0004] Typically, the above-described filter candles made of ceramic materials are rigid and self-supporting. However, a major drawback is that their mechanical strength, particularly tensile strength and bending strength, may be limited. As a result, when the filter candle is subjected to mechanical stress, there is a risk of the filter candle failing, which can occur, for example, when dust bridging between the filter candles occurs.

Summary of the Invention

Problems to be Solved by the Invention

[0005] The object of the present invention is to provide a filter candle having improved mechanical strength.

Means for Solving the Problems

[0006] This problem is solved by the filter candle described in claim 1.

[0007] In the filter candle of the present invention, a support element is provided within one or more cylindrical filter elements. This support element comprises a metal tube, the metal tube itself having considerably higher tensile and bending strength than the porous material of the filter element. After passing through the filter element, the gaseous fluid enters the metal tube through multiple through-holes and flows out of the filter candle through an opening at one end of the tube.

[0008] An annular gap exists between the inner surface and the outer surface of the metal tube so as not to obstruct the flow through the entire inner surface region of one or more filter elements. When a force is applied radially to the filter element, the filter element moves and / or bends until it contacts the metal tube. In this way, the metal tube supports and stabilizes the filter element and improves the overall mechanical strength of the filter candle, particularly its bending strength.

[0009] According to the present invention, one or more filter elements are compressed between a first end sealing disk and a second end sealing disk by utilizing the relatively high compressive strength of the porous material of the filter element. However, the compression of the filter element is such that it allows radial movement between the filter element and the adjacent end sealing disk until the filter element comes into contact with the metal tube as described above. During this movement, the axial end face of the filter element must be tightly covered by the sealing disk.

[0010] According to a first preferred embodiment of the present invention, the filter candle comprises only one filter element. In this case, only two sealing discs are provided on the two axial end faces of this filter element. The filter element preferably has an axial length of about 0.5 m to about 3.0 m, more preferably about 1.0 m to about 2.5 m.

[0011] According to a second preferred embodiment of the present invention, the filter candle comprises a plurality of filter elements arranged in a row. In this case, in addition to two end sealing disks, further internal sealing disks are provided between adjacent filter elements. Such division of the filter candle results in greater flexibility and elasticity against mechanical stress, particularly radial forces acting on the filter candle.

[0012] The total axial length of the multiple filter elements in the second embodiment can be within the same preferred range as the length of a single filter element in the first embodiment. However, division is particularly preferred for longer lengths, such as about 1.5 m to about 5.0 m. In the second embodiment, the filter candle preferably comprises 2 to 8 filter elements, more preferably 3 to 5 filter elements. The filter elements may have the same or different lengths.

[0013] One or more filter elements preferably have an outer diameter of about 30 mm to about 150 mm, more preferably about 60 mm to about 70 mm, and an inner diameter of about 15 mm to about 120 mm, more preferably about 40 mm to about 50 mm. The wall thickness of the hollow cylinder is typically in the range of about 7.5 mm to about 20 mm.

[0014] The radial distance between the filter element and the metal tube is preferably about 1 mm to about 5 mm, more preferably about 3 mm to about 4 mm. In order that the axial end face of the filter element makes complete contact with the sealing disc even when the filter element is in contact with the metal tube, the outer diameter of the annular sealing disc is greater than or equal to the outer diameter of the filter element, and the inner diameter of the sealing disc is smaller than the inner diameter of the filter element.

[0015] In the present invention, each sealing disk preferably comprises an annular metal disk, preferably a steel disk, and gaskets provided on one or both sides of the metal disk in contact with the filter element. That is, the end sealing disk has a gasket on one side, and the internal sealing disk has gaskets on both sides. In this way, a substantially airtight seal is provided between the filter element and the sealing disk, while simultaneously allowing radial movement of the filter element relative to the sealing disk.

[0016] Preferably, the gasket used in the sealing disc of the filter candle of the present invention includes graphite, metal fibers, metal mesh, polymer materials, or combinations thereof. These and more suitable gasket materials are already known from the prior art. The selection of a specific gasket material also depends on the intended application of the filter candle of the present invention and its respective operating conditions. For example, most polymer gasket materials are limited in terms of their operating temperature.

[0017] The gasket used in the sealing disc preferably has a thickness of about 1 mm to about 5 mm, and preferably about 1.5 mm to about 3 mm.

[0018] One or more of the sealing discs may be provided with a resilient compensating element. In particular, it is preferable that one of the end sealing discs be provided with a resilient compensating element. In embodiments of the present invention having two or more filter elements, it is also preferable that the internal sealing disc be provided with a resilient compensating element. This allows for axial bending of two adjacent filter elements relative to each other. The internal sealing disc may be provided with such a compensating element in addition to, or in place of, the annular metal disc.

[0019] One or more filter elements of the filter candle of the present invention are typically made of a ceramic material, preferably a material containing sintered silicon carbide. These ceramic materials, which exhibit high porosity, are known from the prior art. Furthermore, the filter elements may include one or more catalytic materials, particularly for the removal of nitrogen oxides.

[0020] The metal tube acting as a support element for the filter candle of the present invention is preferably a steel tube, more preferably having a wall thickness of about 2 mm to about 10 mm, and particularly about 3 mm to about 6 mm. However, in certain cases, such as when the gaseous fluid to be filtered requires higher corrosion or chemical resistance from the support element, the use of other metals or alloys may also be preferable. This also applies to the annular metal disc of the sealing disc.

[0021] Typically, the metal tube has an axial length greater than the total axial length of the filter element, with the middle section of the metal tube extending into the filter element and the two end sections extending outside the filter element. In this case, through-holes in the walls of the metal tube are uniformly distributed throughout the middle section, while there are no through-holes in the walls of the two end sections.

[0022] The number and size of the through-holes are preferably selected such that the total area of ​​the through-holes is large enough to facilitate the radial flow of gaseous fluid into the metal tube, but small enough to maintain sufficient mechanical stability of the metal tube. Regarding the latter requirement, the wall thickness of the metal tube must also be taken into consideration.

[0023] According to a preferred embodiment of the present invention, a first end section of a metal tube extends outward from the filter element through a first end sealing disc, the first end sealing disc being fixed to the first end section, preferably by welding or screwing. It is even more preferable that the first end section has an axial discharge opening for a gaseous fluid.

[0024] In the above-described embodiment, the second end section of the metal tube can also extend outside the filter element through the second end sealing disc, and the second end sealing disc is axially movable relative to the metal tube. It is further preferred that the second end section is closed at its axial end, thereby enabling the discharge of the gaseous fluid only through the first end section.

[0025] By providing a first end sealing disc fixed to the metal tube and a second end sealing disc movable relative to the metal tube, the difference in thermal expansion between the metal tube and the porous material of the filter element is taken into account.

[0026] Preferably, one or more filter elements are compressed between the first end sealing disc and the second end sealing disc by an axial force exerted on the second end sealing disc via a flange element fixed to the second end section of the metal tube and a spring element, preferably a high-temperature spring, abutting against the second end sealing disc.

[0027] As described above, the metal tube is preferably closed at the second end section, and the gaseous fluid is discharged only through the first end section. Therefore, it is preferable to provide a spring cover so as to surround the second end section including the spring element, thereby protecting the spring element from external dust and the like. The spring cover preferably abuts against the second end sealing disc.

[0028] The plurality of filter candles of the present invention can preferably be arranged parallel to each other to form a filtration assembly, particularly for high-temperature gas filtration.

[0029] The present invention also relates to the use of the filter candle of the present invention, or a filtration assembly comprising a plurality of filter candles of the present invention, for high-temperature gas filtration, particularly for the purification of industrial flue gas or exhaust gas. The present invention provides, for example, the following items: (Item 1) One or more filter elements (12;52) in the shape of a hollow cylinder, Support element (16), At least two annular sealed disks (34, 36; 54) and A filter candle (10;50) for gaseous fluids, particularly for high-temperature gas filtration, comprising: The one or more filter elements (12;52) are made of a porous material, and the multiple filter elements (12;52) have substantially the same inner and outer diameters and are arranged coaxially in a single line with respect to each other. The support element (16) comprises a metal tube (16) disposed within the one or more filter elements (12; 52), the metal tube (16) having an outer diameter smaller than the inner diameter of the filter elements (12; 52), and the metal tube (16) having a wall (24) with a plurality of through holes (26). The at least two annular sealing disks (34, 36; 54) have an outer diameter greater than or equal to the outer diameter of the filter elements (12; 52) and an inner diameter smaller than the inner diameter of the filter elements (12; 52), and the first and second end sealing disks (34, 36) are positioned on the axial end faces on both sides of a single filter element (12), or on the axial end faces on both sides of a plurality of filter elements (52) arranged in a row, and optionally, a further internal sealing disk (54) is positioned between two adjacent filter elements (52) of the plurality of filter elements (52). A filter candle comprising one or more filter elements (12, 52), and optionally the internal sealing disk (54), which is compressed between the first end sealing disk (34) and the second end sealing disk (36). (Item 2) The filter candle (10) according to item 1, comprising only one of the filter elements (12) having an axial length preferably about 0.5 m to about 3.0 m, more preferably about 1.0 m to about 2.5 m. (Item 3) The filter candle (50) according to item 1, comprising a plurality of the filter elements (52) arranged in a row, having an axial total length preferably about 0.5 m to about 6.0 m, preferably about 1.5 m to about 5.0 m. (Item 4) A filter candle (50) according to item 3, comprising two to eight of the filter elements (52), preferably three to five of the filter elements (52). (Item 5) A filter candle (10;50) according to any one of items 1 to 4, wherein one or more filter elements (12;52) have an outer diameter of about 30 mm to about 150 mm, preferably about 60 mm to about 70 mm, and an inner diameter of about 15 mm to about 120 mm, preferably about 40 mm to about 50 mm. (Item 6) A filter candle (10;50) according to any one of items 1 to 5, wherein the radial distance between the filter element (12;52) and the metal tube is about 1 mm to about 5 mm, preferably about 3 mm to about 4 mm. (Item 7) Each of the aforementioned sealed disks (34, 36; 54) To provide a substantially airtight seal between the filter element (12; 52) and the sealing disk (34, 36; 54) and to allow radial movement of the filter element (12; 52) relative to the sealing disk (34, 36; 54), an annular metal disk (46), preferably a steel disk, A gasket (48) is provided on one or both sides of the metal disk (46) in contact with the filter element (12; 52) and A filter candle (10;50) as described in any one of items 1 to 6, comprising the features of item 1 to 6. (Item 8) The filter candle (10;50) according to item 7, wherein the gasket (48) comprises graphite, metal fibers, metal mesh, polymer material, or a combination thereof. (Item 9) A filter candle (10; 50) according to any one of items 1 to 8, wherein one or more of the sealing disks (34, 36; 54), in particular one of the end sealing disks (34, 36) and / or the internal sealing disk (54), comprises an elastic adjustment element (56). (Item 10) A filter candle (10;50) according to any one of items 1 to 9, wherein one or more of the filter elements (12;52) are made of a ceramic material, preferably a material containing sintered silicon carbide. (Item 11) The filter candle (10;50) according to any one of items 1 to 10, wherein the metal tube (16) is a steel tube, preferably having a wall thickness of about 2 mm to about 10 mm, and more particularly about 3 mm to about 6 mm. (Item 12) A filter candle (10;50) according to any one of items 1 to 11, wherein the metal tube (16) has an axial length greater than the total axial length of the filter element (12;52), and the through-holes (26) are uniformly distributed throughout the intermediate section (18) of the metal tube (16) extending into the filter element (12;52). (Item 13) A filter candle (10;50) according to item 12, wherein a first end section (20) of the metal tube (16) preferably having an axial discharge opening (30) for the gaseous fluid extends outward from the filter element (12;52) through the first end sealing disc (34), and the first end sealing disc (34) is preferably fixed to the first end section (20) by welding or screwing. (Item 14) The filter candle (10;50) according to item 13, wherein a second end section (22) of the metal tube (16), preferably closed at an axial end (32), extends outward from the filter element (12;52) through the second end sealing disc (36), and the second end sealing disc (36) is axially movable relative to the metal tube (16). (Item 15) The filter candle (10;50) according to item 14, wherein one or more filter elements (12;52) are compressed between the first end sealing disk (34) and the second end sealing disk (36) by an axial force exerted on the second end sealing disk (36) via a spring element (38), preferably a high-temperature spring, that abuts the second end sealing disk (36) and a flange element (40) fixed to the second end section (22) of the metal pipe. (Item 16) The filter candle (10;50) according to item 15, wherein the compression of one or more filter elements (12;52) allows radial movement between the filter element (12;52) and adjacent sealing disks (34, 36;54) until the filter element (12;52) comes into contact with the metal tube (16).

[0030] The exemplary embodiments described below are helpful in illustrating further details of the invention with reference to the drawings. [Brief explanation of the drawing]

[0031] [Figure 1] This is a longitudinal section view of a first exemplary embodiment of the filter candle of the present invention. [Figure 2] This is a longitudinal section view of a second exemplary embodiment of the filter candle of the present invention. [Modes for carrying out the invention]

[0032] Figure 1 shows a longitudinal section of a first exemplary embodiment of the filter candle 10 of the present invention. The depiction of the filter candle 10 is schematic and not necessarily to scale.

[0033] In this first embodiment, the filter candle 10 comprises a single hollow cylindrical filter element 12. The filter element 12 may, for example, have a length of 1.5 m, an outer diameter of 60 mm, and an inner diameter of 40 mm. The filter element 12 is made of a porous material, typically a porous ceramic material. For example, a porous filter element made of sintered silicon carbide material, also known as a filter candle, is marketed by the applicant under the trademark "Dia-Schumalith".

[0034] Inside the filter element 12, a metal tube 16 (typically a steel tube) is positioned as a support element, extending coaxially with the filter element along the axis of rotation 14. This metal tube 16 comprises an intermediate section 18 extending into the filter element 12 and a first end section 20 and a second end section 22 extending outside the filter element 12. The walls 24 of the metal tube 16 have a plurality of through-holes 26 uniformly distributed throughout the intermediate section 18 of the metal tube 16, but the walls 24 of the first and second end sections 20 and 22 do not have through-holes.

[0035] The metal tube 16 may have, for example, an outer diameter of approximately 34 mm and a wall thickness of 4 mm. In either case, the outer diameter of the metal tube 16 is smaller than the inner diameter of the filter element 12, resulting in the formation of an annular gap 28 between the filter element 12 and the metal tube 16. The width of this gap 28 may be, for example, 3 mm.

[0036] For example, in a typical application of the filter candle 10 for use in high-temperature gas filtration, the gaseous fluid to be filtered passes substantially radially from the outside through the filter element 12 into the annular gap 28 and through the through hole 26 into the metal tube 16. The gaseous fluid then flows out of the metal tube 16 through the axial discharge opening 30 of the first end section 20, while the second end section 22 is closed at its axial end 32.

[0037] The filter candle 10 further comprises two annular sealing discs, namely a first end sealing disc 34 and a second end sealing disc 36. The first end sealing disc 34, as indicated by reference numeral 37, surrounds the first end section 20 of the metal tube 16 and is fixed thereto by welding, thus hermetically sealing the annular gap 28 at the first end section 20. In contrast, the second end sealing ring 36, surrounding the second end section 22 of the metal tube 16, is axially movable relative to the metal tube 16 to allow for different thermal expansions of the metal tube 16 and the filter element 12.

[0038] The filter element 12 is compressed between the first end sealing ring 34 and the second end sealing ring 36, and this compressive force is exerted by a spring element 38, preferably a high-temperature spring. This spring element 38 surrounds the second end section 22 of the metal tube 16 and contacts the second end sealing disc 36 and a flange element 40 fixed to the second end section 22, for example by a screw nut 42.

[0039] The second end section 22 of the metal tube 16, which includes the spring element 38, is covered by a spring cover 44 that abuts against the second end sealing disc 36. The spring cover 44 protects the spring element 38 from dust and other external elements and also retains gaseous fluid that may pass through the small annular gap between the metal tube 16 and the second end sealing disc 36.

[0040] Each of the end sealing discs 34 and 36 comprises a metal disc 46 (typically a steel disc) and a gasket 48. The gasket is in direct contact with the respective axial end faces of the filter element 12, providing an airtight seal while simultaneously allowing radial movement of the filter element 12. The first end sealing disc 34 may further include an elastic adjustment element.

[0041] As a result of the external force acting on the filter element 12, the filter element 12 moves radially along the gasket until it contacts the metal tube 16. At this point, the metal tube 16 supports and stabilizes the filter element 12, ideally preventing it from bending further and breaking. Thus, the metal tube 16 acts as a support element that increases the overall tensile and flexural strength of the filter candle 10.

[0042] To provide an airtight seal to the end face of the filter element 12 at all positions, the outer diameter of the annular sealing discs 34, 36 is greater than or equal to the outer diameter of the filter element 12, and the inner diameter of the sealing discs 34, 36 is smaller than the inner diameter of the filter element 12. In particular, the difference between the outer and inner diameters of the sealing discs 34, 36 should be at least twice the radial distance between the filter element 12 and the metal tube 16.

[0043] Figure 2 shows a second exemplary embodiment of the filter candle 50 of the present invention in a longitudinal section. The filter candle 50 of the second embodiment corresponds to the filter candle 10 of the first embodiment, except for the differences described below. The same or corresponding elements in the first and second embodiments are given the same reference numerals.

[0044] The filter candle 50 of the second embodiment comprises multiple shorter filter elements 52 made of porous material instead of a single filter element. In this example, four filter elements 52 are shown, but fewer or more filter elements are also possible. Each filter element 52 is molded as a hollow cylinder having the same inner and outer diameters and is arranged in a single line coaxially along the rotation axis 14 of the filter candle 50.

[0045] The lengths of the individual filter elements 52 may be the same or different, and their total length may be the same as the total length of a single filter element in the first embodiment (e.g., 1.5 m). However, the use of multiple filter elements 52 is also particularly effective for longer total lengths, such as up to 6 m.

[0046] An internal annular sealing disk 54 is positioned between each of two adjacent filter elements 52. The filter elements 52, together with the internal sealing disk 45, are compressed between a first end sealing disk 36 and a second end sealing disk 38, similar to the filter candle 10 of the first embodiment.

[0047] Dividing the filter into multiple filter elements 52 provides greater flexibility and elasticity of the filter candle 50 against mechanical stress, particularly radial forces acting on the filter candle 50. To this end, the internal sealing disk 54 typically includes elastic adjustment elements 56 that allow axial bending of two adjacent filter elements 52 relative to each other. The elastic adjustment elements 56 are provided with gaskets 58 on both sides.

[0048] Measurement of bending strength The bending strength of the filter candle of the present invention according to the first exemplary embodiment was measured by a four-point bending test. The filter element of the tested filter candle was a hollow cylinder of sintered silicon carbide (Dia-Schumalith) based ceramic material with a length of 1.5 m, an outer diameter of 60 mm, and an inner diameter of 40 mm.

[0049] In a four-point bending test, the filter element of the filter candle of the present invention cracked under a force of approximately 4800 N.

[0050] Typically, conventional filter candles, consisting only of the corresponding filter element without a supporting metal tube, will crack under bending forces in the range of 2500-3500 N.

[0051] Therefore, the bending strength of the filter candle of the present invention is increased by approximately 60% compared to the corresponding conventional filter candle. [Explanation of symbols]

[0052] 10…Filter candle, 12…Filter element, 16…Metal tube, 18…Intermediate section, 20…First end section, 22…Second end section, 24…Wall, 26…Through hole, 34…First end sealing disc, 36…Second end sealing disc, 38…Spring element, 50…Filter candle, 52…Filter element, 54…Internal sealing disc.

Claims

1. One or more filter elements (12; 52) in the shape of a hollow cylinder, Support element (16), At least two annular sealing disks (34, 36; 54) and A filter candle (10; 50) for gaseous fluids, comprising: The one or more filter elements (12; 52) are made of a porous material, and the multiple filter elements (12; 52) have the same inner and outer diameters and are arranged coaxially in a single line with respect to each other. The support element (16) comprises a metal tube (16) disposed within one or more filter elements (12; 52), the metal tube (16) having an outer diameter smaller than the inner diameter of the filter elements (12; 52), and the metal tube (16) having a wall (24) with a plurality of through holes (26). The at least two annular sealing discs (34, 36; 54) have an outer diameter greater than or equal to the outer diameter of the filter elements (12; 52) and an inner diameter smaller than the inner diameter of the filter elements (12; 52), and the first and second end sealing discs (34, 36) are positioned on the axial end faces on both sides of a single filter element (12), or on the axial end faces on both sides of a plurality of filter elements (52) arranged in a row. A filter candle in which one or more filter elements (12, 52) are compressed between the first end-sealed disk (34) and the second end-sealed disk (36).

2. The filter candle (10) according to claim 1, comprising only one of the filter elements (12).

3. The filter candle (50) according to claim 1, comprising a plurality of the filter elements (52) arranged in a row.

4. The filter candle (50) according to claim 3, comprising two to eight of the filter elements (52).

5. The filter candle (10; 50) according to any one of claims 1 to 4, wherein one or more filter elements (12; 52) have an outer diameter of 30 mm to 150 mm.

6. The filter candle (10; 50) according to any one of claims 1 to 5, wherein the radial distance between the filter element (12; 52) and the metal tube is 1 mm to 5 mm.

7. Each of the aforementioned sealing disks (34, 36; 54) A filter candle (10;50) according to any one of claims 1 to 6, comprising an annular metal disc (46) and a gasket (48) provided on one or both sides of the metal disc (46) in contact with the filter element (12;52) to provide an airtight seal between the filter element (12;52) and the sealing disc (34, 36;54) and to allow radial movement of the filter element (12;52) relative to the sealing disc (34, 36;54).

8. The filter candle (10; 50) according to claim 7, wherein the gasket (48) comprises graphite, metal fibers, metal mesh, polymer material, or a combination thereof.

9. The filter candle (10; 50) according to any one of claims 1 to 8, wherein one or more of the first and second end-sealing disks (34, 36) comprises an elastic adjustment element (56).

10. The filter candle (10; 50) according to any one of claims 1 to 9, wherein one or more filter elements (12; 52) are made of a ceramic material.

11. The filter candle (10; 50) according to any one of claims 1 to 10, wherein the metal pipe (16) is a steel pipe.

12. The filter candle (10;50) according to any one of claims 1 to 11, wherein the metal tube (16) has an axial length greater than the total axial length of the filter element (12;52), and the through-holes (26) are uniformly distributed throughout the intermediate section (18) of the metal tube (16) that extends into the filter element (12;52).

13. The filter candle (10;50) according to claim 12, wherein the first end section (20) of the metal tube (16) extends outward from the filter element (12;52) through the first end sealing disk (34), and the first end sealing disk (34) is fixed to the first end section (20).

14. The filter candle (10;50) according to claim 13, wherein the second end section (22) of the metal tube (16) extends outward from the filter element (12;52) through the second end sealing disk (36), and the second end sealing disk (36) is axially movable relative to the metal tube (16).

15. The filter candle (10; 50) according to claim 14, wherein one or more filter elements (12; 52) are compressed between the first end sealing disk (34) and the second end sealing disk (36) by an axial force exerted on the second end sealing disk (36) via a spring element (38) that abuts the second end sealing disk (36) and a flange element (40) fixed to the second end section (22) of the metal pipe.

16. The filter candle (10;50) according to claim 15, wherein the compression of one or more filter elements (12;52) allows radial movement between the filter elements (12;52) and adjacent sealing disks (34, 36;54) until the filter elements (12;52) come into contact with the metal tube (16).

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