Patent Publication Number: US-2007095746-A1

Title: Filter element seal structure and mounting method

Description:
BACKGROUND ART  
      1. Field of the Invention  
      The invention relates to filter vessels used to filter gas and liquid streams and to filter elements for such vessels, and, more specifically, to an improved seal structure and method for mounting the filter elements within the interior of the associated filter vessel.  
      2. Description of Related Art  
      Gas filter elements for filtering dry gas streams as well as for separating solids and liquids from contaminated gas streams are well known, as are gas filter elements for coalescing entrained liquids from a gas stream. These general types of gas filter elements may be installed in single stage or multi-stage vessels, which are in turn installed in a gas pipeline, to perform the required filtering functions. For example, Perry Equipment Corporation of Mineral Wells, Tex., offers the “Series 85, 88 and 90” Gas Filter and Filter/Separator Units.” The “Series 85 Filter/Separator” is a two stage unit. The first stage employs PEACHY filter-coalescing filter elements, also commercially available from Perry Equipment Company. These elements remove the solids contamination and coalesce any entrained liquid droplets. The coalesced liquid is then removed in the second stage high efficiency vane mist eliminator and collected in the liquid sump to be drained. The “Series 90 Filter/Separator” is designed for filtering dry gas or air streams. These units are useful in removing desiccant fines, pipe scale and other solid contaminants on the order of one micron and larger. They employ single stage filtration and are capable of utilizing a number of different filter element styles.  
      In the area of liquid filtration, the PECO® “Series 57” and “PEACH® TRITON LIQUIPUR® Series 58” liquid filtration units meet industrial ASME code for filtering liquid flows ranging from about 1 GPM to 3900 GPM or upwards. They are designed to use a multitude of string/pleated and PEACH® type filter elements for almost any liquid filtering application.  
      In the patent literature, U.S. Pat. No. 5,919,284, issued Jul. 6, 1999, and U.S. Pat. No. 6,168,647, issued Jan. 2, 2001, both to Perry, Jr., and assigned to the assignee of the present invention, disclose multi-stage vessels using individual separator/coalescer filter elements to separate solids, filter liquids, and coalesce liquids. The foregoing multi-stage vessels, as well as a multitude of other similar filtration vessels used in industry utilize solid or hollow core tubular elements, typically formed at least partially a porous filtration media. For example, the PEACHY porous filtration elements useful in the above type of filtration vessels are of the same general type as those that are described in U.S. Pat. No. 5,827,430, issued Oct. 27, 1998 to Perry, Jr., et al., and assigned to the assignee of the present invention.  
      Despite advances made in filter/separator vessel technology, a need continues to exist for an improved filter element seal structure and mounting method for mounting filter elements in vessels of the above discussed type.  
      A need exists for an improved seal structure for filter elements of the above type which is simple in design and relatively economical to manufacture and yet which presents a reliable and effective sealing action in a variety of different sealing applications.  
     BRIEF SUMMARY OF THE INVENTION  
      An improved seal structure is shown for a tubular filter element used to filter a fluid stream in an industrial process where the fluid stream passes through a filter vessel having rigid risers for mounting the filter elements. Each of the filter elements comprises a tubular body with generally cylindrical sidewalls formed of a porous material, an interior, a first end opening and an oppositely arranged second end opening. The improved seal structure of the invention is comprised of a resilient body having conically shaped sidewalls which are tapered with respect to a central axis of the resilient body and which extend between a first lip region and a second lip region of the body. A selected one of the first and second lip regions of the resilient body is adapted to seal on a selected end opening of the filter element. The conically shaped sidewalls of the filter element form a dynamic seal with the riser element of the filter vessel on which the filter element is mounted and with the filter element body when subjected to a pressure differential between an upstream portion of the process and a downstream portion of the process being filtered.  
      A selected one of the first and second lip regions of the body of the seal structure terminates in a flared collar region also formed of a resilient material and with opposing exposed sides. One of the opposing exposed sides of the collar region seals against an end opening of the filter element and the other opposing side seals against the vessel riser. In one version of the seal structure, the collar region is a planar member of generally uniform thickness. The vessel riser may terminate in a flat planar surface or may have a circumferential thimble region which forms a relatively narrow edge at an outer extent thereof, the selected opposing exposed side of the flared collar region of the seal structure forming a compression seal with the edge of the circumferential thimble region of the riser as the edge bites into the collar region of the seal structure in use. The seal formed between the thimble region of the riser and the flared collar region of the seal structure is in the nature of a flat gasket compressive seal, while the seal formed between the conically shaped sidewalls of the seal structure and the riser interior is an annular seal along the length of the conically shaped sidewalls which is energized by the differential pressure created between existing upstream and downstream process conditions.  
      In another version of the seal structure, the collar region forms a circumferential recess on one side thereof to engage one end of the filter element sidewalls. The conically shaped tapered sidewalls of the seal structure form a relatively larger outer diameter flared bottom for the seal structure which extends upwardly toward a relatively narrower top region of the seal structure. The seal structure is received within the interior of the generally tubular body of the filter element with the flared bottom forming a seal with a selected end of the filter element. The vessel riser extends upwardly within the interior of the filter element interior and within an interior region of the seal structure where it contacts and seals against the seal structure in use. The seal structure extends for a predetermined length between the opposing outer lips thereof, whereby the length of the seal structure occupies a given distance within the interior of the filter element and as a result liquid flow through the element from the inside to the outside thereof is directed higher up the interior of the filter element than would occur without the sealing element being present within the interior of the filter element.  
      A filter element and improved seal structure are also shown for an apparatus that is used for filtering a gas or liquid stream such as a natural gas stream or a natural gas processing liquid stream. The apparatus includes a closed vessel having a length and an initially open interior. A partition is disposed within the vessel interior. The partition has a planar inner and planar outer side, respectively, dividing the vessel interior into a first chamber and a second chamber. At least one opening is provided in the partition over which is provided a rigid riser for mounting a filter element. An inlet port is provided in fluid communication with the first chamber. An outlet port also provides fluid communication from the second chamber. At least one tubular filter element is disposed within the vessel and mounted upon the rigid riser. The filter element comprises a tubular body with generally cylindrical sidewalls formed of a porous material, an interior, a first end opening and an oppositely arranged second end opening as previously described. The above described seal structure with its resilient body and conically shaped sidewalls are used to form a secure seal with the vessel riser. The conically shaped sidewalls of the filter element form a dynamic seal with the riser element of the filter vessel on which the filter element is mounted and with the filter element body when subjected to a pressure differential between an upstream portion of the process and a downstream portion of the process being filtered.  
      The above as well as additional objects, features, and advantages of the invention will become apparent in the following detailed description.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a side elevational view, partly broken away, of a gas filter vessel having several filter elements with the seal structure of the invention installed therein.  
       FIG. 2  is a side elevational view, similar to  FIG. 1 , but of a liquid filter vessel having several filter elements with the seal structure of the invention installed therein.  
       FIG. 3  is an exploded view of the improved seal structure of the invention showing the assembly thereof onto a porous filter element.  
       FIG. 4  is an assembled view of the seal structure and filter element of  FIG. 3  with portions of the filter element broken away showing the interior thereof, the seal structure and the riser.  
       FIG. 5  is a view similar to  FIG. 3  of another version of the seal structure of the invention for use in a liquid filtration installation.  
       FIG. 6  is an assembly view of the seal structure and filter element of  FIG. 5  in place on the riser of a liquid filtration vessel.  
       FIGS. 7 and 7 A are simplified, schematic views showing the seal structure and filter element of  FIG. 5  in place on the riser of a liquid filtration vessel with the filter element being subjected to a differential pressure loading.  
       FIG. 8  is a schematic view, similar to  FIG. 7 , but showing the seal structure of the invention in place on a gas filter element and showing the element installed on the riser of a gas filtration vessel.  
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      Turning to  FIG. 1  there as shown a filter vessel of the invention designated generally as  13  of the type which is used to filter a fluid stream in an industrial process. By the term “fluid” in this discussion is meant either “liquid” and/or “gas.” The particular filter vessel  13  which is shown in  FIG. 1  is a dry-gas filter. Filter vessels of the general type illustrated might be utilized, for example, in oil and gas separation processes and similar industrial environments. While  FIG. 1  illustrates one embodiment of a natural gas filtration vessel, it will be understood by those skilled in the art that the filter elements and seal structures covered by the present invention can be applied to a variety of such vessels used in the industry. For example, the filter elements of the invention might be employed in vessels which are used for simultaneously filtering solids, separating liquids, pre-coalescing liquids, and coalescing liquids out of a gas stream. The filter elements might also be utilized in vessels used for coalescing and separating two liquids and for filtering solids out of liquids. Also, while the vessel shown in  FIG. 1  illustrates three principally visible filter elements mounted within the vessel above the vessel partition, it will be understood that some vessel designs will employ a variable number of elements, i.e., either more or less elements, depending upon the end application for the filter vessel.  
      Referring again to  FIG. 1 , it should be understood that although the vessel  13  is shown in a generally vertical configuration, that other vessels of the same general type may also be configured in a generally horizontal embodiment. The vessel  13  has a generally tubular shell  15  which forms a closed vessel having a length and an initially open interior  17 . The shell  15  is enclosed at an outlet end  19  by means of a closure member  21  which, in this case, is a fluid tight flange. The shell  15  is permanently enclosed at an inlet end  23  by a welded base  25 . The flanged closure  21  provides a fluid tight seal with respect to the inlet end  19  as well as access to the filter elements. In the embodiment of  FIG. 1 , three filter elements  27  are supported within the vessel open interior  17  by means of a vessel partition  29  and support elements or “risers”  31 . The vessel  13  is preferably manufactured of steel materials which conform to published pressure-vessel standards, such as ASME Boiler and Pressure Vessel Code, Section VIII, Division 1.  
      The partition  29  which divides the vessel interior into the first and second filtration chambers has a planar inner and planar outer opposing sides  33 , 35 , respectfully. An opening is provided in the partition  29  for each filter element to be mounted thereon. A vertically extending riser  31  is mounted over each partition opening, as by welding, for receiving an end of a filter element. An inlet port  37  is in fluid communication with the first chamber and an outlet port  39  is in communication with the second chamber. The tubular filter elements  27  are disposed within the vessel to sealingly extend within the second chamber and to communicate through the associated riser and its associated opening in the partition  29  into the first chamber of the vessel. Gas flow is through the inlet port  37 , through the first chamber, through the riser interiors, into a hollow interior of the filter elements  27  and out the sidewalls thereof, and through the second chamber to the outlet  39 . The direction of the gas flow is indicated by the arrows in  FIG. 1 .  
      Each of the filter elements  27  ( FIG. 3 ) comprises a tubular body with generally cylindrical sidewalls  41  formed of a porous material. The filter elements have an interior  43 , a first end opening  45 , and an oppositely arranged second end opening  47 . The end opening  47  is surrounded by an end cap  49 , respectively, which may be formed, for example, of metal or rigid plastic.  
      The bodies, or tubular filter walls of the filter elements of the invention can be formed of any material conventionally used in the art. The construction of the filter elements will vary depending upon the particular end application of the filtration vessel. By way of example, the filter elements can be constructed in the manner and of the materials disclosed in U.S. Pat. No. 5,827,430, issued Oct. 27, 1998 to Perry, Jr., et al. Such filter elements are sold commercially under the PEACH® trademark by Perry Equipment Corporation of Mineral Wells, Tex. In a typical application, the filter elements consist of four multi-overlapped layers of non-woven fabric strips of varying composition. The first layer is composed of equal amounts by volume of fibers purchased commercially from Hoechst Celanese under the fiber designations “252,” “271,” and “224,” and has a basis weight of 0.576 ounces per square foot, is ten inches wide, and is overlapped upon itself five times. The denier of fiber “252” is 3 and its length is 1.500 inches. The denier of fiber “271” is 15 and its length is 3.000 inches. The denier of fiber “224” is 6 and its length is 2.000 inches.  
      The second layer is composed of equal amounts by volume of “252,” “271,” and “224,” has a basis weight of 0.576 ounces per square foot, is eight inches wide, and is overlapped upon itself four times. The third layer is composed of equal amounts by volume of “252,” “271,” and “224,” has a basis weight of 0.576 ounces per square foot, is eight inches wide, and is overlapped upon itself four times. The fourth layer is composed of equal amounts by volume of “252” and a fiber sold under the name “Tairilin,” has a basis weight of 0.576 ounces per square foot, is six inches wide, and is overlapped upon itself three times. Fiber “252” being of the core and shell type serves as the binder fiber in each of the aforementioned blends.  
      The above example of particular types of material, fabric denier, number of wrapping layers, etc., is intended to be illustrative only of one type of filter material useful in the practice of the present invention. The seal structure of the elements of the invention could be used with a variety of other conventional filter materials, as well.  
      A seal structure ( 53  in  FIG. 3 ) is used to mount the filter element  27  on the riser element  31  (see  FIG. 4 ). As can be seen in  FIG. 3  and  FIG. 4 , the seal structure  53  comprises a resilient body having conically shaped sidewalls  55  which are tapered with respect to a central axis  57  of the resilient body and which extend between a first lip region  59  and a second lip region  61  of the body. By “resilient body” is meant that the seal structure  53  is comprised of a suitable elastomer, such as a commercially available synthetic or natural rubber, urethane, etc. The resilient body  53  can conveniently be, for example, injection molded rubber or plastic.  
      At least a selected one of the first and second lip regions  59 ,  61  of the resilient body  53  is adapted to seal on a selected end opening  45 ,  47  of the filter element  27 . In the embodiment of the seal structure  53  shown in  FIG. 3 , the first lip region  59  of the body terminates in a flared collar region  63  which is also formed of a resilient material. The collar region  63  has opposing exposed sides  65 ,  67 . As shown in  FIG. 5 , one of the opposing sides  65  of the collar region  63  forms a circumferential recess  66  about the cylindrica sidewalls  55  and receives and engages one end of the filter element  27 . The seal structure thus actually replaces one end cap of the filter element and can be taken on or off by merely sliding the filter end out of the circumferential recess  66 . As will be explained in greater detail, the opposing side  65  of the seal structure  53  forms a compression seal with the filter element  27  due to the forces exerted thereon during the operation of the vessel.  
      Turning briefly now to  FIG. 2  of the drawings, there is shown a typical liquid filter vessel  75  of the invention. The liquid vessel  75  is again a tubular shell  77  having a flanged cover  79  and closed bottom  81 . A plurality of filter elements  83  are mounted on a partition  85  which separates the vessel interior into a first and second chambers. An inlet opening  87  communicates with the first chamber while an outlet  89  communicates with the second chamber. The liquid vessel  75  illustrated in  FIG. 2  is similar structurally in most respects to the gas filter vessel illustrated in  FIG. 1  except that it operates in a “reverse flow” manner where the material to be filtered or coalesced moves from the outside of the filter elements  83  toward the inside of the elements. This type reverse flow is illustrated schematically by the arrows in  FIG. 7  of the drawings.  
       FIGS. 5 and 6  illustrate a filter element  83  formed of a porous material, having external sidewalls  92 , an interior  93 , and an end cap  95 . In this embodiment of the invention, the seal structure  99  is again a resilient body having conically shaped tapered sidewalls which form a relatively large outer diameter flared top region for the seal structure which extends downwardly toward a relatively narrower bottom region of the seal structure. The seal structure  99  again has first and second lip regions  105 ,  107 . The lip region  105  terminates in a flared collar region  103  comparable to the region  63  of the seal illustrated in  FIG. 3 . In this case, however, the collar region  103  is a planar member of generally uniform thickness. There is no annular recess or groove similar to the recess of the seal structure  53  shown in  FIG. 3 .  
      As shown in  FIG. 5 , the collar region  103  forms a circumferential shelf region  109  upon which the filter element end  110  is received. The planar collar region  103  of the seal structure thus forms a seal with the selected end  110  of the filter element with the filter element resting upon the upper planar surface thereof. The opposite side of the collar region forms a compression type seal with the upper extent  32  of the riser  30 . In this case, the upper extent  32  of the riser  30  forms a planar upper surface for supporting the seal structure.  
       FIG. 7  shows another version of the vertical riser  30  and partition  85  in greater detail. In addition to the upwardly extending cylindrical sidewalls, the riser  30  has a flared upper extent  69  which terminates in an upwardly extending thimble region  71 . The thimble region  71  forms a relatively narrow “edge” at an outer extent of the riser. The lower surface  104  of the flared collar region of the seal structure  99  forms a compression seal with the edge of the circumferential thimble region  71  of the riser  30  as the edge bites into the collar region  103  of the seal structure in use.  
      As best seen  FIG. 7A , the sealing effect achieved between the thimble region  71  of the riser  30  and the flared collar region  103  of the seal structure can be roughly analogized to a flat gasket type sealing arrangement. In other words, the knife edge of the thimble region  71  seals the circumferential region of contact with the exposed side of the collar region  103 . As will be appreciated from  FIG. 7A , the filter element body also expands outwardly (shown in exaggerated fashion) to form a seal with the riser interior sidewalls  106  when subjected to a pressure differential between an upstream portion of the process and a downstream portion of the process being filtered. The direction flow of the gas being filtered is from the outside to the interior  93  of the filter and downwardly out the end opening  110 , as illustrated in  FIG. 7A . This creates a high pressure region above the partition and within the filter element and a relatively lower pressure region below the partition in the region of the seal structure. The seal which is formed between the conically shaped sidewalls of the seal structure  99  and the riser interior  106  is thus an “annular” seal along the length of the conically shaped sidewalls which is energized by the differential pressure created between existing upstream and downstream process conditions. This sealing effect can be roughly analogized to an o-ring sliding seal effect.  
       FIG. 8  is a schematic view similar to  FIG. 7  but illustrates the cylindrical sidewalls of the riser which extend vertically upward from the planar partition  29  in the gas filtration vessel of  FIG. 1 . The cylindrical sidewalls  111  of the riser  31  extend upwardly within the interior of the filter element interior  43  and also within an interior region of the seal structure where it contacts and seals against the seal structure in use. The seal structure  53  extends for a predetermined length “l” between the opposing outer lips  59 ,  61  thereof, whereby the length of the seal structure occupies a given distance within the interior of the filter element  27 . As a result, liquid flow through the element from the inside to the outside thereof, (illustrated by arrows in  FIG. 8 ) is directed higher up the interior of the filter element  27  than would occur without the sealing structure  53  being present within the interior of the filter element. The seal structure  53  illustrated in  FIG. 8  thus has multiple areas where the seal will contact the filter element support (riser) to maintain a positive sealing surface. These multiple contact areas provide advantages from standard sealing arrangement that feature only gasket or o-ring type seal structures.  
      An invention has been provided with several advantages. The seal structure of the invention is simple in design and economical to manufacture. The seal structure of the invention has multiple areas where the seal will contact the filter element support structure to maintain positive sealing surfaces. The result is more effective sealing area than was available from the prior art arrangements featuring gasket and o-ring type seals. The seal structure of the invention can be used in a wide variety of process applications involving both liquid and gas filtration. The improved seal structure provides an annular seal which utilizes the differential pressure between the upstream and downstream sides of the filter element to aid in effecting an improved seal.  
      While the invention is shown in only one of its forms, it is not just limited but is susceptible to various changes and modifications without departing from the spirit thereof.