CN220470953U - Nonmetal straight tube pressure balance type expansion joint with leakage monitoring function - Google Patents

Abstract

The utility model provides a nonmetallic straight pipe pressure balance type expansion joint with leakage monitoring, which comprises a front flange, a front middle flange, a rear flange, a pull rod structure and a rolling deformation assembly, wherein the front flange is connected with the rear middle flange through the pull rod structure; the rolling deformation pieces are arranged between the front flange and the front middle flange, the rolling deformation pieces are arranged between the rear flange and the rear middle flange, and the rolling deformation pieces can deform in a rolling deformation mode along the left-right direction, so that the front flange and the front middle flange can perform relative displacement, and/or the rear flange and the rear middle flange can perform relative displacement; the utility model can increase the axial compensation capability, is beneficial to reducing the radial and axial lengths of the expansion joint, optimizes the requirement on the installation space of the expansion joint, and can also reduce the axial rigidity and the radial rigidity of the expansion joint.

Description

Nonmetal straight tube pressure balance type expansion joint with leakage monitoring function

Technical Field

The utility model relates to the technical field of expansion joints, in particular to a nonmetal straight pipe pressure balance type expansion joint with leakage monitoring.

Background

In order to avoid that the pressure thrust generated by the unconstrained expansion joint acts on the equipment to influence the normal operation of the equipment, a straight pipe pressure balance expansion joint is usually selected for constraining the pressure thrust. The existing metal straight pipe pressure balance type expansion joint (figure 1) or nonmetal straight pipe pressure balance type expansion joint (figure 2) is usually composed of two groups of working corrugated pipes, a balance corrugated pipe positioned in the middle, a pull rod, an end plate and other structural members, and is mainly used for absorbing the axial pressure thrust of the corrugated pipes and restraining the pressure thrust of the corrugated pipes.

When the pressure balance expansion joint of the conventional straight pipe structure compensates transverse displacement, three groups of corrugated pipes (two groups of working corrugated pipes and one group of balance corrugated pipes) perform displacement distribution according to the rigidity proportion, so that the large transverse displacement compensation function of the compound corrugated pipes cannot be realized, the compensation transverse displacement capacity is very limited in the limited length dimension range, the rigidity is larger, and larger elastic counter force exists on the pipe orifice of the equipment.

Meanwhile, in the conventional straight pipe pressure balance type expansion joint with a structure of a corrugated pipe, in addition to axial deformation of the corrugated pipe in the process of compensating axial displacement, an elastic element in the corrugated pipe also deforms radially (as shown in fig. 5, the stress deformation of a small section of corrugated structure in the corrugated pipe can be understood to be indicated by the stress deformation of a small section of corrugated structure in the corrugated pipe, and the stress deformation can correspond to a position K in fig. 2), so that the whole corrugated pipe can deform transversely, and the radial rigidity of the whole corrugated pipe is larger, which also leads to the problem that the wall thickness of the corrugated pipe is difficult to adopt a thinner wall thickness in the conventional straight pipe pressure balance type expansion joint.

Therefore, for the straight pipe pressure balance type expansion joint in the prior art, on the premise of given compensation requirement of a pipeline, the expansion joint needs longer installation size, and in some cases, arrangement conflict can be caused; meanwhile, on the premise that the pipe system is limited by allowable installation dimensions, the expansion joint is high in rigidity, and the constraint structural strength of the pipe system or the pipe orifice strength of equipment needs to be enhanced, so that the high requirements on the thick-wall material performance of the expansion joint related parts are clearly met. Both of these cases increase the construction cost.

Disclosure of Invention

In view of the above, the utility model aims to provide a nonmetallic straight pipe pressure balance type expansion joint with leakage monitoring, so as to solve the problems of larger rigidity and oversized conventional straight pipe pressure balance type expansion joint in the prior art.

In order to achieve the above purpose, the technical scheme of the utility model is realized as follows:

the nonmetallic straight pipe pressure balance type expansion joint with the leakage monitoring function comprises a front flange, a front middle flange, a rear flange, a pull rod structure and a rolling deformation assembly, wherein the front flange is connected with the rear middle flange through the pull rod structure, the rear flange is connected with the front middle flange through the pull rod structure, and the front middle flange and the rear middle flange are connected in a manner capable of carrying out relative displacement; the rolling deformation parts are arranged between the front flange and the front middle flange, the rolling deformation parts are arranged between the rear flange and the rear middle flange, and the rolling deformation parts can deform in a rolling deformation mode along the left-right direction, so that relative displacement can be carried out between the front flange and the front middle flange, and/or relative displacement can be carried out between the rear flange and the rear middle flange.

Further, the rolling deformation piece is a U-shaped elastic element, the U-shaped opening of the rolling deformation piece is arranged towards the left or the right, and any one end of the rolling deformation piece can move relative to the other end of the rolling deformation piece in a mode of along the left-right direction, so that the whole rolling deformation piece can deform in a rolling deformation mode in the left-right direction.

Further, a balance cavity is formed among the front flange, the front middle flange, the rear middle flange and the rear flange, the balance cavity is communicated with the pipe cavity of the pipeline, and the U-shaped opening of the rolling deformation piece faces to the balance cavity and is communicated with the balance cavity.

Further, between the front flange and the front middle flange, one end of the rolling deformation piece is connected with the front flange, and the other end of the rolling deformation piece is connected with the front middle flange; and one end of the rolling deformation piece is connected with the rear flange, and the other end of the rolling deformation piece is connected with the rear middle flange.

Further, the front middle flange is provided with an outer backing ring and an outer compression flange in sequence on one side far away from the rear middle flange, the rear middle flange is provided with an outer backing ring and an outer compression flange in sequence on one side far away from the front middle flange, and the rolling deformation piece is connected with the outer backing ring and the outer compression flange in sequence; the front flange is provided with an inner backing ring and an inner compression flange in sequence on one side close to the rear flange, the rear flange is provided with the inner backing ring and the inner compression flange in sequence on one side close to the front flange, and the rolling deformation piece is connected with the inner backing ring and the inner compression flange in sequence.

Further, the rolling deformation piece is of a double-layer structure, the outer backing ring is provided with a detection hole, the outer side of the detection hole is provided with a first monitoring meter, and the detection end of the first monitoring meter penetrates through the detection hole and extends to a position between the inner layer and the outer layer of the rolling deformation piece to detect whether the inner layer of the rolling deformation piece is damaged or not.

Further, a plug connector or a flange groove is formed in one side, facing the rear middle flange, of the front middle flange, a flange groove or a plug connector is formed in one side, facing the front middle flange, of the rear middle flange, the plug connector is arranged in the flange groove, and the plug connector can move left and right along the flange groove.

Further, a sealing element is arranged between the outer wall of the plug connector and the inner wall of the flange groove.

Further, the outer wall of flange groove sets up the second monitoring table, the detection end of second monitoring table runs through flange groove outer wall to with the annular cavity intercommunication between plug connector and the flange groove, be used for detecting whether the sealing member department takes place to damage and reveal.

Further, the pull rod structure comprises a ball stud and a locking assembly, and the pull rod structure has two assembly structural forms: the first form is that the ball stud penetrates through the front flange and the rear middle flange in sequence, and the locking component is arranged on one side, far away from the front flange, of the rear middle flange and is connected with the ball stud; the second type of ball stud penetrates through the rear flange and the front middle flange in sequence, and the locking component is arranged on one side, far away from the rear flange, of the front middle flange and is connected with the ball stud; the first form and the second form are staggered in the circumferential direction along the expansion joint.

Compared with the prior art, the nonmetal straight pipe pressure balance type expansion joint with leakage monitoring has the following advantages:

compared with the straight pipe pressure balance type expansion joint with the corrugated pipe in the prior art, the non-metal straight pipe pressure balance type expansion joint with the leakage monitoring function does not need to be provided with a conventional corrugated pipe, compression and stretching deformation (shown in the figure 5) of a conventional corrugated pipe structure is avoided through the arrangement of the rolling deformation piece, the conventional compression and stretching deformation is changed into rolling deformation (shown in the figure 6) of the rolling deformation piece, and the improvement of the structure can greatly reduce the axial rigidity of the expansion joint in the axial direction, increase the axial compensation capacity, and correspondingly, be beneficial to reducing the radial and axial length of the expansion joint, be beneficial to optimizing and reducing the size of the expansion joint and be beneficial to optimizing the requirement on the installation space of the expansion joint; on the other hand, the expansion joint only generates rolling deformation in the left-right direction, does not participate in radial deformation, does not face the problem that the corrugated pipe generates overall transverse deformation and causes larger radial rigidity, and the overall radial rigidity of the expansion joint can be further reduced.

Meanwhile, for rolling deformation only in the left-right direction, most of the load of the rolling deformation part in the working state is borne by the front flange and the rear flange, and under the condition of the same design pressure, the wall thickness of the rolling deformation part in the application can be smaller than that of the conventional nonmetallic expansion joint elastic element, so that the integral rigidity of the expansion joint is further reduced, the requirement for enhancing the constraint structure strength of a pipe system or the pipe orifice strength of equipment is reduced to a certain extent, and the requirement of the prior art on the performance of thick-wall materials is also avoided.

Drawings

The accompanying drawings, which are included to provide a further understanding of the utility model and are incorporated in and constitute a part of this specification, illustrate embodiments of the utility model and together with the description serve to explain the utility model. In the drawings:

FIG. 1 is a schematic diagram of a conventional metal straight tube pressure balance expansion joint in the prior art;

FIG. 2 is a schematic structural view of a conventional nonmetallic straight pipe pressure-balanced expansion joint in the prior art;

FIG. 3 is a schematic structural diagram of a non-metallic straight pipe pressure balance expansion joint with leakage monitoring according to an embodiment of the present utility model;

FIG. 4 is a schematic illustration of another structure of a pressure balanced expansion joint with leakage monitoring for a non-metallic straight pipe according to an embodiment of the present utility model;

FIG. 5 is a schematic diagram of the deformation of bellows segment in a straight pipe pressure balanced expansion joint according to the prior art;

fig. 6 is a schematic rolling deformation diagram of a rolling deformation member in a non-metallic straight pipe pressure balance expansion joint with leakage monitoring according to an embodiment of the present utility model.

Reference numerals illustrate:

1. a front flange; 2. ball stud; 3. an outer compression flange; 4. rolling the deformation member; 5. shipping the nut; 6. a front middle flange; 7. a seal; 8. a rear middle flange; 9. a locking assembly; 10. an outer backing ring; 11. a rear flange; 12. an inner backing ring; 13. pressing the flange in the inner pressure; 14. a first monitoring table; 15. a second monitoring table; A. an end pipe; B. working corrugated pipes; C. a pull rod; D. balance bellows; E. a first end plate; F. a second end plate; G. a straight pipe flange; H. a double-ended stud; I. a ball taper gasket; J. an end face flange; K. a nonmetallic elastic element; l, middle flange; m, limit screw; n, straight pipe flanges; o, an inner anti-pressing ring; p, reinforcing steel wires; q, an external compression-resistant ring.

Detailed Description

The inventive concepts of the present disclosure will be described below using terms commonly used by those skilled in the art to convey the substance of their work to others skilled in the art. These inventive concepts may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. The terms "left and right" in this application are referenced to the coordinates in fig. 3. Meanwhile, the words such as axial, radial (or transverse), circumferential and the like are common words in the field of straight pipe expansion joints, and refer to the central axis of a pipeline.

It should be noted that, without conflict, the embodiments of the present utility model and features of the embodiments may be combined with each other.

The utility model will be described in detail below with reference to the drawings in connection with embodiments.

For the straight pipe pressure balance type expansion joint in the prior art, the capacity of compensating transverse displacement is very limited in a limited length size range, the rigidity is larger, and larger elastic counterforce exists on a pipe orifice of the equipment. On the premise of given compensation requirements of pipelines, the expansion joint needs longer installation size, and arrangement conflicts can be brought in some cases; meanwhile, on the premise that the pipe system is limited by allowable installation dimensions, the expansion joint is high in rigidity, and the constraint structural strength of the pipe system or the pipe orifice strength of equipment needs to be enhanced, so that the high requirements on the material performance of the related parts of the expansion joint can be clearly met.

In order to solve the problems of larger rigidity and oversized size of the conventional straight pipe pressure balance type expansion joint in the prior art, the embodiment provides a nonmetallic straight pipe pressure balance type expansion joint with leakage monitoring, as shown in figures 3-4, the expansion joint comprises a front flange 1, a front middle flange 6, a rear middle flange 8, a rear flange 11, a pull rod structure and a rolling deformation assembly, wherein the front flange 1 is connected with the rear middle flange 8 through the pull rod structure, the rear flange 11 is connected with the front middle flange 6 through the pull rod structure, and the front middle flange 6 and the rear middle flange 8 are connected in a manner capable of carrying out relative displacement; the rolling deformation pieces 4 are arranged between the front flange 1 and the front middle flange 6, the rolling deformation pieces 4 are arranged between the rear flange 11 and the rear middle flange 8, and the rolling deformation pieces 4 can deform in a rolling deformation mode along the left-right direction, so that relative displacement can be carried out between the front flange 1 and the front middle flange 6, and/or relative displacement can be carried out between the rear flange 11 and the rear middle flange 8.

Specifically, the rolling deformation member 4 is a U-shaped elastic element, the U-shaped opening of the rolling deformation member 4 is disposed towards the left or the right, and any one end of the rolling deformation member 4 can move relative to the other end of the rolling deformation member 4 in a manner along the left-right direction, so that the whole rolling deformation member 4 can deform in a manner of rolling deformation in the left-right direction.

Compared with the straight pipe pressure balance type expansion joint with the corrugated pipe in the prior art, the expansion joint is free from the conventional corrugated pipe mode, compression and stretching deformation (shown in the attached drawing 5) of the conventional corrugated pipe structure is avoided by arranging the rolling deformation piece 4, and the conventional compression and stretching deformation is changed into rolling deformation (shown in the attached drawing 6) of the rolling deformation piece 4; on the other hand, the expansion joint only generates rolling deformation in the left-right direction, does not participate in radial deformation, does not face the problem that the corrugated pipe generates overall transverse deformation and causes larger radial rigidity, and the overall radial rigidity of the expansion joint can be further reduced.

Meanwhile, for rolling deformation in the left-right direction only, most of the load of the rolling deformation piece 4 in the working state is borne by the front flange 1 and the rear flange 11, and under the condition of the same design pressure, the wall thickness of the rolling deformation piece 4 in the application can be smaller than that of a conventional nonmetallic expansion joint elastic element, so that the integral rigidity of the expansion joint is further reduced, the requirement for enhancing the constraint structural strength of a pipe system or the strength of a pipe orifice of equipment is reduced to a certain extent, and the requirement of the prior art on the performance of thick-wall materials is also avoided.

Balance cavities are formed among the front flange 1, the front middle flange 6, the rear middle flange 8 and the rear flange 11, specifically, a cavity is defined among the front flange 1, the rolling deformation piece 4, the front middle flange 6, the rear middle flange 8, the rolling deformation piece 4 and the rear flange 11; the balance cavity is communicated with the pipe cavity of the pipeline, and for any rolling deformation piece 4, the U-shaped opening of the rolling deformation piece 4 faces the balance cavity and is communicated with the balance cavity, so that the rolling deformation piece 4 can correspondingly deform along with pressure change in the pipeline.

Between the front flange 1 and the front middle flange 6, one end of the rolling deformation 4 is connected with the front flange 1, and the other end is connected with the front middle flange 6; between the rear flange 11 and the rear middle flange 8, one end of the rolling deformation 4 is connected with the rear flange 11, and the other end is connected with the rear middle flange 8.

The expansion joint balancing principle of the present application is the same as that of the conventional pressure balancing expansion joint, and the effective area of the balancing assembly formed by the front middle flange 6 and the rear middle flange 8 is twice that of the rolling deformation 4, namely ap=2×ag

Wherein Ap is the effective area of the balancing component; ag is the effective area of the rolling deformation 4;

at this time, the pressure thrust acting on the annular region where the rear middle flange 8 contacts the medium is equal and opposite to the pressure thrust acting on the annular region where the front flange 1 contacts the medium, and force is conducted through the tie rod structure between the rear middle flange 8 and the front flange 1, thereby achieving force balance. The force balance between the front middle flange 6 and the rear flange 11 is the same and will not be described again.

For the connection of the two ends of the rolling deformation 4, the application is further improved:

the front middle flange 6 is provided with an outer backing ring 10 and an outer compression flange 3 in sequence on one side far away from the rear middle flange 8, the rear middle flange 8 is provided with the outer backing ring 10 and the outer compression flange 3 in sequence on one side far away from the front middle flange 6, and for any one rolling deformation element 4, the rolling deformation element 4 is connected with the outer backing ring 10 and the outer compression flange 3 in sequence except for the connection with a middle flange structure (the front middle flange 6 or the rear middle flange 8);

the front flange 1 is provided with an inner backing ring 12 and an inner compression flange 13 in sequence on one side close to the rear flange 11, the rear flange 11 is provided with the inner backing ring 12 and the inner compression flange 13 in sequence on one side close to the front flange 1, and for any one rolling deformation element 4, the rolling deformation element 4 is connected with the inner backing ring 12 and the inner compression flange 13 in sequence except for the connection with an end flange structure (the front flange 1 or the rear flange 11).

Therefore, through further improvement of the connecting structures at the two ends of the rolling deformation piece 4, on one hand, the connection firmness and the tightness of the end positions of the rolling deformation piece 4 are improved, and on the other hand, the outer pressing flange 3 and the inner pressing flange 13 are arranged at the two ends of the rolling deformation piece 4, so that the rolling deformation piece 4 is limited in the radial direction, the rolling deformation piece 4 can only roll and deform in the left-right direction, and the outer pressing flange 3 and the inner pressing flange 13 can bear partial loads of the rolling deformation piece 4 under the bearing pressure respectively, thereby being beneficial to reducing the self bearing pressure of the rolling deformation piece 4, further reducing the thickness of the rolling deformation piece 4 and further reducing the integral rigidity of the expansion joint. Preferably, both ends of the rolling deformation 4 are welded to the above-described respective related components (middle flange structure, end flange structure, outer packing ring 10, outer pressing flange 3, inner packing ring 12, inner pressing flange 13, etc.).

For the connection between the front middle flange 6 and the rear middle flange 8, a plug-in element is arranged on the side of the front middle flange 6 facing the rear middle flange 8, a flange groove is arranged on the side of the rear middle flange 8 facing the front middle flange 6, the plug-in element is arranged in the flange groove, and the plug-in element can move left and right along the flange groove. Preferably, a sealing element 7 is arranged between the outer wall of the plug connector and the inner wall of the flange groove, so that the sealing effect can be provided for the balance cavity while the relative movement between the front middle flange 6 and the rear middle flange 8 is ensured. The seal 7 may be a single-sided lip seal (as in fig. 3) or a double-sided lip seal (as in fig. 4). Correspondingly, the structure can be exchanged, the flange groove is formed in the front middle flange 6, the plug connector is arranged in the front middle flange 6, the assembly form and the sealing form between the flange groove and the plug connector are unchanged, and the repeated description is omitted. The flange groove is an annular groove, the plug connector is an annular part, and the sealing part is an annular sealing part.

For the pull rod structure, the pull rod structure comprises a ball stud 2 and a locking assembly 9, and the pull rod structure has two assembly structural forms:

the first form is that the ball stud 2 sequentially penetrates through the front flange 1 and the rear middle flange 8, and the locking component 9 is arranged on one side, far away from the front flange 1, of the rear middle flange 8 and is connected with the ball stud 2;

the second type of ball stud 2 sequentially penetrates through the rear flange 11 and the front middle flange 6, and the locking assembly 9 is arranged on one side, far away from the rear flange 11, of the front middle flange 6 and is connected with the ball stud 2;

the first form and the second form are staggered in the circumferential direction along the expansion joint.

The locking assembly 9 comprises slotted nuts and ball cone washers, and the staggered arrangement of the pull rod structures and the use of the slotted nuts and the ball cone washers are beneficial to improving the capacity of the expansion joint for compensating transverse displacement. In addition, considering the space obstruction possibly generated by the structural dimensions of the front middle flange 6 and the rear middle flange 8, the ball stud 2 in the first form can sequentially penetrate through the front flange 1, the front middle flange 6 and the rear middle flange 8, and the ball stud 2 in the second form can sequentially penetrate through the rear flange 11, the rear middle flange 8 and the front middle flange 6; accordingly, the shipping nut 5 in the drawings is disposed on the side of the front middle flange 6 remote from the rear middle flange 8 in the first form and is connected to the ball stud 2, and is disposed on the side of the rear middle flange 8 remote from the front middle flange 6 in the second form and is connected to the ball stud 2. The shipment nut 5 is arranged, and related components of the expansion joint are mainly locked in the shipment process, so that unnecessary displacement of the components in the shipment process is avoided, and correspondingly, the shipment nut 5 needs to be removed before the expansion joint is used, i.e. the expansion joint is not provided with the shipment nut 5 in a normal use state.

The expansion joint comprises leakage monitoring means for detecting a broken leakage condition at the rolling deformation 4 and/or the seal 7.

For detection at the rolling deformation 4, this can be achieved by means of a first monitoring table 14; the rolling deformation piece 4 is of a double-layer structure, the outer backing ring 10 is provided with a detection hole, the outer side of the detection hole is provided with a first monitoring meter 14, and the detection end of the first monitoring meter 14 penetrates through the detection hole and extends between the inner layer and the outer layer of the rolling deformation piece 4 to detect whether the inner layer of the rolling deformation piece 4 is damaged or not.

For detection at the seal 7, mainly for double lip seals (as in fig. 4), this can be achieved by means of a second monitoring table 15; the outer wall of the flange groove of the rear middle flange 8 (the flange groove of the front middle flange 6 can be also used for the structural exchange) is provided with a second monitoring meter 15, and the detection end of the second monitoring meter 15 penetrates through the outer wall of the flange groove and is communicated with the annular cavity between the plug connector and the flange groove for detecting whether the sealing element 7 (especially the inner side lip sealing element of the double lip seal) is damaged and leaked.

The foregoing description of the preferred embodiments of the utility model is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the utility model.

Claims (10)

1. The nonmetal straight pipe pressure balance type expansion joint with the leakage monitoring function is characterized by comprising a front flange (1), a front middle flange (6), a rear middle flange (8), a rear flange (11), a pull rod structure and a rolling deformation assembly, wherein the front flange (1) is connected with the rear middle flange (8) through the pull rod structure, the rear flange (11) is connected with the front middle flange (6) through the pull rod structure, and the front middle flange (6) and the rear middle flange (8) are connected in a manner capable of carrying out relative displacement; set up between preceding flange (1), preceding well flange (6) and roll deformation spare (4), set up between back flange (11), the back well flange (8) and roll deformation spare (4), roll deformation spare (4) can be along controlling the direction and roll deformation's mode for can carry out relative displacement between preceding flange (1) and the preceding well flange (6), and/or can carry out relative displacement between back flange (11) and the back well flange (8).

2. The nonmetallic straight pipe pressure balance type expansion joint with leakage monitoring according to claim 1, wherein the rolling deformation piece (4) is a U-shaped elastic element, the U-shaped opening of the rolling deformation piece (4) is arranged leftwards or rightwards, and any one end of the rolling deformation piece (4) can move relative to the other end of the rolling deformation piece (4) in a mode along the left-right direction, so that the whole of the rolling deformation piece (4) can deform in a rolling deformation mode along the left-right direction.

3. The nonmetallic straight pipe pressure balance type expansion joint with leakage monitoring according to claim 1, wherein a balance cavity is formed among the front flange (1), the front middle flange (6), the rear middle flange (8) and the rear flange (11), the balance cavity is communicated with a pipe cavity of a pipeline, and a U-shaped opening of the rolling deformation piece (4) faces to the balance cavity and is communicated with the balance cavity.

4. The nonmetallic straight pipe pressure balance expansion joint with leakage monitoring according to claim 1, wherein one end of the rolling deformation piece (4) is connected with the front flange (1) and the other end is connected with the front middle flange (6) between the front flange (1) and the front middle flange (6); and one end of the rolling deformation piece (4) is connected with the rear flange (11) and the other end is connected with the rear middle flange (8) between the rear flange (11) and the rear middle flange (8).

5. The nonmetallic straight pipe pressure balance expansion joint with leakage monitoring according to claim 1, wherein an outer backing ring (10) and an outer compression flange (3) are sequentially arranged on one side, far away from a rear middle flange (8), of the front middle flange (6), an outer backing ring (10) and an outer compression flange (3) are sequentially arranged on one side, far away from the front middle flange (6), of the rear middle flange (8), and the rolling deformation piece (4) is sequentially connected with the outer backing ring (10) and the outer compression flange (3); the front flange (1) is provided with an inner backing ring (12) and an inner pressing flange (13) in sequence on one side close to the rear flange (11), the rear flange (11) is provided with the inner backing ring (12) and the inner pressing flange (13) in sequence on one side close to the front flange (1), and the rolling deformation piece (4) is connected with the inner backing ring (12) and the inner pressing flange (13) in sequence.

6. The nonmetallic straight pipe pressure balance type expansion joint with leakage monitoring according to claim 5, wherein the rolling deformation piece (4) is of a double-layer structure, the outer backing ring (10) is provided with a detection hole, the outer side of the detection hole is provided with a first monitoring meter (14), and the detection end of the first monitoring meter (14) penetrates through the detection hole and extends to a position between the inner layer and the outer layer of the rolling deformation piece (4) for detecting whether the inner layer of the rolling deformation piece (4) is damaged or not.

7. The nonmetallic straight pipe pressure balance expansion joint with leakage monitoring according to claim 1, wherein a plug connector or a flange groove is arranged on one side of the front middle flange (6) facing the rear middle flange (8), a flange groove or a plug connector is arranged on one side of the rear middle flange (8) facing the front middle flange (6), the plug connector is arranged in the flange groove, and the plug connector can move left and right along the flange groove.

8. The nonmetallic straight pipe pressure balance type expansion joint with leakage monitoring according to claim 7, wherein a sealing element (7) is arranged between the outer wall of the plug-in connector and the inner wall of the flange groove.

9. The nonmetallic straight pipe pressure balance type expansion joint with leakage monitoring according to claim 8, wherein a second monitoring meter (15) is arranged on the outer wall of the flange groove, and the detection end of the second monitoring meter (15) penetrates through the outer wall of the flange groove and is communicated with the annular cavity between the plug connector and the flange groove for detecting whether damage leakage occurs at the sealing element (7).

10. A non-metallic straight pipe pressure balanced expansion joint with leakage monitoring according to claim 1, characterized in that the tie rod structure comprises a ball stud (2), a locking assembly (9), the tie rod structure having two assembly configurations:

the ball stud (2) sequentially penetrates through the front flange (1) and the rear middle flange (8), and the locking assembly (9) is arranged on one side, far away from the front flange (1), of the rear middle flange (8) and is connected with the ball stud (2);

the second type is that the ball stud (2) sequentially penetrates through the rear flange (11) and the front middle flange (6), and the locking assembly (9) is arranged on one side, far away from the rear flange (11), of the front middle flange (6) and is connected with the ball stud (2);

the first form and the second form are staggered in the circumferential direction along the expansion joint.