Scored reverse buckling rupture disk assembly

Abstract: A scored reverse buckling rupture disk assembly (10) comprising a reverse buckling rupture disk (22) having one or more scores (42) on a surface thereof forming lines of weakness which define a blow-out portion (32) connected by a hinge area (36) in the rupture disk. An annular rupture disk support member (34) is positioned adjacent the concave side of the rupture disk, and a supporting member (50), for preventing the blow-out portion from fragmenting or tearing away from the rupture disk at the hinge thereof, is disposed within the concave recess (40) in the rupture disk.

Description: The present invention relates generally to a scored reverse buckling rupture disk assembly. Many pressure relief devices of the rupture disk type have been developed and used heretofore. Generally, such devices include a rupture disk supported between a pair of support members or flanges which are in turn connected to a relief connection in a vessel or system containing fluid pressure. When the fluid pressure within the vessel or system exceeds the design rupture pressure of the disk, rupture occurs causing pressurized fluid to be relieved from the vessel or system. Reverse buckling rupture disks include a domed portion and the fluid pressure from the vessel or system being protected is exerted on the convex side of the disk. Upon failure, the domed portion of the disk reverses and then ruptures. Originally, all reverse buckling rupture disk assemblies included knife blades positioned adjacent the rupture disks thereof on the outlet sides of the disks. Upon reversal, the disks impaled on the knife blades causing them to open in a predetermined manner. US-A-3484817 discloses reverse buckling rupture disks having weakness, so that upon reversal, the disk tears along the lines of weakness. A method of manufacturing scored reverse buckling rupture disks is described in US-A-3921556. While scored reverse buckling rupture disks have been used successfully and have obviated the need for knife blades in a number of applications, fragmentation of scored reverse buckling rupture disks has been a problem in applications involving high pressures, because then fragmentation often occurs due to the high speed at which the disk reverses and the explosive nature of the ensuing rupture. Also, if some of the heretofore used reverse buckling rupture disks are damaged in installation or handling, they can revers and not open until fluid pressure high than the design rupture pressure is exerted thereon causing an unsafe condition to exist. In order to lessen this fragmentation problem, C-scored reverse buckling rupture disk assemblies including means for catching and supporting the hinge areas of the disks have been developed and used heretofore. For example, US-A-4759460 describes such a rupture disk assembly which includes an arcuate inwardly extending projection on the downstream side of the rupture disk. The projection is positioned whereby upon rupture, the blow-out portion defined by the C-score wraps about the projection and the hinge connecting the blow-out portion to the rupture disk is supported. In order to ensure that the reversal of the rupture disk starts adjacent the projection, a dent is included in the rupture disk or a portion of the rupture disk support member adjacent the hinge includes a relieved area therein. EP 0055909 shows a rupture disk assembly in which a projection is provided downstream of the rupture disk and about which it deforms on reversal. EP 0083473 shows a reverse buckling rupture disk assembly in which an abutment is provided projecting inwardly from a point in the bore of the assembly downstream of the rupture disk, and about which the rupture disk is to be wrapped on reversal. While the use of the projection of US-A-4759460 and other similar supporting means in scored reverse buckling rupture disk assemblies have reduced the incidence of fragmentation in high pressure applications, fragmentation has still occurred as a result of the blow-out portions of such rupture disks tearing at the hinge areas whereby they are disconnected from the rupture disks. GB-A-2114666 discloses a scored reverse bukling rupture disk assembly comprising a reverse buckling rupture disk, having a convex protrusion on one side and a corresponding concave recess on the other side, defining a dome therein, and having at least one score on a side thereof, forming a line of weakness therein, which defines a blow-out portion connected by a hinge area in said rupture disk, and an annular rupture disk support member positioned adjacent the side of said rupture disk having said concave recess therein whereby, upon reversal and rupture of said rupture disk, said blow-out portion is moved into contact with and is supported at the hinge area by said support member, so as to prevent said blow-out portion from fragmenting or tearing away from said rupture disk, the annular rupture disk support member comprising a supporting member extending into said concave recess in said rupture disk and adjacent the hinge area thereof. The precharacterising portion of claim 1 is based on this disclosure. The rupture disk of the present invention forms an improvement on such a rupture disk which is characterised in that the supporting member includes a surface which faces the rupture disk, but does not contact it, whereby reversal and rupture of the disk are slowed down, without interfering with the start of the reversal process. With such a construction fragmentation of the rupture disk upon the reversal and rupture thereof can be substantially eliminated, and even if the rupture disk is damaged it will still rupture below its design rupture pressure. In order that the present invention may more readily be understood, the following description is given, merely by way of example, reference being made to the accompanying drawings in which:- Figure 1 is a side cross-sectional view of one embodiment of scored reverse buckling rupture disk assembly of the present invention clamped between conventional pipe flanges. Figure 2 is a side cross-sectional view of the assembly of Figure 1 illustrating the rupture disk thereof after reversal and rupture. Figure 3 is a view taken along line 3-3 of Figure 1. Figure 4 is a side cross-sectional view of an assembly of the present invention including an alternative form of blow-out portion supporting member. Figure 5 is a side cross-sectional view of an assembly of the invention including another form of blow-out portion supporting member. Figure 6 is a top plan view of the assembly of Figure 5. Figure 7 is a side cross-sectional view of the assembly of Figure 5 after reversal and rupture of the rupture disk thereof. Figure 8 is a side cross-sectional view of an assembly of the present invention including a still further form of blow-out portion supporting member. Figure 9 is a side cross-sectional view of the assembly of Figure 8, but showing the rupture disk thereof after reversal and initial rupture has taken place. Figure 10 is a side cross-sectional view of the assembly of Figure 8, after the blow-out portion of the rupture disk has partially wrapped around the supporting member. Figure 11 is a side cross-sectional view of the assembly of Figure 8 after the blow-out portion of the rupture disk has completely wrapped around the supporting member. Referring now to Figures 1-3, a scored reverse buckling rupture disk assembly 10 is shown clamped between a pair of conventional pipe flanges 12,14 by a plurality of bolts 16. The flange 12 is sealingly connected to a conduit 18 which is in turn connected to a vessel or system (not shown) containing fluid pressure to be protected. The flange 14 is sealingly connected to a conduit 20, which leads pressurized fluid vented through the rupture disk assembly 10 to a point of disposal, storage or the like. The assembly 10 includes a scored reverse buckling rupture disk 22 clamped between inlet and outlet annular support members 24,26, with gaskets 28,30 positioned between the pipe flanges 12,14 and support members 24,26. As best shown in Figures 1 and 3, the scored reverse buckling rupture disk 22 is substantially circular and includes a domed portion 32 connected to an annular flat flange portion 34 by a transition connection 36. The domed portion 32 is formed by a convex protrusion 38 and a corresponding concave recess 40 on the sides of the disk facing the inlet and outlet support members 24,26, respectively. The annular flat flange portion 34 is clamped between annular sealing surfaces provided on the annular support members 24,26. In order to provide support to the transition connection 36 of the rupture disk 22, the outlet annular support member 26 can have a smaller internal diameter than the inlet support member 24, although this is not illustrated. A single score 42 is formed in the convex side of the domed portion 32 of the rupture disk 22 and forms a line of weakness in the rupture disk 22, which defines a substantially circular blow-out portion 43 therein (Figure 3), connected to the remaining portion of the rupture disk 22 by a hinge area 44 between the ends of the score 42. The term "score(s)" is used herein to mean one or more grooves, indentations or the like which form one or more lines of weakness in a rupture disk, whereby, upon failure of the rupture disk, it tears along such lines of weakness. A single score 42 can be utilized as illustrated in Figure 3, or a plurality of scores (similar to a dashed line) can be used to form a line of weakness and the score or scores can be located on either side of the rupture disk 22, in the domed portion 32 of the rupture disk 22 or in the annular flat flange portion 34 thereof. Also, the score or scores can define a blow-out portion having a different shape, e.g. a square, triangular, etc. shape. Further, the hinge area can be unscored or the hinge area can contain a shallow score or scores (not shown) to improve the accuracy of the disk, i.e., to narrow the fluid pressure range which causes reversal and rupture. Referring still to Figure 1-3, the outlet annular rupture disk support member 26 includes a supporting member 50 for supporting the area of the rupture disk 22 containing the hinge 44 upon the reversal and rupture of the disk 22. In the form illustrated in Figures 1-3, the supporting member 50 is an integral part of the annular support member 26 and extends radially inwardly and upwardly into the concave recess 40 of the rupture disk 22. The support member 50 terminates radially inwardly in a vertical straight wall 52 which is on a line corresponding to a chord intersecting the interior walls of the annular support member 26 and terminates, in the upward direction, in a smooth, rounded surface 56 close to, but not touching, the rupture disk 22. The hinge area 44 of the rupture disk i.e., the area between the ends of the score 42, is positioned directly adjacent the rounded surface 56 of the member 50. The distance between the rounded surface 56 and the side of the rupture disk 22 adjacent thereto is such that the rupture disk 22 does not contact the surface 56 until the domed portion 32 of the rupture disk 22 begins its reversal process. As shown in Figure 3, the supporting member 50 extends radially inwardly past the hinge area 44, so that upon contact of the rupture disk 22 with the support member 50, the hinge 44 is supported on the rounded surface 56 of the support member 50. In operation, when the fluid pressure from the vessel or system being protected exceeds the design rupture pressure of the rupture disk 22, the domed portion 32 thereof reverses, i.e., inverts, and then tears along the lines of weakness formed by the score 42. As a result, the substantially circular blow-out portion 43 of the rupture disk 22 moved downwardly into and through the interior of the annular support member 26 and into the pipe flange 14 and conduit 20. As the domed portion 32 reverses, the area thereof containing the hinge 44 contacts and is supported by the surface 56 of supporting member 50. The blow-out portion 43 of the rupture disk 22 tears away along the lines of weakness formed by the score 42, but remains attached to the remaining portion of the rupture disk 22 by the supported hinge 44 as illustrated in Figure 2. Additionally, because of the contact between the rupture disk 22 and the supporting member 50, the reversal and rupture process of the disk 22 is slowed down, whereby fragmentation of the blow-out portion 43 does not take place. The required hinge support and slowing down of the reversal and rupture process to prevent fragmentation does not take place unless the surface 56 of the supporting member 50 extends into the concave recess 40 of the rupture disk 22 into close proximity with the surface of the rupture disk 22 in the area of the hinge 44. However, the surface 56 of the supporting member 50 must not contact the rupture disk 22 or be so close thereto that it interferes with the start of the reversal process. For a 10 cm nominal size rupture disk, the surface 56 is spaced from the rupture disk a distance in the range of from about 0.25 to 2.5 mm. If the rupture disk 22 is damaged, and as a result, reverses without rupture, the surface 56 of the supporting member 50 contacts the disk and causes a concentrated stress in a portion of the score whereby rupture occurs at a fluid pressure below the design rupture pressure of the disk. When a C-scored rupture disk without the supporting member 50 reverses without rupture, a pressure greater than the design rupture pressure is generally required to cause rupture making the use of the disk potentially unsafe. The concentration of tearing forces in a portion of the score after reversal due to the contact with the supporting member 50 as described above also allows the assembly 10 to be effectively utilized in liquid service. Prior art C-scored reverse buckling rupture disk assemblies are generally limited to applications where the pressurized fluid is a gas. Referring now to Figure 4, the illustrated apparatus 60 is identical to the apparatus 10 except for the form of the supporting member 68, and includes a scored reverse buckling rupture disk 62 clamped between inlet and outlet annular support members 64,66. Instead of the supporting member 68 being an integral part of the annular support member 66, it is attached to an annular flat flange 69 which is clamped between the annular flat flange 63 of the rupture disk 62 and the outlet annular support member 66. As before, the supporting member 68 extends radially inwardly and upwardly into the concave recess in the rupture disk 62 and terminates in a rounded surface 70, which is positioned close to the surface of the hinge area of the rupture disk 62, but does not contact it. Again, the supporting member 68 terminates inwardly in an axial side surface 72 corresponding to a chord of the circular interior opening of the annular support member 66. The operation of the assembly 60 is identical to the operation of the assembly 10 as described above. Referring now to Figures 5-7, the illustrated assembly 80 again includes a domed reverse buckling rupture disk 82 having a convex protrusion 84 on one side and a corresponding concave recess 86 in the other side. The convex side of the rupture disk 82 includes a score 88 therein, which forms a line of weakness defining a partially circular blow-out portion 90 connected by a hinge 92 (Figure 6) in the rupture disk 82. The domed portion 84 of the rupture disk 82 is connected to an annular flat flange portion 94 which is clamped between inlet and outlet annular rupture disk support member 96,98, respectively. A blow-out portion supporting member 100, disposed within the concave recess 86 of the rupture disk 82, is attached to an annular flat flange 102 positioned between the annular flat flange 94 of the rupture disk 82 and the annular support member 98. The supporting member 100 extends radially inwardly and upwardly into the concave recess 86 of the rupture disk 82, and a non-collapsible first portion 104 terminates along a line corresponding to a chord of the circular opening in the annular support member 98. The non-collapsible portion 104 of the supporting member 100 is positioned immediately below the portion of the rupture disk 82 containing the non-weakened hinge 92. The upper surface 106 of the non-collapsible portion 104 generally corresponds in shape to the adjacent part of the concave recess 86, but does not contact the surface thereof. The supporting member 100 additionally includes a collapsible finger portion 108 which extends radially inwardly within the concave recess 86 of the rupture disk 82 and terminates adjacent a central portion of the rupture disk 82. The upper surface 110 of the finger portion 108 of the supporting member 100 generally corresponds in shape to the surface of the concave recess 86, but does not contact such surface. In operation, as shown in Figure 7, when the fluid pressure exerted on the convex side of the rupture disk 82 exceeds the design rupture pressure of the disk, the disk reverses and tears along the lines of weakness created by the score 88. As the rupture disk 82 reverses, it comes into contact with the non-collapsible portion 104 and with the collapsible finger portion 108 of the supporting member 100. The non-collapsible portion 104 supports the hinge 92 defined in the rupture disk 82, whereby tearing at the hinge area is prevented. The collapsible finger portion 108 moves with the rupture disk 82, during reversal, and collapses beneath the blow-out portion 90 and functions to absorb energy and to slow down the blow-out portion 90, thereby preventing fragmentation of the blow-out portion 90. As will be understood, the supporting member 100 can be attached to or be a part of the outlet annular support member 98 rather than being attached to the annular flange portion 94. Also, the finger portion 108 of the support member 100 can take a variety of shapes other than the substantially rectangular shape illustrated. Figures 8-11, show a further embodiment of assembly 120 which again includes a domed reverse buckling rupture disk 122, having a convex protrusion 124 on one side and a corresponding concave recess 126 in the other side. A score 128 is formed in the convex side of the rupture disk 122 which forms a line of weakness, defining a partially circular blow-out portion 130 connected by a hinge 132 in the rupture disk 122. The domed portion 124 of the rupture disk 122 is connected to an annular flat flange portion 134, which is clamped between inlet and outlet annular rupture disk support members 136,138, respectively. Here, the blow-out portion supporting member 140 is attached to the outlet support member 138 and extends radially inwardly and upwardly into the concave recess 126 of the rupture disk 122 in a manner identical to the support member 50 of the assembly 10 described above. In addition, the supporting member 140 includes a recess 142 in the bottom thereof forming a downwardly projecting lipped portion 144 extending along the inside bottom edge of the supporting member 140. In operation, as shown in Figures 9-11, when the fluid pressure exerted on the convex side of the rupture disk 122 exceeds the design rupture pressure of the disk, the disk reverses an tears along the lines of weakness created by the score 128 (Figure 9). As the rupture disk 122 reverses it comes into contact with the rounded upper surface of the supporting member 140 and forcibly moves into contact with the internal side of the support member 140 (Figure 10), whereby the portion of the blow-out portion 130 extending below the lip 144 is caused to deform into the recess 142 as shown in Figure 11. Thus, the presence of the recess 142 and lip 144 at the bottom of the supporting member 140 causes the blow-out portion 130 to be latched onto the supporting member 140, ensuring that the blow-out portion 130 does not subsequently fatigue and break off, e.g. due to the flow of relieved pressurized fluids.

Claims: A scored reverse buckling rupture disk assembly (10,60,80,120) comprising a reverse buckling rupture disk (22,62,82,122), having a convex protrusion (38,84,124) on one side and a corresponding concave recess (40,86,126) on the other side, defining a dome (32) therein, and having at least one score (42,88) on a side thereof, forming a line of weakness therein, which defines a blow-out portion (43,90) connected by a hinge area in said rupture disk, and an annular rupture disk support member (26,66,98,138) positioned adjacent the side of said rupture disk having said concave recess therein whereby, upon reversal and rupture of said rupture disk, said blow-out portion (43,90) is moved into contact with and is supported at the hinge area by said support member, so as to prevent said blow-out portion from fragmenting or tearing away from said rupture disk, the annular rupture disk support member comprising a supporting member (50,68,100,140) extending into said concave recess (40,86,126) in said rupture disk and adjacent the hinge area (44,92,132) thereof, characterised in that the supporting member (50,68,100,140) includes a surface (56,70,106) which faces the rupture disk, but does not contact it, whereby reversal and rupture of the disk are slowed down, without interfering with the start of the reversal process. An assembly according to claim 1, characterised in that said supporting member (50,140) is attached to the interior of said annular rupture disk support member (26,138). An assembly according to claim 1, wherein said convex protrusion (38,84,124) and said corresponding concave recess (40,86,126) define a dome (32) in said rupture disk which is circular in peripheral shape and is connected to an annular flat flange portion (34,63,94,134) of said rupture disk, characterized in that said supporting member (68,10) is attached to an annular flat flange (69,102) disposed between the annular flat flange portion (63,94) of said rupture disk and said annular rupture disk support member (66,98). An assembly according to claim 3, characterised in that said supporting member further includes a collapsible finger (108) extending radially inwardly within said concave recess (86) in said rupture disk, whereby, upon reversal and rupture of said rupture disk, said blow-out portion contacts and collapses said finger. An assembly according to claim 3, characterised in that said blow-out portion supporting member (68) includes a rounded portion (70) defined by an axial side surface (72) lying adjacent to and along the length of said hinge. An assembly according to any preceding claim, characterised in that weakness defines a substantially circular blow-out portion in said rupture disk and said hinge defined in said rupture disk corresponds to a chord (52) of said blow-out portion and in that said supporting member includes a rounded surface positioned adjacent to and along the length of said hinge without contacting said rupture disk. An assembly according to any preceding claim, characterised in that said supporting member (140) includes a lip (144) at a location spaced from the concave face of the rupture disk, said lip defining a recess (142) into which the end of the blow-out portion (130) engages and is latched thereby.

Inventors: ELLIS JIM E, MUNDT ARNOLD L, SHORT EDWARD H III, TYLER JOHN L, ELLIS, JIM E., MUNDT, ARNOLD L., SHORT, EDWARD H., III, TYLER, JOHN L.
Applicants: BS & B SAFETY SYSTEMS INC, BS & B SAFETY SYSTEMS, INC.
Application year: 1990
Main classification: F16K17
IPC codes: F16K17