Heating device and method for preheating and post-heating welding of tube-tube plate of shell-and-tube heat exchanger

Abstract

The invention provides a heating device and a heating method for preheating and post-heating welding of a tube-tube plate of a shell-and-tube heat exchanger, and belongs to the field of welding auxiliary equipment. The problems that due to the fact that an existing heating device directly heats the outer wall of the tube plate in the annular direction, heating in the surface direction of the tube plate is not uniform, heat is prone to being dissipated and lost from the surface of the tube plate, and the temperature is not suitable to control are solved. The device comprises an outer wall annular heater and a surface heater, the outer wall annular heater is located on the outer side wall of the tube plate and used for heating and heat preservation of the tube plate. The surface heater is located on the outer surface of the tube plate and used for heating the tube plate. The device is mainly used for preheating and post-heating the welded tube of the tube plate of the shell-and-tube heat exchanger.

Description

Technical Field

[0001] The invention belongs to the field of welding auxiliary equipment, and in particular relates to a heating device and a heating method for preheating and postheating of tube-tube sheet welding of a shell and tube heat exchanger. Background Art

[0002] Shell and tube heat exchangers are widely used in the petrochemical industry. The effective connection between the heat exchanger tube sheet and the tube is the key to ensure the normal operation of the heat exchanger. In order to meet the requirements of relevant standards and ensure the welding quality between the heat exchanger tube sheet and the tube, welding preheating and post-heat treatment are required. At present, the device of circumferential heating on the outer wall of the tube sheet is generally used. This device has problems such as uneven heating on the surface of the tube sheet, easy heat loss from the surface of the tube sheet, and difficult temperature control. Summary of the invention

[0003] In view of this, in order to solve the problems that the currently used heating device directly heats the outer wall of the tube sheet in an annular direction, the surface of the tube sheet is heated unevenly, the heat is easily lost from the surface of the tube sheet, and the temperature is difficult to control. The present invention proposes a heating device and a heating method for preheating and post-heating of tube-tube sheet welding of a shell and tube heat exchanger. The present invention uses electric heating materials and thermal insulation materials to form a layered heating device, which heats the welding area from the outer wall of the tube sheet and the surface of the tube sheet at the same time, and the heating speed is fast; the cooperation of the two parts of the structure can also effectively reduce the heat dissipation loss, further improve the preheating efficiency, can extend the effective time of the preheating process, and ensure the uniformity of the overall temperature of the tube sheet, which is conducive to ensuring the welding quality of the tube-tube sheet in the shell and tube heat exchanger.

[0004] To achieve the above object, the present invention adopts the following technical scheme: a heating device for preheating and postheating of tube-tube sheet welding in a shell-and-tube heat exchanger, comprising an outer wall annular heater and a surface heater; the shell-and-tube heat exchanger is in the shape of a cylinder with a bottom, and the bottom is the tube sheet; the outer wall annular heater is located on the outer side wall of the tube sheet, and is used to heat and keep the tube sheet warm; the surface heater is located on the outer surface of the tube sheet, and is used to heat the tube sheet;

[0005] The outer wall annular heater comprises an arc plate, a side wall insulation layer and a side wall electric heating layer, wherein the side wall electric heating layer, the side wall insulation layer and the arc plate are arranged in sequence from the inside to the outside and fit each other;

[0006] The surface heater includes a supporting cover, a thermal insulation layer and an electric heating layer. One side of the thermal insulation layer is in contact with the electric heating layer, and the other side is in contact with the supporting cover. The supporting cover buckles and fixes the electric heating layer and the thermal insulation layer to form a disc-shaped surface heater.

[0007] Furthermore, the outer wall annular heater also includes a connecting device, which includes a pair of nuts, a pair of sleeves, a pair of clips and studs. A plurality of pairs of notches are symmetrically provided on the two arc-shaped sides of the arc plate. The pair of clips are symmetrically arranged in a pair of notches of the arc plate to clamp and fix the side wall electric heating layer, the side wall insulation layer and the arc plate. A hole is vertically provided on one side foot of the clip. The stud passes through the pair of clips through the hole. A pair of sleeves are respectively inserted into the studs from both sides and fit with the pair of clips respectively. A pair of nuts are located at both ends of the studs and are threadedly connected to them. The pair of sleeves and the pair of clips are clamped and fixed from both sides.

[0008] Furthermore, the outer wall annular heater includes a symmetrically arranged left semicircular outer wall annular heater and a right semicircular outer wall annular heater, and the arc plate, the side wall insulation layer and the side wall electric heating layer each include two parts and a plurality of connecting devices to respectively constitute the left semicircular outer wall annular heater and the right semicircular outer wall annular heater.

[0009] Furthermore, the outer wall annular heater also includes a first supporting and moving device, which is fixedly connected to the arc plate and is used to support, fix and drive the outer wall annular heater; the surface heater also includes a second supporting and moving device, which is fixedly connected to the supporting pressure cover and is used to support, fix and drive the surface heater.

[0010] Furthermore, the first supporting and traveling device includes two supporting and traveling units, which are respectively arranged on both sides of the outer wall annular heater, and the supporting and traveling units include a cross-arm frame body, a support rod, a counterweight, a base one and a plurality of first traveling wheels, one side of the cross-arm frame body is fixedly connected to the support rod, the other side is fixedly connected to the counterweight, the bottom is fixedly connected to the base one, a plurality of first traveling wheels are arranged on the bottom surface of the base one, and the support rod is fixedly connected to the arc plate.

[0011] Furthermore, the second supporting travel device includes a frame, a second base and a plurality of second running wheels, the frame is fixedly connected to the second base, a plurality of second running wheels are arranged on the bottom surface of the second base, and the frame is fixedly connected to the supporting pressure cover.

[0012] Furthermore, the surface heater includes a central circular heating component, a first annular heating component and a second annular heating component which are concentrically arranged with each other from the inside to the outside; the supporting pressure cover includes a central circular pressure cover, a first annular pressure cover and a second annular pressure cover which are concentrically arranged with each other from the inside to the outside; the thermal insulation layer and the electric heating layer each include multiple parts, each part is respectively combined with the central circular pressure cover, the first annular pressure cover and the second annular pressure cover to form the central circular heating component, the first annular heating component and the second annular heating component, and the second supporting travel device is fixedly connected to the central circular pressure cover, the first annular pressure cover and the second annular pressure cover.

[0013] Furthermore, the arc-shaped plate is made of carbon steel, and the side wall insulation layer and the insulation layer are both made of aluminum silicate fiber material.

[0014] Furthermore, the side wall electric heating layer and the electric heating layer both use rope heaters or crawler belt heaters.

[0015] A heating method of a heating device for preheating and postheating of tube-tube sheet welding of a shell and tube heat exchanger, comprising the following steps:

[0016] S1. Install the outer wall annular heater on the outer side wall of the tube sheet, energize it to heat the tube sheet, and simultaneously weld a plurality of first thermocouples to measure and control the temperature of the tube sheet;

[0017] S2. Multiple second thermocouples are welded on different areas of the outer surface of the tube sheet to measure and control the temperature of the tube sheet;

[0018] S3, installing the surface heater on the outer surface of the tube sheet, applying power, and heating the tube sheet;

[0019] S4. When the temperatures displayed by the first thermocouples all reach the required temperature of +30 to 50°C, the outer wall annular heater is powered off. At this time, the outer wall annular heater is used to keep the tube sheet warm.

[0020] S5. When the temperatures displayed by the multiple second thermocouples reach the required temperature of +30 to 50°C, the surface heater is powered off;

[0021] S6. Remove the surface heater and weld the tubes on the tube sheet of the shell and tube heat exchanger;

[0022] S7. When the multiple second thermocouples show that the tube sheet temperature is lower than the value required by the process document, stop welding, install the surface heater again, and turn on the power for heating;

[0023] S8. Repeat steps S5-S7 until all areas of the tube sheet of the shell and tube heat exchanger are welded to the tubes.

[0024] Compared with the prior art, the heating device and heating method for preheating and postheating of tube-tube sheet welding of a shell and tube heat exchanger described in the present invention have the following beneficial effects:

[0025] 1. The present invention uses an outer wall annular heater and a surface heater to preheat the product from two positions at the same time, thereby accelerating the preheating speed.

[0026] 2. The present invention uses the outer wall annular heater and the surface heater to cooperate with each other, thereby avoiding the heat loss generated by a single heating structure. After the temperature in the preheating area of ​​the outer wall annular heater reaches the standard and the power is turned off, the outer wall annular heater can still play a role in keeping the workpiece warm.

[0027] 3. The present invention utilizes an arc plate, a gland, an electric heating layer and a heat preservation layer to form a layered heater, which has a large heating area and uniform heating of the tube sheet, thereby improving the preheating efficiency and reducing energy consumption.

[0028] 4. The outer wall annular heater of the present invention is a left and right semicircular splicing structure, which is easy to be assembled with the product.

[0029] 5. The surface heater of the present invention can be divided into multiple heating areas and can be flexibly combined and used according to different working conditions.

[0030] 6. The present invention is provided with a supporting and traveling device, which can fix the product in mid-air, facilitating the welding process. The driving structure makes the present invention easy to install and disassemble. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0032] Figure 1 It is a front view of the overall structure of the heating device of the present invention;

[0033] Figure 2 A top view of the overall structure of the heating device of the present invention;

[0034] Figure 3 It is a schematic diagram of the main structure of the curved plate of the heating device of the present invention;

[0035] Figure 4 It is a schematic diagram of the main structure of the heating device clip of the present invention;

[0036] Figure 5 It is a schematic diagram of the main structure of the heating device connecting device of the present invention;

[0037] Figure 6 This is a schematic diagram of the installation position of the heating device supporting the traveling device of the present invention;

[0038] Figure 7 It is a schematic diagram of the main structure of the first supporting traveling device of the heating device of the present invention;

[0039] Figure 8 It is a top view of the main structure of the first supporting traveling device of the heating device of the present invention;

[0040] Fig. 9 It is a schematic diagram of the main structure of the second supporting and traveling device of the heating device of the present invention;

[0041] Fig.10 It is a top view of the main structure of the second supporting and traveling device of the heating device of the present invention;

[0042] Fig.11 It is a schematic diagram of the overall structure of the surface heater of the heating device of the present invention being divided into a plurality of heating areas;

[0043] Fig.12 A top view of the overall structure of the surface heater of the heating device of the present invention divided into a plurality of heating areas;

[0044] Fig.13 An exploded view of a surface heater of a heating device of the present invention divided into a plurality of heating areas;

[0045] In the figure: 1-arc plate; 2-side wall insulation layer; 3-side wall electric heating layer; 4-connecting device; 5-first supporting and traveling device; 6-second supporting and traveling device; 8-supporting gland; 9-insulation layer; 10-electric heating layer; A-workpiece;

[0046] 11-notch; 41-nut; 42-sleeve; 43-clip; 44-stud; 431-hole; 51-cross arm frame; 52-support rod; 53-counterweight; 54-base one; 55-first running wheel; 61-frame; 62-base two; 63-second running wheel;

[0047] 81 - central circular gland; 82 - first annular gland; 83 - second annular gland. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely explain the technical solutions in the embodiments of the present invention. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict, and the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0049] 1. Specific implementation method 1, see Figure 1-13 To explain this embodiment, a heating device for preheating and postheating of tube-tube sheet welding of a shell-and-tube heat exchanger includes an outer wall annular heater and a surface heater; the shell-and-tube heat exchanger is in the shape of a cylinder with a bottom on one or both sides, the bottom being the tube sheet, and a plurality of tubes to be welded are inserted on the inner tube sheet of the cylinder; the outer wall annular heater is located on the outer side wall of the tube sheet, and is used for heating and keeping the tube sheet warm; the surface heater is located on the outer surface of the tube sheet, and is used for heating the tube sheet;

[0050] The outer wall annular heater comprises an arc plate 1, a side wall insulation layer 2 and a side wall electric heating layer 3, wherein the side wall electric heating layer 3, the side wall insulation layer 2 and the arc plate 1 are arranged in sequence from the inside to the outside and fit each other;

[0051] The surface heater includes a supporting cover 8, an insulating layer 9 and an electric heating layer 10. One side of the insulating layer 9 is in contact with the electric heating layer 10, and the other side is in contact with the supporting cover 8. The supporting cover 8 buckles and fixes the electric heating layer 10 and the insulating layer 9 to form a disc-shaped surface heater.

[0052] The present invention preheats the product from two positions, the outer wall of the tube sheet and the surface of the tube sheet, to improve the preheating efficiency. It avoids the problem of heat loss on the surface of the tube sheet when heating only from the side wall and the problem of uneven heating of the tube sheet and the inappropriate temperature. And the problem of heat loss generated by the side wall when heating only from the surface of the tube sheet, improves the preheating efficiency, and the side wall heating structure can still play a heat preservation role after power failure, extending the duration of the tube sheet at the standard temperature after preheating. The present invention uses an electric heating layer as a heating component, and the temperature control is accurate. For temperature-sensitive materials, accurate temperature control can effectively avoid overheating or insufficient heating. The electric heating layer can evenly distribute heat, avoid local overheating or uneven heating, and uniform heating helps to reduce welding stress and deformation, and improve welding quality. The present invention is also provided with an insulation layer, which can reduce heat loss, so that the heat generated by the electric heating layer acts more concentratedly on the workpiece. Prevent the surface temperature of the workpiece from dropping rapidly, ensure that the preheating temperature remains stable during the welding process, reduce the loss of heat to the surrounding environment, and reduce the power demand of the electric heating layer.

[0053] The outer wall annular heater described in the present application also includes a connecting device 4, which includes a pair of nuts 41, a pair of sleeves 42, a pair of clips 43 and studs 44. The arc plate 1 has two arc sides symmetrically provided with multiple pairs of notches 11. The pair of clips 43 are symmetrically arranged in a pair of notches 11 of the arc plate 1 to clamp and fix the side wall electric heating layer 3, the side wall insulation layer 2 and the arc plate 1. A hole 431 is vertically provided on one side foot of the clip 43. The stud 44 passes through the pair of clips 43 through the hole 431. A pair of sleeves 42 are respectively inserted into the stud 44 and fit with the pair of clips 43 from both sides. A pair of nuts 41 are located at both ends of the stud 44 and are threadedly connected thereto, and a pair of sleeves 42 and a pair of clips 43 are clamped and fixed from both sides. The present invention is provided with a connecting device 4 that uses the clips 43 to clamp and fix multiple layered components from both sides, so that the multiple layered components form an integral structure, and the notches 11 are used to limit and fix the clips 43 to prevent them from slipping. A pair of clamps 43 are fixed in the axial direction by a pair of nuts 41, a pair of sleeves 42 and studs 44. The sleeves 42 keep the fastening position of the bolts 41 away from the clamps 43 to prevent interference during installation, which is convenient for screwing and installing the bolts 41. The outer wall annular heater forms an integral structure, which is convenient for tooling with the workpiece.

[0054] The outer wall annular heater described in the present application includes a symmetrically arranged left semicircular outer wall annular heater and a right semicircular outer wall annular heater, and the arc plate 1, the side wall insulation layer 2 and the side wall electric heating layer 3 each include two parts and a plurality of connecting devices 4 to respectively form a left semicircular outer wall annular heater and a right semicircular outer wall annular heater. The present invention divides the outer wall annular heater into a left and right semicircular splicing structure, which is convenient for tooling with a workpiece in practical applications.

[0055] The outer wall annular heater described in the present application also includes a first support travel device 5, which is fixedly connected to the arc plate 1 and is used to support, fix and drive the outer wall annular heater; the surface heater also includes a second support travel device 6, which is fixedly connected to the support cover 8 and is used to support, fix and drive the surface heater. The present invention is also provided with a support travel device, which can accurately control the position of the workpiece and improve the preheating accuracy, and the support drive device can reduce the risk of manual contact with high-temperature workpieces and improve the safety of the operation.

[0056] The first supporting and traveling device 5 of the present application includes two supporting and traveling units, which are respectively arranged on both sides of the outer wall annular heater, and the supporting and traveling units include a cross arm frame body 51, a support rod 52, a counterweight 53, a base 54 and a plurality of first running wheels 55. One side of the cross arm frame body 51 is fixedly connected to the support rod 52, the other side is fixedly connected to the counterweight 53, and the bottom is fixedly connected to the base 54. A plurality of first running wheels 55 are arranged on the bottom surface of the base 54, and the support rod 52 is fixedly connected to the arc plate 1. The present invention adopts a cross arm frame body 51, which has strong structural stability and uniform load distribution, can reduce local stress concentration, has small deformation when bearing load, and can maintain high support accuracy.

[0057] The second supporting traveling device 6 of the present application includes a frame 61, a second base 62 and a plurality of second running wheels 63, the frame 61 is fixedly connected to the second base 62, a plurality of second running wheels 63 are arranged on the bottom surface of the second base 62, and the frame 61 is fixedly connected to the supporting pressure cover 8.

[0058] The first running wheel 55 and the second running wheel 63 of the present invention can also be used in conjunction with a track. The track provides a clear path guide to ensure that they can move accurately along the predetermined route, reduce the risk of deviation, and improve the operation accuracy.

[0059] The surface heater described in the present application includes a central circular heating component, a first annular heating component and a second annular heating component which are arranged concentrically from the inside to the outside; the support gland 8 includes a central circular gland 81, a first annular gland 82 and a second annular gland 83 which are arranged concentrically from the inside to the outside; the insulation layer 9 and the electric heating layer 10 each include multiple parts, each of which is respectively combined with the central circular gland 81, the first annular gland 82 and the second annular gland 83 to form a central circular heating component, a first annular heating component and a second annular heating component, and the second support travel device 6 is fixedly connected to the central circular gland 81, the first annular gland 82 and the second annular gland 83. The surface heater is appropriately divided according to the diameter of the product tube sheet and the needs of the subsequent tube-tube sheet welding work. Since there are many tube holes on the tube sheet, welding cannot be performed at the same time. First, use the surface heater to preheat all the tube holes on the tube sheet at the same time. When the preheating temperature is reached, the entire surface heater is removed, and the outer wall annular heater is still located on the side wall of the product to insulate the product, and the tube-tube sheet welding process is performed. Since only a local area of ​​the tube sheet can be welded in a short time, as the welding progresses, the temperature of the welded area and the area to be welded will gradually decrease, and the unwelded area needs to be preheated again. Therefore, the surface heater is divided into multiple parts according to needs, and different heating components are installed according to different working conditions. Only the unwelded area is preheated during subsequent operation. The central circular gland 81, the first annular gland 82 and the second annular gland 83 can also be fixedly connected to the second supporting travel device 6 by adding a connecting device, so that each heating component is easier to disassemble and assemble.

[0060] The material of the arc plate 1 described in the present application is carbon steel, and the side wall insulation layer 2 and the insulation layer 9 are both made of aluminum silicate fiber material. Aluminum silicate fiber has good insulation effect and low density, and is a lightweight insulation material that can reduce the overall load of the equipment. The width of the insulation layer is greater than the width of the electric heating layer to ensure a small temperature gradient. The material of the arc plate 1 of the present invention can also be other conventional metal materials such as low alloy steel.

[0061] The side wall electric heating layer 3 and the electric heating layer 10 described in the present application both use rope heaters or track heaters. Both rope heaters and track heaters can fit the surface of the heated object well, provide relatively uniform heat distribution, and reduce the risk of local overheating.

[0062] The above description is only for the horizontal assembly of shell and tube heat exchange tubes, that is, the radial axis of the tube sheet is parallel to the ground. The present invention is also applicable to the vertical assembly of shell and tube heat exchangers, that is, the radial axis of the tube sheet is perpendicular to the ground. In this case, the support rod 52 is bolted and rotated 90° to be fixedly connected to one side of the cross arm frame 51, and the second support travel device 6 is replaced by other lifting tools such as a crane, and the other parts remain unchanged.

[0063] A heating method for a heating device for preheating and postheating of tube-tube sheet welding in a shell and tube heat exchanger, comprising the following steps:

[0064] S1, installing the outer wall annular heater on the outer side wall of the tube sheet, energizing it to heat the tube sheet, and welding a plurality of first thermocouples at the same time. The number of first thermocouples may be 4, which are respectively located at the 3 o'clock position, 6 o'clock position, 9 o'clock position and 12 o'clock position of the edge of the tube sheet, for measuring and controlling the temperature of the tube sheet;

[0065] S2. Multiple second thermocouples are welded on different areas of the outer surface of the tube sheet to measure and control the temperature of the tube sheet;

[0066] S3, installing the surface heater on the outer surface of the tube sheet, applying power, and heating the tube sheet;

[0067] S4. When the temperatures displayed by the first thermocouples all reach the required temperature of +30 to 50°C, the outer wall annular heater is powered off. At this time, the outer wall annular heater is used to keep the tube sheet warm.

[0068] S5. When the temperatures displayed by the multiple second thermocouples reach the required temperature of +30 to 50°C, the surface heater is powered off;

[0069] S6. Remove the surface heater and weld the tubes on the tube sheet of the shell and tube heat exchanger;

[0070] S7. When the multiple second thermocouples show that the tube sheet temperature is lower than the value required by the process document, stop welding, install the surface heater again, and turn on the power for heating;

[0071] S8. Repeat steps S5-S7 until all areas of the tube sheet of the shell and tube heat exchanger are welded to the tubes.

[0072] The heating method of the heating device of the present invention has simple steps and high preheating efficiency. The outer wall annular heater and the surface heater are used in combination to quickly preheat the product. The preheating temperature is monitored in real time with a thermocouple, the preheating process is accurately controlled, and the preheating accuracy is high.

[0073] The embodiments of the present invention disclosed above are only used to help illustrate the present invention. The embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. According to the content of this specification, many modifications and changes can be made. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well.

Claims

1. A heating device for preheating and postheating of tube-tube sheet welding of a shell and tube heat exchanger, characterized in that: It includes an outer wall annular heater and a surface heater; the outer wall annular heater is located on the outer side wall of the tube sheet and is used to heat and keep the tube sheet warm; the surface heater is located on the outer surface of the tube sheet and is used to heat the tube sheet; The outer wall annular heater comprises an arc-shaped plate (1), a side wall heat-insulating layer (2) and a side wall electric heating layer (3); the side wall electric heating layer (3), the side wall heat-insulating layer (2) and the arc-shaped plate (1) are arranged in sequence from the inside to the outside and are in contact with each other; The surface heater comprises a supporting cover (8), a heat-insulating layer (9) and an electric heating layer (10); one side of the heat-insulating layer (9) is in contact with the electric heating layer (10), and the other side of the heat-insulating layer (9) is in contact with the supporting cover (8); the supporting cover (8) fastens and fixes the electric heating layer (10) and the heat-insulating layer (9) to form a disc-shaped surface heater.

2. A heating device for preheating and postheating of tube-tube sheet welding of a shell and tube heat exchanger according to claim 1, characterized in that: The outer wall annular heater also includes a connecting device (4), which includes a pair of nuts (41), a pair of sleeves (42), a pair of clips (43) and a stud (44). A plurality of pairs of notches (11) are symmetrically provided on two arcuate sides of the arc plate (1). The pair of clips (43) are symmetrically arranged in a pair of notches (11) of the arc plate (1) to clamp and fix the side wall electric heating layer (3), the side wall thermal insulation layer (2) and the arc plate (1). A hole (431) is vertically provided on one side leg of the clip (43). The stud (44) passes through the pair of clips (43) through the hole (431). A pair of sleeves (42) are respectively inserted into the stud (44) from both sides and fit with the pair of clips (43) respectively. A pair of nuts (41) are located at both ends of the stud (44) and are threadedly connected thereto. The pair of sleeves (42) and the pair of clips (43) are clamped and fixed from both sides.

3. A heating device for preheating and postheating of tube-tube sheet welding of a shell and tube heat exchanger according to claim 2, characterized in that: The outer wall annular heater comprises a symmetrically arranged left semicircular outer wall annular heater and a right semicircular outer wall annular heater, and the arc plate (1), the side wall insulation layer (2) and the side wall electric heating layer (3) each comprise two parts and a plurality of connecting devices (4) to respectively constitute the left semicircular outer wall annular heater and the right semicircular outer wall annular heater.

4. A heating device for preheating and postheating of tube-tube sheet welding of a shell and tube heat exchanger according to claim 3, characterized in that: The outer wall annular heater also includes a first supporting and moving device (5), which is fixedly connected to the arc plate (1) and is used to support, fix and drive the outer wall annular heater; the surface heater also includes a second supporting and moving device (6), which is fixedly connected to the supporting pressure cover (8) and is used to support, fix and drive the surface heater.

5. A heating device for preheating and postheating of tube-tube sheet welding of a shell and tube heat exchanger according to claim 4, characterized in that: The first supporting and traveling device (5) comprises two supporting and traveling units, and the two supporting and traveling units are respectively arranged on both sides of the outer wall annular heater, and the supporting and traveling units comprise a cross arm frame body (51), a supporting rod (52), a counterweight (53), a base one (54) and a plurality of first traveling wheels (55). One side of the cross arm frame body (51) is fixedly connected to the supporting rod (52), and the other side is fixedly connected to the counterweight (53), and the bottom is fixedly connected to the base one (54). A plurality of first traveling wheels (55) are arranged on the bottom surface of the base one (54), and the supporting rod (52) is fixedly connected to the arc plate (1).

6. A heating device for preheating and postheating of tube-tube sheet welding of a shell and tube heat exchanger according to claim 4, characterized in that: The second supporting travel device (6) comprises a frame (61), a second base (62) and a plurality of second running wheels (63); the frame (61) is fixedly connected to the second base (62); a plurality of second running wheels (63) are provided on the bottom surface of the second base (62); and the frame (61) is fixedly connected to the supporting pressure cover (8).

7. A heating device for preheating and postheating of tube-tube sheet welding of a shell and tube heat exchanger according to claim 4, characterized in that: The surface heater comprises a central circular heating component, a first annular heating component and a second annular heating component which are arranged concentrically with each other from the inside to the outside; the support cover (8) comprises a central circular cover (81), a first annular cover (82) and a second annular cover (83) which are arranged concentrically with each other from the inside to the outside; the thermal insulation layer (9) and the electric heating layer (10) both comprise a plurality of parts, each of which is respectively combined with the central circular cover (81), the first annular cover (82) and the second annular cover (83) to form the central circular heating component, the first annular heating component and the second annular heating component; the second support travel device (6) is fixedly connected to the central circular cover (81), the first annular cover (82) and the second annular cover (83).

8. A heating device for preheating and postheating of tube-tube sheet welding of a shell and tube heat exchanger according to claim 1, characterized in that: The arc-shaped plate (1) is made of carbon steel, and the side wall insulation layer (2) and the insulation layer (9) are both made of aluminum silicate fiber material.

9. A heating device for preheating and postheating of tube-tube sheet welding of a shell and tube heat exchanger according to claim 1, characterized in that: The side wall electric heating layer (3) and the electric heating layer (10) both adopt rope-shaped heaters or crawler-type heaters.

10. A heating method using the heating device for preheating and postheating of tube-tube sheet welding of a shell and tube heat exchanger according to any one of claims 1 to 9, characterized in that: The steps include: S1. Install the outer wall annular heater on the outer side wall of the tube sheet, energize it to heat the tube sheet, and simultaneously weld a plurality of first thermocouples to measure and control the temperature of the tube sheet; S2. Multiple second thermocouples are welded on different areas of the outer surface of the tube sheet to measure and control the temperature of the tube sheet; S3, installing the surface heater on the outer surface of the tube sheet, applying power, and heating the tube sheet; S4. When the temperatures displayed by the first thermocouples all reach the required temperature of +30 to 50°C, the outer wall annular heater is powered off. At this time, the outer wall annular heater is used to keep the tube sheet warm. S5. When the temperatures displayed by the multiple second thermocouples reach the required temperature of +30 to 50°C, the surface heater is powered off; S6. Remove the surface heater and weld the tubes on the tube sheet of the shell and tube heat exchanger; S7. When the multiple second thermocouples show that the tube sheet temperature is lower than the value required by the process document, stop welding, install the surface heater again, and turn on the power for heating; S8. Repeat steps S5-S7 until all areas of the tube sheet of the shell and tube heat exchanger are welded to the tubes.

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