Patent Number: 056053614
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENTS Although the preferred embodiments illustrated in the drawings are described below in connection with replacement of a welded nozzle in the pressurizer vessel of a nuclear power facility and the replacement of a nozzle in a large bore pipe, the invention is not limited to that and encompasses installation of nozzles in other vessels and piping. The invention further encompasses the initial installation of nozzles in new as well as in existing vessels and piping. In the embodiments of replacement nozzles depicted in FIGS. 3-15, the original welded nozzle (FIG. 2) has been completely removed, leaving the J-welds 34 and the cladding 29 surrounding the bore 30 for the nozzle substantially in tact The old nozzle may be machined or drilled out; therefore destroying the nozzle. In the embodiments depicted in FIGS. 3-6, 9 and 16-18, the replacement nozzle 40, 40a, 40b, 61, 71b, 120 is clamped in the bore or hole 30, 30a, 30b, 60, 74b, 124, respectively. Referring to FIG. 3, replacement nozzle 40 includes a tubular nozzle body 42 having an interior end 44 positioned in the interior of the vessel 20 at the entrance to the bore 30 and an interior flange 46 radically extending about the periphery of nozzle end 44. The flange 46 may be attached to the nozzle body 42 in any suitable manner, e.g., by welding (if welded the nozzle should be stress relieved prior to installation), or may be formed as one piece with the nozzle body 42. The opposite end 48 of the nozzle body 42 projects from the exterior of the vessel 20 and includes a threaded portion 50 positioned exteriorly to the vessel. The nozzle 40 is inserted into bore 30 from the interior of the vessel 20, a nut 52 is threaded to the threaded portion 50 of the nozzle body 42 and, as tightened, draws the flange 46 into engagement with the interior of the vessel while the nut 52 bears against the exterior of the vessel through a spacer 54. The surface 55 of spacer 54 adjacent the exterior of the pressurizer is curved to follow the contour of the vessel exterior. This arrangement mechanically attaches the nozzle body 42 to the vessel 20. Substantially the same procedure may be used to attach a nozzle to a large bore pipe. With continued reference to FIG. 3, a mechanical seal is obtained without welding between the exterior of the nozzle body 42 and the vessel by a polished flange to polished vessel seal (discussed above) or gasket material 56 positioned and compressed between the interior flange 46 and the interior of the vessel. As discussed above, the gasket material 56 may be a nickel alloy plated to the flange or other suitable seal material. Depending upon pressure ratings and thermal transient conditions, a spring washer 55 may be positioned between the nut 52 and the spacer 54 to maintain a constant pressure on the nozzle and vessel. The spring washer overcomes the differential thermal growth of the vessel and nozzle during thermal transient conditions of the vessel by forcing the flange 46 (through any intervening gasket material 56) in contact with the vessel. The nut 52, the spacer 54, the flange 46 and the nozzle body may all be made of Alloy 690 or other suitable material such as stainless steel for the application just described as a replacement nozzle for a nuclear power plant pressure vessel. This arrangement mechanically seals the exterior of nozzle 40 with the vessel 20. Replacement nozzle 40a depicted in FIG. 4 is also clamped to the vessel 20. Replacement nozzle 40a includes a tapered nozzle body 42a having an interior end 44a positioned at or in the interior of the vessel 20 at the entrance to the bore 30a. Bore 30a is also tapered, rather than cylindrical, and the tapered bore and tapered nozzle body portion form one part of the mechanical clamping system for the nozzle 40a, as described below. The nozzle body 42a and bore 30a both taper from a larger diameter at the interior end 44a of the nozzle body 42a to a smaller diameter at the exterior end 48a of the nozzle body, which requires that the nozzle body 42a be inserted into the bore 30a from inside the vessel. The opposite end 48a of the nozzle body 42a projects from the exterior of the vessel 20 and includes a cylindrical portion 50a positioned exteriorly of the vessel. Like replacement nozzle 40 depicted in FIG. 3, portion 50a is threaded, and replacement nozzle 40a includes a nut 52a threaded onto the threaded portion 50a, and a spacer 54a having a curved surface 55a adjacent the vessel 20 to follow the contour of the vessel exterior, which form another part of the clamping system. However, this other bore part of the clamping system employs interfering portions of the nozzle body 42a and the bore 30a bearing against each other instead of the interior flange 46 in the FIG. 3 embodiment bearing against the interior of the vessel. The nozzle body 42a within bore 30a is tapered the same as bore 30a, but tapers to a larger diameter than the largest diameter within bore 30a. As a result, tightening nut 52a on the threaded portion 50a of the nozzle body 42a draws the nozzle body within bore 30a into engagement with the bore 30a to clamp nozzle 42a to vessel 20. This arrangement mechanically attaches the nozzle body 42a to the vessel 20. Nozzle 40 may use interfering portions of the nozzle and bore as described for nozzle 40a for part of the clamping system, but the taper directions of the tapered bore and nozzle would be reversed from that shown in FIG. 4. With continued reference to FIG. 4, a mechanical seal is obtained between the polished exterior of the nozzle body 42a and the polished wall of bore 30a by engagement of the two polished surfaces. Nut 52a is tightened sufficiently to ensure that the seal is obtained. If necessary, a spring washer (not shown in FIG. 4) may be positioned between nut 52a and spacer 54a. Instead of polished surfaces, gasket material 56, similar to that shown in FIG. 8 but not shown in FIG. 4, may be positioned within bore 30a between the bore wall and the exterior of the nozzle body 42a to create the seal. Replacement nozzle 40b depicted in FIG. 5 employs a clamping system similar to that for nozzle 40a in FIG. 4, but does not include a spacer. The exterior of vessel 20 includes a flat 54b against which the nut 52b bears. Similar to nozzle 40a in FIG. 4, the nozzle body 42b and the bore 30b are tapered, and the clamping system employs interfering portions of the nozzle body and the bore which function as part of the mechanical clamping system to form the mechanical seal of the exterior of the nozzle with the vessel as described for nozzle 40a. If necessary, a spring washer as described for nozzle 40a may be employed between nut 52b and flat 54b. The surfaces of the interfering portions may be polished or a gasket material 56 similar to that shown in FIG. 8 but not shown in FIG. 5 may be provided between nozzle body 42b and the walls of the bore 30b. Replacement nozzle 61 depicted in FIG. 6 employs still another clamping system for mechanically attaching the nozzle to vessel 20. Replacement nozzle 61 includes a nozzle body 62 having a tapered portion 63 ending in a smaller diameter end 64 projecting from the interior entrance of the bore 60 in the vessel 20 and a large diameter end 65 within bore 60. The nozzle body 62 also includes a tubular portion 66 projecting from the exterior of the vessel 20. The diameter of the tubular portion 66 is smaller than the larger diameter end 65 of the tapered portion 63, and a flange 67 is formed where the diameter of the bore changes from the smaller to larger diameter. The nozzle 61 also includes an externally threaded cylindrical sleeve 68, and the bore 60 includes a threaded cylindrical portion 69 and a tapered portion 70. Tightening the sleeve 68 using the wrenching flats thereof in the threaded bore portion 69 against the flange 67 of the nozzle body forces the tapered portion 63 of the nozzle body into mechanical engagement with the tapered portion 70 of the bore 60 to mechanically clamp the nozzle body 62 to the vessel 20. A mechanical seal is obtained between the contacting surfaces of the tapered nozzle portion 63 and the tapered bore portion 70 as described above. If necessary, a spring washer as described for nozzle 40a may be employed between nozzle sleeve 68 and the flange 67 of the nozzle body 62. FIGS. 7, 8, 10 and 11 depict embodiments of replacement nozzles 71, 71a, 71c, 71d which are bolted to the vessel 20. Although the nozzle 71b depicted in FIG. 9 is clamped to the vessel 20, it is discussed below with the bolted embodiments because it is similar to the bolted arrangement of FIGS. 10 and 11 in that a flange 86 engaging the nozzle 71b is bolted to the vessel 20. Referring to FIG. 7, replacement nozzle 71 includes a tapered nozzle body 72 having a smaller diameter end 73 at the interior entrance of the tapered bore 74 in the vessel 20, a tubular end 75 projecting from the exterior of the vessel 20 and a larger diameter, tubular threaded portion 76. The diameter of the nozzle body 72 increases from the interior end 73 to the threaded portion 76. The diameter of bore 74 similarly increases from the interior end of the bore to a cylindrical threaded portion 77 at the exterior end of the bore. Wrenching flats are provided on nozzle body 72 adjacent the threaded portion 76 for tightening the nozzle into the threaded portion 77 of the bore 74. The nozzle 71 is structurally attached to the vessel 20 by tightening the nozzle into the bore. The tapered portion of the nozzle body 72 and the tapered portion of the bore 74 cooperate when the nozzle is tightened into the bore to provide a mechanical seal between the nozzle body and the bore, as described generally for nozzle 40a shown in FIG. 4, except that the tapers of the nozzles and holes are reversed, i.e., nozzle 71 is inserted into bore 74 from the exterior of the vessel as opposed to being inserted from the interior of the vessel in FIG. 4. The interfering portions of the nozzle body 72 and bore 74 are polished, or gasket material 56 similar to that shown in FIG. 8 but not shown in FIG. 7 may be provided between nozzle body 72 and the walls of the bore 74. The replacement nozzle 71a and bore 74a depicted in FIG. 8 are similar to those depicted in FIG. 7 except that the tapers are reversed so that the nozzle is inserted into the bore from the interior of the pressurizer. A mechanical seal is obtained as described above. Replacement nozzle 71b depicted in FIG. 9 is clamped to vessel 20, and is similar to nozzle 71 in FIG. 7, except that it is clamped to the vessel 20 by an exterior flange 86 bolted to the vessel 20 by bolts 88 and threaded holes 90 in the exterior wall of the vessel, instead of bolted to the vessel by threaded portions on the nozzle body and in the bore of the vessel. Exterior flange 86 is a separate piece from nozzle 71b, and is engaged with nozzle 71b as follows. Nozzle 71b includes a tubular end 75b of reduced diameter projecting from the vessel 20 which forms a circular shoulder or flange 92. Flange 86 includes a circular recess 94 with a central hole 96 therein. The shoulder 92 on the nozzle 71b is received in the recess 94 in the flange 86 with the tubular portion 75b of the nozzle passing through the central hole 96 in the flange's recess 94. Bore 74b and nozzle body 72b are tapered generally as described for nozzle 71 in FIG. 7, and tightening bolts 88 causes the flange 86 to draw the nozzle body 72b into bore 74b into frictional engagement therewith. If necessary, spring washers (not shown) may be provided between the heads of bolts 88 and flange 86. A mechanical seal is obtained between the exterior of the nozzle body 72b and the walls of bore 74b, as described above. Referring to FIG. 10, replacement nozzle 71c is bolted to vessel 20 by an exterior flange 86c and bolts 88c. Both the nozzle body 72c and the bore 30 are cylindrical, and the mechanical attachment of the nozzle 71c to the vessel is achieved by bolting the flange 86c directly against the exterior wall of the vessel. The flange 86c is a separate piece from the nozzle body 72c and may be attached to the nozzle body in any suitable manner, e.g., by a weld 87 (which should be stressed relieved prior to installation). However, the flange 86c and nozzle body 72c may be formed as one piece, as shown in FIG. 11. The flange 86c is contoured to follow the contour of the exterior wall of the vessel 20 against which it bears. Spacers 91 are provided between the heads of bolts 88c and the flange 86c. A thin corrosion resistant sleeve 89, e.g., made of Alloy 690, is shrink fitted or rolled into bore 30 so as to mechanically seal the sleeve 89 to the bore 30. Gasket material 56 between flange 86c and the exterior vessel wall provides the mechanical seal. Referring to FIG. 11, nozzle 71d is mechanically attached as described for nozzle 71c of FIG. 10, includes a seal between flange 86d and the vessel, and is also sealed against bore 30d by O-rings 100 made of gasket material received in grooves 101 in the wall of bore 30d. Also, exterior flange 86d and nozzle body 72d are formed as one piece (or welded as shown in FIG. 10). In an alternate embodiment of nozzle 70d, which is not shown, the mechanical seal may be provided entirely by the O rings 100 in grooves 101 in the wall of bore 30d. In this alternate embodiment, the gasket material 56 may be omitted between flange 86d and the vessel. Replacement nozzle 110 shown in FIG. 12 is frictionally attached to the vessel 20 and mechanically sealed by an interference fit of nozzle 110 in bore 30. Nozzle 110 is tubular and bore 30 is cylindrical. At equal temperatures of the nozzle 110 and the vessel portion surrounding the bore 30, the diameter of the nozzle is slightly larger than the diameter of the bore. The nozzle 110 is inserted into the bore by creating a substantial temperature gradient between the two so that the diameter of the nozzle is reduced or the diameter of the bore is increased, or both. The temperature of the vessel 20 surrounding the bore 30 is increased to expand the diameter of the bore, or the nozzle 110 is cooled to reduce its diameter, or both. After the nozzle 110 has been inserted into the bore 30, the temperature gradient is reduced so that the nozzle 110 frictionally engages the wall of the bore 30 in an interference fit to both mechanically attach the nozzle and mechanically seal its exterior with the wall of the bore at the operating temperatures of interest. The exterior of the nozzle and the bore are polished to assist in creating a seal therebetween. If desired, a mechanical seal or seals, in addition to the mechanical seal obtained from the interference fit and polished surfaces, may be provided as discussed herein. Replacement nozzle 110a depicted in FIGS. 13-15 is mechanically attached and sealed in bore 30 as described for nozzle 110 in FIG. 12, and includes an anti-ejection feature provided by a molley-bolt arrangement which activates flanges 118 (FIGS. 14 and 15) formed from slots 119 (FIG. 13) in the interior end 114a of the nozzle. Nozzle 110a includes an internally threaded portion at its interior end 114a. After nozzle 110a has been mechanically attached in the bore 30, as described above in connection with nozzle 110 of FIG. 12, a threaded bolt 120 is tightened into nozzle 110a, which causes the interior end 114a of the nozzle to deform in molley-bolt fashion and form the flanges 118 (FIG. 14). After activation (formation) of the flanges 118 and engagement thereof with the vessel 20, the bolt 120 is removed (FIG. 15). Depending on the curvature of the interior wall of the (although only one flange is shown in engagement in FIGS. 14 and 15) to ensure that the nozzle will not be ejected from the vessel if the mechanical attachment should fail. All of the embodiments depicted in FIGS. 3-15 may be used in large bore piping, as well as pressure vessels in general. The embodiments of FIGS. 3, 4, 5 and 8 require entry into the pipe or a remote system to install them. FIGS. 16-18 illustrate a method for attaching a nozzle 120 specifically to large bore piping 122. Referring to FIG. 16, piping 122 includes a bore 124 therein which may have pre-existed and in which a nozzle may have been attached by welding or otherwise, or which may be formed to accept a nozzle for the first time. The nozzle 120 includes a tapered portion 130 (FIGS. 17 and 18) which is received in bore 124, a tubular portion 132 which projects from hole 124, and a flange 134 positioned at the transition of the nozzle from tapered to tubular. The flange 134 is contoured to follow the exterior contour of the piping. The diameter of the tapered portion 130 of the nozzle 120 adjacent the flange 134 is approximately the same as the diameter of the bore 124. Accordingly, the tapered portion 130 of the nozzle interferes with the bore 124 and the flange 134 bears against the exterior of the piping to secure the nozzle against movement into the piping. Gasket material 56 is positioned between the flange 134 and the piping 122, which produces a mechanical seal when the flange 134 is clamped by the clamping device 136 shown in FIG. 18. Clamping device 136 includes split cylinder halves 138, each of which have flanged longitudinal edges 140, 141 with spaced holes 142 therein. The split cylinder halves 138 are sized to fit on the piping 122 with one cylinder halve over the nozzle's flange 134 and with the flanged edges 140, 141 slightly spaced apart. Nuts (not shown) are provided or the holes 142 in one of the cylinder halves are threaded so that tightening bolts 144 passing through holes 142 in the flanged edges 140, 141 of the cylinder halves results in clamping the nozzle's flange 134 to the piping. A mechanical seal is provided by compression of the gasket material 56 between the nozzle's flange 134 and the piping 122. In the embodiments described above, a structurally welded and seal welded nozzle may be removed by cutting or machining operations. As mentioned, the invention is also applicable to replacement of nozzles attached and sealed in other ways, (e.g., as described in the prior art discussed above and by mechanical attachment and sealing as described in the prior art discussed above and by mechanical attachment and sealing as described herein). Further, the invention is applicable to the new installation of nozzles as opposed to replacement of existing nozzles. In the claims, the term vessel is used in a broad sense and is meant to include, but not to be limited to, vessels, piping, etc., of different types which may operate under pressure and which may be used in different nuclear and non-nuclear ASME applications, and the term nozzle is used in a broad sense and is meant to include, but not be limited to, nozzles, sleeves, large bore pipes, pipe portions, etc. While the invention has been described and illustrated in connection with preferred embodiments, many variations and modifications, as will be evident to those skilled in this art, may be made without departing from the spirit and scope of the invention. The invention, as set forth in the appended claims, is thus not to be limited to the precise details of construction set forth above, as such variations and modifications are intended to be included within the spirit and scope of the invention as defined in the appended claims.