WO1982000877A1

WO1982000877A1 - Joint assembly for heat exchangers

Info

Publication number: WO1982000877A1
Application number: PCT/GB1981/000171
Authority: WO
Inventors: Ind Ltd Serck
Original assignee: Serck Industries Ltd
Current assignee: Serck Industries Ltd
Priority date: 1980-08-28
Filing date: 1981-08-28
Publication date: 1982-03-18
Anticipated expiration: 1983-02-28
Also published as: EP0059197A1; GB2093549A

Abstract

Un ensemble formant joint entre deux parties (10 et 11) est forme par un renfoncement (16) dirige vers l'interieur dans la peripherie interne de la partie (10) qui entoure la partie (11), et un renfoncement (18) dirige vers l'exterieur dans la partie (11) et dispose en face du renfoncement (16). Un organe (19) allonge flexible, tel qu'une barre ductile, est dispose entre les parties (10 et 11) et s'engage dans les deux renfoncements (16 et 18) afin d'empecher une separation des parties. L'organe (19) est introduit dans les renfoncements (16 et 18) au travers d'un passage (20) qui s'etend depuis le renfoncement (16) jusqu'a la surface exterieure de la partie (10). L'organe (19) peut etre remplace par une pluralite d'elements individuels, tels que des billes, qui sont inserees separement au travers du passage (20). L'ensemble de joint peut etre utilise pour relier un capot a la coquille d'un echangeur de chaleur du type a coquille et tuyau, ou peut etre utilise pour retenir a l'interieur de la coquille une plaque de support qui supporte par exemple des tuyaux a l'interieur de la coquille.A joint assembly between two parts (10 and 11) is formed by a recess (16) facing inwards in the inner periphery of the part (10) which surrounds the part (11), and a recess (18) facing outwards in the part (11) and has opposite the recess (16). A flexible elongate member (19), such as a ductile bar, is disposed between the parts (10 and 11) and engages the two recesses (16 and 18) to prevent separation of the parts. The member (19) is introduced into the recesses (16 and 18) through a passage (20) which extends from the recess (16) to the outer surface of the part (10). The member (19) can be replaced by a plurality of individual elements, such as balls, which are inserted separately through the passage (20). The gasket assembly may be used to connect a cover to the shell of a shell and pipe type heat exchanger, or may be used to retain within the shell a support plate which supports, for example, pipes inside the shell.

Description

"JOINT ASSEMBLY FOR HEAT EXCHANGERS"

This invention relates to heat exchangers, and more particularly to a joint assembly for joining together its component parts.

It is common practice to secure an end cover to the cylindrical body or shell of a shell and tube type heat exchanger by providing outwardly extending peripheral flanges on the end cover and on the cylindrical body and fastening the flanges together using bolts which pass through aligned apertures in the flanges. However, such a flange and bolt construction has the disadvantage that it increases the external space occupied by the heat exchanger and also increases the weight thereof.

It is an object of the present invention to obviate or mitigate the above disadvantages.

According to one aspect of the present: invention, there is provided a heat exchanger including or having associated therewith a joint assembly comprising a first part having a hollow therein, a second part which extends into or is disposed in said hollow, an inwardly directed recess in the first part which, extends around sai'd hollow, an outwardly directed recess which extends around the second part and lies opposite the inwardly directed recess, a passage extending from the inwardly directed recess to an external surface of the first part, and retaining means disposed between the first and second parts and being engaged in both of the recesses so as to retain the first and second parts against separation, the retaining means and the passage being arranged so that the retaining means can be disposed in position between the first and second parts by insertion through the passage in the first part.

The retaining means may take the form of a flexible elongate member. A most preferred example of such a member is a ductile rod, but the flexible elongate member may alternatively be a ductile tube or a helical spring. Alternatively, the retaining means may taics the form of a plurality of individual elements, such as halls, which are inserted separately into the passage.

It is preferred for the recesses to extend completely around the first and second parts respectively.

The passage is preferably provided with a plug or the like to prevent unwanted disengagement of the retaining means from the recesses.

If a seal is required between the first and second parts, this can be provided by disposing at least one sealing ring in a respective separate recess in the first or tiie second part. Where two or more such sealing rings are provided, they are engaged in respective recesses at least one of which is disposed on the opposite side of the inwardly and outwardly directed recesses to the remaining recesses. In this case, in order that leakage of fluid past the seals may readily be detected, a hole is preferably formed in the first part so as to open at one end thereof into the hollow between the recesses in which the sealing rings are engaged and to open at the other end thereof onto an external surface of the first part. Most preferably, the hole opens into said inwardly directed recess.

In the case where the first and second parts are capable of relative rotation and the retaining means is a flexible elongate member, it is particularly convenient to provide the second part with a formation with which one end of the flexible elongate member can be engaged after having been inserted through the passage, whereby the flexible elongate member can be moved into position in the inwardly and outwardly facing recesses by effecting relative rotation between the first and second parts. With such an arrangement, it is also preferred for the opposite end of the flexible elongate member to engage a formation on the first and second parts after the flexible elongate member has been properly engaged in the inwardly and outwardly directed recesses. In the case where the first and second parts axe of a shape such that they are capable of relative rotation and where the retaining means takes the form of balls or the like which inherently do not prevent such relative rotation, it is preferred to provide a retaining device to retain the first and second parts in a predetermined angular relation. The retaining device may be composed of a retaining member mounted for movement into and out of engagement with a recess in the second part. Where the retaining means comprises a plurality of individual elements, the retaining member can have a wedge-shaped portion which engages between adjacent ones of the elements to force the latter apart and prevent any rotation between the first and second parts.

The joint assembly has a variety of applications in the heat exchanger. Fox example, said first part can be a hollow tubular casing of the heat exchanger and said second part can be eithex an end cover which closes an end of the casing ox a tube plate which supports a plurality of tubes within the casing. Alternatively, said fixst and second parts can be constituted by a fluid inlet port in a casing of the heat exchanger and fluid supply pipework. In a further alternative arrangement, two such joint assemblies are employed with the respective first parts thereof being defined by a sleeve and the respective second parts thereof being formed on ends of two pipes which are inserted into the sleeve, the pipes and sleeve forming part of connecting pipework for the heat exchanger.

According to a second aspect of the present invention, there is provided a heat exchanger comprising a hollow tubular casing through the interior of which a first fluid is passed in use, end covers closing the ends of the casing, a plurality of tubes disposed in the casing and through which a second fluid is passed in use for heat-exchange with the first fluid, the tubes being supported in the casing by means of at least one support member, the end covers and/ or said at least one support member being joined to the casing by means of joint assemblies each of which includes an inwardly directed recess provided in the casing and extending around the end cover or the support member, an outwardly dixected recess provided in the end cover or the support member and positioned opposite the inwardly directed recess, a passage extending from the inwardly directed recess to an external surface of the casing, and retaining means disposed between the casing and the end covex or the support member, the retaining means being engaged in both of said recesses so as to retain the casing and the end cover or the support member against separation and being inserted into said recesses through the passage.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in whichs:—

Figure 1 is an axial section through part of a heat exchanger according to the present invention;

Figure 2 is an axial section of one embodiment of a joint assembly which forms part of the heat exchanger shown in Figure 1 ;

Figure 3 is a section on the line III—III of Figure 2;

Figure 4 is an axial section of a second embodiment of the joint assembly;

Figure 5 is an axial section through part of the joint assembly shown in either of Figures 2 and 4 showing in detail the manner in which the parts of the joint assembly are engaged with one another;

Figure 6 is a schematic illustration of a third embodiment of the joint assembly;

Figure 7 is a cross—section of a fourth embodiment of a joint assembly;

Figure 8 is an axial section of a modification of the joint assembly of Figure 7;

Figure 9 is a. cross—section of the joint assembly shown in Figure 8 ; and

Figure 10 is an axial section showing the use of two joint assemblies for joining fluid supply connections of the heat exchanger to fluid pipework or for joining together two lengths of pipe.

Referring first to Figure 1 , the heat exchanger shown therein is of the shell and tube type, and comprises an outer casing or shell 10 whose ends are closed by respective end covers 11 (only one shown). A plurality of tubes 12 are disposed within the shell 10 and are supported by means of tube plates 13 (again, only one shown). Ports 14 and 15 in the shell respectively permit a first fluid to be passed through the interior of the shell 10 and a second fluid to be passed through the tubes 12 fox heat—exchange with the first fluid. The end covers 11 and the tube plates 13 are fixed relative to the shell 10 by means of respective joint assemblies which will now be described with more particular reference to Figures 2 and 3.

Each of the joint assemblies comprises an inwardly directed recess 16 in the internal surface of the shell 10 which extends completely around the external periphery of the tube plate 13 or a cylindrical extension 17 of the end cover 11 which is received within the shell, as the case may be. An outwardly directed recess 18 is provided in the tube plate 13 or the extension 17 and is disposed opposite the recess 16. A flexible elongate member 19 is disposed between the shell 10 and the end cover 11 or the tube plate 13 and engages in both of the recesses 16 and 18 to retain these parts against separation. The member 19 is introduced into the recesses 16 and 18 through a passage 20 which extends tangentially from the recess 16 to the external surface of the shell 10. In order to prevent unwanted disengagement of the member 19 from the recesses 16 and 18, the passage 20 is provided with a plug 21. The plug is however only one example of many suitable means which can be employed to prevent disengagement of the member 19 from the recesses 16 and 18. In the arrangement illustrated in Figures 2 and 3, the plug 21 is externally threaded and engages internal threading in the passage 20. However, the plug 21 and the passage 20 may instead be plain so that the plug is an interference fit in the passage.

The flexible elongate member 19 preferably takes the form of a ductile rod or a ductile tube, as shown. However, it is also possible for the membex 19 to be in the form of a helical spring.

The joint assembly is made by inserting the portion 17 of the end cover 11 ox the tube plate 13, as the case may be, into the shell 10 until the recesses 16 and 18 come into mutual alignment. In the case of the end cap 11, this will pccur when it abuts against the end of the casing 10, as illustrated in Figure 2. One end of the member 19 is then inserted through the passage 20 and into the recesses 16 and 18, the flexible nature of the member 19 permitting it to be slid readily into place until its leading end abuts against its tail end, as shown in Figure 3. The member 19 is then retained in position by screwing the plug 21 into the passage 20. To extract the member 19, the plug 21 is removed and a suitable extractor tool is inserted into the passage 20 to grip the tail end of the membex 19. In the case where the member19 is a helical spring, the extractor tool has screw- threading thereon and is simply screwed into the tail end of the member 19, this being possible because the coils of the spring form screw—threading on the interior of the member 19. Such a helical spring can easily be extracted because the greater the removal pressure applied by the extractor tool, the greater the stretch of the spring and the smaller the diameter thereof. In the limiting case, the spring will be reduced to a length of straight wire. Where a seal is required between the shell 10 and the end cover 11 or the tube plate 13 as the case may be, the joint assembly shown in Figure 4 may be employed. In this construction, a pair of annular recesses 22 axe pxovided in the portion 17 of the end cover 11 or in the external periphery of the tube plate 13 on opposite sides of the recess 18, and rubber sealing rings 23 are disposed in these recesses respectively. Although it is preferred for two such sealing rings and recesses to be provided for the purpose of balancing and vibration damping, only one sealing ring and recess may be provided if desired, such as is shown fox the end cover 11 in Figure 1. In the heat exchanger of Figure 1 , the seals can act not only to sepaxate the fixst and second fluids from each other but, in relation to the end cover 11 , also to prevent the ingress of moisture or other external fluid.

It will be appreciated that either or both of the recesses 22 could be provided in the internal periphery of the shell 10. Alternatively, in the case of the end cover 11, one of the seals may be provided between the axial end of the shell 10 and the axially opposed portion of the end cover. In order to provide evidence of leakage past either or both of the sealing rings 23, a small hole 24 is provided in the inwardly directed recess 16 and communicates with the external, surface of the shell 10.

Referring back to Figure 1 , the end cover 11 on the one hand and the tube plate 13 on the other hand may be rotatable relative to the shell 10, for example for the purpose of assisting insextion of the flexible elongate membex 19 into the recesses 16 and 18 in a manner to be described later. To facilitate such rotation by means of .a suitable tool, the end cover and tube plate have respective hexagonal bosses 25 and 26 thereon. If it is desired to ensure that the end cover or the tube plate are fixed in a predetermined angular relationship, a retaining device may be provided for this purpose. The retaining device may take any convenient form, such as a dowel pin which is inserted into aligned holes in the shell 10 and the end cover or tube plate.

In Figure 1, the joint assembly associated with the tube plate 13 is shown as having the same dimensions as that associated with the end cover 11. However, the joint assemblies may be of different dimensions if the heat exchanger so requires.

Referring now to Figure 5, the shapes of the recesses 16 and 18 are shown in greater detail. The inwardly directed recess 16 is semi-circular in cross—section, with the centre thereof being disposed at or even slightly radially inwardly of the internal wall surface of the shell 10. In the construction actually shown, the centre lies in the internal wall surface of the shell 10. In contrast, the recess 18 has a part—circular cross—section of the same radius as that of the recess 16 but the centre of the radius is disposed radially inwardly of the external peripheral surface of the portion 17 of the end cover 11 or the external surface of the tube plate 13, as the case may be. The flexible elongate member 19 has an external diameter which is slightly less than twice the radius of the recess 16. Because the member 19 is straight in its unstressed state, when it is inserted between the shell 10 and the end cover 11 or the tube plate 13, its inhexent tendency to straighten means that it will engage against the base of the recess 16 in the manner illustrated in Figure 5. This leaves a clearance 27 between the member 19 and the base of the recess 18. The provision of such a clearance 27 is of advantage since minor irregularities on the external surface of the membex 19 (due, for example, to cutting to length), ox the inherent reluctance of the end of the member to bend, may necessitate the provision of such a clearance to ensure easy insertion. In use, when a force P is exerted on the end cover 11 or the tube plate 13 in the direction indicated in Figure 5, side edge 28 of the recess 18 abuts against the member 19 and the load is restrained by the member 19 abutting against side edge 29 of the recess 16. Particularly in the case where the member 19 is in the form of a ductile tube or a helical spring, it can deform from its original circular shape to an ovoid, thus filling some of the clearance 27 and providing further load spreading. The use of a ductile rod or tube is preferred for the member 19 because it avoids deformation of the side walls of the recesses 16 and 18 in the presence of high end pressure on the end cover 11 or the tube plate 13.

Referring now to Figure 6, the embodiment of joint assembly illustrated therein is similar to those described hereinabove with reference to Figures 2 to 5. However, in this embodiment, engagement of the member 19 between the shell 10 and the portion 17 of the end cover 11 or the rube plate 13, as the case may be, is effected by rotation of the latter relative to the shell 10 in the direction of the arrow shown in Figure 6. For this purpose, the passage 20 is made in the form of a relatively large cut—out in the wall of the shell 10, a blind bore 30 is provided in the base of the recess 18 to extend radially inwardly of the portion 17 or the tube plate 13, and a leading end 31 of the member 19 is bent over at 90 with respect to the main body of the member 19. A tail end 32 of the member is bent over at 90 to the main body of the member and with respect to the leading end 31. In use, the end cover 11 or the tube plate 13, as the case may be, is angularly orientated relative to the shell 10 until the bore 30 can be viewed through the passage 20. The leading end 31 of the member 19 is inserted into the bore 30 and the end cover 11 or the tube plate 13 is rotated in the direction of the arrow in Figure 6, thus drawing the member 19 into the recesses 16 and 18 until further rotation is prevented by the bent-over tail end 32 of the membex 19 engaging in a slot 33. The slot 33 extends from the passage 20 and is of a size to accommodate the tail end 32 of the member 19. Removal of the member 19 is effected by reverse rotation of the end cover 11 or the tube plate 13 once the tail end 32 has been removed from the slot 33 so that the member is driven out of the passage 20. If the embodiment of Figure 6 is provided with sealing rings 23 as in the embodiment of Figure 4, it is found that the inherent friction generated by these sealing rings opposes rotation between the end cover 11 or tube plate 13 and the shell 10 in service. If additional security is required against relative rotation between these parts, a dowel pin arrangement may be used in the manner described previously.

Where rotation of the end cover 11 is employed to insert the member 19, it is particularly advantageous to arrange for this to occur by anti-clockwise rotation of the end cover 11 (as shown in Figure 6) since the external appearance to the end cap fitted to the cylinder suggests that the end cap is secured to the cylinder by a screw—thread arrangement which would normally be unscrewed in an antclockwise direction. This affords some measure against tampering, particularly if the end cover 11 is formed so as to have a hexagonal shape in the manner of a conventional nut.

Referring now to Figure 7, the joint assembly illustrated therein employs a milltiplicity of -ball bearings 34 in the place of the flexible elongate member 19. The screw—threaded plug 21 is now replaced by a round—ended dowel 35 which is driven into the passage 20 which, in this embodiment, is not screw—threaded. Because the ball bearings 34 can easily roll and because they can be manufactured to much finer tolerances than a helical spring, for example, it is not necessary for a large clearance to be provided for them. Accordingly, it is possible to provide the recesses 16 and 18 in such a way that they define a passage of circular cross—section having a diameter which is only marginally greater than the diameter of the ball bearings 34 .

However, as shown in Figures 8 and 9, it is possible for each of the recesses 16 and 18 to have a flat base and side edges which converge towards the base so that rhe recesses together define a hexagonal passage for the balls 34. In this embodiment, and as particularly shown in Figure 9, the rangentially extending passage 20 is replaced by a radially extending, internally screw-threaded passage 3β fitted with an externally screw—threaded rod 37 having a slotted outer end 38 and a lock-nut 39. The inner end region of the rod 37 bas a frus^*coconically tapered portion •40 and a dowel portion 41. The dowel portion 4l is engageable in a blind bore 42 in the portion 17 of the end cover 11 or the tube plate 13, as the case may be. In this embodiment, with the rod 37 removed from the passage 36, the end cover 11 or the tube plate 13 is inserted into rhe shell 10 until the recesses 16 and 18 lie opposite one another, and the end cover or tube plate 13 is rotated until the blind bore 42 can be viewed through the passage 36. Then, the ball bearings 34 are inserted through the passage 36. The rod 37 may alternatively be unthreaded and driven into the passage 3°^"»

The number of ball bearings 34 added is at least one less than that required to fill completely the passage defined by the recesses 16 and 18. The rod 37 is then screwed down using a screwdriver in the slot 38, until the dowel portion 41 is engaged in the blind bore 42. The tapered portion 40 forces the ball beaxings 34 into contact with each other and into contact with the convergent side edges of the grooves 16 and 18 and so locks them firmly in position against vibration in service. The engagement of the dowel portion 41 in the blind bore 42 also serves to lock the end cover 11 ox tube plate 13 against angular movement relative to the shell 10. The lock-nut 39 serves to prevent the rod 37 from vibrating loose in service. If desired, more than one rod 37 may be employed and located in a respective passage 36 in. the shell 10. In this case, the number of ball bearings 34 will be correspondingly reduced.

It is to be appreciated that any of the joint assemblies described above with reference to Figures 2 to 9 can also be used to replace rhe usual bolted flange connections or screw-theaded connections in, for example, relief valves or temperature sensing device/which may be fitted to the heat exchanger.

It is possible to utilise two joint assemblies to couple pipe lengths together and this is shown in Figure 10 where, in effect, two joint assemblies are employed with the appropriate parts thereof being provided on a single sleeve 43, and the remaining parts thereof being provided on pipe lengths 44 and 45 respectively. The sleeve 43 has a pair of inwardly directed recesses 46 and 47 which axe spaced apaxt axially of the sleeve 43. Each pipe 44 or 45 nas a respective outwardly directed recess 48 or 49 which is disposed opposite the respective recess 46 or 47 when the pipes are connected together. A respective flexible elongate member 50, 51 is engaged with each pair of recesses 46, 48 and 47, 49. Each joint assembly operates in the manner descxibed with reference to Figures 2 and 3. In order to ensure sealing of the joint, sealing rings 52 and 53 are disposed in respective recesses 54, 55 in the sleeve 43 and engage with, and seal against, the outer surfaces of the respective pipes 44 and 45. A connection of this type may be employed, for example, to join together pipes in fluid supply pipework of the heat exchanger shown in Figure 1, or to join such pipework to the ports 14 and 15 in the shell 10.

In all of the above—described embodiments, the recesses 16 and 18 have been illustrated as being circular or hexagonal in cross—section and are disposed within respective parts of circular cross—section. However, it is within the scope of the present invention to apply the joint assembly to parts which are of non-circular cross—section and/or provide alternative forms of non—circular recesses 16 and 18. Examples of such non-circular shapes are oval, rectangular, square or other polygonal form. When using retaining means in the form of a flexible elongate member, suitably proportioned comer radii must be provided to enable the member to travel easily into the required position. It may be necessary to employ more than one length of flexible elongate member to achieve the desired resuits.

Claims

C L A I M S :

1. A heat exchanger including or having associated therewith a joint assembly comprising a first part having a hollow therein, a second part which extends into or is disposed in said hollow, an inwardly directed recess in the first part which extends around said hollow, an outwardly directed recess which extends around the second part and lies opposite the inwardly directed recess, a passage extending from the inwardly directed recess to an external surface of the first part, and retaining means disposed between the first and second parts and being engaged in both of said recesses so as to retain the first and second parts against separation, the retaining means and the passage being arranged so that the retaining means can be disposed in position between the first and second parts by insertion through the passage in the first part.

2. A heat exchanger as claimed in Claim 1, wherein the retaining means is in the form of a flexible elongate member.

3. A heat exchanger as claimed in Claim 2, wherein the retaining means is in the form of a ductile rod.

4. A heat exchanger as claimed in Claim 2 , wherein the retaining means is in the form of a ductile tube.

5. A heat exchanger as claimed in Claim 2, wherein the retaining means is in the form of a helical spring.

6. A heat exchanger as claimed in any one of Claims 2 to

5, wherein the first and second parts axe capable of relative rotation, and the second part has a formation thereon with which an end of the flexible member can be engaged after having been inserted through the passage, whereby the flexible elongate member can be moved into position in the inwardly and outwardly facing recesses by effecting relative rotation between the first and second parts.

7. A heat exchanger as claimed in Claim 6, wherein the opposite end of the flexible elongate member engages a formation on the first part to prevent further relative rotation between the first and second parts after the flexible elongate member has been properly engaged in said recesses.

8. A heat exchanger as claimed in Claim 1, wherein the retaining means is in the form of a plurality of individual elements which axe insexted sepaxately into the passage.

9. A heat exchangex as claimed in Claim 8, whexein the retaining means comprises a plurality of balls.

10. A heat exchanger as claimed in any preceding Claim, wherein the paissage is provided with a plug or the like to prevent unwanted disengagement of the retaining means from the recesses.

11. A heat exchanger as claimed in any preceding Claim, wherein a seal is provided between the first and second parts and is composed of at least one sealing ring disposed in a respective separate recess in the first or the second part.

12. A heat exchanger as claimed in Claim 11, wherein the seal is composed of at least two such sealing rings engaged in respective recesses at least one of which is disposed on the opposite side of the inwardly and outwardly directed recesses to the remaining recesses.

13. A heat exchanger as claimed in Claim 12, wherein a hole is formed in the first part so as to open at one end thereof into the hollow between the recesses in which the sealing rings are engaged and to open at the other end thereof onto an external surface of the first part.

14. A heat exchanger as claimed in Claim 13, wherein said hole opens into said inwardly directed recess.

15. A beat exchanger as claimed in any preceding Claim, wherein the fixst and second paxts are capable of relative rotation, and a retaining device is provided to retain the first and second paxts in a predeteimined angular relation.

116. A heat exchanger as claimed in Claim 15, wherein the retaining device is composed of a retaining member mounted dn the first part for movement into and out of engagement with a recess in the second part.

17. A heat exchangex as claimed in Claim 16, wherein the retaining means comprises a plurality of individual elements, and the retaining member has a wedge—shaped portion which engages between adjacent ones of said elements to force the latter apart and prevent any rotation between the first and second parts.

18. A heat exchanger as claimed in any preceding Claim, wherein the inwardly and outwardly facing recesses are each part—circular in transverse cross—section.

19. A heat exchanger as claimed in any one of Claims

1 to 17, wherein the inwardly and outwardly facing recesses each have a flat base wall and sloping side walls.

20. A heat exchanger as claimed in any preceding Claim, wherein the inwardly and outwaxdly directed recesses extend completely around the first and second paxts respectively.

21. A heat exchanger as claimed in Claim 20, wherein the inwardly and outwaxdly directed recesses are provided in respective portions of the first and second paxts which are generally of circular cylindrical configuration, and the passage extends generally tangentially to the recesses.

22. A heat exchanger as claimed in any one of Claims 1 to 19, wherein the hollow in said first part and the external surface of the second part are of complementary polygonal cross—sections, and separate inwardly and outwardly directed recesses, separate retaining means and a separate passage are provided for each side of the polygon.

23. A heat exchanger as claimed in any preceding Claim, wherein said fixst part is a hollow tubular casing of the heat exchanger and said second part is an end cover which closes as end of said casing.

24. A heat exchanger as claimed in any one of Claims 1 to 22, wherein said first part is a hollow tubular casing of the heat exchanger and said second part is a tube plate which supports a plurality of tubes within said casing.

25. A heat exchanger as claimed in any one of Claims 1 to 22, wherein said first and second parts are constituted by a fluid inlet port in a casing of the heat exchanger and fluid supply pipework.

26. A heat exchanger as claimed in any one of Claims 1 to 22, wherein two such joint assemblies are employed with the respective first parts thereof being defined by a sleeve and the respective second parts thereof being formed on ends of two pipes which are inserted into the sleeve, said pipes and said sleeve forming part of connecting pipework of the heat exchanger.

27. A. heat exchanger comprising a hollow tubular casing through the interior of which a first fluid is passed in use, end covers closing the ends of the casing, a plurality of tubes disposed in the casing and through which a second fluid is p ass ed in use fox heat-exchange with the first fluid, the tubes being supported in the casing by means of at least one support member, the end covers and/or said at least one support member being joined to the casing by means of joint assemblies each of which includes an inwardly directed recess provided in the casing and extending around the end cover or the support member, an outwardly directed recess provided in the end cover or the support member and positioned opposite the inwardly directed recess, a passage extending from the inwardly directed recess to an external surface of the casing, and retaining means disposed between the casing and the end cover or the support member, the retaining means being engaged in both of said recesses so as to retain the casing and the end cover or the support member against separation and being inserted into said recesses through the passage.