Abstract:
A non-reclosing, over-pressure relief device comprising a unitary pressure support having a central dome including a convex surface and an opposed concave surface, a flange surrounding the dome, the flange including a transition portion joining the flange to the dome and an elliptically shaped blow-out portion included in the dome formed by at least one cut-through line of an elliptical shape. In a preferred embodiment, the blow-out portion has at least one connecting member connectably bridging the cut-through line to connect the blow-out portion to an adjacent portion of the dome to thereby retain the blow-out portion, and at least one pressure seal in juxtaposition with the device.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to an overpressure relief device, and more particularly to a non-reclosing, over-pressure relief device or reverse rupture acting style disc having an elliptical cut-through line. 
       BACKGROUND OF THE INVENTION 
       [0002]    Rupture discs have been known in this art for many years. Normally, rupture discs are manufactured to have a rupturable membrane to provide a safety mechanism to relieve excessive pressure within a pressurized system or vessel. The rupture disc and or rupture disc assemblies are adapted to be attached to a system or vessel so as to prevent the flow of a liquid or a gas through such a device until the rupture disc, having a known weakness, ruptures through excessive or over-pressure loads. Generally speaking, rupture discs are pre-weakened by scoring, cutting, or, via other conventional methods, the pressure supporting membrane to enable the disc to fail at a predetermined pressure. 
       SUMMARY OF THE INVENTION 
       [0003]    With the present invention, it has been found that by providing an composite assembly including a dome shaped pressure support having a 345° generally elliptical, substantially cut-through pattern or line, a formed metal pressure support ring fitted to the concave side of the pressure support, and a pressure seal fitted to the convex side of the pressure support, that disadvantages of using solid metal disks with conventional pre-weakening methods are overcome as the novel assembly of the present invention permits a wider range of application for varying liquid and gas usages, and varying burst pressures. 
         [0004]    Another aspect of the present invention to provide a domed pressure support in combination with a pressure support ring, the pressure support having a substantially cut-through pattern or line having a generally elliptical configuration. At least one or more interruptions in the substantially cut-through line may be provided to stabilize the dome portion of the support and control the tensile strength when desired. 
         [0005]    A seal is provided on the convex side of the pressure support to prevent leakage of fluids or the like through the pressure support from the convex side. In addition an optional seal can be placed on the concave side of the pressure support to prevent leakage of fluids or the like through the support from the concave side. 
         [0006]    In accordance with another aspect of the present invention, there is provided a non-reclosing, over-pressure relief device comprising a unitary pressure support having a central dome including a convex surface and an opposed concave surface, a flange surrounding the dome, the flange including a transition portion joining the flange to the dome, an elliptically shaped blow-out portion included in the dome formed by at least one cut-through line of an elliptical shape, and at least one pressure seal in juxtaposition with said device. 
         [0007]    In a further aspect, there is provided a reverse acting style rupture disc and holder assembly incorporating the relief device together with a disc holding assembly including at least one assembly ring in juxtaposition with the device. Desirably, the above aspects further include a blow-out portion having at least one connecting member connectably bridging the cut-through line to connect the blow-out portion to an adjacent portion of the dome to thereby retain the blow-out portion in a desired position. 
         [0008]    In another aspect of the present invention, there is provided in a reverse acting style rupture disc having an annual flat flange and a concave convex disc dome, the improvement wherein the disc comprises a dome portion having a generally elliptical cut-through score line extending between the concave and convex surfaces to form an elliptically shaped blow-out portion of the dome, the blow-out portion being connected by at least one connecting member connecting the blow-out portion to a non-blow-out portion of the dome. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a side view of a first embodiment of a disc assembly according to the present invention; 
           [0010]      FIG. 2  is a top down view of a disc assembly illustrating an alternative embodiment of an elliptical score line and projection members; 
           [0011]      FIG. 3  is an elevational exploded view of the components as illustrated in  FIG. 2 ; 
           [0012]      FIG. 4  is a side view of the components as illustrated in  FIG. 2 ; and 
           [0013]      FIG. 5  is an elevational view of the reverse bursting disc of  FIG. 2  in a bursting member assembly. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0014]    In accordance with one aspect of the present invention, there is provided a reverse composite disc adapted to have an optimum relieving capacity, durability, low burst pressure and non-fragmentation in a reverse buckling design. In a preferred alternative embodiment, the disc (generally identified by reference numeral  10 ) is of a composite reverse acting design having at least three primary components, including a domed shaped pressure support  30 , an outer rim portion or seat  32 , a shoulder portion or transition radius  34 , a dome  36  and a 345° (preferably) elliptical slot  80  or cut-through line or portion in the dome  36 , defining a hinge member  38 . A second component is a formed metal pressure support ring (generally identified as reference numeral  40 ) adapted to be fitted to the concave side of the dome shaped pressure support  30 . The pressure support ring  40  includes a 360° elliptical cut out (generally identified as reference numeral  42 ), having a slightly smaller inside diameter than the elliptical slot  80  in the pressure support  30 , which creates a ledge  44  for an edge of the pressure support to rest upon when assembled. A third component is pressure seal  50 , which is adapted to be form fitted to the convex side of the pressure support  30 . The various components and their preferred materials and/or manufacture are described in greater detail hereinbelow. 
         [0015]    In use, the disc assembly (components  30 ,  40  and  50 ) is installed with the normal system pressure (direction of flow generally identified by reference numeral  20 ) applied to the convex side of the seal  50 , which places the assembly into compression. As the system pressure increases, the dome  34  of the pressure support  30  becomes unstable, and eventually buckles due to the increased pressure, which allows the pressure support  30  to fold back through the support ring  40  and out of the way exposing the seal  50  to the full system pressure which overcomes the tensile strength of the seal material and subsequently bursts. 
         [0016]    The elliptical cut  80  in the pressure support, which extends completely through the material (partially scored or otherwise partially cut) provides for a non-uniform collapse of the pressure support dome. The slot or cut-through  80  provides advantages over other design discs, discussed in greater detail below. A preferred range for the elliptical cut is between 270 and 355°, desirably 300 and 345°, and most preferably is 345°. 
         [0017]    The elliptical cut  80  in the pressure support may include at least one or more interruptions or tabs to provide additional strength or support to the dome portion when desired. This additional feature is discussed in greater detail below. 
         [0018]    As illustrated in Drawing  FIGS. 2 through 5 , reference numeral  100  generally designates a non-reclosing over-pressure relief device according to a preferred embodiment of the present invention. The assembly  100  includes a lower assembly ring  120 , a lower pressure seal  130 , a dome shaped pressure support  140 , a support ring  150 , an upper pressure seal  160 , and a top assembly ring  170 . 
         [0019]    When viewed from a pressure side to a non-pressure side of the rupture disc assembly  100 , (i.e. from the convex to the concave side generally indicated by reference numeral  110 ), there is provided a lower assembly ring  120 , which is positioned against the lower surface of a lower pressure seal  130 . The lower assembly ring  120  may be constructed of any suitable material known in the art. The lower pressure seal  130 , configured to be form fitted to the convex side of the support  140 , is adapted to provide a secure seal against leakage between a pressure support  140  and the lower assembly ring  130 , and ultimately to prevent leakage about or through the pressure support  140  when the complete system is in an assembled condition and placed within a pressured system. The lower and upper pressure seals  130  and  160 , respectively, may be constructed from a conventional material, such as plastic, Teflon, metal, or other flexible material known in the art. 
         [0020]    With reference to the dome shaped pressure support generally identified by reference numeral  140 , the pressure support  140  is referred to as a reverse rupture acting style disc. The pressure support  140  may be constructed from any conventional material such as steel, steel alloys or other metals, and is adapted to open along a predetermined cut line, discussed in greater detail below. The pressure support  140 , as illustrated in drawing  FIG. 5 , includes an outer rim portion or seat  142 , a shoulder portion or transition radius  144 , a dome portion  146  and a hinge or non-cut portion  148 . 
         [0021]    As illustrated in the drawing Figures, support  140  of the present invention includes an elliptical cut-through pattern or line  180 , as illustrated in  FIGS. 2 and 5 . The cut-through line  180  is preferably a 345° elliptical slot in the dome portion  146  of the disc, although other suitable radii may be used as desired. The cut-through portion may preferably have a length of up to about 345°, preferably leaving a hinge or non-cut-through portion of about 15°. As will be understood by those skilled in the art, other radii may be used as desired in accordance with the teachings of the present invention. 
         [0022]    In a preferred embodiment, the elliptical slot or cut-through pattern may include at least one or more non-cut out portions or interruptions, such as tabs  190 , whereby tabs  190  or similar members are located in the elliptical slot or cut line. As illustrated, and for exemplary purposes only, the tabs  190  are located at a 10 and 2 o&#39;clock orientation in relation to the hinge member  148 . The tabs  190  are adapted to hold or maintain the dome shaped pressure support or disc  140  in the closed position on the support ring  150 . Other orientations and number of tabs may be incorporated as desired, depending upon the strength or support desired in the pressure support. 
         [0023]    The pressure support ring  150  includes an annular circumferential outer ring  152 , and an annular flat seat or surface  154  which is adapted to receive the pressure support member  140 . The support ring  150  further includes a circumferential raised inner rim or member  156 , which is positioned inwardly of the outer ring  152 . When in a fully assembled condition, the raised rim  156  is adapted to secure the pressure support  140  against the support ring  150 . The support ring  150  includes a 360° opening pattern or elliptical cut out  158 , having a slightly smaller inside diameter than that of the elliptical slot  180  of the pressure support dome which creates a ledge or support member for an edge of the dome portion of the pressure support  140  to rest upon. The inside diameter of the pressure support ring can be manufactured with razor sharp teeth or other similar means to assist in cutting the pressure seal open after the pressure support dome collapses and the pressure seal is pushed through the pressure support ring by the system pressure. 
         [0024]    As illustrated in  FIGS. 2 ,  3  and  4 , the support ring  150  extends into the concave portion of the dome portion  146  of the pressure support  140 . The opening pattern  158  is of a general elliptical shape, extending continuously on the inner peripheral portion of the supporting ring  150  and which depends from a horizontal plane of the supporting ring  150  towards and within the dome portion of the pressure support  140 . 
         [0025]    As best seen in drawing  FIG. 3 , an upper pressure seal  160  is provided between the support ring  160  and the upper support ring  170 . As noted hereinabove, the upper pressure seal is adapted to provide a secure seal against backflow when exposed to vacuum or back pressure. 
         [0026]    The top assembly ring  170  is provided to secure the safety device together when an assembled conditioned securing the various other components between the top assembly ring and the bottom assembly ring. 
         [0027]    In use, the disc assembly  100  (including a holder, such as steel rings clamped on the seat, not shown) is attached to a pressure system (not shown) with the lower ring  120  placed towards the pressure flow, followed in sequential order by the lower pressure seal  130 , the pressure support  140 , the support ring  150 , the upper pressure seal  160 , and top assembly ring  170 , such that any pressure must first contact the pressure seal  130 . The disc assembly  100  is installed with the normal system pressure applied to the convex side of the dome, placing assembly into compression. As the system pressure increases, the dome of the pressure support disc becomes unstable and eventually buckles to the increased pressure, allowing the pressure support to fold back through the support ring and exposes the seal to the full system pressure which overcomes tensile strength of the sealing material and bursts. 
         [0028]    More specifically, when a pressure in the system is greater than the designated rupture pressure of the rupture disc  140 , the disc pressure load is exceeded and upon rupture, the pressure is relieved through the assembly  100  whereby the dome portion  146  of the pressure support  140  upon failure, reverses or collapses into itself about the elliptical cut  180  and “hinges” upon the non-cut portion of the support  140  over the support ring  150 . Upon failure, the short side of the dome  146  collapses first, followed by the remainder of the pressure support  140 , as a result of the non-uniform elliptical cut-through or line in the dome  146 . The seals  130  and  150 , being of a flexible material and having a lower pressure failure, each reverses upon itself similar to the dome portion  146  and bursts. In use, when a pressure load exceeds the predetermined pressure load of the rupture disc  140 , the dome is adapted to open along the elliptical cut-through line  180  and reverse fold back or hinge along the rim about the portion of the support ring  160 . 
         [0029]    Numerous advantages are associated with the novel elliptical cut-through or elliptical slit disc, such as the compression loaded structure allows for operation at pressure of up to 90% of its marked burst pressure. Further, the elliptical slot (12 or 80) or substantially cut-through line in the pressure support is much weaker than a score or other weakening means in conventional discs, which permits the use of much thicker material and a 20-30% lower dome heights, providing greater durability and corrosion resistance. 
         [0030]    Further advantages also include ultra low reversible pressures with full and complete opening achieved due to the 20-30% lower dome heights, which is not available in other conventional reverse rupture discs. Further, the elliptical slot or cut-through pattern allows for the supporting dome to buckle or collapse non-uniformly and swing or otherwise hinge through the support ring without becoming hung up on the ring thus providing consistently greater relieving capacity. 
         [0031]    Further, controlling the length of the elliptical slot or cut-through line up to a 345° maximum, leaves a strong 15% permanent hinge to retain the pressure support after bursts preventing fragmentation of the pressure support itself. This assembly may be manufactured to resist vacuum. Further, the support may be adapted to burst at both positive and negative pressures by adding an atmospheric seal and adjusting the strength of the tabs and the slot of the pressure support. Another advantage is that the disc may be used within all types of service, such as gas, liquid or two phase flow. The ratio of positive to negative burst pressure can be controlled if desired by adjusting the strength of the seal material and/or the strength of the tabs in the slot or slit portion of the disc in order to provide a fail safe design. 
         [0032]    Although embodiments of the invention have been described above, it is not limited thereto and it will be apparent to those skilled in the art that numerous modifications form part of the present invention insofar as they do not depart from the spirit, nature and scope of the claimed and described invention.