Carbon rupture disk element and assembly

Abstract: A replaceable carbon rupture disk element (20) comprising a carbon disk (22) having a pair of opposing bores (30,32) extending thereinto whereby an integral blow-out portion (34) having a particular rupture pressure is formed in the disk connected to an enlarged rim portion. A reinforcing ring (38) is attached to the rim portion 928) of the carbon disk having a height substantially equal to or greater than the height of the rim portion (28) of the disk, which prevents the rim portion from being subjected to compressive forces which might change the rupture pressure of the blow-out portion.

Description: The present invention relates to a carbon rupture disk element and assembly, and more particularly, to a replaceable carbon rupture disk element and a holder-element assembly as defined in the preamble of claim 1 and known from DE-A-2 615 146. A great variety of rupture disks for preventing excessive fluid pressure in vessels or systems have been developed and used heretofore. Such rupture disks have been formed of various materials including metals, plastics and carbon, e.g., graphite and baked carbon. Graphite rupture disks which have been impregnated with resins to make them gas tight have been found to be advantageous in that they are economical to produce, have excellent chemical corrosion resistance, do not creep and fatigue as a result of pressure variations and reliably fail at their predetermined rupture pressure regardless of temperature variations. The first and most common type of carbon rupture disk is of monoblock form, comprising a carbon disk having a central bore machined therein which extends from one side of the disk towards the other, the depth of the bore being such that the carbon material remaining between the bottom of the bore and the other side of the disk is of a thickness and strength whereby it ruptures at a predetermined desired rupture pressure. The disk is of a large size so that it can be bolted directly between pipe flanges or the like. The second type of known carbon rupture disk unit includes a replaceable carbon element, the unit comprising an assembly of a carbon rupture disk element positioned between annular holders formed of carbon or other material. The holder-rupture disk element unit is sealingly clamped between pipe flanges or the like whereby the rupture disk element is in turn sealingly clamped between the holders. Upon rupture, the rupture disk element can be replaced without replacing the holders. While such known carbon rupture disks and assemblies have achieved varying degrees of success, they suffer from the disadvantages that they are sensitive to compressive forces and they rupture at the predetermined rupture pressure in only one direction. When excessive compressive forces are exerted on the disks as a result of being clamped between holders and/or pipe flanges, to ensure a pressurized fluid seal, stresses are introduced into the brittle carbon material which change the pressure at which the disk ruptures. The directional rupture aspect of prior carbon rupture disks requires that such a disk be installed between holders and/or pipe flanges with a particular side of the disk facing the fluid pressure. If the rupture disk is inadvertently installed upside down, the fluid pressure at which the disk ruptures is changed which can bring about a premature rupture or a dangerous overpressure condition. According to the present invention there is provided a carbon rupture disk element comprising a carbon disk having opposite faces, a rim portion and a central bore machined therein whereby an integral blow-out portion having a particular rupture pressure is formed in said disk connected to said rim portion, which extends from a first face towards the second face, the depth of the bore being such that the carbon material of the blow-out portion remaining between the bottom of the bore and the other side of the disk is of a thickness and strength to burst at a predetermined rupture pressure, and a reinforcing ring of a height substantially equal to or greater than the height of said rim portion whereby when said reinforcing ring and said disk are clamped between holders or flanges, said reinforcing ring prevents said rim portion of said disk from being subjected to compressive forces which might change said rupture pressure of said disk, characterised in that a second opposing bore extends from said second face and into said disk, each of said bores having a depth less than half the distance between said faces, and in that the reinforcing ring is attached to said rim portion of said disk. Furthermore, the carbon rupture disk element can be subjected to excessive compressive forces without altering the rupture pressure of the rupture disk. Preferably the carbon disk rim and reinforcing ring are substantially circular, the faces of the ring are parallel and the opposing bores cylindrical. The invention also provides a carbon rupture disk assembly comprising a replaceable carbon rupture disk of the invention and a pair of annular holders adapted for sealingly clamping the rupture disk element therebetween. 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 a pair of pipe flanges having the improved replaceable carbon rupture disk element and holder assembly of the present invention clamped therebetween; and Figure 2 is a cross-sectional view taken along line 2-2 of Figure 1. Referring now to the drawing, the carbon rupture disk element and holder assembly 10 of the present invention is illustrated sealingly clamped between a pair of pipe flanges 12,14, by means of a plurality of bolts 15. A conduit 16 is welded to the pipe flange 12, and to a vessel or system containing a fluid under pressure (not shown). The pressurized fluid from the vessel or system is communicated by way of the conduit 16 and pipe flange 12 to the rupture disk assembly 10 as shown by the arrow 19, and the force of the pressurized fluid is exerted on the side of the rupture disk assembly 10 facing the pipe flange 12. The pipe flange 14 is connected to a conduit 18 which leads pressurized fluid relieved through the assembly 10 to a containment vessel or other location. The assembly 10 comprises a rupture disk element 20 which includes a carbon disk 22 having opposite faces 24,26 and a rim 28. A pair of opposing blind bores 30,32 extend through the faces 24,26 respectively into the disk 22, each of the bores having a depth less than half the distance between the faces 24,26 whereby an integral blow-out portion 34 having a particular rupture pressure is formed in the disk 22. The blow-out portion 34 is integrally connected to an enlarged annular rim portion 36. The carbon disk 22 is preferably formed of graphite impregnated on both sides with a resinous or plastic filler that plugs the pores of the graphite and renders the disk impervious to gases. A particularly suitable resin for this purpose is high temperature epoxy resin. The disk 22 is also preferably circular in peripheral shape with the faces 24,26 thereof being substantially parallel. The opposing bores 30,32 are preferably cylindrical and substantially identical in diameter and depth whereby the blow-out portion 34 of the disk 22 has substantially the same rupture pressure regardless of which side of the disk fluid pressure is exerted on. The element 20 includes a reinforcing ring 38 attached to the rim 28, the reinforcing ring 38 being of a height substantially equal to or greater than the height of the rim portion 36 of the carbon disk 22, whereby compressive forces resulting from clamping the element 20 between holders or flanges are transmitted to and resisted by the reinforcing ring 38 rather than being transmitted to the rim 36 of the disk 22. The reinforcing ring 38 is preferably bonded to the rim 28 of the disk 22 using a suitable adhesive, and the reinforcing ring 38 is formed of a material having the rigidity required to resist deformation as a result of compressive forces exerted on it. Generally, the reinforcing ring 38 can be formed of plastics, or preferably metal with stainless steel being particularly preferred. The replaceable rupture disk element 20 can be clamped directly between the pipe flanges 12,14 with or without conventional gaskets therebetween. In a more preferred assembly, the rupture disk element 20 is clamped between a pair of annular holders 40,42, which can take various cross-sectional shapes, but the L-shape illustrated in the drawing is presently preferred. Gaskets 44 can be disposed between the holders 40,42 and the rupture disk element 20, and gaskets 46 can be disposed between the holders 40,42 and the pipe flanges 12,14, respectively. The holders 40,42 can be formed of a variety of materials including carbon, metals or plastics. The selection of a particular holder material depends on the particularly application in which the assembly 10 is utilized and other factors. In relatively low pressure applications and/or where economy is a factor, holders formed of graphite are preferred. In other higher pressure applications, stainless steel is generally preferred. The holder-rupture disk element assembly 10 can be assembled in any convenient sequence whereby the rupture disk element 20 is positioned between the holders 40,42 as illustrated in Figure 1 with the gaskets 44 (if used) positioned between the enlarged rim portion 36 of the carbon rupture disk 22 and the ends of the annular reinforcing ring 38. The carbon rupture disk element 20 can be installed with either side facing the pressurized fluid without affecting the rupture pressure of the blow-out portion 34 thereof as described above. The holder-element assembly 10 is then installed between the pipe flanges 12,14 with the gaskets 46 (if used) positioned between the holders 40,42 and the flanges 12,14, respectively. The pipe flanges 12,14 are sealingly clamped against the holder-element assembly 10 by the bolts 15, which in turn causes the holders 40,42 to be sealingly clamped against the rupture disk element 20. When the pressure exerted on the blow-out portion 34 of the carbon rupture disk 22 of the element 20 reaches the predetermined pressure at which the blow-out portion ruptures, the blow-out portion 34 fails and pressurized fluid from the vessel or system being protected flows through the assembly 10 and pipe flanges 12,14 to a containment vessel or other location. Thus, the replaceable carbon rupture disk element of this invention is non-direction and is unaffected by excessive compressive forces exerted on it due to over torquing the bolts of the flanges or other members between which it is clamped.

Claims: A carbon rupture disk element (20) comprising a carbon disk (22) having opposite faces (24,26), a rim portion (28) and a central bore (30) machined therein whereby an integral blow-out portion (34) having a particular rupture pressure is formed in said disk connected to said rim portion, which extends from a first face (24) towards the second face (26), the depth of the bore being such that the carbon material of the blow-out portion (34) remaining between the bottom of the bore and the other side of the disk is of a thickness and strength to burst at a predetermined rupture pressure, and a reinforcing ring (38) of a height substantially equal to or greater than the height of said rim portion whereby when said reinforcing ring and said disk are clamped between holders or flanges, said reinforcing ring (38) prevents said rim portion (28) of said disk from being subjected to compressive forces which might change said rupture pressure of said disk, characterised in that a second opposing bore (32) extends from said second face (26) and into said disk, each of said bores having a depth less than half the distance between said faces, and in that the reinforcing ring is attached to said rim portion (28) of said disk. A rupture disk element according to claim 1, characterised in that said carbon disk rim portion (28) and said reinforcing ring (38) are substantially circular. A rupture disk element according to claim 1 or 2, characterised in that said opposite faces (24,26) of said carbon disk are substantially parallel. A rupture disk element according to claims 1, 2 or 3, characterised in that said opposing bores 930,32) in said carbon disk are substantially cylindrical. A rupture disk element according to any preceding claim, characterised in that said opposing bores (30,32) in said carbon disk are substantially identical in shape and depth, whereby said blow-out portion (34) of said disk has substantially the same rupture pressure regardless of which side of said disk said pressure is exerted on. A rupture disk element according to any preceding claim, characterised in that said carbon disk is formed of graphite. A rupture disk element according to any preceding claim, characterised in that said reinforcing ring is formed of metal or plastic. A rupture disk element according to claim 7, characterised in that said reinforcing ring is formed of stainless steel. A replaceable carbon rupture disk element (20) according to any preceding claim, and a pair of annular holders adapted for sealingly clamping said rupture disk element therebetween. An assembly according to claim 9, characterised in that gaskets (44) are positioned between said annular holders and the rim portion (28) and its surrounding reinforcing ring (38).

Inventors: ELLIS JIM E, ELLIS, JIM E.
Applicants: BS & B SAFETY SYSTEMS INC, BS & B SAFETY SYSTEMS, INC.
Application year: 1992
Main classification: F16K17
IPC codes: C01B31, F16K17