Holding device for electrically heated steel pipes

Abstract

The invention relates to a holding device (11) for electrically heated steel pipes (15, 16, 17), comprising an annular center part (12) for receiving a first steel pipe (15) and an annular side part (13) for receiving a second steel pipe (16), wherein the annular center part (12) is connected to the annular side part (13). The end of one of the two steel pipes (15, 16) is supported in a cutout (19) in the furnace wall (18), and the end of the other steel pipe (15, 16) is held or supported only by means of the holding device (11).

Description

[0001] HOLDING DEVICE FOR ELECTRICALLY HEATED RADIANT TUBES

[0002] The subject of this invention is a holding device for electrically heated radiant tubes such as those used for the heat treatment of metal strips in furnaces.

[0003] For the heat treatment of metals, it is known (DE 20 2008 009 065 Ul) to provide radiant tube units which can be heated with the aid of burners and which have two outer tubes extending from a central tube connected to the burner and lying parallel to the central tube in a common axial plane, so that with the aid of the outer tubes which are connected to the central tube at their ends via pipe bends, a partial flow of the hot exhaust gases from the burner flowing into the central tube can be circulated.

[0004] The gas-heated radiant tube units of this design are also known as "Double-P Radiant Tubes". The metal strip to be treated, which is conveyed parallel to the common axial plane of the tubes of the radiant tube unit with a feed direction running transverse to the tube axes, is heated by the thermal radiation emitted by the tubes of the radiant tube unit. Due to the high temperatures of the radiant tubes, the bearings of the radiant tube unit must be designed in such a way that the thermal expansion of the tubes in the axial direction is taken into account. For this purpose, the center tube has a hollow bearing journal at its end opposite the burner, which is mounted in a recess in the furnace wall. Conventional furnaces with gas-heated radiant tubes therefore usually have an opening in the furnace wall for each radiant tube unit to support the radiant tube unit.Such a bearing is described, for example, in AT 508368 Bl and also shown in Figure 1.

[0005] Other solutions are now known in which electrically heated radiant pipes are used instead of gas-heated radiant pipes. In this case, two or three parallel electrically heated radiant pipes could be used instead of a double-P radiant pipe unit. These radiant pipes are essentially cylindrical. Even with electrically heated radiant pipes, it is advantageous if they are supported at their free end. For this purpose, for example, recesses could be provided in the furnace wall in which the respective radiant pipe end is then supported. However, this recess leads to increased heat losses through the furnace wall. The object of the invention is therefore to disclose an improved mechanical support for electrically heated radiant pipes.

[0006] This object is achieved by a holding device for electrically heated jet pipes according to claim 1. The holding device according to the invention essentially consists of an annular central part for receiving a first jet pipe and an annular side part. Both parts are connected to one another, for example, via an elongated intermediate part.

[0007] The annular center section and the annular side section can each accommodate one end of an electrically heated radiant tube. One of the two radiant tubes is supported by its end in an opening in the furnace wall, while the end of the other radiant tube is supported only by the retaining device. This has the advantage that only one recess in the furnace wall is required to support two electrically heated radiant tubes.

[0008] Preferably, the holding device also includes a support for a third electrically heated radiant tube. This support is attached to the central part on the side opposite the annular side part. As a result, only one of the two lower radiant tubes needs to be supported in a recess in the furnace wall, with the other two radiant tubes then being held by the holding device.

[0009] The holding device according to the invention allows existing furnaces currently heated with fossil fuels such as gas to be easily converted to electrically heated radiant tubes without the need for extensive modifications to the furnace wall. Conventional openings / supports in the furnace wall can be used to support the electric radiant tubes, and no additional recesses in the furnace wall are required. This reduces energy losses.

[0010] It is advantageous if the holding device is made of metal, in particular of a heat-resistant metal, for example (please provide examples).

[0011] In a further embodiment, the central part is connected to the side part via an elongated intermediate part, wherein it is advantageous if the intermediate part has reinforcing ribs. The prior art and the invention are described below with reference to drawings.

[0012] Fig. 1 shows a bearing arrangement for gas-heated radiant tubes according to the state of the art.

[0013] Fig. 2 shows a mounting of electrically heated jet pipes using the holding device according to the invention.

[0014] Fig. 3 shows the holding device according to the invention in plan view.

[0015] Fig. 4 shows a side view of the holding device according to the invention.

[0016] Figure 1 shows a prior art embodiment. The device shown for the heat treatment of metal strips 6 has a gas-heated radiant tube unit 1 which comprises a central tube 2 and two parallel outer tubes 3 lying in a common axial plane with the central tube 2. The outer tubes 3 are each fluidly connected to the central tube 2 via end pipe bends 4. The hot exhaust gases flowing into the central tube 2 from a burner connected to an extension 5 of the central tube 2 are thus partially circulated via the two outer tubes 3. With the aid of the radiant heat radiated by the tubes 2, 3, a metal strip 6 indicated by a dash-dotted line is heated and is guided parallel to the common axial plane of the tubes 2, 3, in a feed direction 7 which runs transversely to the tube axes.The radiant tube unit 1 according to the prior art is mounted on both sides of the tubes 2 and 3, resulting in a largely even distribution of the weight load between the two lateral supports. While the support which receives the extension 5 of the central tube 2 and is not shown for reasons of clarity fixes the radiant tube unit 1 axially, the opposite support 8 supports the radiant tube unit 1 in an axially displaceable manner. For this purpose, the radiant tube unit 1 carries a usually tubular bearing pin 9 at the end of the central tube 2 opposite the extension 5, which is supported in an axially displaceable manner in a sleeve-shaped pin receptacle 10 in the furnace wall.

[0017] Figure 2 shows a device for the heat treatment of metal strips 6 with the aid of electrically heated radiant tubes 15, 16, 17. The middle electrically heated radiant tube is referred to here as the first electrically heated steel tube 15. Its end is mounted in a recess 19 in the furnace wall 18. In the present example, the electrically heated radiant tube 15 has a bearing pin 22 at its end which projects into the recess 19. The two other electrically heated radiant tubes 16 and 17 are supported or held at their respective ends by the holding device 11 according to the invention.

[0018] Figure 3 shows an exemplary embodiment of a holding device 11 according to the invention. It consists of an annular central part 12 and an annular side part 13. The central part 12 and the side part 13 are connected to one another via an elongated intermediate part 14. In the present example, the intermediate part 14 has reinforcing ribs 20. The annular central part 12 is pushed over the first electrically heated radiant pipe 15. This radiant pipe 15 is also supported by its end in the furnace wall 18. The annular side part 13 receives the free end of the second radiant pipe 16. This end is held only by the holding device 11 and does not have to be supported on the furnace wall 18. In the present example, the holding device 11 also has a support 21 for supporting a third electrically heated radiant pipe 17.This support 21 of the holding device 11 is connected to the annular central part 12 and is located on the opposite side of the side part 13. The support 21 can also have reinforcing ribs 20.

[0019] These reinforcing ribs 20 are also clearly visible in Figure 4.

[0020] It is also conceivable that the holding device 11 is used for electrically heated jet pipe units consisting of only two jet pipes 15, 16. In this case, the illustrated support 21 for the third jet pipe 17 is superfluous.

[0021] The embodiments shown in the drawings represent only a preferred embodiment of the invention. The invention also encompasses other embodiments in which, for example, the lower electrically heated radiant tube 16 is mounted in the recess 19 in the furnace wall 18 and the ends of the two radiant tubes 15, 17 located above it are supported only by the holding device 11. Reference symbol

[0022] 1 gas-heated radiant tube unit

[0023] 2 Center pipe of a gas-heated radiant tube unit

[0024] 3 parallel outer tubes

[0025] 4 pipe bends

[0026] 5 Extension

[0027] 6 metal band

[0028] 7 Feed direction

[0029] 8 supports

[0030] 9 bearing journals

[0031] 10 tenon holder

[0032] 11 Holding device

[0033] 12 ring-shaped middle part

[0034] 13 ring-shaped side part

[0035] 14 Intermediate part

[0036] 15 first electrically heated jet pipe

[0037] 16 second electrically heated jet pipe

[0038] 17 third electrically heated jet pipe

[0039] 18 Furnace wall

[0040] 19 Recess in the furnace wall 18

[0041] 20 reinforcing ribs

[0042] 21 supports

[0043] 22 bearing journals

Claims

Patent claims 1. Holding device (11) for electrically heated radiant pipes (15, 16, 17), comprising an annular central part (12) for receiving a first radiant pipe (15) and comprising an annular side part (13) for receiving a second radiant pipe (16), wherein the annular central part (12) is connected to the annular side part (13), wherein one of the two radiant pipes (15, 16) is mounted with its end in a recess (19) in the furnace wall (18) and wherein the end of the respective other radiant pipe (15, 16) is held or mounted only via the holding device (11).

2. Holding device (11) according to claim 1, characterized in that a support (21) is fastened to the annular central part (12) on the side opposite the annular side part (13), on which support the end of a third jet pipe (17) can be supported.

3. Holding device (11) according to claim 1 or 2, characterized in that the holding device (11) is made of metal, in particular of a heat-resistant metal.

4. Holding device (11) according to one of claims 1 to 3, characterized in that the central part (12) is connected to the side part (13) via an elongated intermediate part (14).

5. Holding device (11) according to claim 4, characterized in that the elongated intermediate part (14) has reinforcing ribs (20).

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