Abstract:
In a flame arrester arrangement having a housing ( 1 ) for holding at least two flame arrester inserts ( 6, 6′ ) having a large number of axial passage gaps dimensioned for a combustible gas, and having an intermediate layer ( 7 ) arranged between two flame arrester inserts ( 6, 6′ ), which permits a radial distribution of the gas flow emerging from one flame arrester insert ( 6, 6′ ) and entering an adjacent downstream flame arrester insert ( 6, 6′ ), the ability of the flame arrester inserts ( 6, 6′ ) to be easily assembled and disassembled for servicing purposes without restricting the functional integrity can be achieved by at least one separate closed seal ( 11, 11′, 15, 17, 17′, 20 ) being arranged between a flame arrester insert ( 6, 6′ ) and the housing ( 1 ) or between two flame arrester inserts ( 6, 6′ ) in such a way that a flow around the flame arrester insert ( 6, 6′ ) in a space ( 12 ) located radially outside the passage gaps is prevented.

Description:
FIELD OF THE INVENTION 
     The invention relates to a flame arrester arrangement having a housing for holding at least two flame arrester inserts having a large number of axial passage gaps dimensioned for a combustible gas, and having an intermediate layer arranged between two flame arrester inserts, which permits a radial distribution of the gas flow emerging from one flame arrester insert and entering an adjacent downstream flame arrester insert. 
     BACKGROUND 
     The flame arrester inserts of these flame arrester arrangements are predominantly produced in a winding process using thin stainless steel strips. Here, a smooth metal strip is wound up together with a uniformly corrugated metal strip and the two thus form turns of a preferably disc-like arrangement. The passage gaps result from the corrugated metal strip resting on the two adjacent smooth metal strips, so that defined passage gaps are produced. Depending on the flammability of the gas, the passage gaps, given a predefined axial length, must not exceed a predefined cross-sectional surface area. In order to ensure an adequate flow velocity for easily flammable gases, it may therefore be necessary to wind up the flame arrester inserts with a large cross-sectional surface area, that is to say to produce them with a large winding radius. The turns are preferably arranged such that they lie on one another spirally, but also, in the form of closed circular turns, can each comprise a smooth metal strip and a corrugated metal strip. 
     It has been found that, given a predefined maximum cross section of the passage gaps, it is expedient to implement the gap length required for the cooling of the gas not with a single flame arrester insert but with a plurality of flame arrester inserts, that is to say at least two, it being advantageous to arrange an intermediate layer between the flame arrester inserts, which permits a radial distribution of the gas flow emerging from the one flame arrester insert and entering the adjacent downstream flame arrester insert. 
     If the flame arrester inserts are laid directly on one another without an intermediate layer, on the other hand, the passage gaps are not aligned with one another accurately, so that the flame arrester inserts lying on one another form resultant channels of which the effective passage gaps are reduced in size in an undefined way as compared with the passage gaps of a flame arrester insert, since the free cross-sectional surface area of the assembly of flame arrester inserts lying on one another is reduced. As a result, the pressure loss during the flow through is increased sharply. The intermediate layers provided in the flame arrester arrangement of the generic type thus serve as spacer elements, which prevent a reduction in the free cross-sectional surface area of the flame arrester inserts lying one behind another. In a conventional design, the housing of the flame arrester arrangement forms an enclosing cage having a closed shell wall. Since the gas can expand in the radial direction between the flame arrester inserts, care must be taken that the gaps produced between the edge of the flame arrester inserts and the inner wall of the enclosing cage are smaller than the gaps in the flame arrester inserts themselves. Otherwise, there would be a diversionary path around the flame arrester insert, on which the gas is not cooled in the manner provided by the respective flame arrester insert, so that a flashback through the flame arrester arrangement possibly occurs, which means that a catastrophe can be triggered if, for example, an explosion progresses into a gas storage tank which is intended to be protected by the flame arrester arrangement. 
     In particular during the production of large flame arrester inserts, which can have diameters up to 2 m, it is problematic in fabrication terms to avoid the occurrence of relatively large gaps between the flame arrester insert and the surrounding housing. Such large flame arrester inserts cannot usually be produced to be exactly round. It is therefore known to wind such a flame arrester insert directly in the enclosing cage and, at the points at which relatively large gaps form, then to assemble in smooth filter strip, in order in this way to produce reliable edge contact between the flame arrester insert and the enclosing cage. However, this has the disadvantage that the flame arrester insert is fitted so firmly in the enclosing cage that it cannot be removed in practice for cleaning and renewal purposes, in particular when large amounts of contamination or even corrosion occur/s between the filter and the enclosing cage. 
     In order to be able to remove a flame arrester insert simply for servicing purposes, a gap that is as large as possible between the flame arrester insert and the enclosing cage is expedient. However, it is necessary to prevent the flame from the gas flow from flowing around one or more flame arrester inserts via the radially outer gap and thus rendering the flame arrester useless. 
     If at most two flame arrester inserts are used, radially outer supporting rings can bear directly axially on the outside of the flame arrester inserts, so that a radially outer flow around the latter by the gas running through the flame arrester arrangement is not possible. In the case of more than two flame arrester inserts, it is known to use an enclosing cage having stepped walls, in which each flame arrester insert bears in a sealing manner on the metal of the enclosing cage. Such an enclosing cage is very expensive to produce and cannot be mass-produced, since different models and diameters are necessary, depending on the number of flame arrester elements. Furthermore, in order to be suitable for different gases, the flame arrester inserts have to be produced in different sizes. 
     SUMMARY 
     The invention is therefore based on the object of designing a flame arrester arrangement of the type mentioned at the beginning in such a way that the assembly and disassembly of the flame arrester inserts is made easier, in particular when three or more flame arrester inserts are used, and an unintended flow around the flame arrester inserts is reliably avoided. 
     In order to achieve this object, a flame arrester arrangement of the type mentioned at the beginning is characterized in that at least one separate closed seal is arranged between a flame arrester insert and the housing or between two flame arrester inserts in such a way that a flow around the flame arrester insert in a space located radially outside the passage gaps is prevented. 
     The flame arrester arrangement according to the invention can thus have an arbitrarily large space radially outside the passage gaps of the flame arrester inserts, so that simple assembly and disassembly of the flame arrester inserts is possible. 
     In the alternative, in which the closed seal is located between the housing and a flame arrester insert, the interspace between the housing and the flame arrester insert for an axial through flow can be closed by the seal. In another, preferred embodiment of the invention, it is however also possible to design the seals provided radially outside the flame arrester inserts to adjoin one another axially without any gaps, so that they are clamped in between axially clamped housing parts and thus effect radial sealing against the flow of the gas out of the intermediate layers. In this case, it is advantageous if the seals are formed by turns of a smooth metal strip wound spirally on one another, so that the seal can be fitted following the production of the flame arrester insert, preferably by the winding technique. In this case, the smooth metal strip used for the production of the seal can have the width of the metal strip of the flame arrester insert or can have a greater width (axial length with respect to the flame arrester arrangement), which corresponds to the joint axial length of flame arrester insert and intermediate layer. If the width of the metal strip for the wound seal is equal to the width of the metal strips for the production of the flame arrester insert, an intermediate ring is expediently inserted in the intermediate layer between the wound seals, so that, in the axial direction, the wound seals and the intermediate rings form a length which corresponds to the length of the flame arrester inserts with their intermediate layers. 
     In an alternative embodiment, a closed seal can be arranged between the radial edges of the flame arrester inserts, so that sealing radially towards the outside is carried out between the flame arrester inserts. In this case, the intermediate layer is preferably designed to be smaller by the radial width of the closed seal, so that the intermediate layer can be inserted between the flame arrester inserts and the closed sealing ring located between the latter. 
     An advantageous refinement of the flame arrester arrangement according to the invention is achieved with flame arrester inserts which are provided radially outside the passage gaps with a circumferential solid edge, the edges being clamped as a stack between the housing parts, which are clamped axially against one another. The sealing radially towards the outside is thus carried out by the solid edges of the flame arrester inserts resting on one another and clamped against one another. Annular seals can also be inserted between the edges, and can then make axial clamping of the edges of the flame arrester inserts unnecessary. 
     If the flame arrester inserts are provided with appropriate solid edges, the provision of a shell-like enclosing housing is rendered superfluous, so that the flame arrester inserts in this case no longer have to be surrounded by an additional lateral housing. As a result, the flame arrester inserts can easily be removed for servicing purposes after only, if appropriate, clamping screws for the axial clamping of housing parts have been loosened or removed. 
     In other embodiments, the intermediate layer can be formed, for example, by a wire mesh, which merely serves as a spacer between the flame arrester inserts. In order to make assembly easier, the intermediate layers can be joined to an associated flame arrester insert by spot welding, brazing and the like. Likewise, in order to make assembly easier, when intermediate rings are used between the radially outwardly fitted, preferably wound seals of the flame arrester inserts, it is possible to provide a corresponding joint between the intermediate layer and the associated intermediate ring, so that joint handling of the intermediate layer and intermediate ring is possible. Of course, it is also possible to join the intermediate ring to the adjacent seal of the flame arrester insert by welding, brazing and the like. 
     The present invention is preferably implemented with wound flame arrester inserts. However, it can, of course, also be implemented with all other conventional flame arrester inserts, for example with flame arrester inserts made of sintered metal, metal foams, woven wire meshes, expanded metal meshes, porous ceramics, drilled plates of metal or plastic (in particular PTFE) or the like. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The invention will be explained in more detail below by using exemplary embodiments illustrated in the drawings, in which: 
         FIG. 1  shows a partial section through a flame arrester arrangement having four flame arrester inserts and four associated radial closed seals 
         FIG. 2  shows an arrangement analogous to  FIG. 1  in which the radially closed seals are combined with intermediate sealing rings 
         FIGS. 2   a  and  2   b  show details of the fixing of the intermediate layers to the intermediate sealing rings 
         FIG. 3  shows a schematic illustration for a flame arrester arrangement having an axial seal running around the edge of the flame arrester inserts 
         FIG. 4  shows a plan view of an intermediate layer in the form of a wire mesh 
         FIG. 5  shows a schematic illustration of a flame arrester arrangement having three radially outer circumferential seals which close an axial flow path through a radially outer gap 
         FIG. 6  shows an arrangement according to  FIG. 5  having a single radial seal on the central flame arrester insert 
         FIG. 7  shows an arrangement according to  FIG. 5  having another embodiment of the radial seal 
         FIG. 8  shows an arrangement according to  FIG. 6  having another embodiment of the radial seal 
         FIG. 9  shows an arrangement, similar to  FIG. 1 , having a withdrawal device for a housing part in the form of a radially ribbed ring 
         FIG. 10  shows a schematic illustration of an arrangement of seven flame arrester inserts which have a circumferential solid edge 
         FIG. 11  shows variants of the arrangement according to  FIG. 10   
         FIG. 12  shows a welded housing cage having an arrangement having in each case one radial seal for two flame arrester inserts and a modification of the arrangement having in each case one radial seal for one flame arrester insert. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  reveals a housing  1  having two flange-like housing parts  2 ,  3 , which can be clamped axially to each other via clamping screws (not illustrated). The flange-like housing parts  2 ,  3  act on housing rings  4 , joined to them, between which four flame arrester inserts  6  each having an intermediate layer  7  are inserted axially. The housing rings  4 ,  5  have circumferential grooves  8  on their circumferential surface pointing radially outwards, into which sealing rings  9  in the form of O rings are inserted. Pushed over the housing rings  4 ,  5  is a cylindrical shell wall  10  which, with the sealing rings  9 , seals the space for the flame arrester inserts  6 . The flame arrester inserts end radially at a distance from the cylindrical shell wall  10  and, on their outer side, are provided with closed seals  11 , the axial length of which corresponds to the sum of the axial lengths of flame arrester insert with associated intermediate layer  7 . Via the housing parts  2 ,  3  and the housing rings  4 ,  5 , the clamping pressure for the axial clamping is exerted on the seals  11  resting on one another, which are thus pressed against one another over their axial lengths and therefore form a radial seal for the intermediate layers  7 . The seals  11  are preferably formed by spiral turns of a metal strip with a width equal to the axial length of the seal  11 . The wound assembly of turns for the seal  11  is chosen to be sufficiently large that the covering area F, i.e. the radial thickness of the seal  11 , is sufficiently large for the seals  11  to be able to absorb the clamping pressure. 
     It can be seen in  FIG. 1  that radially outside the seals  11  there may be a radially outer gap  12  in relation to the cylindrical shell wall, since the sealing in the radial direction is carried out reliably over the axial length of the assembly of flame arrester inserts  6  with the intermediate layers  7 . 
     In the embodiment illustrated in  FIG. 2 , the seals  11  have an axial length which corresponds to the axial length of the flame arrester inserts  6 . For the axial length of the intermediate layers  7 , intermediate sealing rings  13  are inserted between the seals  11  and ensure that the stack comprising seals  11  and intermediate sealing rings  13  has the same axial length as the flame arrester inserts  6  with the intermediate layers  7 . 
       FIG. 2   a  makes it clear that a welded joint  14  is provided between the intermediate sealing ring  13  and the intermediate layer  7 , which is formed as a wire mesh, so that the intermediate layer  7  can be handled together with the intermediate sealing ring  13 . 
     In the variant according to  FIG. 2   b , welded joints  14  are located both between the intermediate layer  7  and the intermediate sealing ring  13  and between the seal  11  and the intermediate sealing ring  13 , so that the flame arrester insert  6  with the intermediate layer  7  joined to it by welded or brazed spots, the seal  11  and the intermediate sealing ring  13  form a component that can be handled as a single unit. 
     In the variant according to  FIG. 3 , two flame arrester inserts  6  together with an intermediate layer  7 , which is indicated schematically, are clamped in between the housing rings  4 ,  5 , the intermediate layer  7  having a radial extent which is somewhat smaller than the radial extent of the flame arrester inserts  6 . In the remaining radial edge region of the flame arrester inserts there is a sealing ring  15  as a flat metallic seal. By means of the pressure exerted by the housing rings  4 ,  5 , the flame arrester inserts  6  and the sealing ring  15  are pressed against one another in a sealing manner, so that no gas can emerge radially outwards from the intermediate layer  7  into the radial gap  12 , which is also provided here. 
       FIG. 4  shows in an elevation the design of the intermediate layer  7 , which in this case, in the form of a wire mesh, is joined integrally to the sealing ring  15 , for example by welding. 
     In the embodiment illustrated in  FIG. 5 , three flame arrester inserts  6  having intermediate layers  7  located between them are arranged, and clamped axially, between the housing rings  4 ,  5 . The cylindrical shell wall  10  here has three circumferential grooves  16  on its inside, into which there are inserted sealing rings  17 , which close the radially outer gap  12  in the axial direction for a flow through. Accordingly, although gas from the intermediate layer can enter the radially outer gap, it cannot flow externally around any of the flame arrester inserts  6 , since the axial passage is blocked by the sealing rings  17 . 
       FIG. 6  shows a similar arrangement, in which only the central flame arrester insert  6  is sealed radially to the outside by a sealing ring  17 . This is sufficient if the housing rings  4 ,  5  rest in a sealing manner on the radial edges of the outer flame arrester inserts  6 , so that flow around the outer flame arrester inserts  6  is already impossible as a result of the clamping of the outer flame arrester inserts  6 . The sealing ring  17  therefore serves to prevent the flow around the central flame arrester insert  6 . 
       FIG. 7  shows an arrangement similar to  FIG. 5 , in which the sealing rings  17 ′ are implemented not as flat sealing rings but as sealing rings having a circular cross section in the manner of an O ring. A corresponding modification to the embodiment according to  FIG. 6  it can be found in  FIG. 8 . In some cases, it will be possible to form the sealing rings  17 ,  17 ′ from thermally stable plastic or elastomer. However, preference is given to the formation of the sealing rings  17 ,  17 ′ from a soft metal, for example soft copper. 
     The embodiment of a flame arrester arrangement illustrated in  FIG. 9  provides for a threaded bolt  18  to be screwed into the housing ring  5 , the bolt having its blunt end supported on one end of the cylindrical shell wall  10 . The housing ring  5  preferably has a plurality of such threaded bolts  16 , which make disassembly of the flame arrester arrangement easier. This is because, by virtue of the threaded bolt  18  being screwed in, the housing ring  5  can be drawn off the cylindrical shell wall  10  by screwing, by which means the access to the arrangement comprising the flame arrester inserts  6 , the intermediate layers  7  and the seals  11  is freed. Since the outer radial gap  12  in relation to the cylindrical shell wall is provided, the flame arrester inserts  6  with the intermediate layers  7  and the seals  11  can be removed singly or jointly in a straightforward manner and cleaned or replaced for servicing purposes. 
     The flame arrester inserts  6  illustrated in the exemplary embodiments up to this point comprise spiral or concentric turns resting on one another, which each comprise a smooth metal strip and a corrugated metal strip. The corrugated metal strip here is preferably implemented with corrugations which are inclined with respect to the longitudinal direction of the strip. The oppositely directed running hatchings in the drawings here express the fact that, in order to even out the flow through the flame arrester inserts  6 , flame arrester inserts wound in different directions adjoin one another, so that the gas flows through the assembly of flame arrester inserts in the manner of a zigzag course, since the passage gaps caused by the corrugated strip run in different inclined directions. 
     In the exemplary embodiment illustrated in  FIG. 10 , the flame arrester inserts  6 ′ are provided with a circumferential solid edge  19  which, on one side, has a circumferential open groove to accommodate a seal  20 . In this embodiment, the housing rings  4 ,  5  are provided with attachments  21  which have openings for a clamping screw  22  to be led through. The clamping bolt  22  rests on one of the attachments  21  with a screw head  23  and on the other of the attachments  21  with a nut  24  surrounding the screw, so that, by means of a plurality of such clamping screws  22  distributed over the circumference, the housing rings  4 ,  5  are pulled axially towards each other and clamp in between them the stack formed from the flame arrester inserts  6 ′. 
     In the embodiment according to  FIG. 10 , each of the flame arrester inserts  6 ′ is stabilized by a bolt bored radially through them. Such stabilization of flame arrester inserts  6 ′ is known in principle for large wound flame arrester inserts  6 ′. 
       FIG. 11  shows two variants of the embodiment of the clamping screw  22  in conjunction with the housing rings  4 ,  5  in order to carry out the axial clamping. 
     In the variant according to  FIG. 11   b , the clamping screw extends through passage holes in the solid edges  19  of the flame arrester inserts  6 ′, which ensures additional alignment of the flame arrester inserts  6 ′. 
     In the embodiments of  FIG. 12 , eight flame arrester inserts  6  are provided, which are arranged between housing rings  4 ,  5 . In this embodiment, the cylindrical shell wall  10  is joined to the housing  1  by weld seams  26 . 
     The seals  11 ′ according to  FIG. 12   a  are designed with an axial length which corresponds to the sum of the axial lengths of two flame arrester inserts  6  and two intermediate layers  7 . For the eight flame arrester inserts  6  with the eight intermediate layers  7 , four closed seals  11 ′ are thus used, and these are clamped in between the housing rings  4 ,  5 . In order to join the seals  11 ′ to the flame arrester inserts  6 , radial bolt sections  25 ′ are introduced, this preferably being done by spark erosion, while maintaining the defined passage gaps of the flame arrester inserts  6 . As distinct from the bolts  25  according to  FIG. 10 , the bolt sections  25 ′ extend only over a radial subregion, while the bolts  25  extend over the entire diameter of the flame arrester insert  6 ′. 
       FIG. 12   b  makes it clear that the stabilization with the bolt sections  25 ′ is of course also possible when, as in  FIG. 1 , the seals  11  have the axial length of only one flame arrester insert  6  with the associated intermediate layer  7 . 
     From the descriptions of the exemplary embodiments, it can readily be seen that, within the context of the claimed invention, further different designs are possible. For instance, it is also possible to use cylindrical shell walls  10  or housing rings  4 ,  5  having stepped wall regions, which permit a stepped arrangement of flame arrester inserts  6  of different sizes. However, preference is given to the use of flame arrester inserts  6  of equal size, in order to avoid the disadvantages of increased outlay for the fabrication of the housing and the clamping of the stack of flame arrester inserts  6 .