Expansion joint structure and expansion joint cover member

Abstract

To provide an expansion joint structure capable of reducing generation of pitting corrosion and reducing a maintenance load, and an expansion joint cover member.SOLUTION: An expansion joint structure comprises: an expansion joint that is provided between a pair of ducts, and has an expansion part that is expandable and contractible in a direction in which the pair of ducts are connected; and an expansion joint cover member that has an attachment part formed in an annular shape over a circumferential direction of the expansion joint and attached to one end side of the expansion joint, and cover part extending from an inner edge of the attachment part to a terminal end side of the expansion part in an axial direction of the expansion joint and covering an inner wall of the expansion part in the circumferential direction of the expansion joint. The attachment part is formed to be attachable to and detachable from the expansion joint.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an expansion joint structure that connects, for example, a pair of ducts, and a cover member for the expansion joint. [Background technology]

[0002] Combustion facilities such as thermal power plants, steel mills, and waste incinerators exhaust high-temperature gases generated during their operation from ducts to the outside. When the ducts expand due to the heat of the gas, for example, a force in the connection direction is applied to the joints connecting the ducts. For this reason, expansion joints are used in the joints to absorb the thermal expansion of the ducts due to the heat of the gas.

[0003] For example, when gas containing corrosive substances, such as gas generated in a steel mill, is discharged to the outside, an expansion joint using a metal bellows with excellent corrosion resistance is used to connect the ducts.

[0004] Bellows are formed thinly due to their elasticity. Therefore, even if the material is corrosion-resistant, it will corrode and cause pitting if it is exposed to a corrosive substance for a long period of time. If pitting occurs in the bellows, gas may leak to the outside, that is, the gas may be released into the atmosphere before it is subjected to the required treatment. In addition, if gas leaks to the outside, the thermal energy recovered from the gas is lost, which causes a problem of reduced efficiency in plant operation.

[0005] Therefore, in the past, gas leakage to the outside of the expansion joint has been prevented by increasing the durability of the expansion joint. For example, Patent Document 1 discloses an expansion joint in which a first metal layer, a mesh layer, a heat-resistant layer, and a second metal layer are laminated in this order from the outer periphery. In Patent Document 1, the second metal layer is laminated on the heat-resistant layer to prevent the intrusion of water, dust, and the like into the heat-resistant layer (inside the expansion joint), which has the main function of the expansion joint, and to prevent the occurrence of pitting corrosion.

[0006] Patent Document 2 discloses an expansion joint having an inorganic fiber woven fabric covering the inner peripheral surface of a metal bellows. It discloses that covering the inner peripheral surface of the metal bellows with an inorganic fiber woven fabric prevents dust from accumulating in the grooves of the metal bellows, and shortens the cleaning time required to remove dust. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2009-299731 A [Patent Document 2] JP 2000-220777 A Summary of the Invention [Problem to be solved by the invention]

[0008] It is preferable to use a metal layer such as a thin film for each metal layer used in the expansion joint described in Patent Document 1 in order to ensure the expansion property of the expansion joint. Therefore, with a metal layer such as a thin film, there is a problem that it is difficult to ensure a layer thickness for obtaining sufficient corrosion resistance and durability.

[0009] Furthermore, the expansion joint of Patent Document 2 is not designed to be used in an environment where condensation occurs, and therefore has the problem that it cannot suppress corrosion of the metal bellows caused by condensation.

[0010] In particular, the inorganic fiber woven fabric described in Patent Document 2 changes in slack depending on the operating state of the plant. As the slack of the inorganic fiber woven fabric changes, solid matter accumulated on the inorganic fiber woven fabric may fall onto the metal bellows. As a result, the reaction between water generated by condensation and the fallen solid matter may lead to a state in which corrosion of the metal bellows is likely to progress.

[0011] The present invention has been made in consideration of the above problems, and has an object to provide an expansion joint structure and a cover member for an expansion joint that are capable of reducing the occurrence of pitting corrosion and reducing the maintenance load. [Means for solving the problem]

[0012] [1] an expansion joint provided between a pair of ducts and having an expansion / contraction portion that is expandable and contractible in a connection direction of the pair of ducts; The cover member of the expansion joint includes an attachment portion that is formed in an annular shape around the circumferential direction of the expansion joint and is attached to one end side of the expansion joint, and a cover portion that extends from the inner edge of the attachment portion to the terminal side of the expansion portion in the axial direction of the expansion joint and covers the inner wall of the expansion portion around the circumferential direction of the expansion joint, The mounting portion is formed to be detachable from the expansion joint. [2] The expansion joint structure according to [1], wherein the mounting portion is formed so as to be fastened by a bolt to a joint flange formed on one end side of the expansion joint. [3] The cover portion is provided at a distance from an inner wall of the expansion joint in a direction perpendicular to the axial direction of the expansion joint, The expansion joint structure according to [1] or [2], wherein in a cross section of the terminal side of the expansion section perpendicular to the axial direction of the expansion joint, an area of ​​a first region surrounded by the end of the cover section is larger than an area of ​​a second region surrounded by the end of the expansion section and the end of the cover section. [4] The expansion joint structure according to [3], wherein the relationship between the area A2 of the second region and the area A1 of the first region satisfies the following formula: 0.0002≦A2 / A1≦0.0450 [5] A cover member for an expansion joint that connects a pair of ducts and is attached to an expansion joint having an expansion part that is expandable and contractible in a connection direction of the pair of ducts, An attachment portion that is annularly formed around the circumferential direction of the expansion joint and is attached to one end side of the expansion joint; A cover portion extending from an inner edge of the mounting portion to a terminal end side of the expansion portion in the axial direction of the expansion joint and facing the expansion portion along the circumferential direction of the expansion joint, The mounting portion is a cover member for the expansion joint that is formed to be detachable from the expansion joint. [6] The cover member for an expansion joint described in [5], wherein the mounting portion is formed so as to be fastened by a bolt to a joint flange formed on one end side of the expansion joint. [7] The cover member of the expansion joint described in [5] or [6], wherein the cover portion is formed to be freely expandable and contractible in the connection direction and has an adjustment portion that adjusts the length in the connection direction. [8] The cover member for an expansion joint described in [5] or [6], wherein the cover portion comprises a base material layer and a coating layer including an anticorrosive paint formed on the base material layer. [9] The cover member for an expansion joint described in [7], wherein the cover portion comprises a base material layer and a coating layer including an anticorrosive paint formed on the base material layer. Effect of the Invention

[0013] According to the present invention, for example, when used to connect ducts through which gas containing a corrosive substance flows, the cover portion covering the inner wall of the expansion portion of the expansion joint can suppress the corrosion. Therefore, the occurrence of pitting caused by the progression of corrosion due to the corrosive substance can be suppressed, and the leakage of gas from the expansion joint to the outside can be suppressed. In addition, since the cover member of the expansion joint is configured to be detachable from the expansion joint, for example, the progress of corrosion can be visually confirmed by removing the cover member of the expansion joint. This makes it possible to quickly grasp the presence or absence of corrosion and to take appropriate measures according to the progress of corrosion. Therefore, the maintenance burden such as repair and replacement of the expansion joint can be reduced. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a cross-sectional view of an expansion joint structure according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view of the expansion joint structure taken along line I1-I1 in FIG. [Diagram 3] FIG. 4 is a cross-sectional view showing an expansion joint structure according to a second embodiment of the present invention. [Figure 4] FIG. 4 is a cross-sectional view of the expansion joint structure taken along line I2-I2 in FIG. [Diagram 5] FIG. 11 is a perspective view showing a cover member of an expansion joint according to a third embodiment of the present invention. [Figure 6] FIG. 6 is a cross-sectional view of a cover member of the expansion joint of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] (First embodiment) Fig. 1 is a diagram showing an expansion joint structure according to a first embodiment of the present invention. As shown in Fig. 1, the expansion joint structure 100 connects a pair of ducts D1, D2 to each other. The expansion joint structure 100 includes an expansion joint 10 provided between the pair of ducts D1, D2, and an expansion joint cover member 20 attached to one end side of the expansion joint 10.

[0016] The ducts D1 and D2 are provided in combustion facilities such as thermal power plants, steel mills, and waste incineration plants. The ducts D1 and D2 in this embodiment form a flow path for exhaust gas (hereinafter also referred to as gas) that is discharged from these facilities and has a relatively high temperature and contains corrosive substances. In this embodiment, a case will be described in which the duct D1 is located upstream of the flow path with respect to the duct D2.

[0017] Duct D2 is connected to a processing device (not shown) that performs a predetermined process such as a catalyst at its terminal end. Therefore, the gas that has passed through ducts D1 and D2 is released into the atmosphere after the predetermined process. Thermal energy may be recovered from the gas that has passed through ducts D1 and D2. For example, a thermal energy recovery device (not shown) may be provided at the terminal end of duct D2.

[0018] The ducts D1 and D2 are formed in a tubular shape. In this embodiment, the ducts D1 and D2 are formed in a cylindrical shape. The ducts D1 and D2 are provided at both ends with annular flanges DF for connecting to other members. The flanges DF are formed with a plurality of mounting holes (not shown) through which bolts can be inserted, for example, along the edge of the ring.

[0019] The shape of each of the ducts D1 and D2 is not limited to a cylindrical shape as long as a flow path is formed through which the gas can move. The ducts D1 and D2 may be, for example, a rectangular column. The material of each of the ducts D1 and D2 is not particularly limited, but it is preferable to use stainless steel in terms of corrosion resistance.

[0020] Each duct D1, D2 is configured to be capable of flowing a large amount of high-temperature gas. For example, if each duct D1, D2 is cylindrical, the inner diameter may be 0.4 m or more and 10.0 m or less. Also, if each duct D1, D2 is prismatic, the length of each side of the cross section perpendicular to the axial direction of each duct D1, D2 may be 0.4 m or more and 10.0 m or less. The flow rate of gas in each duct D1, D2 may be, for example, 500 m. 3 / min or more 5000m 3 It is recommended to keep it below / min.

[0021] The expansion joint 10 has an expansion section 11 that is expandable and contractable in the connecting direction of a pair of ducts D1, D2, and connection sections 12 provided on one end side and the terminal end side of the expansion section 11.

[0022] The expansion section 11 may be, for example, a so-called bellows type. In this embodiment, the expansion section 11 is formed in a bellows shape that is expandable and contractable in the axial direction AX of the expansion joint 10. Therefore, the expansion joint 10 is configured to be able to absorb the expansion and contraction of each of the ducts D1, D2 that occurs in the axial direction AX of the expansion joint 10. In this embodiment, the axis AX of the expansion joint 10 is the same as the connection direction of the pair of ducts D1, D2.

[0023] Furthermore, because the expansion and contraction section 11 is formed in such a bellows shape, even if vibrations occur in each duct D1, D2 due to fluctuations in gas pressure or flow rate, or vibrations of external equipment, the bellows section can absorb the vibrations by expanding and contracting.

[0024] It is preferable that the stretchable portion 11 is made of, for example, a corrosion-resistant material. An example of such a corrosion-resistant material is stainless steel.

[0025] The inner diameter of the expandable portion 11 is preferably set to be approximately the same as the inner diameters of the ducts D1 and D2. Here, the inner diameter of the expandable portion 11 means the smallest inner diameter (the inner diameter at the edge of the bellows-shaped groove) among the inner diameters of the bellows-shaped expandable portion 11.

[0026] Furthermore, in the case of a bellows type, the plate thickness of the expandable portion 11 is preferably set to about 0.5 mm or more and 3.5 mm or less from the viewpoint of the expandable portion 11's expandability, corrosion resistance, durability against fatigue, and the like.

[0027] The expansion section 11 only needs to be configured to absorb the expansion and contraction of the ducts D1, D2 in the axial direction AX of the expansion joint 10 and to absorb vibrations of the components thereof. For example, the expansion section 11 may be a so-called sleeve type instead of a bellows type. In the case of the sleeve type, for example, one having one pipe, another pipe housed in the first pipe and arranged so as to be slidable in the axial direction of the first pipe, and a sealing material that maintains airtightness between the first pipe and the other pipe can be used.

[0028] Each of the connection parts 12 has an annular flange formed to protrude outward in a direction (radial direction) perpendicular to the axis AX of the expansion joint 10. Each flange of the connection part 12 has a plurality of mounting holes (not shown) formed along the edge of the ring, through which bolts can be inserted, for example.

[0029] The cover member 20 of the expansion joint has an attachment portion 21 that is attached to one end side of the expansion joint 10, and a cover portion 22 that covers the inner wall of the expansion portion 11 around the circumferential direction of the expansion joint 10.

[0030] The mounting portion 21 has a flange (joint flange) formed in an annular shape around the circumferential direction of the expansion joint 10. The flange (joint flange) of the mounting portion 21 has a plurality of mounting holes (not shown) formed along the edge of the ring, through which bolts can be inserted, for example.

[0031] The cover part 22 is formed in a cylindrical shape, extending from the inner edge of the mounting part 21 to the terminal side of the expansion part 11 in the axial direction AX of the expansion joint 10, and is formed so as to cover the expansion part 11 (facing the expansion part 11) around the circumferential direction of the expansion joint 10. In this embodiment, the cover part 22 is formed in a cylindrical shape.

[0032] The cover part 22 may be formed so as to extend from the vicinity of the inner edge of the mounting part 21 along the axial direction AX of the expansion joint 10. In other words, the cover part 22 may be formed so as to extend from the surface of the mounting part 21 facing the downstream duct D2 along the axial direction AX of the expansion joint 10.

[0033] Here, "so as to cover the expansion section 11" means that condition (1): when viewed from a direction perpendicular to the axis AX of the expansion joint 10, the expansion section 11 and the cover section 22 are arranged so as to overlap (face) each other, and condition (2): at least 80% of the total length L of the expansion section 11 is arranged so as to overlap (face) the cover section 22.

[0034] Incidentally, the condition (2) can be appropriately changed according to the spring constant of the telescopic portion 11 and the manner of expansion of the ducts D1 and D2. That is, each of the ducts D1 and D2 thermally expands due to the high-temperature gas discharged from the plant, and the telescopic portion 11 contracts accordingly (the total length L shortens). Therefore, when the telescopic portion 11 is in a contracted state, the telescopic portion 11 and the cover portion 22 are preferably arranged so that the telescopic portion 11 overlaps with the cover portion 22 from one end side to the terminal end side. In other words, the cover portion 22 should have a length that overlaps with at least 80% of the total length L of the telescopic portion 11 at room temperature, where the telescopic portion 11 is not affected by the thermal expansion of the ducts D1 and D2, for example.

[0035] 1, the cover part 22 is formed to be longer than the overall length L of the extension part 11. In addition, the cover part 22 is arranged so as to satisfy the condition (1), and is arranged so as to overlap (face) 100% of the overall length of the extension part 11 at room temperature where the extension part 11 is not affected by thermal expansion from the ducts D1 and D2, and therefore is arranged so as to satisfy the condition (2).

[0036] The flange DF of the duct D1, the connection portion 12 of the expansion joint 10, and the mounting portion 21 of the cover member 20 of the expansion joint are each assembled airtightly. The cover member 20 of the expansion joint is detachably assembled to the expansion joint 10. When providing the expansion joint structure 100 in this manner, it is preferable to arrange the duct D1 so that it is located upstream of the duct D2.

[0037] Specifically, in this embodiment, the flange DF of the duct D1, the connection portion 12 of the expansion joint 10, and the mounting portion 21 of the cover member 20 of the expansion joint are fastened by inserting a bolt into each mounting hole of these members and screwing a nut. A sealant (not shown) such as a packing or a gasket may be provided between each of the flange DF of the duct D1, the connection portion 12 of the expansion joint 10, and the mounting portion 21 of the cover member 20 of the expansion joint. In addition, the mounting portion 21 of the cover member 20 of the expansion joint may be formed so as to be detachable from the expansion joint 10. For example, the flange DF of the duct D1, the connection portion 12 of the expansion joint 10, and the mounting portion 21 of the cover member 20 of the expansion joint may be fastened using a fastener such as a C-clamp in addition to the above-mentioned embodiment.

[0038] The flange DF of the duct D2 and the connection portion 12 of the expansion joint 10 are assembled in an airtight manner. Specifically, in this embodiment, the flange DF of the duct D2 and the connection portion 12 of the expansion joint 10 are fastened by inserting bolts into the mounting holes of these members and screwing nuts. A sealant (not shown), such as a packing or a gasket, may be provided between the flange DF of the duct D2 and the connection portion 12 of the expansion joint 10.

[0039] Fig. 2 shows a cross section of the terminal end side of the expansion part of the expansion joint structure taken along line I1-I1 in Fig. 1, i.e., a cross section perpendicular to the axial direction AX of the expansion joint 10. As shown in Fig. 2, the cover part 22 is provided with a gap G between it and the inner wall of the expansion joint 10 (expansion part 11) in a direction perpendicular to the axial direction of the expansion joint 10. In this embodiment, the gap G is provided so as to be constant in the circumferential direction of the expansion joint 10.

[0040] The cover portion 22 preferably includes a base material layer 23 and a coating layer 24 formed on the base material layer 23 and including an anticorrosive paint.

[0041] The base layer 23 is made of a material that is not particularly limited, but has the strength and corrosion resistance to withstand vibrations caused by gas movement. An example of such a material is stainless steel. The base layer 23 is preferably about 1.0 mm or more and 10.0 mm or less.

[0042] Any paint having anticorrosive properties against corrosive substances can be used as the anticorrosive paint contained in the coating layer 24. Examples of such paint include paints containing silicone resin.

[0043] For example, when the expansion joint structure 100 is used to connect ducts used in power plants, etc., the anticorrosive paint contained in the coating layer 24 preferably has heat resistance as well as anticorrosive properties, since high-temperature gas will flow through it.

[0044] In such an environment, it is advisable to use a paint that has heat resistance and corrosion resistance from room temperature to about 300° C. An example of such a paint is Santomo DHX (product name) manufactured by Taiho Paint Co., Ltd.

[0045] The anticorrosive coating contained in the coating layer 24 may have any other components added thereto to improve its mechanical strength. For example, by adding glass flakes as a coating component, it is possible to increase the heat resistance and mechanical strength of the anticorrosive coating. An example of such a coating is Flake Guard (product name) manufactured by Nippon Chemical Coating Co., Ltd.

[0046] The thickness of the coating layer, excluding the base adjustment layer (unevenness adjustment layer), is preferably 15 to 2000 μm, more preferably 250 to 2000 μm, and even more preferably 550 to 2000 μm. By making the thickness of the coating layer 15 μm or more, sufficient corrosion resistance can be imparted. By making the thickness of the coating layer 2000 μm or less, the anticorrosion treatment cost can be suppressed.

[0047] The coating layer 24 is preferably provided at a position where there is a possibility that the gas flowing through the ducts D1, D2 may come into contact with the cover portion 22. Examples of such positions include the inner wall surface and the outer wall surface of the cover portion 22. Of these, it is preferable that the coating layer 24 is provided on the inner wall surface, since it is particularly likely to be exposed to the gas. In this embodiment, the coating layer 24 is provided on the inner wall surface of the cover portion 22.

[0048] For example, when factors that cause corrosion, such as the movement of gas containing a corrosive substance, the occurrence of condensation, or the generation of an aqueous solution of a corrosive substance, occur, the provision of the coating layer 24 on the cover portion 22 can suppress corrosion of the cover portion 22. As a result, the frequency of maintenance of the expansion joint structure 100 can be reduced. Note that the coating layer 24 may be provided not only on the inner wall surface and outer wall surface of the cover portion 22, but also on the inner wall surface of the expansion portion 11. By providing the coating layer 24 on the inner wall surface of the expansion portion 11, the progression of corrosion of the expansion joint 10 can be further suppressed.

[0049] 2, a first region surrounded by the inner wall of the end of the cover portion 22 is formed larger than a second region surrounded by the inner wall of the end of the expansion portion 11 and the outer wall of the end of the cover portion 22. In other words, the area A1 of the first region as viewed from the axial direction AX of the expansion joint 10 is larger than the area A2 of the second region (hereinafter referred to as the area A1 of the first region and the area A2 of the second region).

[0050] Therefore, for example, if a hole is formed in the expandable portion 11 due to the progression of corrosion, the area A2 of the second region is smaller than the area A1 of the first region, and therefore when gas flows from duct D1 to duct D2, the static pressure in the first region is lower than that in the second region according to Bernoulli's theorem. That is, the static pressure in the first region, where the flow velocity is higher than that in the second region, is lower than that in the second region. As a result, a gas flow is generated from the second region, where the static pressure is higher, toward the first region, where the static pressure is lower.

[0051] Therefore, outside air flows in through the holes in the expansion section 11, and a gas flow is generated in which the outside air merges with the gas flowing through the expansion joint 10. This makes it possible to prevent the gas flowing through the expansion joint 10 from leaking to the outside, even if a hole is formed in the expansion section 11.

[0052] It is preferable that the relationship between the area A2 of the second region and the area A1 of the first region satisfies the relationship of the following formula (1). 0.0002≦A2 / A1≦0.0450 (1)

[0053] That is, when the relationship between the area A2 of the second region and the area A1 of the first region satisfies the formula (1), the flow of outside air flowing in through the holes of the stretchable section 11 can be made appropriate.

[0054] For example, in the above formula (1), when the area ratio (A2 / A1) of the area A2 of the second region to the area A1 of the first region is the lower limit value of 0.0002, the area A2 of the second region is 0.02% of the area A1 of the first region.

[0055] If the ratio of the area A2 of the second region to the area A1 of the first region falls below the lower limit, the pressure loss of the outside air flowing in through the holes in the expansion section 11 increases, and it tends to become difficult for the outside air to be sucked into the expansion joint 10.

[0056] Furthermore, for example, when the area ratio (A2 / A1) of the area A2 of the second region to the area A1 of the first region is the upper limit value of 0.0450, the area A2 of the second region is 4.50% of the area A1 of the first region.

[0057] If the area A2 of the second region relative to the area A1 of the first region exceeds the upper limit, the effect of reducing the static pressure of the first region according to Bernoulli's theorem decreases. Therefore, it tends to be difficult for outside air to be sucked into the expansion joint 10 through the holes in the expansion section 11.

[0058] The operation of the expansion joint structure 100 according to the embodiment of the present invention described above will be described. For example, when the operation of a combustion facility (not shown) is started, high-temperature gas generated by combustion passes through each of the ducts D1 and D2 and the expansion joint structure 100.

[0059] In an embodiment of the present invention, the expansion portion 11 of the expansion joint 10 is covered by the cover portion 22 of the expansion joint cover member 20. Therefore, soot and corrosive substances contained in the gas can be prevented from accumulating on the expansion portion 11, and the progress of corrosion of the expansion portion 11 can be prevented.

[0060] As described above, according to the expansion joint structure 100 of this embodiment, the mounting portion 21 of the expansion joint cover member 20 is detachably fastened with a bolt to the joint flange (located upstream in the gas flow direction) of the connection portion 12 of the expansion joint 10. Therefore, the user can remove the expansion joint cover member 20 during inspection and visually check the corrosion state of the expansion joint 10 and the expansion joint cover member 20. Therefore, corrosion of the expansion portion 11 due to a fluid containing a corrosive substance can be discovered early, and gas leakage to the outside can be prevented, while the maintenance load such as repair and replacement of the expansion joint 10 can be reduced.

[0061] Next, a case will be described in which so-called pitting corrosion occurs in the expansion section 11. For example, when a corrosive substance dissolves in the condensation inside the expansion joint 10, the aqueous solution gradually corrodes the expansion section 11, forming holes.

[0062] As described above, when outside air flows in through the holes in the expansion and contraction section 11, the outside air flows from the second region toward the duct D2 according to Bernoulli's theorem. Therefore, even if corrosion occurs in the expansion and contraction section 11 and a hole 14 is formed, it is possible to prevent the gas flowing through the expansion joint 10 from leaking to the outside. As a result, the maintenance load, such as repair and replacement of the expansion joint 10, can be reduced.

[0063] Second Embodiment In the above-described first embodiment, an example has been described in which the gap G between the outer wall of the cover portion 22 and the expansion portion 11 is constant in the circumferential direction of the expansion joint 10. The gap G between the outer wall of the cover portion 22 and the expansion portion 11 may be varied depending on the position in the vertical direction.

[0064] Fig. 3 shows an expansion joint structure 100 according to a second embodiment. Fig. 4 shows a cross section of the expansion joint structure 100 taken along line I2-I2 in Fig. 3. As shown in Figs. 3 and 4, the distance between the outer wall of the cover portion 22 and the expansion portion 11 varies depending on the position in the vertical direction. Specifically, the distance Gdown between the outer wall of the cover portion 22 located on the lower side in the vertical direction and the expansion portion 11 is narrower than the distance Gup between the outer wall of the cover portion 22 located on the upper side in the vertical direction and the expansion portion 11.

[0065] For example, condensation occurring in the expansion and contraction section 11 is more likely to accumulate on the lower side in the vertical direction than on the upper side. Therefore, pitting corrosion is more likely to occur on the lower side of the expansion and contraction section 11 in the vertical direction. Therefore, by making the gap Gdown narrower than the gap Gup, the flow velocity of the outside air can be made faster on the lower side in the vertical direction than on the upper side. This can promote the inflow of outside air into the expansion joint 10.

[0066] Third embodiment In the above embodiment, the cover part 22 has been described as having a constant length in the axial direction AX of the expansion joint 10. The cover part 22 may be formed to be expandable and contractible in the axial direction AX of the expansion joint 10 (the connection direction of the ducts D1, D1).

[0067] Fig. 5 shows an example of a cover member 30 for an expansion joint according to a third embodiment of the present invention. Fig. 6 shows a cross section along the axial direction of the cover member 30 for the expansion joint in Fig. 5. As shown in Figs. 5 and 6, the cover member 30 for the expansion joint has an attachment portion 31 that is attached to one end side of the expansion joint 10, and a cover portion 32 that covers the inner wall of the expansion portion 11 around the circumferential direction of the expansion joint 10.

[0068] The mounting portion 31 has a flange (joint flange) formed in an annular shape around the circumferential direction of the expansion joint 10. The flange (joint flange) of the mounting portion 31 has a plurality of mounting holes 31a formed along the edge of the ring, through which bolts can be inserted, for example.

[0069] The cover part 32 has a cylindrical first cover part 32a fixed to the mounting part 31, a cylindrical second cover part 32b housed in the first cover part 32a and slidable in the axial direction AX of the expansion joint 10 relative to the first cover part 32a, and an adjustment part 35 that adjusts the sliding amount of the second cover part 32b.

[0070] In this embodiment, the first cover portion 32a and the second cover portion 32b are both formed in a cylindrical shape. That is, the cover portion 32 includes the first cover portion 32a and the second cover portion 32b, which are a pair of cylinders (double cylinders) having a common axis.

[0071] A sealant such as a packing or gasket is provided between the first cover part 32a and the second cover part 32b to maintain airtightness. Therefore, the second cover part 32b is housed in the first cover part 32a while maintaining an airtight state. In this manner, the cover part 32 can be configured as a so-called sleeve type.

[0072] The adjustment portion 35 has a plurality of screw holes (not shown) formed on the peripheral surfaces of the first cover portion 32a and the second cover portion 32b, a bolt 35a that can be inserted into the screw holes, and a nut 35b that can be screwed onto the bolt 35a.

[0073] The screw holes formed in the first cover part 32a and the second cover part 32b may be formed in two or more places along the axis AX of the expansion joint 10. In this embodiment, they are formed in a row at four places on the axis AX of the expansion joint 10. By forming the screw holes in this manner, the screw holes of the first cover member 32a and the second cover part 32b can be aligned at desired positions and fastened with the bolts 35a and nuts 35b. This makes it possible to adjust the expansion and contraction of the second cover part 32b relative to the first cover part 32a.

[0074] The screw holes formed in the first cover portion 32a and the second cover portion 32b may be blocked by a member other than the bolt 35a. For example, when the second cover portion 31b is in the most extended state, the three screw holes arranged on the mounting portion 31 side of the first cover member 32a may be blocked by a blocking member other than the bolt 35a. Examples of such blocking members include a gasket, putty, etc.

[0075] Moreover, the screw holes formed in the first cover part 32a and the second cover part 32b may be formed at two or more locations in the circumferential direction. In this embodiment, the screw holes are formed at two locations that are symmetrical with respect to the axis AX of the expansion joint 10. By forming the screw holes in this manner, the second cover part 32b can be more firmly fixed to the first cover part 32a.

[0076] That is, the bolts 35a and nuts 35b of the adjustment part 35 are easily affected by vibrations transmitted from the ducts D1 and D2. However, by forming a plurality of screw holes in the circumferential direction of the first cover part 32a and the second cover part 32b, it is possible to disperse the influence on these members in the circumferential direction. This makes it possible to stably maintain the fixed state of the first cover part 32a and the second cover part 32b.

[0077] By configuring the cover part 32 to be expandable and contractible in the direction of the axis AX of the expansion joint 10 in this way, it becomes possible to adjust its overall length in the direction along the fluid flow direction. Therefore, the cover member of the expansion joint 10 of this embodiment can be attached to multiple types of expansion joints 10 having different overall lengths L of the expansion part 11. Therefore, it can be attached regardless of the type of expansion joint 10 according to the overall length L of the expansion joint 10, which makes it possible to increase versatility.

[0078] The expansion joint cover member 30 can be attached to the expansion joint 10 as in the above-described embodiment, and used as the expansion joint structure 100. By using the expansion joint structure 100 in this way to connect the ducts D1 and D2, it is possible to obtain the same functions and effects as in the above-described embodiment.

[0079] Furthermore, according to the cover member 30 for the expansion joint of this embodiment, it can be used for various types of expansion joints 10 according to the overall length L of the expansion section 11 to form an expansion joint structure 100.

[0080] For example, when corrosion progresses and it becomes necessary to replace the cover portion 32, by using the cover member 30 of the expansion joint of this embodiment, it becomes unnecessary to use a dedicated product specially designed for the expansion joint 10. Therefore, it becomes possible to reduce the costs for maintenance and inspection of the equipment. [Explanation of symbols]

[0081] 100 Expansion joint structure 10 Expansion joints 11 Telescopic part 20 Cover member for expansion joint 21 Mounting part 22 Cover part 23 Base material layer 24 Coating layer 25 Adjustment part A1 Area of ​​the first region A2 Area of ​​the second region AX Axis of expansion joint (direction of connection of pair of ducts) D1, D2 duct

Claims

1. an expansion joint provided between a pair of ducts and having an expansion / contraction portion that is expandable and contractible in a connection direction of the pair of ducts; The cover member of the expansion joint includes an attachment portion that is formed in an annular shape around the circumferential direction of the expansion joint and is attached to one end side of the expansion joint, and a cover portion that extends from the inner edge of the attachment portion to the terminal side of the expansion portion in the axial direction of the expansion joint and covers the inner wall of the expansion portion around the circumferential direction of the expansion joint, The mounting portion is formed to be detachable from the expansion joint, The cover portion is provided at a distance from an inner wall of the expansion joint in a direction perpendicular to the axial direction of the expansion joint, In a cross section of the terminal side of the expansion section perpendicular to the axial direction of the expansion joint, the area of ​​a first region surrounded by the end of the cover section is larger than the area of ​​a second region surrounded by the end of the expansion section and the end of the cover section, The expansion joint structure, wherein the relationship between the area A2 of the second region and the area A1 of the first region satisfies the following formula: 0.0002≦A2 / A1≦0.0450

2. The expansion joint structure according to claim 1 , wherein the mounting portion is formed so as to be fastened by a bolt to a joint flange formed on one end side of the expansion joint.

3. A cover member for an expansion joint that connects a pair of ducts and is attached to the inside of an expansion joint having an expansion part that is expandable and contractible in a connection direction of the pair of ducts, An attachment portion that is annularly formed around the circumferential direction of the expansion joint and is attached to one end side of the expansion joint; A cover portion extending from an inner edge of the mounting portion to a terminal end side of the expansion portion in the axial direction of the expansion joint and facing the expansion portion along the circumferential direction of the expansion joint, The mounting portion is formed to be detachable from the expansion joint, the cover portion is formed to be expandable and contractible in the connection direction and has an adjustment portion that adjusts the length in the connection direction, The cover portion includes a base material layer and a coating layer including an anticorrosive coating formed on the base material layer, The cover member of an expansion joint, wherein the coating layer comprises glass flakes.

4. The cover member for an expansion joint according to claim 3 , wherein the mounting portion is formed so as to be fastened by a bolt to a joint flange formed on one end side of the expansion joint.

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