DISTRIBUTOR CASING FOR HEAT EXCHANGERS WITH CORROSION-PROOF LINING

Abstract: Distributor casing (10) of the type suitable for fitting onto the head of tube nests of heat exchangers and internally lined with corrosion-proof material (12), comprising a cylindrical wall (11) peripherally abutting onto a discoidal base plate (13) welded thereto through which pass said tube nests (14), said plate (13) being provided with an annular groove (19) with its concavity substantially tangent to the seam between the plate (13) and cylindrical wall (11), said groove (19) containing a coupling element (15) made of corrosion-proof material, complementary to the recess and with its inward facing surface connecting the lining (23) of the base plate (13) to the lining (12) of the wall (11) so as not to create a stress raiser. Said coupling elements (15) comprises a cylindrical extension (16) welded thereto designed to adhere to the side wall (11). All the seams between the lining (12, 23) and the coupling element (15) are covered with butt straps (17, 18).The corrosion-proofmaterial is preferably titanium.

Description: The invention relates to a heat exchanger comprising the features as indicated in the precharacterising part of claim 1. It is known that pressure vessels for heat exchange equipment (for example, distributor casings for heat exchangers, reactors, stripper, etc.) can be made with internal surfaces lined with materials which are highly resistant to corrosion. It is further known for the tube plate to be made in the shape of a tank with radiused bottom and sides so as not to have sharp corners, which are possible stress raisers, and so as to bring the seam between the tube plate and the cylindrical wall of the vessel on the same plane, as is customary with pressure vessels. Finally it is known that one type of higly corrosion proof internal lining can be made from titanium. This material however is difficult to use, since it cannot be welded onto the steel of which the parts to be lined are made. Use is therefore made of titanium-plated steel (usually by explosive cladding). The state of the art is shown, for example, in Titze "Elemente des Apparatebaues" 1963, Springer-Verlag, Berlin, pag. 198-9. One disadvantage shown by the known technique is linked to the difficultly of ensuring the continuity of the titanium lining on the seams between the parts making up the vessel, also in view of the characteristics that such seams must have in order to withstand the high pressures to which they are subjected. In particular, it is critical the seam between the cylindrical part of the vessels and the tube plate which closes one end of them. In fact, since the cladding of the tube plate is achieved by explosion, the shape of the tank gives rise to problems in obtaining a coating of uniform thickness, and considerable stress on the upper edges of the tank during the explosion, due to the fact that they obstruct the expansion of the explosion gases. The stress could lead to chipping of the rim of the plate, resulting in irreparable damage to the plate itself and its consequent rejection. Moreover, due to the radius between the bottom and wall of the tube plate, the tubes of the latter can only be fitted in its central area, thus wasting a considerable amount of surface inside the vessel. It is the object of this invention to remedy the aforementioned problems by providing a pressure vessel, such as a distributor casing for heat exchangers, with a continuous titanium lining and in which the seams, especially between the tube plate and the cylindrical side wall are easy to carry out and highly reliable. In accordance with the invention, this object is solved by a heat exchanger comprising a distributor casing with a cylindrical wall peripherally abutting onto a discoidal base plate welded thereto and penetrated by a plurality of tubes, the casing and the tube plate being internally lined with corrosion proof material, characterized in that, said plate being provided with an annular groove, the outer edge of the groove being in correspondence with the internal perimeter of the cylindrical wall of the distributor casing, in proximity of the joint between wall and plate, said groove containing a coupling element made out of corrosion proof material and having a form complementary to said groove, said coupling element, welded in place, connecting with its surface, facing the inside of the casing, the lining of the tube plate to the lining of the cylindrical wall and welded thereto. In order to give a clearer explanation of this invent ion and its advantages with respect to the known technique, a description is given hereunder, with reference to the accompanying drawings, of a possible exemplary embodiment using such principles, in which: figure 1 shows a schematic side elevation cross-sectional view of a distributor casing constructed according to the innovatory principles claimed herein; figure 2 shows an enlarged partial view of the casing of figure 1. With reference to the figures, a distributor casing 10 of the type fitted to the head of tube nests for heat exchangers comprises according to the invention, as can be seen in figure 1, a cylindrical portion 11 fitted with a lining consisting of a suitably shaped sheet 12 of corrosion-proof material, for example titanium-plated steel. A disc-shaped tube plate 13 carrying a plurality of tubes 14 is made substantially flat and explosion cladded on its central area 23 with titanium. Said plate is butt welded to the cylindrical portion 11 (reference 22 indicates the weld bead between the parts). The upper part of the casing is closed by a dome-shaped section 20 made and connected to the cylindrical portion according to the known technique and is also covered with titanium according to the known method. There are conduits and devices, also made according to known techniques and consequently not shown or described herein, to enable the casing to carry out the function for which it is designed. As can be more clearly seen in figure 2, the tube plate is provided with a semicircular section annular groove 19 in correspondence with the internal perimeter of the cylindrical wall, with its concavity substantially tangent to the seam between the plate 13 and the wall 11. A coupling element 15 made of titanium, complementary to the recess 19 and welded in place, is provided with an inward facing surface which connects the lining of the tube plate to the lining of the wall 11. In order to make said coupling element easier to fit, a titanium insert 16 is positioned and welded between the edge of the lateral lining and the seam itself in correspondence with a step 21 on the wall 11. Said step serves the purpose of bringing the external surface of the coupling 15 up to the same level as that of the lining 12, which is of a different thickness. Titanium butt straps 17, 18 are positioned and welded between the cylindrical wall and the coupling 15 and between the coupling 15 and the tube plate so as to ensure continuity of the titanium lining also in correspondence with the weld and couplings between said parts. In order to make them easier to fit in position, the coupling 15, insert 16 and butt straps 17, 18 may be made in radially cut segments, as can be easily inferred by anyone expert in the art. Due to the shape of the coupling 15 it is possible to bring the weldings between the linings of the wall 11 and of the plate 13 onto the same plane thereby avoiding stress raisers and sharp corners between the internal wall of the vessel. The connection between the tube plate and the cylindrical wall described herein offers numerous advantages which make it possible to produce high quality vessels. By making the tube plate substantially flat in shape it can be uniformly cladded without damage to its outer edges during the cladding process, as occurs with tank-shaped tube plates made by means of the known technique. Furthermore, the shape of the coupling 15 enables the entire surface of the tube plate to be utilized for passage of the heat exchanger tubes, as far as the coupling, thereby making it possible to obtain distributor casings, with the same number of tube nests, with more limited dimensions than those obtainable with tank-shaped tube plates. Although titanium has been found to be the material most advantageously used for the lining, any other suitable corrosion-proof material can obviously be used.

Claims: Heat exchanger, comprising a distributor casing (10), with a cylindrical wall (11) peripherally abutting onto a discoidal base plate (13) welded thereto and penetrated by a plurality of tubes (14), the casing (10) and the tube plate (13) being internally lined with corrosion proof material, characterized in that said plate (13) being provided with an annular groove (19), the outer edge of the groove being in correspondence with the internal perimeter of the cylindrical wall (11) of the distributor casing (10), in proximity of the joint between wall and plate, said groove (19) containing a coupling element (15) made out of corrosion proof material and having a form complementary to said groove (19), said coupling element (15), welded in place, connecting with its surface, facing the inside of the casing (10), the lining of the tube plate (13) to the lining of the cylindrical wall (11) and welded thereto. Heat exchanger as claimed in claim 1, characterized by the fact that said coupling element (15) comprises a cylindrical extension (16) designed to adhere to the lateral wall (11). Heat exchanger as claimed in claim 1, characterized by the fact that said coupling element (15) is made of a plurality of segments (15) welded together after being fitted into the groove (19). Heat exchanger as claimed in claim 1, characterized by the fact that said groove (19) has a substantially semicircular cross section. Heat exchanger as claimed in claim 2, characterized by the fact that said extension (16) is housed in a depressed annular seat (21) in the cylindrical wall (11). Heat exchanger as claimed in claim 5, characterized by the fact that the external edge of said extension (16) is in the form of a welded element (16) after being fitted into the depressed annular seat (21). Heat exchanger as claimed in claim 1, characterized by the fact that butt straps (17, 18) made of corrosion-proof material welded laterally to the underlying parts are provided on the seams between the lining and the coupling element (15) and between the parts of the latter. Heat exchanger as claimed in claim 1, characterized by the fact that the lining of the cylindrical wall (11) consists of a sheet (12) of corrosion-proof material at least partially comprising its surface facing towards the inside of the cylinder, bent in order to adapt to the internal wall (11) of the cylinder. Heat exchanger as claimed in claim 1, characterized by the fact that the lining of the base plate (13) consists of a corrosion proof material applied by means of explosive cladding. Heat exchanger as claimed in the previous claims, characterized by the fact that the corrosion-proof material is titanium.

Inventors: COLLI, LUIGI, FORLANI, GIULIO
Applicants: FBM-HUDSON ITALIANA S.P.A.
Application year: 1989
Main classification: F28F19
IPC codes: F28F19, B01D1, F28F9