Flange joint structure

Abstract

To provide a flange joint structure which can prevent leakage and corrosion of a fluid from a flange joint part.SOLUTION: In a flange joint structure 1, an outer periphery of a flange joint part 3 comprising a pair of flanges 3A, 3B fastened by a bolt 17 and a nut 18 is sealed by a leakage prevention device 30 and connection holes 3c, 3c formed at the pair of flanges 3A, 3B is sealed. The flange joint structure 1 includes: a seal washer 11 which is inserted into a shaft part 17a of the bolt 17 and seals the connection hole 3c; an insulation washer 12 which is inserted into the shaft part 17a of the bolt 17 and disposed closer to the end side than the seal washer 11 at the shaft part 17a; and an insulation sleeve 14 covering an outer peripheral surface of the shaft part 17a of the bolt 17. The insulation sleeve 14 is provided extending in an axial direction over the connection hole 3c, the seal washer 11, and the insulation washer 12 on the outer peripheral surface of the shaft part 17a of the bolt 17.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a flange joint structure that prevents fluid leakage and corrosion from a flange joint. [Background technology]

[0002] Conventionally, in flange joints that connect flanges formed on the ends of existing fluid pipes or piping components such as valves that control internal fluids, there is a risk of fluid leaking from the gaps between the flanges due to unforeseen external forces such as earthquakes or due to aging, etc.

[0003] One such device for preventing leakage of fluids is composed of a leakage prevention member arranged along the outer peripheral surface of the flange joint portion and an outer fitting member that houses this leakage prevention member and is fitted onto the flange joint portion, thereby preventing leakage by sealing along the outer peripheral surface of the flange joint portion, and also sealing the bolt insertion hole with a seal washer arranged between the flange portion and the seat surface of the bolt and nut that connects the flange portions together, thereby preventing leakage of fluid from the bolt insertion hole through which the bolt is inserted (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6026122 (pages 5-6, Figures 4-6) [Patent Document 2] Patent No. 6105342 (page 6, figures 3-4) Summary of the Invention [Problem to be solved by the invention]

[0005] Meanwhile, these fluid pipes and piping components may be made of pipes made of various materials depending on the structural strength, earthquake resistance, weather resistance, cost, etc. required at each piping position. When the flanges to be connected are made of different metal materials, for example, a stainless steel pipe and a ductile cast iron pipe, so-called galvanic corrosion occurs at the electrical contact portion connecting the flanges of the metal materials due to the potential difference between the different metals via an internal fluid such as water, and the corroded area increases over time, which may cause leakage between the flanges.

[0006] In the flange joints described in Patent Documents 1 and 2, for example, an insulating member such as a gasket is disposed between the opposing surfaces of the flanges to prevent corrosion caused by a potential difference between dissimilar metals. However, when the metal frame members constituting the bolts, nuts, and seal washers are made of metal, the flanges may be electrically connected to each other via the bolts and frame members, which creates the problem that the occurrence of galvanic corrosion cannot be prevented.

[0007] The present invention has been made in view of these problems, and has an object to provide a flange joint structure that can prevent fluid leakage and corrosion from the flange joint portion. [Means for solving the problem]

[0008] In order to solve the above problems, the flange joint structure of the present invention comprises: A flange joint structure in which an outer periphery of a flange joint portion consisting of a pair of flanges fastened by bolts and nuts is sealed, and bolt insertion holes formed in the pair of flanges are sealed, a seal washer that is inserted into a shaft portion of the bolt and seals the bolt insertion hole; an insulating washer that is inserted into the shank of the bolt and is disposed on the shank of the bolt closer to an end than the seal washer; an insulating sleeve covering an outer circumferential surface of the shaft portion of the bolt; The insulating sleeve is characterized in that it extends in the axial direction across the bolt insertion hole on the outer circumferential surface of the shank of the bolt, the seal washer, and the insulating washer. According to this feature, the insulating washer is positioned closer to the end of the bolt shank than the seal washer, and an insulating sleeve is interposed between the outer surface of the bolt shank and the bolt insertion hole, the seal washer, and the insulating washer. This makes it possible to avoid electrical connection between the flange and the bolt via the seal washer, thereby preventing fluid leakage and corrosion from the flange joint.

[0009] The insulating sleeve is characterized by covering the body portion of the shank of the bolt excluding the male thread portion. According to this feature, the insulating sleeve can be attached to the outer periphery of the bolt without stripping the male thread portion.

[0010] The insulating sleeve has an outer diameter that is substantially the same as an outer diameter of the male thread portion. According to this feature, there is no risk of the bolts being hindered from being inserted into the bolt insertion holes of the flange.

[0011] A protective washer is provided between the sealing washer and the insulating washer. According to this feature, damage to the sealing washer and the insulating washer can be prevented when the bolt and the nut are tightened.

[0012] The sealing washer is characterized in that it is composed of a sealing member made of an elastic material and a frame member that is harder than the sealing member and is positioned closer to the end of the bolt shaft than the sealing member. According to this feature, when the bolt and nut are fastened, the seal member is pressed against the peripheral edge of the bolt insertion hole in the flange by the frame member, thereby preventing leakage of fluid from the bolt insertion hole.

[0013] The bolt is characterized in that a thickness adjusting washer is disposed on the shank of the bolt closer to the end than the insulating washer. According to this feature, it is possible to prevent the insulating washer from protruding too far toward the end side from the insulating sleeve, and the nut from being positioned on the body portion excluding the male thread portion, making it impossible to fasten the nut.

[0014] The sealing washer, the insulating washer and the insulating sleeve are disposed on both sides of the pair of flanges, respectively. According to this feature, since both of the pair of flanges can be insulated, the insulating effect can be improved.

[0015] The insulating sleeve is loosely fitted onto the shank of the bolt. According to this feature, when the shank of the bolt rotates in the circumferential direction, the insulating sleeve rotates relative to the shank, thereby preventing loss of sealing performance with the seal washer. [Brief description of the drawings]

[0016] [Figure 1] FIG. 2 is a partially cutaway front view showing a flange joint portion to which a leakage prevention device is attached. [Diagram 2] 2 is a cross-sectional view taken along line AA in FIG. 1. [Diagram 3] 1A is a diagram showing the attachment process (temporary installation) of the divided body, and FIG. 1B is a cross-sectional view taken along the line BB of FIG. [Figure 4] FIG. 4 is an enlarged cross-sectional view showing a flange joint structure when the fastening dimension is less than a predetermined dimension. [Diagram 5] FIG. [Figure 6] FIG. 4 is an exploded cross-sectional view showing the configuration of a fastening member. [Figure 7] FIG. 1A is an explanatory diagram for explaining an insulating state, and FIG. 1B is an explanatory diagram showing a modified example of FIG. [Figure 8] FIG. 4 is a cross-sectional view showing a flange joint structure when the fastening dimension is equal to or larger than a predetermined dimension. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A flange joint structure according to the present invention will now be described with reference to the accompanying drawings. EXAMPLES

[0018] A flange joint structure according to an embodiment of the present invention will be described with reference to Figures 1 to 7. In the following description, the near side of Figure 1 will be referred to as the front side (front surface side) of the flange joint portion, and the far side will be referred to as the rear side.

[0019] As shown in Fig. 1, existing fluid pipes 1A and 1B that transport a fluid from the upstream side to the downstream side are connected by a flange joint structure 1 according to an embodiment of the present invention. In this embodiment, the fluid in the fluid pipes 1A, 1B and the flow path 1c (see Fig. 4) is clean water, but it is not limited to clean water and may be liquid such as industrial water, agricultural water, or sewage, or may be gas or a gas-liquid mixture of gas and liquid.

[0020] Fluid pipes 1A, 1B are formed in a roughly cylindrical shape when viewed in cross section, and one of fluid pipes 1A, 1B is made of ductile cast iron and has an inner surface coated with an epoxy resin layer (not shown), while the other fluid pipe is made of stainless steel. Since the two are made of different types of metal pipes, they are connected in an insulated state as described below.

[0021] The fluid pipes 1A, 1B according to the present invention may be made of other metals such as cast iron, steel, etc., as long as they are different types of metal pipes. Furthermore, the inner circumferential surface of the fluid pipe is not limited to an epoxy resin layer, and may be coated with, for example, mortar, or the inner circumferential surface of the fluid pipe may be coated with an appropriate material by powder coating.

[0022] 1, 2 and 3, annular flanges 3A, 3B are formed around the entire circumference at one end of each of the fluid pipes 1A, 1B, protruding radially outward. A plurality of connection holes 3c (see FIG. 4) facing the pipe axis direction are formed in the flanges 3A, 3B of the fluid pipes 1A, 1B in the circumferential direction, and the flanges 3A, 3B are connected to each other by a fastening member 7 with sealing properties by inserting bolts 17 (described later) into each connection hole 3c and attaching and fastening nuts 18.

[0023] A leakage prevention device 30 is attached to the flange joint 3, which is composed of a pair of flanges 3A, 3B fastened in the pipe axial direction by a fastening member 7, and sealed around the outer periphery of the flange joint 3, thereby preventing leakage at the flange joint 3.

[0024] 1, 2 and 3, the leakage prevention device 30 is mainly composed of a plurality of divided bodies 31A, 31B (two in this embodiment) that can be attached from above and below to the outer periphery of the flange joint portion 3, and bolts and nuts 32 that connect (couple) the divided bodies 31A, 31B together to form a ring shape. Note that, in this embodiment, the leakage prevention device 30 is composed of two divided bodies, upper and lower 31A, 31B, but it may be composed of three or more divided bodies.

[0025] Each divided body 31A, 31B is provided with a gasket 33A, 33B as a leakage prevention member that seals around the outer periphery of the flange joint portion 3, and a mounting member 34A, 34B having a groove portion 39 (accommodating portion) that accommodates the gasket 33A, 33B and having an approximately C-shaped cross section that is fitted onto the flange joint portion 3.

[0026] Next, the mounting members 34A and 34B will be described. Since the mounting member 34A of the upper divided body 31A and the mounting member 34B of the lower divided body 31B have substantially the same configuration, the following description will focus on the mounting member 34B, and a detailed description of the mounting member 34A will be omitted.

[0027] As shown in Figs. 3(a) and (b), the mounting member 34B of the divided body 31B is made of ductile cast iron and includes a semicircular body 35 and connecting portions 36, 36 provided at both ends of the body 35. The connecting portions 36, 36 are used when connecting to the other mounting member 34A, and are formed so as to protrude radially outward at the ends of the body 35. A through hole 37 through which the bolts and nuts 32, 32 are inserted is provided on the radially outer side of the connecting portions 36, 36, and fitting portions 43, 43 into which the packings 33A, 33B can be fitted are formed on the radially inner side. The through hole 37 is provided perpendicular to the connecting portions 36, 36.

[0028] In addition, in this embodiment, the mounting member 34B (mounting member 34A) is made of ductile cast iron, but the material is not limited to the above and may be made of other materials, such as steel.

[0029] Next, the packings 33A and 33B will be described. Since the packing 33A of the upper divided body 31A and the packing 33B of the lower divided body 31B have substantially the same configuration, the following description will focus on the packing 33B, and a detailed description of the packing 33A will be omitted.

[0030] 3(a) and (b), the packing 33B of the divided body 31B is made of an elastic material such as styrene-butadiene rubber, and includes a semicircular arc-shaped main body 55 and connection portions 56, 56 that are provided at both circumferential ends of the main body 55 and are used to connect to the other packing 33A. Note that the packing may be any material having elasticity, such as nitrile rubber, ethylene propylene rubber, or fluororubber.

[0031] The connection portions 56, 56 are formed at the end of the main body portion 55 so as to protrude radially outward, and are capable of fitting into the fitting portion 43 of the mounting member 34B. Furthermore, a connection protrusion 55a that protrudes in the circumferential direction relative to the connection portion 56 is formed at one end of the main body portion 55, and a connection recess 55b that is recessed in the circumferential direction relative to the connection portion 56 is formed at the other end of the main body portion 55. In other words, one side is composed of the connection portion 56 and the connection protrusion 55a, and the other side is composed of the connection portion 56 and the connection recess 55b.

[0032] As shown in Fig. 3(a), the main body 55 has a substantially uniform cross-sectional shape in the circumferential direction, and includes a base 57 that is fitted into the groove 39 of the mounting member 34B, a first bulging portion 58 that is semicircular in cross section and bulges in the circumferential direction from the center of the base 57 in the inner diameter direction, and second bulging portions 59, 59 that bulge in the circumferential direction in the inner diameter direction from the base 57 so as to sandwich the first bulging portion 58 in the tube axis direction. Recesses 57a, 57a are formed in the circumferential direction on both side surfaces of the base 57 in the tube axis direction. The first bulging portion 58 and the second bulging portions 59, 59 function as sealing portions that seal the outer peripheries of the flanges 3A, 3B as described later.

[0033] Then, the main body portions 55 of the gaskets 33A, 33B are pushed radially inwardly into the groove portions 39 of the mounting members 34A, 34B to accommodate them, and the connection portions 56, 56 of the gaskets 33A, 33B are placed in the fitting portions 43, 43 of the mounting members 34A, 34B to form the divided bodies 31A, 31B.

[0034] Next, the upper and lower halves 31A, 31B are butted against each other, bolts are inserted into the through holes 37 of the connecting parts 36, 36 of the mounting members 34A, 34B, nuts are screwed in, and the connecting parts 36, 36 are connected to each other with the bolts and nuts 32, 32 to form a ring shape. At this time, the connecting protrusions 55a on one side of the packings 33A, 33B and the connecting recesses 55b on the other side are pressed against each other in the circumferential direction.

[0035] (Installation process of leakage prevention device) Next, the installation process of the leakage prevention device 30 will be described. First, the existing fastening members (bolts and nuts, not shown) connecting the flanges 3A, 3B are removed and replaced one by one or several by fastening members 7 having high sealing properties, which will be described later (see Figs. 3(a) and (b)). The fastening members 7 are provided with seal washers 11, 11, which will be described later, on both sides in the axial direction of the flanges 3A, 3B, thereby preventing leakage from the connection hole 3c. Details of the fastening members 7 will be described later. When installing the fastening members 7 to newly installed piping, the process of removing the existing fastening members as described above may be omitted.

[0036] Next, packings 33A, 33B are accommodated in the grooves 39 of the mounting members 34A, 34B to form the divisional bodies 31A, 31B, and the divisional bodies 31A, 31B are arranged one above the other on the outer periphery of the flange joint portion 3. Then, the upper divisional body 31A is moved radially inward (downward) to be fitted onto the upper half of the outer periphery 3d of the flange joint portion 3, and the lower divisional body 31B is moved radially inward (upward) to be fitted onto the lower half of the outer periphery 3d of the flange joint portion 3.

[0037] Here, the first bulging portion 58 bulging most radially inward is inserted into the gap between the opposing surfaces 3b, 3b of the flanges 3A, 3B. In detail, since the width dimension of the first bulging portion 58 in the tube axis direction is larger than the separation width dimension of the flanges 3A, 3B, the first bulging portion 58 is inserted into the gap between the opposing surfaces 3b, 3b of the flanges 3A, 3B while being pressed against the edge portion formed by the opposing surfaces 3b, 3b and the outer peripheral surfaces 3d, 3d of the flanges 3A, 3B (see FIG. 4). Therefore, the portion of the first bulging portion 58 on the outer diameter side of the edge portion (the portion not inserted into the gap between the opposing surfaces 3b, 3b) is inserted into the gap between the opposing surfaces 3b, 3b of the flanges 3A, 3B while being elastically deformed so as to bulge in the tube axis direction (obtaining a reaction force in the tube axis direction), and accordingly the second bulging portions 59, 59 on both sides are positioned in the tube axis direction.

[0038] 4, the first bulging portion 58 is inserted into the gap between the opposing surfaces 3b, 3b of the flanges 3A, 3B at both ends in the circumferential direction before the center portion, and the portion inserted into the gap expands toward the circumferential center portion as the divided bodies 31A, 31B move radially inward. When the portion of the first bulging portion 58 inserted into the gap expands toward the circumferential center portion, both sides in the circumferential direction of the second bulging portions 59, 59 abut against the outer circumferential surfaces 3d, 3d of the flanges 3A, 3B before the center portion. Then, as the divided bodies 31A, 31B move radially inward, the second bulging portions 59, 59 are crushed toward the radially outward direction, and the crushed portion expands toward the circumferential center portion.

[0039] Thereafter, when the connection portions 36, 36 of the upper and lower halves 31A, 31B are brought close to each other, a bolt is inserted into each through hole 37 and a nut is screwed into it. The connection portions 36, 36 are connected to each other with the bolts and nuts 32, 32 and temporarily installed, and the bolts and nuts 32, 32 are then tightened to secure them. As a result, the connection convex portion 55a on one side and the connection concave portion 55b on the other side of the gaskets 33A, 33B fit into each other circumferentially and are pressed against each other, so that the connection portions 56, 56 are connected in a sealed state, and a continuous annular gasket is formed.

[0040] In this way, the connection parts 36, 36 of the divided bodies 31A, 31B are connected by the bolts and nuts 32, 32 and the bolts and nuts 32, 32 are fastened, whereby the leakage prevention device 30 is fixed to the flange joint part 3 (see FIG. 1). As shown in FIG. 4, the first bulging part 58 can seal between the opposing faces 3b, 3b of the flanges 3A, 3B and the edge parts, and the second bulging parts 59, 59 can seal the outer peripheral faces 3d, 3d of the flanges 3A, 3B. In other words, a planar sealing area is formed from the opposing faces 3b, 3b of the flanges 3A, 3B to the outer peripheral faces 3d, 3d, so that a sufficient sealing force can be obtained to prevent leakage against the fluid pressure inside the flange joint part 3, and the mounting members 34A, 34B can be easily installed by simply fitting the packings 33A, 33B to the flanges 3A, 3B.

[0041] Moreover, the first bulging portion 58 is pressed against the opposing surfaces 3b, 3b of the flanges 3A, 3B in the pipe axis direction, and the second bulging portions 59, 59 are pressed against the outer circumferential surfaces 3d, 3d of the flanges 3A, 3B in the radial direction. That is, since the first bulging portion 58 and the second bulging portions 59, 59 are independent of each other, they can resist the pressure of the internal fluid from various directions.

[0042] (Flange joint structure) 4, an insulating gasket 9 having a water-stopping function is provided between the protrusions 3e, 3e formed in an annular shape around the openings on the opposing surfaces 3b, 3b of the flanges 3A, 3B. The insulating gasket 9 is an annular ring made of an elastic material such as resin or rubber, and in addition to isolating and insulating the fluid pipes 1A, 1B, it maintains flexibility against earth pressure and the like during use and has the function of preventing water leakage due to misalignment of the connection caused by earth pressure.

[0043] The fastening member 7 for fastening the flanges 3A, 3B mainly comprises a bolt 17, a nut 18 that can be screwed onto the bolt 17, a seal washer 11 consisting of a seal ring 11a and a seal ring rubber 11b, an insulating washer 12, protective washers 12a, 12b that protect the insulating washer 12, an annular spacer 13, and an insulating sleeve 14 that is attached to the outer circumferential surface of the shaft of the bolt 17.

[0044] The bolt 17, nut 18, seal ring 11a, spacer 13 and protective washers 12a, 12b are made of a metal material such as stainless steel, the seal ring rubber 11b is made of an elastic material having insulating properties such as rubber, the insulating washer 12 is made of glass fiber reinforced epoxy resin, and the insulating sleeve 14 is made of fluororesin.

[0045] Furthermore, the materials of the bolt 17, nut 18, seal ring 11a, spacer 13, and protective washers 12a and 12b are not limited to stainless steel, and other metal materials or resin materials may be used. Also, the material of the seal ring rubber 11b is not limited to a specific type as long as it is an elastic rubber material. Additionally, the materials of the insulating washer 12 and insulating sleeve 14 are not limited to the above resin material, and other polyethylene resins, polyacetal resins, etc. may be used as long as they are insulating resin materials.

[0046] As shown in FIG. 5, the bolt 17 is composed of a columnar shaft portion 17a and a head portion 17b provided on the base end side of the shaft portion 17a. A male thread portion 17c is formed on the outer peripheral surface of the tip end side of the shaft portion 17a, and the portion of the outer peripheral surface of the shaft portion 17a excluding the male thread portion 17c is a body portion 17d having a constant outer diameter in the axial direction without a male thread formed thereon.

[0047] The outer diameter dimension L1 of the body portion 17d is smaller than the outer diameter dimension L2 of the crest of the male thread portion 17c (L1 < L2) and is approximately the same as the root diameter dimension L3 of the male thread portion 17c (L1 ≒ L3). The outer diameter dimension L11 of the insulating sleeve 14 is approximately the same as the outer diameter dimension L2 of the crest of the male thread portion 17c (L11 ≒ L2), and the thickness dimension L12 of the insulating sleeve 14 is approximately the same as the thread height dimension L4 (L12 ≒ L4). Incidentally, the thickness dimension L12 may be slightly shorter than the thread height dimension L4 (L12 < L4). Also, the length dimension L13 of the insulating sleeve 14 is approximately the same as the length dimension L5 of the body portion 17d (L13 ≒ L5).

[0048] The insulating sleeve 14 is elastic and formed into a cylindrical shape that has no end in the circumferential direction, and is elastically expanded from the tip side of the shaft portion 17a, sliding over the outer periphery of the male thread portion 17c and press-fitted in the axial direction toward the head portion 17b, and is attached so that it elastically restores its original shape when it passes the male thread portion 17c and covers the outer periphery of the body portion 17d. When the insulating sleeve 14 is attached, one end face in the axial direction abuts against the head portion 17b, and the other end face abuts against the terminal end portion 17e of the male thread portion 17c, thereby restricting axial movement. Furthermore, when the insulating sleeve 14 is attached, its inner periphery abuts or is in close contact with the outer periphery of the body portion 17d without any gaps.

[0049] In this embodiment, the outer diameter L1 of the body 17d is smaller than the outer diameter L2 of the male threaded portion 17c, and the outer diameter L11 of the attached insulating sleeve 14 is approximately the same as the outer diameter L2 of the male threaded portion 17c. Therefore, the outer diameter L11 of the insulating sleeve 14 attached to the body 17d does not become larger than the outer diameter L2 of the male threaded portion 17c, which makes it difficult to insert the insulating sleeve 14 into the connection hole 3c. In addition, since it is not necessary to make the thickness L12 of the insulating sleeve 14 small, it is possible to suppress the insulating sleeve 14 from becoming easily damaged or from losing its insulating effect.

[0050] In addition, the bolt 17 does not form the male thread portion 17c over the entire longitudinal direction of the shaft portion 17a, and the length dimension L13 of the body portion 17d is longer than the length dimension L14 of the male thread portion 17c (L13>L14). In this way, the male thread portion 17c is made as short as possible, and the insulating area by the insulating sleeve 14 is made longer, thereby improving the insulating effect. In addition, if the seal ring rubber 11b of the seal washer 11 is attached to the outer periphery of the male thread portion 17c, a gap may be generated between the valley of the male thread portion 17c and the seal ring rubber 11b, making it difficult to prevent leakage of fluid. Therefore, it is preferable that the seal ring rubber 11b is in close contact with the outer periphery of the insulating sleeve 14 attached to the body portion 17d, rather than the male thread portion 17c.

[0051] 6, the seal washer 11 is annularly configured with an annular portion 11c having a hole 11e through which the shaft portion 17a of the bolt 17 can be inserted, and a tubular portion 11d extending in the axial direction from the outer circumferential edge of the annular portion 11c, and is formed to be able to accommodate a part of the seal ring rubber 11b. The seal ring rubber 11b has a hole 11f through which the shaft portion 17a of the bolt 17 can be inserted, and a protrusion 11g is provided around the hole 11f on one side surface to protrude in the axial direction, and is adapted to enter the connection hole 3c when attached to improve the sealing condition.

[0052] The insulating washer 12 and the protective washers 12a, 12b are formed with holes 12c, 12d into which the shaft portion 17a of the bolt 17 can be inserted. The insulating washer 12 and the protective washers 12a, 12b are formed to have approximately the same outer diameter, inner diameter, and axial thickness, but the insulating washer 12 and the protective washers 12a, 12b may have different thicknesses.

[0053] The spacer 13 is formed with a hole 13a into which the shaft portion 17a of the bolt 17 can be inserted, and has a predetermined thickness dimension L25. Then, the fastening dimension L21 between the outer surfaces of the flanges 3A, 3B is actually measured, and whether or not to use the spacer 13 is determined according to the actual measurement value, so that the flanges 3A, 3B can be fastened together with the nut 18 screwed into the male thread portion 17c.

[0054] Specifically, when the fastening dimension L21 between the outer surfaces of the flanges 3A and 3B is less than a predetermined dimension L20 (L21 < L20), as shown in FIG. 4, by arranging two spacers 13 on both sides, the flanges 3A and 3B can be fastened with the nut 18 screwed onto the male screw portion 17c. Incidentally, when the fastening dimension L21 is slightly longer, the nut 18 can be screwed onto the male screw portion 17c by arranging only one spacer 13. When the fastening dimension L21 is shorter, the nut 18 can be screwed onto the male screw portion 17c by arranging three or more spacers 13. On the other hand, when the fastening dimension L22 between the outer surfaces of the flanges 3A and 3B is greater than or equal to the predetermined dimension L20 (L22 ≧ L20), as shown in FIG. 8, the flanges 3A and 3B can be fastened with the nut 18 screwed onto the male screw portion 17c without using the spacer 13.

[0055] Next, a case where an existing fastening member (bolt and nut, not shown) connecting the flanges 3A and 3B is removed and the fastening member 7 of the present embodiment is attached will be described.

[0056] As shown in FIG. 6, first, the members are inserted and attached to the shaft portion 17a of the bolt 17 in the order of the spacer 13, the protective washer 12b, the insulating washer 12, the protective washer 12a, the seal ring 11a, and the seal ring rubber 11b.

[0057] Next, the shaft portion 17a of the bolt 17 is inserted into the connection holes 3c and 3c of the flanges 3A and 3B. Then, the members are inserted and attached to the shaft portion 17a protruding from the connection hole 3c of the flange 3B in the reverse order of the seal ring rubber 11b, the seal ring 11a, the protective washer 12a, the insulating washer 12, the protective washer 12b, and the spacer 13. Finally, the nut 18 is screwed onto the male screw portion 17c and tightened.

[0058] Regarding the tightening management of the plurality of bolts 17 and nuts 18 constituting the fastening member 7, it is desirable to evenly tighten to a predetermined tightening torque (for example, 100 N·m when the nominal diameter of the bolt is M20) using tools and jigs such as a torque wrench while paying attention not to cause uneven tightening in the circumferential direction.

[0059] The thus configured fastening member 7 fastens the flanges 3A, 3B together in an insulated state (see FIG. 4). In more detail, as shown in FIG. 7(a), by fastening the nut 18, the spacer 13, the protective washer 12b, the insulating washer 12, the protective washer 12a, the seal ring 11a, and the seal ring rubber 11b are axially pressed toward the flanges 3A, 3B. As a result, the seal ring rubber 11b is brought into close contact with the periphery of the connection hole 3c on the outer surface of the flanges 3A, 3B by the seal ring 11a, and the protrusion 11g is pressed into the connection hole 3c and is also brought into close contact with the outer periphery of the insulating sleeve 14, so that the gap between the connection hole 3c and the insulating sleeve 14 of the bolt 17 is sealed to prevent leakage.

[0060] The insulating sleeve 14 extends in the axial direction over the connection hole 3c on the outer circumferential surface of the shaft portion 17a of the bolt 17, the seal washer 11, the protective washer 12a, the insulating washer 12, the protective washer 12b, and the spacer 13. More specifically, the insulating sleeve 14 extends from the periphery of the connection hole 3c on the opposing surface 3b side into the hole portion 13a of the spacer 13.

[0061] Here, the insulating sleeve 14 is interposed between the inner peripheral surface of the connection hole 3c of the flanges 3A, 3B and the outer peripheral surface of the shaft portion 17a of the bolt 17, thereby insulating the conduction route R1 where the flanges 3A, 3B and the shaft portion 17a of the bolt 17 come into electrical contact (hereinafter simply referred to as contact) directly or via a fluid. The seal ring rubber 11b insulates the connection hole 3c and the seal ring 11a from the insulating sleeve 14 while preventing leakage of fluid.

[0062] Furthermore, by tightening the nut 18, the cylindrical portion 11d of the seal ring 11a comes into contact with the outer surfaces of the flanges 3A, 3B. However, since the insulating sleeve 14 is interposed between the inner surface of the hole portion 11e of the seal ring 11a and the outer surface of the shaft portion 17a of the bolt 17, the conductive route R2 in which the flanges 3A, 3B and the shaft portion 17a of the bolt 17 indirectly come into contact with each other via the seal ring 11a is insulated.

[0063] In addition, since an insulating sleeve 14 is interposed between the inner surface of the hole portion 12d of the protective washer 12a and the outer surface of the shaft portion 17a of the bolt 17, the conductive route R3 in which the flanges 3A, 3B and the shaft portion 17a of the bolt 17 indirectly contact each other via the seal ring 11a and the protective washer 12a is insulated.

[0064] In addition, since the insulating washer 12 is interposed between the protective washers 12a and 12b, the conductive routes R5 and R6 in which the flanges 3A and 3B and the shaft portion 17a of the bolt 17 indirectly contact each other via the seal ring 11a, the protective washers 12a and 12b, the spacer 13 or the nut 18 are insulated.

[0065] In this way, the insulating sleeve 14 is interposed between the outer surface of the shaft portion 17a of the bolt 17 and the inner surfaces of the connection holes 3c of the flanges 3A and 3B, the hole portion 11e of the seal ring 11a, the hole portion 12d of the protective washers 12a and 12b, and the hole portion 13a of the spacer 13, thereby insulating the radial conductive routes R1 to R3, and the insulating washers 12, 12 are interposed between the flange 3B and the nut 18 on the tip side of the shaft portion 17a rather than the seal ring 11a, and between the flange 3A and the head 17b on the base end side of the shaft portion 17a rather than the seal ring 11a.

[0066] In other words, by arranging the insulating washers 12, 12 perpendicularly at a predetermined position in the longitudinal direction of the insulating sleeve 14, not only the radial conductive routes R1 to R3 but also the axial conductive routes R5, R6 are blocked and insulated, thereby preventing the flanges 3A, 3B from contacting each other via the bolts 17 and nuts 18.

[0067] In this embodiment, the insulating sleeve 14 is illustrated as extending axially over the connection hole 3c on the outer peripheral surface of the shaft portion 17a of the bolt 17, the seal washer 11, the protective washer 12a, the insulating washer 12, the protective washer 12b, and the spacer 13. However, the present invention is not limited to this. As shown in FIG. 7(b), the conductive routes R1 to R6 can be insulated by extending axially at least over the connection hole 3c on the outer peripheral surface of the shaft portion 17a of the bolt 17, the seal washer 11, the protective washer 12a, and the insulating washer 12.

[0068] (Action and effect) As described above, in the flange joint structure 1 as an embodiment of the present invention, the outer periphery of the flange joint part 3 consisting of a pair of flanges 3A, 3B fastened by bolts 17 and nuts 18 is sealed by the leakage prevention device 30, and the connection holes 3c, 3c formed in the pair of flanges 3A, 3B are sealed. The flange joint structure 1 includes a seal washer 11 inserted into the shank 17a of the bolt 17 to seal the connection hole 3c, an insulating washer 12 inserted into the shank 17a of the bolt 17 and positioned closer to the end side of the shank 17a than the seal washer 11, and an insulating sleeve 14 covering the outer periphery of the shank 17a of the bolt 17, and the insulating sleeve 14 extends in the axial direction from the connection hole 3c on the outer periphery of the shank 17a of the bolt 17 to the seal washer 11 and the insulating washer 12.

[0069] According to this, the insulating washer 12 is positioned closer to the end of the shaft portion 17a of the bolt 17 than the seal washer 11, and an insulating sleeve 14 is interposed between the outer surface of the shaft portion 17a of the bolt 17 and the connection hole 3c, the seal washer 11 and the insulating washer 12, thereby preventing the flanges 3A, 3B and the bolt 17 from being electrically connected via the seal washer 11, and therefore preventing fluid leakage and corrosion from the flange joint portion 3.

[0070] Furthermore, by covering the body portion 17d of the shaft portion 17a of the bolt 17 except for the male thread portion 17c, the insulating sleeve 14 can be attached to the outer periphery of the bolt 17 without crushing the male thread portion 17c.

[0071] Furthermore, since the outer diameter L11 of the insulating sleeve 14 is substantially the same as the outer diameter L2 of the male threaded portion 17c, there is no risk of any hindrance to the insertion of the bolt 17 into the connection hole 3c of the flanges 3A, 3B.

[0072] Furthermore, since the protective washer 12a is provided between the seal washer 11 and the insulating washer 12, the seal washer 11 and the insulating washer 12 can be prevented from being damaged when the bolt 17 and the nut 18 are fastened.

[0073] In addition, the seal washer 11 is composed of a seal ring rubber 11b as a sealing member made of an elastic member, and a seal ring 11a as a frame member that is harder than the seal ring rubber 11b and is arranged on the end side of the shaft portion 17a of the bolt 17 relative to the seal ring rubber 11b.When the bolt 17 and the nut 18 are tightened, the seal ring rubber 11b is pressed against the peripheral portion of the connection hole 3c in the flanges 3A, 3B by the seal ring 11a, thereby preventing leakage of fluid from the connection hole 3c.

[0074] In addition, by arranging a spacer 13 as a thickness adjusting washer on the end side of the insulating washer 12 on the shaft portion 17a of the bolt 17, it is possible to prevent the insulating washer 12 from protruding too far toward the end side from the insulating sleeve 14, and the nut 18 from being positioned on the body portion 17d excluding the male thread portion 17c, making it impossible to tighten the bolt.

[0075] In addition, since the sealing washer 11, the insulating washer 12 and the insulating sleeve 14 are respectively arranged on both axial sides of the pair of flanges 3A, 3B, both of the pair of flanges 3A, 3B can be insulated, thereby improving the insulating effect.

[0076] In this embodiment, the seal washer 11, the insulating washer 12, and the insulating sleeve 14 are disposed on both sides of the pair of flanges 3A and 3B in the axial direction, that is, between the flange 3A and the head 17b of the bolt 17 and between the flange 3B and the nut 18, respectively, but the present invention is not limited to this, and the seal washer 11, the insulating washer 12, and the insulating sleeve 14 do not necessarily have to be disposed on both sides of the axial direction of the flanges 3A and 3B as long as they are disposed at least either between the flange 3A and the head 17b of the bolt 17 or between the flange 3B and the nut 18. In other words, the insulating sleeve 14 may be provided only in a half region of the body 17d on the head 17b side or the nut 18 side.

[0077] Although the embodiments of the present invention have been described above with reference to the drawings, the specific configuration is not limited to these embodiments, and the present invention also includes modifications and additions that do not deviate from the gist of the present invention.

[0078] For example, in the above embodiment, the insulating sleeve 14 is press-fitted into the body 17d of the shaft 17a of the bolt 17, but the present invention is not limited to this, and the insulating sleeve 14 may be loosely fitted into the body 17d. In this way, when the shaft 17a of the bolt 17 rotates in the circumferential direction when the nut 18 is fastened, the insulating sleeve 14 only rotates relative to the shaft 17a, preventing the seal ring rubber 11b from rotating relative to the insulating sleeve 14, and thus preventing loss of sealing performance with the seal washer 11.

[0079] In addition, in the above embodiment, the flanges 3A, 3B constituting the flange joint portion 3 are exemplified as being protruded in the outer diameter direction from one end of the fluid pipes 1A, 1B, but the present invention is not limited to this, and the flanges may not only be provided on the fluid pipes, but may also be flanges formed on various flow path constituent members including fluid pipes and connecting members that constitute at least a part of the flow path, such as connecting members (e.g., casings, work valves, gate valves, plugs, air valves, repair valves, etc.) connected to the fluid pipes 1A, 1B, etc.

[0080] In the above embodiment, the fastening member 7 is mainly composed of the bolt 17, the nut 18, the seal washer 11 consisting of the seal ring 11a and the seal ring rubber 11b, the insulating washer 12, the protective washers 12a and 12b, the spacer 13, and the insulating sleeve 14. However, the present invention is not limited to this, and as long as the fastening member 7 has at least the bolt 17, the nut 18, the seal washer 11, the insulating washer 12, and the insulating sleeve 14, the protective washers 12a and 12b and the spacer 13 are not necessarily required. Also, the fastening member 7 may have members other than the protective washers 12a and 12b and the spacer 13.

[0081] In the above embodiment, the insulating sleeve 14 is attached to almost the entire outer circumferential surface of the body 17d where the male thread portion 17c is not formed, but the present invention is not limited to this. The insulating sleeve 14 may be attached to a part of the outer circumferential surface of the body 17d, or may be attached so that a part of the outer circumferential surface of the male thread portion 17c overlaps with the outer circumferential surface of the male thread portion 17c. In addition, a heat-shrinkable tube that is attached by shrinking when heated may be used as the insulating sleeve. In this way, by using a heat-shrinkable tube as the insulating sleeve of the present invention, the large-diameter tube before heat shrinking can be inserted into the body 17d without contacting the male thread portion 17c of the bolt 17, and then the tube can be heat-shrinked to fit closely to the body 17d without any gaps.

[0082] In the above embodiment, the outer periphery of the flange joint portion 3 is sealed by the leakage prevention device 30, but the present invention is not limited to this, and the outer periphery may be sealed by a sealing means other than the leakage prevention device 30. In addition, the connection hole 3c serving as a bolt insertion hole is sealed by the seal ring rubber 11b, but the present invention is not limited to this, and the connection hole 3c may be sealed by a leakage prevention member other than the seal ring rubber 11b. In other words, the configuration of the leakage prevention device 30 and the seal ring rubber 11b are arbitrary and can be modified in various ways. [Explanation of symbols]

[0083] 1 Flange joint structure 1A,1B Fluid pipe 1c Flow path 3 Flange joint 3A, 3B flange 3b Opposite surface 3c Connection hole (bolt insertion hole) 3d outer surface 3e Protrusion 7 Fastening members 9 Insulation gasket 11 Seal washer 11a Seal ring (frame member) 11b Seal ring rubber (sealing material) 12 Insulating washer 12a, 12b Protective washer 13 Spacer (thickness adjustment washer) 14 Insulating sleeve 17 Volts 17a Shaft 17b Head 17c Male thread 17d Torso 17e Termination 18 Nut 30 Leak prevention device 31A,31B Split body 33A, 33B Gasket 34A, 34B Mounting parts

Claims

1. A flange joint structure that seals an outer periphery of a flange joint portion consisting of a pair of flanges fastened by bolts and nuts, and seals bolt insertion holes formed in the pair of flanges, a seal washer that is inserted into the bolt and seals the bolt insertion hole; an insulating washer that is inserted into the bolt and is disposed on an end side of the shank of the bolt relative to the seal washer; an insulating sleeve covering an outer circumferential surface of the shaft portion of the bolt; A flange joint structure, characterized in that the insulating sleeve extends in the axial direction across the bolt insertion hole on the outer circumferential surface of the shaft portion of the bolt, the seal washer, and the insulating washer.

2. 2. The flange joint structure according to claim 1, wherein the insulating sleeve covers a body portion of the shank of the bolt excluding a male thread portion.

3. 3. The flange joint structure according to claim 2, wherein an outer diameter of the insulating sleeve is substantially the same as an outer diameter of the male thread portion.

4. 2. The flange joint structure according to claim 1, further comprising a protective washer provided between said sealing washer and said insulating washer.

5. 2. The flange joint structure according to claim 1, wherein the seal washer comprises a seal member made of an elastic material, and a frame member which is harder than the seal member and is disposed closer to the end of the shank of the bolt than the seal member.

6. 2. The flange joint structure according to claim 1, further comprising a thickness adjusting washer disposed on the shank of the bolt closer to the end than the insulating washer.

7. 2. The flange joint structure according to claim 1, wherein the sealing washer, the insulating washer and the insulating sleeve are disposed on both sides of the pair of flanges, respectively.

8. 2. The flange joint structure according to claim 1, wherein the insulating sleeve is loosely fitted over the shank of the bolt to cover the shank.

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