Shell-and-tube equipment with antivibration baffles and related assembling method

Abstract

Shell-and-tube equipment includes baffles supporting the tubes, each baffle having seats for receiving the tubes shaped so as to receive one or more tubes in at least one free play condition and in a locking condition; each baffle is displaceable with respect to the tube bundle between an assembly position and a working position; in the assembly position the tubes can be received by the baffles in the free play condition while in the working position the tubes are locked.

Claims

1. A shell-and-tube equipment comprising a shell, a bundle of tubes, a plurality of baffles supporting the tubes, each baffle having a plurality of seats for receiving the tubes, each seat receiving at least one tube, wherein: each of said seats comprises at least one first region designed to receive said at least one tube with a predefined first play, and at least one second region designed to receive said at least one tube with a second play smaller than the first play, or with no play, each baffle is configured so as to be displaceable, with respect to the tube bundle, between an assembly position, and a working position, each tube of the bundle being received in the at least one first region of a respective seat when the baffle is in said assembly position, and in the at least one second region of the respective seat when the baffle is in said working position.

2. The equipment according to claim 1, wherein each baffle is displaceable from said assembly position in said working position with a linear displacement.

3. The equipment according to claim 1, wherein each baffle is configured so as to be displaceable from said assembly position in said working position with an angular rotation.

4. The equipment according to claim 3, wherein each baffle is configured so as to be displaceable from said assembly position in said working position with an angular rotation performed about an axis of the tube bundle.

5. The equipment according to claim 3, wherein: the tubes are arranged in concentric rows; the baffles comprise a plurality of concentric rings and said tubes receiving seats are formed as recesses of said circular rings.

6. The equipment according to claim 1, wherein adjacent baffles have tubes receiving seats with a conjugate shape and/or arrangement so that said adjacent baffles pass from the working position to the assembly position with opposite movements.

7. The equipment according to claim 1, wherein each of said tubes receiving seats comprises at least one effective surface which: is spaced from a respective tube when the baffle is in said assembly position, and is in contact with said tube when the baffle is in said working position.

8. The equipment according to claim 7, each of the receiving seats comprising two effective surfaces which converge to form a wedge to define said second region.

9. The equipment according to claim 8, the receiving seats having a trapezoidal shape.

10. The equipment according to claim 1, wherein the baffles consist of flat metal sheets and the tubes receiving seats are represented by windows formed in the baffles.

11. The equipment according to claim 1, wherein the baffles are locked in respective working positions, spaced by a predefined pitch, directly by the shell of the equipment.

12. The equipment according to claim 1, wherein the tubes are straight tubes or U-shaped tubes in which the baffles are mounted on respective straight portions.

13. The equipment according to claim 1, wherein the equipment is an axial-flow heat exchanger in which a shell-side fluid passes through the baffles and each seat receives a plurality of tubes.

Description

DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows a simplified diagram of shell-and-tube equipment comprising a series of antivibration baffles.

(2) FIG. 2 shows in schematic form a series of baffles of the equipment shown in FIG. 1, according to a first embodiment of the invention.

(3) FIGS. 3 and 4 show locking of a tube in a respective window of one of the baffles, according to the embodiment of FIG. 2.

(4) FIGS. 5 to 7 are similar to FIGS. 2 to 4 and show another embodiment of the invention.

(5) FIG. 8 shows a preferred embodiment for the windows of the baffles, in particular for the embodiments of the type shown in FIGS. 5-7.

(6) FIGS. 9 and 10 show other embodiments of the windows of the baffles intended to receive the tubes.

(7) FIGS. 11 and 12 show an example with baffles having windows designed to receive a plurality of tubes, with free and locked tubes, respectively.

(8) FIG. 13 shows a preferred arrangement of the windows in consecutive baffles of the type shown in FIG. 11.

(9) FIG. 14 shows another embodiment of the invention in which the baffles consist essentially of concentric rings.

(10) FIG. 15 shows a detail of FIG. 14 illustrating locking of a tube.

DETAILED DESCRIPTION

(11) FIG. 1 shows in schematic form a shell-and-tube equipment 1 comprising a shell 2; a bundle 3 of straight tubes 4; a plurality of baffles 5 spaced by a pitch p and acting as antivibration supports for the tubes 4; two tube plates 6. FIG. 1 shows only the axes of the tubes for the sake of simplicity.

(12) FIG. 2 relates to a first embodiment of the invention and, for the sake of simplicity, shows a single tube 4 passing through the baffles 5. Each baffle 5 comprises a series of passing-through openings in the form of windows 7 which allow the passage of tubes. The reference number 5 denotes collectively the set of baffles and the reference number 7 denotes collectively the windows formed in the baffles. In the example according to FIG. 2 the windows 7 have a trapezoidal form, more preferably the form of an isosceles trapezium.

(13) As shown in FIGS. 3 and 4, a trapezoidal window 7 comprises a region 8 in the proximity of the long base which may receive a tube 4 with a certain play g and a second region 9 close to the short base of the trapezium in which, instead, a tube 4 is received substantially with no play (i.e. locked), bearing against internal surfaces 10 defined by the two converging sides of the window 7 (FIG. 4.).

(14) The play g allows the tube 4 to freely slide through the window 7. A slight misalignment between tube and window is in fact compensated for by the play g during the assembly. In the region 9 instead the converging sides of the trapezoidal window 7 form a wedge-like zone which eliminates the play g and lock the tube 4 which finds two points of contact 11 with said surfaces 10. Therefore, it can be noted that the arrangement shown in FIG. 3 allows easier assembly while the arrangement shown in FIG. 4, during operation, ensures an effective action against the vibrations thanks to the bearing contact of the tube against the surfaces 10.

(15) Locking of the tube 4 inside the window 7 (i.e. the passage of the tube from the receiving region 8 with play to the substantially locked region 9) is the result of a linear displacement f of the window 7 with respect to said tube.

(16) It should be noted that the locking is the result of a suitable inclination of the surfaces 10 relative to the locking direction (FIG. 4). Here, said surfaces 10 are termed effective surfaces since they provide the tube with the desired antivibration support. The locking direction may be defined as being the direction in which the tube moves towards the region 9 (and therefore towards the surfaces 10) which, in this example, is the direction of the displacement f. For short, said angle is also called locking angle.

(17) In the example, for each tube 4 there are two surfaces 10 which converge defining a wedge-like locking zone. More generally it is preferable to provide at least one surface inclined with respect to a locking direction of the tubes.

(18) With reference still to FIG. 2, it is shown a preferred embodiment in which the set of baffles 5 comprises a first series of baffles 5A with a first orientation of the windows 7, and a second series of baffles 5B with windows 7B having a second orientation. As a result of the different orientation, the baffles of the two series denoted by A and B respectively have different locking directions, for example the baffles 5A are locked with a displacement +f and the baffles 5B are locked with an equal and opposite displacement f.

(19) It should be noted that the locking operation brings the baffles back into axial alignment with the tube bundle, i.e. eliminates the misalignment shown in FIG. 2. FIG. 2 shows the centre of a baffle and the axis 12 of the equipment. The figure thus highlights the misalignment of the baffles during the assembly, which is eliminated by the displacement +f or f.

(20) FIGS. 5 to 7 are similar to FIGS. 2 to 4, and show an embodiment where the locking of the tubes is obtained with a rotation about the axis 12 of the equipment 1. In particular, it is shown an embodiment with series of baffles A and B which can be locked with equal and opposite rotations +, .

(21) Locking of the tubes can be seen in FIGS. 5 and 6: the rotation of a baffle through an angle brings a tube 4 towards the wedge-like zone 9 of the associated window 7 where locking takes place. The angle of inclination of the surfaces 10 in this case may be defined with respect to the line 13 tangential to the circular arc travelled by the window 7 upon rotation (FIG. 7).

(22) An embodiment of the type shown in FIG. 2 is called shift-lock, while an embodiment of the type shown in FIG. 5 is called twist-lock.

(23) The windows 7 of a single baffle 5 may be all identical or may have different shape and/or orientation, depending on various embodiments of the invention.

(24) In the twist-lock embodiments, the provision of windows 7 with a different shape depending on the distance from the axis of rotation may be preferred, in order to obtain uniform locking, thus compensating for the greater displacement of the peripheral windows with respect to those close to the axis. In order to compensate for this difference, preferably, the baffles 5 comprise two or more concentric rows of windows 7 with a varied shape.

(25) For example, as shown in FIG. 8, a window 7.1 at a distance r1 from the axis of rotation preferably has effective surfaces 10 with a locking angle greater than a window 7.2 situated at a greater distance r2 from the axis. The greater locking angle compensates for the smaller arc travelled by the window 7.1 close to the axis, for the same rotation . In greater detail, FIG. 8 has 1>2 where 1 is the locking angle of the window 7.1 close to the axis and 2 is the locking angle of the window 7.2 distant from the axis. In other words, the windows close to the axis have a sharper wedge-like locking zone 9 so as to obtain the desired locking despite the relatively small displacement.

(26) The twist-lock configuration according to FIG. 5 is advantageously applicable to equipment with tubes arranged on concentric circumferences, rather than in a square or triangular pitch. Equipment with this arrangement of tubes is commonly used for example to realize heat exchangers inside reactors for the ammonia synthesis which have the tubes arranged on circular ranks.

(27) FIGS. 2-4 and 5-7 show embodiments where the set of baffles 5 comprises a first series of baffles 5A and a second series of baffles 5B which can be locked with displacements or rotations of the same magnitude having opposite direction or sense. In both cases the baffles of the first series and the second series are alternated. Consequently the tubes 4 are supported alternately according to different planes. These embodiments are suitable for supporting tubes in a square or triangular arrangement, which fit most applications. Some embodiments may envisage a greater number of series of baffles having a different geometry, for example forming a sequence of baffles 5, 5, . . . 5.sup.(n) repeated along the tube bundle.

(28) FIGS. 9 and 10 show variants in which the single windows 7, for example trapezoidal, are connected without a solution of continuity, for example being formed by means of saw cuts 14 made in the baffles 5. The variant of FIG. 9 applies to the shift-lock embodiments and the variant of FIG. 10 applies to the twist-lock embodiments. This variant may be preferred when the tubes are quite close to each other.

(29) In the embodiments according to FIGS. 1-10 the tube receiving seats are represented by the above described windows 7, each intended to receive a single tube 4 of the bundle. Other embodiments are possible wherein each seat of the baffles 5 is configured to receive a plurality of tubes.

(30) A preferred application of the invention relates to axial-flow heat exchangers, wherein the shell-side fluid passes through the baffles; in this case, in order to avoid an excessive obstruction of the section for the passage of fluid through the baffles (which would cause an excessive increase of the load losses) each seat advantageously receives a plurality of tubes.

(31) For example, FIG. 11 shows an embodiment of the invention in which the tube receiving seats are in the form of windows 27 designed to receive four tubes with shift-lock.

(32) A window 27 has a substantially rectangular shape and comprises four corner lobes designed to receive respective tubes 4. A lobe comprises a surface in the form of a circle arc which defines a zone 28 for receiving the tube 4 with play, and an effective surface 20 inclined with respect to the locking direction and defining a locking zone 29. The point 21 (FIG. 12) indicates the point of contact with the tube resulting from the displacement of the window 27 into the working position.

(33) FIG. 11 shows the assembly position in which the tubes 4 are located in the regions 28 of the lobes and consequently are received with a certain play. The figure also shows some characteristic parameters of the window 27, namely the length L of the effective surface 20 and the locking angle .

(34) FIG. 12 shows the working condition in which each of the four tubes is locked making contact at point 21 with a respective effective surface 20.

(35) FIG. 13 shows, respectively with continuous and broken lines, a preferred arrangement of windows 27A and 27B belonging to two adjacent baffles, which can be locked with opposite displacements during operation (for example two baffles 5A and 5B, as shown in FIG. 2). It is noted that the windows of adjacent baffles are staggered horizontally and vertically by an offset distance equal to the tube pitch so as to receive different groups of tubes 4.

(36) FIGS. 14 and 15 show another embodiment of the twist-lock type, namely with tubes arranged in concentric rows and baffles lockable by rotation. In this embodiment a baffle is formed essentially by concentric rings connected by bridge portions.

(37) The tube receiving seats are formed on the edges of the concentric rings, in the form of substantially semicircular recesses 37 comprising a straight portion inclined relative to the locking direction, which defines the effective surface 30. The reference numbers 38 and 39 (similar to the reference numbers 8, 9 and 28, 29) indicate the receiving zones with play and the zones for locking the tubes in the recess 37; the reference numbers 31 (similar to the reference numbers 11 and 21) indicate the point of contact of the tube against the effective surfaces 30.

(38) In the example reference is made to two series of baffles denoted by A and B (in a similar manner to FIGS. 2 and 5) and lockable by means of opposite rotations +, . The Figure shows two rings 32A of a first baffle 5A and two rings 32B of a second baffle 5B with the respective bridge portions 33A and 33B.

(39) It should be noted that each tube 4, in the working position, rests alternately on a ring of a baffle 5A belonging to the first series and on a ring of a baffle 5B belonging to the second series. This is due to the fact that two adjacent rings of a single baffle are separated by a distance 34 which is twice the radial distance 35 between two consecutive rows of tubes and the fact that adjacent baffles are staggered by a distance equal to said radial distance 35 as shown for example in FIG. 14.

(40) The method for assembling the equipment 1 comprises essentially the following steps.

(41) The baffles 5 are arranged in a provisional assembly configuration such as for example the configuration of FIG. 2 or FIG. 5. In said provisional configuration, the seats 7 are arranged so that the tubes 4 can be inserted through the baffles and received with play in the regions 8. During this step the baffles 5 are advantageously kept at the correct distance (pitch p of FIG. 1) via suitable provisional means.

(42) The insertion of the tubes is greatly facilitated by the play existing between tubes and seats of the baffles, and also the last tubes of the bundle may be positioned without difficulty. After completing the tube bundle, the baffles 5 are displaced and moved into the working position, for example by means of the linear displacements +f, f or the rotations +, . As a result, the tubes 4 are locked in the regions 9 of the baffles.

(43) An embodiment such as that of FIGS. 11-13 or such as that of FIGS. 14-15 is assembled in a similar manner.

(44) In a particularly preferred embodiment, after reaching the working condition (locked tubes), the baffles 5 are blocked by the insertion of the bundle into the shell 2 and structural cooperation with said shell.