RU2752212C2 - Shell-and-tube device with partitions - Google Patents

Abstract

FIELD: heat engineering.

SUBSTANCE: invention relates to the field of heat engineering, it can be used in tubular heat exchangers. In a shell-and-tube device containing a plurality of partitions (5) that are installed along the tube bundle perpendicular to its axis and through which the tubes of this tube bundle pass, each partition is a flat body with holes (11) through which the tubes pass, and the partition contains plate protrusions (12) in the area of the holes that extend from the surface of the partition.

EFFECT: technical result is the creation of a shell-and-tube device with improved characteristics both from the point of view of design and from the point of view of the dynamics of the fluid flow inside the device.

15 cl, 15 dwg

Description

Technology area

The present invention relates to shell-and-tube apparatus.

State of the art

Shell and tube devices are commonly used as devices for transferring heat between the fluid flowing through the pipes and the fluid flowing in the annular space.

Known shell-and-tube devices contain baffles that perform essentially two functions: the function of dynamic deflection and / or acceleration of the fluid flow in the annular space, as a result of which the heat transfer coefficient is increased; and the function of the structural members to prevent vibration of the pipes.

US Pat. Nos. 5,058,664 and US Pat. No. 5,642,778 disclose a known method of manufacturing partitions, which are a bar structure with a supporting frame.

EP 2469215 discloses baffles formed by thin plates that intersect to form a grid and are inclined to deflect flow in the annulus.

The disadvantage of the above technical solutions is that each partition is composed of several parts, which must be welded and / or otherwise attached to each other, so that the construction cost is relatively high. In addition, installing pipes when partitions are installed is not an easy task.

Another disadvantage of such devices is that the heat transfer coefficient is largely influenced by the flow in the annular space. As you know, baffles inside the apparatus are usually used for the appropriate direction of flow in the annular space, however, they cause additional head losses.

Prior art shell-and-tube assemblies typically use lateral annulus flow. That is, the flow of the gaseous medium outside and around the pipes is substantially perpendicular to the axis of the pipes. This design typically includes a series of passages through different sections of the tube bundle between successive baffles.

Cross-flow in the annular space is preferred because it provides good heat exchange between the flow of the gaseous medium and the surface of the tubes. However, this results in a significant drop in pressure and requires that the baffles provide adequate sealing of the sections of the tube bundle to prevent gas from passing from one section to another via bypass routes. The baffle must form a lip seal around each pipe, but this can add to the cost of construction and / or further complicate the installation of the pipes.

For example, documents BE 1018891 and US 4834173 describe cross-flow heat exchangers in the shell side.

In document EP 3115734, baffles are described that allow the free introduction of pipes and their subsequent locking. Disclosure of invention

The object of the present invention is to provide a new method of manufacturing baffles for a shell-and-tube apparatus, which has improved characteristics, both in terms of design and in terms of the dynamics of fluid flow within the apparatus.

This problem is solved using the apparatus described in the claims.

Baffles contain a metal plate with holes for pipes to pass through the baffle. At these holes, the partitions have lamellar protrusions extending from the surface of the partition. These plate-like protrusions provide a change in the dynamics of the fluid flow and / or perform the function of preventing vibrations, as will be described below with some examples.

Preferably, the baffles are substantially flat elements extending perpendicular to the axis of the tubes (i.e., the axis of the tube bundle). The lamellar projections extend from the surface of the corresponding partition in a direction parallel to the axis of the tube bundle, or in a direction inclined relative to this axis.

Each lamellar protrusion may extend over an area equal to or less than the area of the corresponding hole formed in the metal plate.

Such lamellar protrusions can be configured to provide a function of changing the dynamics of fluid flow by deflecting the flow in the annular space and / or a function of resilient pipe supports. Lamellar protrusions capable of causing significant deflection of the fluid flow in the annular space are referred to as flow dynamics altering elements.

In preferred embodiments, the gaseous stream in the annular space flows longitudinally or predominantly longitudinally. Accordingly, gas inlets and outlets are provided in the casing of the apparatus to provide said longitudinal or predominantly longitudinal flow. In some embodiments, at least some of the lamellar protrusions are elements adapted to deflect (eg, deflect by a predetermined angle) the gaseous flow in the annular space from the main, longitudinal direction.

Preferably, the plate-like projections of the baffles are positioned throughout so as to impart a movement component in the direction transverse to the longitudinal axis of the tubes or tube bundle to the fluid flow in the annular space.

More preferably, the plate projections are positioned to provide a substantially sinusoidal or substantially helical fluid flow in the annulus.

The arrangement of the plate-like protrusions providing a substantially sinusoidal fluid flow in the annular space is preferred when the pipes are arranged in a square or triangular pattern. The arrangement of the lamellar protrusions providing a substantially helical fluid flow in the annular space is preferred when the tubes are arranged in circumferential directions, although sinusoidal flow can also be achieved in this case.

In a preferred embodiment, the apparatus comprises baffles provided with differently configured lamellar protrusions. The apparatus may contain two or more sets of baffles, each set having a specific configuration of lamellar protrusions. The term "configuration" can define one or more features such as, for example, the shape, size and orientation of the plate-like protrusions. Baffles with different configurations can be suitably distributed along the length of the tube bundle, for example, they can alternate with each other.

It should be noted that different configurations of the plate projections can change both the function of controlling the dynamics of fluid flow and the function of forming the structure.

In some embodiments of the invention, a sequence of baffles provided with differently configured plate-like protrusions imparts a desired shape to the fluid flow in the annular space and / or creates some degree of turbulence in this flow. A suitable flow shape and / or increased turbulence can improve heat transfer.

Instead, or in addition to this, the series of baffles can form pipe supports in different planes to effectively dampen vibrations. For this purpose, the lamellar projections of adjacent partitions are pressed against the same pipe in different support planes.

In a preferred embodiment, the apparatus of the present invention comprises at least a first set of baffles with a first configuration of lamellar protrusions and a second set of baffles with a second configuration of lamellar protrusions, the second configuration being associated with the first configuration, and the baffles of the first set and the second set alternating at least parts of the tube bundle. Thus, the partition with the first plate-like configuration faces an adjacent partition with the second plate-like configuration, and so on.

Therefore, the lamellar protrusions of the first configuration and the lamellar protrusions of the second configuration act alternately on the flow in the annular space. The lamellar protrusions in a mating configuration interact to provide the necessary effect on the dynamics of the fluid flow in the annular space. In preferred embodiments, such exposure produces substantially sinusoidal or substantially helical flow lines.

Casing sinusoidal flow options and shell side spiral flow options can be combined, for example, by using baffles to produce sinusoidal flow on at least a portion of the tube flow and spiral flow on at least another portion of the tube flow.

In some embodiments, a single baffle may include plate-like protrusions having different configurations. Accordingly, for example, some parts of the same baffle can influence the dynamics of the fluid flow in different ways.

The lamellar protrusions can have different shapes. In the first embodiment, the plate-like protrusions have a substantially two-dimensional shape, in which one dimension, for example thickness, is significantly less than the other two dimensions. In another embodiment, the plate-like protrusions have a substantially one-dimensional shape, in which one dimension is much larger than the other two. The lamellar protrusions can be polygonal or more complex.

In preferred embodiments, each opening for one or more pipes comprises at least a first zone suitable for inserting a pipe or pipes with play and a second zone suitable for inserting a pipe or pipes with less or substantially no play. By arranging the baffles in a so-called assembly configuration, the first orifice zones are aligned to allow free insertion of the tubes, in which case each tube passes with play through the baffle openings.

In this assembly position, the baffles are linearly offset or rotated relative to their operating configuration. When moving the baffles from the assembly position to the operating position, the pipes are transferred from the first zones to the second hole zones, in which they are essentially locked in the desired position. The movement that moves the baffles from the assembly position to the operating position can be linear displacement (a variant of the so-called "slip-lock") or a pivot (a variant of the so-called "rotation-lock").

These variants, allowing the free laying of pipes through the baffles with subsequent locking, are described in more detail in the already mentioned patent application EP 3115734.

In the aforementioned embodiments of blocking pipes after assembly, the plate-like protrusions are preferably formed to provide resilient support for the pipes when the baffle is in the locking position. Thus, the invention provides an additional positive effect by providing a system with a certain degree of resilience and flexibility.

Preferably, the baffles are made of sheet steel. The baffle can be a monolithic element formed by a cut or punched out metal plate, or it can contain additional elements such as a female reinforcing ring. In some embodiments, the metal plate may include multiple folded metal sheets. Preferably, the metal plate is in the form of a disc or part of a disc.

Each baffle can cover all or substantially all of the cross-sectional area of the annular space, or it can cover only a part of this area. Baffles covering only part of the cross-sectional area of the annular space may alternate with other baffles, for example, overlapping other parts of this area.

The advantages of the invention lie in the simplicity of the design and also in the fact that the baffles actively change the fluid flow and / or serve as structural elements. For example, the invention provides the possibility of implementing an apparatus in which the baffles interact with the fluid flow in the annular space to change its direction and, in addition, provide an elastic support for the pipes.

In some embodiments, the plate-like protrusions extending from the surface of the baffle act essentially as bendable brackets and therefore provide resilient support for the pipes. This is an important positive feature, since the known pipe and baffle assembly systems are problematic in this respect: a relatively loose connection is not able to effectively resist vibrations, whereas a precise fit makes it difficult to install the structure and makes the pipe and baffle system too rigid. The present invention solves the problem by providing accurate mounting while providing a certain resilience to the system due to the fact that the plate protrusions can bend.

Changing the dynamics of the fluid flow increases the heat transfer coefficient and optimizes the flow in the annular space using baffle passages for this purpose without introducing significant additional head losses. Casing flow, suitably directed, for example with sinusoidal or spiral flow lines, flows around all tubes and ensures full utilization of the tube bundle.

In the first embodiments of the invention, pipe holes are formed in the metal plate of the baffle, preferably using punching or cutting, and the lamellar protrusions are formed by strips of metal sheet material obtained by punching or cutting the holes and bent accordingly. The preferred cutting methods are laser cutting and waterjet cutting.

In second embodiments of the invention, the lamellar projections are formed by members rigidly attached to the metal plate near the holes. Preferably, the lamellar projections are sheet metal elements installed using welding, preferably using spot welds (electric resistance welding).

In the first embodiments of the invention, the baffles preferably comprise a plate having a small thickness so that the plate-like protrusions are resilient and bend easily. To increase the rigidity of the baffles, a reinforcing ring welded to the peripheral edge of the plate can be used.

The advantage of the second variants (installed lamellar projections) is that the thickness of the lamellar projections may differ from the thickness of the metal plate forming the partition. For example, the plate-like protrusions can be thinner so that they are resilient and bend easily.

In particular, the preferred embodiment of the baffle contains a metal plate of the required thickness with holes for pipes obtained by laser or waterjet cutting, and the plate protrusions that change the dynamics of the fluid flow are made of thin sheet metal and are attached to the baffle in the area of the holes by means of spot welds seams.

In some embodiments, the metal plate is composed of two superimposed metal sheets of different thicknesses to facilitate positioning and welding of the lamellar protrusions. The first metal sheet having a relatively large thickness serves as a structural component and has through-holes for the passage of pipes. A second metal sheet having a smaller thickness (less than the thickness of the first sheet) is mounted on the first sheet and contains lamellar protrusions for changing the dynamics of fluid flow. In this embodiment, the plate-like protrusions can be formed by bending the strips or part of the strips extending outside the holes. The lamellar protrusions can be bent prior to or during insertion of the tubes.

In addition to improving heat transfer efficiency, both of the above methods provide faster and cheaper assembly of the structure compared to traditional methods, which provide for the formation of baffles by assembling a large number of linear elements, such as rods.

It should be noted that the present invention can be effectively used for heat exchangers with or without the described pipe locking system during assembly.

Preferably, the apparatus of the present invention is a chemical reactor for use in a chemical plant. In some embodiments, the chemical reactor may contain a catalyst.

Another advantage of the invention lies in the possibility of providing on one partition plate-like projections having different configurations. Thus, it is possible to improve the control of the dynamics of the fluid flow in the annular space.

The invention can be applied to devices with straight tubes and in devices with U-shaped tubes. In the second case, the baffles are installed along the straight part of the U-shaped pipes.

Another advantage of the invention is that the flow passes in the annular space in the longitudinal or predominantly longitudinal direction, as a result of which the pressure drop will be less compared to the flow in the transverse direction. In this case, the baffles do not have to provide a gas-tight seal around the pipes, thereby facilitating their introduction. By virtue of the action of the plate projections on the fluid flow dynamics, the invention provides good heat transfer while at the same time providing a low pressure drop typical of axial flow designs.

The advantages of the present invention will be better understood upon reading the detailed description below, which discusses several preferred embodiments.

Brief Description of Drawings

FIG. 1 is a simplified schematic view of a shell-and-tube apparatus containing a set of anti-vibration baffles.

in fig. 2 is a view of a pipe passing through a baffle in one embodiment of the invention;

in fig. 3 is a schematic view of a set of baffles of the apparatus shown in FIG. 1 in accordance with a first embodiment of the invention;

in fig. 4 is a schematic cross-sectional view of the baffles and pipes shown in FIG. 3, which shows the flow lines in the annular space;

in fig. 5 is a view of a portion of FIG. 4;

in fig. 6 is a view of a set of baffles in a second embodiment of the invention;

in fig. 7 is a view of a set of baffles in a third embodiment of the invention;

in fig. 8 is a schematic cross-sectional view of the baffles and pipes shown in FIG. 7;

in fig. 9 is a view of a set of baffles in a fourth embodiment of the invention;

in fig. 10-13 are views of various modifications of the lamellar protrusions of the partitions;

in fig. 14, 15 - views of other variants of lamellar protrusions of the partitions.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a schematic view of a shell-and-tube apparatus 1, comprising: a casing 2; straight tube bundle 3; a lot of partitions 5 spaced apart from each other at a distance p; two tube sheets 6. FIG. 1, only the pipe axes are shown to simplify the drawing. In addition, the central axis 20 of the tube bundle 3 is shown parallel to the axes of the tubes.

Each of the baffles 5 (Fig. 2) is essentially a metal disc 10, in which holes 11 are formed through which pipes 4 can pass. In the region of these holes 11, or at least some of them, the baffle 5 contains lamellar protrusions 12 formed by strips of material of the disc 10 that extend from one side 13 of the disc 10.

The holes 11 and the lamellar protrusions 12 can be formed using various methods. For example: the holes 11 are obtained by incomplete punching, and the lamellar protrusions 12 are formed by strips of material of the disc 10, which are not removed but remain attached to the disc; the holes 11 can be obtained using a suitable cutting method, preferably laser or waterjet cutting, followed by bending the strips to form the lamellar protrusions 12; the plate projections 12 may be thin sheet metal members mounted on the disc 10. These examples are shown as non-limiting examples, so other techniques are possible.

Through each hole 11 there is a pipe 4 or several pipes 4 (depending on the specific version).

FIG. 3-5 illustrates a variant in which the pipes 4 can be freely inserted into the holes 11 with some play, when all the baffles 5 are displaced in the assembly position. After the insertion of the tubes is complete, the baffles can be fixed to the tubes by conjugate linear displacements of + f or -f so that the baffles are aligned with each other. The direction of the indicated linear offsets + f, -f is also called the closing direction. Preferably, adjacent partitions are locked by linear displacements in opposite directions.

For this purpose, for example, the openings 11 have a substantially trapezoidal shape with a base suitable for the introduction of a pipe with some play and with sides converging upward towards a tapered top to seal the pipe. This is also illustrated in FIG. 10-15.

The set of baffles 5 includes first baffles 5a having a first configuration of lamellar protrusions 112a and second baffles 5b having a second configuration of lamellar protrusions 112b, the first baffles 5a and second baffles 5b alternating with each other in the longitudinal direction of the tube bundle. The figures (Fig. 3) also show the tube sheet 6. In this example, the baffles 5a and 5b can be fixed on the tubes of the bundle by linear displacements + f, -f, respectively.

Lamellar protrusions 112a in said first configuration extend from the respective partitions 5a in a first direction, in which they form in the reference plane a first angle a1 with the direction of the axis 14 of the tubes and the axis 20 of the tube bundle 3.

Lamellar protrusions 112b in said second configuration extend from respective partitions 5b in a second direction in which they form, with axes 14 and 20, in the same reference plane, a second angle a2 opposite in sign to the first angle a1 (FIG. 5).

Preferably, the second angle is equal and opposite in sign to the first angle, that is, a2 = -a1.

More preferably, the absolute value (modulus) of the first angle a1 and the second angle a2 is in the range of 30 to 60 degrees, and is preferably 45 degrees.

This reference plane is the plane shown in FIG. 4.

As shown in FIG. 5, the upper surface 120 of the plate protrusion 112a faces the opening 11 and has a flat surface inclined at an angle a1 relative to the direction of the tube bundle axis 20. Likewise, the upper surface 121 of the plate-like protrusion 112b has a flat surface extending at an angle a2 with respect to said axis 20.

Such a configuration, shown in particular in FIG. 4, the plate-like projections 112a and 112b deflect the flow in the annular space within the apparatus 1 alternately in two different directions, for example, up and down, as a result of which substantially sinusoidal flow lines Fs are formed, deflecting up or down when passing the first baffles 5a or the second baffles 5b, respectively.

As shown in FIG. 3-5, the lamellar protrusions 112a, 112b are on one side of the hole 11, which moves towards the pipe 4 as a result of the locking movement + f or -f, for example, on the smaller side of the trapezoidal holes 11. Thus, the above-described lamellar protrusions provide elastic support for pipes 4 when the baffles 5a, 5b are moved from the assembled position to the locked position.

In particular, in FIG. 5, it can be seen that the pipe 4 is pressed for support alternately in one direction and in another opposite direction, for example up and down. In the locked position, the pipes 4 are sandwiched between the inclined sides of the holes 11, and the lamellar protrusions 112a, 112b are resilient elements that eliminate backlash associated with manufacturing tolerances.

From the above, it can be understood that the lamellar protrusions 112a, 112b serve the function of changing the dynamics of the fluid flow, forming sinusoidal flow lines, and the function of structural elements that provide elastic support to the pipes 4, compensate for backlash associated with manufacturing tolerances and damp vibrations.

FIG. 6 illustrates a modification of the embodiment shown in FIG. 3-5, in which the plate-like projections 112a, 112b are located transversely with respect to the direction of closing of the partitions 5, for example, along the converging sides of the trapezoidal holes 11.

FIG. 7, 8 illustrate a variant of the design of the locking by turning, in which the baffles 5 are transferred from the assembly position, in which the pipes are freely introduced with play into the holes 11, to the locking position by means of conjugate rotations at angles + ϕ or -ϕ around the axis 20. In preferred embodiments, adjacent baffles provide pipe locking by turning in opposite directions.

In such a twist-locking embodiment, the set of baffles 5 preferably comprises first baffles 5a and second baffles 5b with lamellar protrusions 212a, 212b configured to provide a spiral movement of fluid in the annular space.

More specifically, in this embodiment, the plate-like projections 212a, 212b extend from opposite sides of the baffles, for example, the baffles 212a extend from the front sides 13a of the baffles 5a, and the plates 212b extend from the rear sides 13b of the baffles 5b. The plate-like projections 212a, 212b are also angularly offset. With this configuration shown in FIG. 7, 8, the lamellar protrusions 212a, 212b deflect the flow in the annular space to spiral around the axes 14 and 20 so that substantially helical Fe flow lines are formed.

FIG. 7, 8, the plate projections 212a, 212b are positioned relative to the holes 11 so that the pipes 4 move in the direction of these projections 212a, 212b when the partition is moved from the assembly position to the operating position. Thus, the lamellar protrusions also act as resilient supports for pipes and to eliminate backlash (similar to the design shown in FIGS. 3-5).

FIG. 9 illustrates the embodiment shown in FIG. 7, 8, in which the plate-like projections 212a, 212b are located in the transverse direction with respect to the movement of the locking (similar to the structure shown in Fig. 6). With the configuration of the plate-like protrusions shown in FIG. 9, a sinusoidal flow is obtained in the pivot locking structure.

FIG. 10-13 show embodiments of the plate-like projections indicated by the reference numeral 12. FIG. 14 and 15 show other embodiments of the lamellar protrusions. These variants, shown in FIG. 10-15 can be similarly applied in the various embodiments shown in FIGS. 1-9.

FIG. 10 illustrates an embodiment in which the plate-like projections 12 have a substantially polygonal trapezoidal shape and are connected to a sheet metal disc on one side 15.

FIG. 11 illustrates a variant in which only a part of the material cut from the disc 10 forms a lamellar protrusion 12, and, accordingly, the area of the lamellar protrusions 12 is less than the area of the holes 11.

FIG. 12 illustrates an embodiment in which the plate-like protrusions 12 are attached to the base 16 of the opening 11, which has a substantially trapezoidal shape.

FIG. 13 illustrates a variant in which each opening 11 is provided with two lamellar protrusions 12 that extend from opposite sides relative to the plane of the partition.

The holes having a substantially trapezoidal shape as shown in FIG. 10-12 are generally suitable for one passing pipe 4, and, accordingly, the number of holes 11 in the partition should be equal to the number of pipes 4. In FIG. 13 shows a variant of the opening 11 for a linear displacement closure structure suitable for the passage of four pipes.

FIG. 14 and 15, an embodiment is shown in which the lamellar protrusions 12 are formed by thin sheet metal elements that are mounted on the disc 10, for example using spot welds 25.

It should be noted that the structure shown in FIG. 14 and 15 can be applied in all embodiments of the invention.

Finally, it should be noted that embodiments of the invention, for example similar to those shown in FIG. 1-9 are also possible without the use of a linear offset locking system or with a pivoting of the baffles.

Claims (23)

1. A shell-and-tube apparatus containing a plurality of partitions (5), which are located along the tube bundle perpendicular to the axis (20) of the tube bundle (3) and through which the pipes pass, and: each baffle is a substantially flat body and contains a metal plate (10) with holes (11) for pipes to pass through the baffle; at said holes (11), the partition has lamellar protrusions extending away from the metal plate; moreover, the lamellar protrusions are configured to function as elastic supports for pipes and / or as elements for changing the dynamics of the fluid flow, adapted to deflect the fluid crossing the annular space of the apparatus, characterized in that the gaseous flow in the annular space is provided longitudinally or predominantly longitudinally and at least some of the lamellar projections are lamellar projections for changing fluid flow dynamics adapted to deflect the gaseous flow in the annular space from the main, longitudinal direction. 2. Apparatus according to claim 1, wherein all of the lamellar projections of each baffle extend from the same side (13) of the corresponding baffle. 3. Apparatus according to any one of paragraphs. 1 or 2, comprising first baffles (5a) having a first configuration of plate-like protrusions, and second baffles (5b) having a second configuration of plate-like protrusions, wherein the first baffles and second baffles alternate along at least a portion of the tube bundle, and the first configuration and the second the configuration of the lamellar protrusions are coupled to impart a movement component transverse to the axis (20) of the tube bundle (3) to the flow in the annular space. 4. Apparatus according to claim 3, in which: the first baffles (5a) have lamellar protrusions (112a) configured to direct the flow in the annular space in a first direction making a first angle (a1) with the axis of the pipes in the reference plane; the second baffles (5b) have lamellar protrusions (112b) configured to direct the flow in the annular space in a second direction making a second angle (a2) in the reference plane with the axis of the pipes, the sign of the second angle being opposite to the sign of the first angle; As a result, flow lines are formed in the annular space, which, passing through the baffles, alternately deviate in different directions. 5. The apparatus of claim. 4, wherein the flow lines in the annular space are substantially sinusoidal. 6. Apparatus according to claim 3, wherein the first baffles (5a) and second baffles (5b) have plate-like projections (212a, 212b) directed so as to impart a substantially helical movement to the fluid in the annular space around the axis of the tube bundle ... 7. Apparatus according to claim 6, wherein the lamellar projections (212a, 212b) extend from opposite sides (13a, 13b) of the respective first baffles and second baffles (5a, 5b), and the lamellar projections of the baffles facing each other are offset along corner. 8. An apparatus according to any one of the preceding claims, wherein the at least one baffle comprises plate-like projections of various configurations. 9. An apparatus according to any of the preceding claims, wherein each baffle occupies all or substantially all of the cross-sectional area of the annular space or only a portion of said area. 10. An apparatus according to any one of the preceding claims, wherein the lamellar projections of adjacent baffles are supported on opposite sides of each pipe. 11. Apparatus according to any of the previous paragraphs, in which the partitions are formed so that: each opening for one or more pipes comprises at least a first zone suitable for receiving a pipe or pipes with play and a second zone suitable for receiving a pipe or pipes with less or substantially no play; each pipe is received in the first zone of the corresponding seat when the baffle is in the so-called assembly position, and is received in the second zone of the seat when the baffle is in the operating position. 12. Apparatus according to claim. 11, in which the plate projections are positioned relative to the holes (11) such that the pipes move in the direction of the plate projections when the baffles are set in position, so that the plate projections provide resilient support for the pipes when the baffles are in working position. 13. An apparatus according to any one of the preceding claims, wherein the plate-like projections are formed by sheet metal members mounted on the metal plate in correspondence with the holes. 14. Apparatus according to any one of paragraphs. 1-12, in which holes are punched or cut in the metal plate and the lamellar protrusions are formed by strips of metal plate material obtained by punching or cutting holes and bent accordingly. 15. Apparatus according to any one of the preceding claims, wherein the baffles comprise an outer reinforcing ring that is thicker than the metal sheet.

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