JP2668201B2 - Leakage fluid diffusion prevention structure in cryogenic fluid transport pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low temperature fluid transport pipe for transporting a low temperature fluid such as LN gas, LP gas, etc., in which a fluid leaking portion such as a flange joint is hermetically surrounded by a cover member to prevent diffusion of the leaking fluid. And a leakage fluid diffusion preventing structure.

[0002]

2. Description of the Related Art Various types of leakage fluid diffusion preventing structures have been proposed in the past, but generally, a flange joint portion, which is a fluid leakage point in a low temperature fluid transport pipe, is circumferentially divided into a cylindrical cover. While being surrounded by a member, a sheet-shaped first seal member (sheet-shaped gasket) and an annular shape are provided between the respective divided surfaces of the cover member and between the opposite peripheral surfaces of both ends of the cover member and the cryogenic fluid transport pipe, respectively. There is a well-known structure in which a second string-shaped sealing member (string packing) is used for sealing.

In such a conventional leakage fluid diffusion preventing structure (hereinafter referred to as "conventional structure"), the cover member is provided with a pair of flanges for fastening the respective divided surfaces via the first seal member. A pair of circumferentially-divided staffin box forming bodies capable of forming a staffin box for filling the second seal member with the low-temperature fluid transport pipe by forming an annular shape by fastening the flange, and fastening the flange. The cover body has a tubular shape and is circumferentially divided so as to surround a fluid leakage portion of the low temperature fluid transport pipe.
That is, each divided surface of the cover member is formed by a flange surface (hereinafter, referred to as a “fastened seal surface”) and a divided surface of the staphin box forming body (hereinafter, referred to as a “non-fastened seal surface”) connected thereto. The divided surfaces are sealed by the first seal member by fastening the flanges with the first seal member interposed therebetween. In addition, the inner peripheral surface of each stuffing box forming body has a stepped shape, and an annular stuffing box is formed between the large diameter portion and the outer peripheral surface of the low-temperature fluid transport pipe. I have. Then, the second seal member filled in this stuffing box is axially pressed by the circumferentially divided annular seal pressing body attached to the stuffing box forming body to form the end of the cover member, that is, the stafin box forming. A seal is provided between the inner peripheral surface (large diameter portion) of the body and the outer peripheral surface portion of the cryogenic fluid transport pipe facing the inner peripheral surface. Therefore, the flange joint portion of the low-temperature fluid transport pipe is hermetically surrounded by the cover member, and even if the low-temperature fluid leaks from the flange joint portion, the diffusion of the leaked fluid can be effectively prevented.

[0004]

However, in the conventional structure, due to the structure of the cover member, between the divided surfaces of the cover member and the staffin box (between the opposing peripheral surfaces of the cover member and the cryogenic fluid transport pipe). In fact, the seal at the communication point is insufficient, and the diffusion of the leakage fluid cannot be reliably prevented.

[0005] That is, among the divided surfaces of the cover member,
Between the fastening seal faces, which are the facing faces of the flange,
Since these are directly fastened, the tightening surface pressure of the first seal member can be sufficiently secured, and the first seal member can perform good sealing. On the other hand, between the non-fastened seal faces, which are the split faces of the stuffing box forming body, these are not directly fastened but only indirectly press the first seal member by the fastening force of the flange. . Therefore, regardless of the portion between the non-fastening seal surfaces close to the flange, the portion at the above-mentioned communication point far from the flange (hereinafter referred to as "communication side portion"),
There is a risk that the clamping force of the first seal member, that is, the tightening surface pressure, which is given by the fastening force of the flange, is insufficient, and the seal by the first seal member is not sufficiently exerted.

The cover member is made of LN gas, LP
Since the low-temperature fluid such as gas comes into contact with the low-temperature resistance, it is necessary that the low-temperature resistance is low. It is a one-piece molded product. However, since such low temperature resistant metal is soft and easily deformed, there is a limit in increasing the fastening force of the flange. Therefore, it is difficult to eliminate the insufficient tightening surface pressure of the first seal member between the non-fastened seal surfaces by increasing the fastening force of the flange.

Further, when the second seal member is pushed into the stuffing box by the seal pressing member, a force in the direction of opening the cover member is applied between the divided surfaces of the cover member. The tightening surface pressure of the first seal member between the seal surfaces is not directly tightened between the non-fastened seal surfaces, so that the cover member is made of a material which is easily deformed as described above, It will be further reduced.

Further, since the space between the divided surfaces of the cover member and the stuffing box are separately and independently sealed by separate seal members, the communicating portion is sealed by both the first and second seal members. A part that is not protected (hereinafter referred to as "shielded part") occurs. That is, the end of the first seal member located at the communication side portion between the non-fastened seal surfaces and the outer peripheral portion of the second seal member located within the stuffing box are merely in contact with each other. However, since they are not in pressure contact with each other, a sealed dead portion that is not sealed is generated between both parts due to insufficient contact force between the first seal member and the second seal member.

[0009] As described above, at the communicating portion between the divided surfaces of the cover member and the staffin box, the tightening surface pressure of the first seal member and the existence of the sealed dead portion cause
The sealing action is not sufficiently performed, and the diffusion of the leakage fluid cannot be reliably prevented.

The insufficient tightening surface pressure of the first seal member can be solved to some extent by making the cover member thick so as to obtain sufficient strength. It is not practical to make the cover member thicker than necessary because the cover member is extremely expensive because the low temperature resistant metal such as aluminum is expensive. In addition, since the low-temperature fluid transport pipe generally has a large diameter, the cover member surrounding the flange joint portion is also quite large. However, if the thick member is used as described above, the cover member becomes heavy. It becomes difficult to handle such as mounting to a low temperature fluid transportation pipe. Of course, the generation of the sealed dead portion cannot be avoided by increasing the thickness of the cover member.

The present invention is directed to a low-temperature fluid transport pipe capable of reliably preventing a leakage fluid from leaking from a low-temperature fluid transport pipe such as a flange joint without causing such a problem. It is intended to provide a prevention structure.

[0012]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a structure for preventing diffusion of a leaked fluid in a low-temperature fluid transport pipe according to the present invention is provided.
A fluid leakage point in the low-temperature fluid transport pipe is surrounded by a circumferentially divided tubular cover member, and the divided surfaces of the cover member are fastened with a sheet-shaped first seal member interposed therebetween. An annular string-shaped second seal member is filled in a compressed state between opposing peripheral surfaces of the cover member and the low-temperature fluid transport pipe, and one end is provided between the first seal member and the second seal member. The side part is one of the divided surfaces of the cover member and the first part.
It is pinched between the cover member and the second seal member while being pinched between the seal member and the other end portion while passing between the first seal member and the second seal member. A sheet-shaped third seal member is interposed. For such a leakage fluid diffusion prevention structure,
The cover member forms an annular shape by fastening the flanges with a pair of flanges for fastening the respective divided surfaces via the first sealing member, and fills the second sealing member between the cryogenic fluid transport pipe. A pair of circumferentially-divided stafin box forming bodies that can form a stafin box, and a cylindrical shape by fastening a flange to surround a fluid leakage point of a cryogenic fluid transport pipe. Body and
Each of the divided portions of the cover body is made of sheet metal made of low temperature resistant metal, and each of the flanges and each divided portion of the staffin box forming body is welded to each other of the divided portions of the cover body. A non-sheet metal member made of a low-temperature resistant metal, and a circumferentially-divided annular seal pressing body is provided on each staffin box forming body so as to press the second seal member in the axial direction of the low-temperature fluid transport pipe. Preferably, it is mounted so that it can be freely tightened. Further, the first seal member has a three-layer structure in which metal foil is interposed between sheets of expanded graphite, and the second seal member has a cord-like braided packing and spiral graphite wound around the outer peripheral surface thereof. It is preferable that the third sealing member is an expanded graphite sheet having a fine corrugated cross section.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The first embodiment of the present invention will be described below.
A specific description will be given based on FIGS. In the following description, front and rear mean left and right in FIGS.

As shown in FIG. 1 to FIG. 4, the structure for preventing leakage fluid diffusion according to this embodiment
Fluid pipe connection for transporting low-temperature fluid such as P gas to the low-temperature fluid transport pipes 1, 1 where the pipe end flanges 1b, 1b are fastened via appropriate flange seal members (not shown) The flange joint portion 1a, which is a partial portion, is surrounded by a substantially hexagonal cylindrical cover member 2 which is divided into four in the circumferential direction, an annular seal pressing body 3 which is divided into two in the circumferential direction, and the seal members 4, 5 and 6 which surround the seal. Have been. In this example, the cryogenic fluid transport pipe 1 has an outer diameter of 609.6 mm, and the pipe end flange 1b has an outer diameter of 815 mm.

The cover member 2 is made of a low-temperature resistant metal such as aluminum or an aluminum alloy. As shown in FIGS. 1 to 8, a cover member 7 divided into four parts in the circumferential direction and a pair of front and rear It comprises box forming bodies 8, 8 and flanges 9 for connecting these divided surfaces.

That is, as shown in FIGS. 1 to 8, the cover body 7 has a circumferentially divided shape composed of four cover body parts 17 consisting of a peripheral wall 17a and a pair of front and rear side walls 17b, 17b. Are assembled into a hexagonal cylindrical shape capable of surrounding the flange joint portion 1a by fastening the flanges 9. Each cover body portion 17 is a sheet metal product of aluminum and has the same shape. The thickness of the cover portion 17 is preferably set as thin as possible in consideration of the size of the cover member 2 and the number of divisions, and is 8 mm in this example. In addition, one cover body portion 17 has a drain passage (FIG. 1) for discharging the leakage fluid inside the cover member 2 when the pressure inside the cover member 2 becomes equal to or higher than a predetermined value due to the leakage fluid from the flange joint portion 1a. (Not shown) is connected.

Each staffin box forming body 8 is shown in FIGS.
As shown in FIG. 8, the inner peripheral surface has a large diameter portion 18a and a small diameter portion 18b.
It is a circumferentially divided shape composed of four staffin box forming body portions 18 having a stepped shape consisting of, and is externally fitted to a portion near the pipe end of the fluid transport pipe 1 by fastening the flanges 9 ... It is assembled into a possible annular shape. In the assembled form, the large diameter portions 18a.
An annular staffin box 8a is formed between the annular surface formed by the above and the outer peripheral surface of the fluid transport pipe 1. Each stuffing box former part 18 is 1/4
It is a circular arc shaped aluminum body,
The outer peripheral portion of the inner end surface is welded to the inner peripheral portion of the outer end surface of the side wall 17b of each cover body portion 7 to be fixed to the cover body portion 7. The cross-sectional area of each staffin box forming body portion 18 is appropriately set on the condition that the staffin box 8a has sufficient strength to fill and hold the first seal member 3 in a predetermined compressed state. However, in this example, the axial thickness of the stuffing box forming portion 18 is 30 mm, the outer diameter is 680 mm, the diameter of the small diameter portion 18a is 627 mm, and the diameter of the large diameter portion 18b is 612 mm. Also,
On the outer end face of each staffin box forming part 18,
A plurality of screw holes 18c which do not penetrate in the axial direction are formed, so that a so-called double-cut bolt 10 having no head can be screwed and implanted.

Each flange 9 is, as shown in FIGS.
It is a U-shaped plate made of aluminum, and has a peripheral wall 17a and both side walls 17b, 17b of each cover body portion 17.
Of the outer surface and each staffin box forming part 1
8 is welded to the outer peripheral edge. A plurality of bolt insertion holes 9a ... Are bored in each flange 9, and bolts 11 ... And nuts 12 ... Are fastened between the opposing flanges 9, 9. The cross-sectional area of each flange 9 is set on condition that sufficient fastening strength can be ensured. In this example, the width is set to be the same as the axial thickness of the stuffing box forming part 18 (30 mm) and the thickness is set to 30 mm. 25 mm. Thus, each divided surface of the cover member 2 includes a fastening seal surface 9 ′, which is a surface of the flange 9, and a divided surface of the staphin box forming body 8 connected to the fastening seal surface 9 ′, that is, both circumferential end faces 18 of the staffin box forming body portion 18. ´, 1
8 '.

As shown in FIGS. 1, 4, 6 and 8, the seal pressing body 3 is an annular body divided into two in the circumferential direction. It is a semi-circular body having an L-shaped cross section and comprising a fastening portion 13a and a pressing portion 13b. Each seal pressing body portion 13 was screwed to each bolt 10 after each bolt 10 implanted in each staffin box forming body portion 18 was inserted into each bolt insertion hole 13c formed in the fastening portion 13a. By tightening the nut 15, the pressing portion 13b is moved to the staffin box 8a.
It is adapted to be moved in the direction toward the small diameter portion 18b. The outer diameter of each seal pressing portion 13 is set such that it can be slidably fitted in the large diameter portion 18a of the stuffing box forming portion 18 in the axial direction. In this example, the bolts / nuts 10, 11, 12, 15 and the seal pressing body portion 13 are made of SUS304.

Each of the first seal members 4 for sealing between the divided surfaces of the cover member 2 is shown in FIGS. 3, 5, 7, and 8.
Is a U-shaped sheet gasket in which bolt insertion holes 4c... Matching the bolt insertion holes 9a... Of the flange 9 are formed. A pressure is applied between the fastening seal surfaces 9'and 9'and between the non-fastening seal surfaces 18 'and 18' connected to the fastening seal surfaces 9'and 9 '. In this example, each first seal member 4
As shown in FIG. 9, a sheet gasket having a three-layer structure in which a metal foil 4a is sandwiched between expanded graphite sheets 4b, 4b is used.

A second sealing member 5 for sealing between the opposing peripheral surfaces of the cover member 2 and each low-temperature fluid transport pipe 1 is shown in FIG.
As shown in FIGS. 8 and 10, a string-shaped braided packing 5a
Is formed by spirally winding and covering an expanded graphite tape 5b around the outer periphery of the staple box 8a. In this example, as the braided packing 5a, a material having excellent low-temperature resistance properties, which is lattice-knitted in a rectangular cross section using a knitting yarn mainly composed of expanded graphite material, is used as an expanded graphite tape 5b, and an adhesive layer is formed on the back surface. Is used.

Each third seal member 6 for sealing between the first seal member 4 and the second seal member 5 is shown in FIG.
As shown in FIGS. 5, 7 and 8, one end side portion 6 is formed by bending a rectangular expanded graphite sheet into an L shape.
a is sandwiched between the non-fastened sealing surface 18 ′ and the first sealing member 4, and the other end portion 6 b is located between the large-diameter portion 18 a of the staphin box forming body portion 18 and the second sealing member 5. Is pinched. Thus, the width of each third seal member 6 is set to a size sufficient to entirely overlap the outer peripheral surface of the second seal member 5 pressed and filled in the stuffing box 8a in the axial direction. Further, the length of each third seal member 6 is such that the one end side portion 6a has at least the non-fastened seal surface 1.
Together with the first seal member 4, the communication side portion between 8 ′ and 18 ′ (that is, the inner diameter side end portion where sufficient tightening surface pressure cannot be applied to the first seal member 4 due to the fastening force of the flanges 9 and 9). While being pinched, the other end side portion 6b passes between the first seal member 4 and the second seal member 5, and the large diameter portion 18a of the staffin box forming body portion 18 and the second seal member 5 are separated from each other. It is set so as to be sandwiched between them. In this example, as the third seal member 6, as shown in FIG. 11, an expanded graphite tape (width 2
5.4 mm, thickness 0.38 mm) cut into appropriate dimensions 6 '(FIG. 2A) and bent into an L-shape (FIG. 1B) are used.

In the structure for preventing the leakage fluid diffusion constructed as described above, the flanges 9 and 9 are provided between the respective divided surfaces of the cover member 2 and between the cover member 2 and the low temperature fluid transport pipes 1, respectively. Are sealed by the first seal member 4 and the seal pressing body 3 pressed by the fastening of the second seal member 5 pressed and filled in the staffin box 8a. At this time, the first seal member 4, the metal foil 4a, the expanded graphite sheet 4
Since it is a three-layer structure sandwiched between b and 4b, the flange 9,
The sealing function of the first seal member 4 can be satisfactorily exerted with a low tightening surface pressure without excessively tightening the space between the nine members. Also,
Since the second seal member 5 is formed by winding and covering the braided packing 5a with the expanded graphite tape 5b, the seal pressing member 3
Accordingly, the sealing function of the second seal member 5 is favorably exerted with a low tightening surface pressure without pressing more than necessary.

Moreover, in the communication side portion between the non-fastened seal surfaces 18 ', 18', which cannot apply a sufficient pinching force to the first seal member 4 by fastening the flanges 9, 9,
One end side portion 6a of the first seal member 4 and the third seal member 6
Since the and are intervening in an overlapping state, both the seal members 4 and 5 are sandwiched by a sufficient tightening surface pressure, and good sealing is performed. Further, the first seal member 4 and the second seal member 5
Between the non-fastening seal surfaces 18 'and 18' as described above, and the other end side portion 6a.
The third seal member 6 pressed between the large-diameter portion 18a of the stuffing box forming body portion 18 which is the outer peripheral surface of the stuffing box 8a and the outer peripheral surface of the second sealing member 5 provides a sealing effect. Since they are connected, there is no unsealed portion between the two sealing members 4 and 5. This effect becomes remarkable when the third seal member 6 is made of the expanded graphite sheet having the corrugated cross section as described above. That is, since it has a corrugated cross-section, insufficient tightening surface pressure of the first seal member 4 between the non-fastening seal surfaces 18 ′ and 18 ′ can be well resolved.
Moreover, the seal between the first seal member 4 and the non-fastened seal surface 18 ′ and between the first seal member 4 and the second seal member 5 can be sufficiently performed. Furthermore, even if it is made of brittle expanded graphite, there is no fear that the bent portion between the one end portion 6a and the other end portion 6b is broken.

Accordingly, the first portion is also provided between the divided surfaces of the cover member 2 and the connecting portion between the staffin box 8a.
Good sealing can be achieved without insufficient tightening surface pressure of the seal member 4 or a sealed dead portion. In addition, since it is not necessary to increase the fastening force of the flanges 9 and 9 and the pressing force by the seal pressing body 3 more than necessary, each of the flanges 9 and the stuffing box forming body portion 18 can secure a certain strength. The strength of the cover 7 need not be increased more than necessary. For this reason, as described above, the cover member 7 occupying most of the cover member 2, that is, the cover portion 17 can be made of sheet metal, and the cover member 2 can be inexpensive. Of course,
By making each cover body portion 17 a sheet metal product, the weight of the entire cover member 2 is reduced, and handling such as mounting to the low-temperature fluid transport pipes 1 and 1 becomes easy.

It should be noted that the present invention is not limited to the above-described embodiment, and can be appropriately changed and improved without departing from the basic principle of the present invention. For example, the number of divisions of the cover member 2 and the seal pressing body 3 is arbitrary,
3 may be divided into the same number.

[0027]

As can be easily understood from the above description, according to the invention of claim 1, between the divided surfaces of the cover member and the staffin box (opposing peripheral surface of the cover member and the cryogenic fluid transport pipe). The third seal member can reliably prevent the tightening surface pressure of the first seal member and the occurrence of a sealed dead portion at a place communicating with the space. Therefore, it is possible to satisfactorily seal and surround the leakage location such as the flange joint portion in the low temperature fluid transport pipe, and reliably prevent the diffusion of the leakage fluid.

According to the second aspect of the invention, since the cover body occupying most of the cover member is made of sheet metal, the cover member can be provided at a low cost and the mounting and the like can be handled easily. .

Furthermore, according to the third aspect of the present invention, it is possible to perform better sealing between the divided surfaces of the cover member and between the opposed peripheral surfaces of the cover member and the cryogenic fluid transport pipe and at their communicating points.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional front view showing a structure for preventing leakage fluid diffusion in a low-temperature fluid transport pipe according to the present invention.

FIG. 2 is a longitudinal rear view of the same structure (a cross section is taken along line II-II in FIG. 3).

FIG. 3 is a sectional view taken along the line III-III in FIG. 1;

FIG. 4 is a sectional view taken along line IV-IV in FIG.

FIG. 5 is an enlarged detail view showing a main part of FIG. 3;

FIG. 6 is an enlarged detail view showing a main part of FIG. 4;

FIG. 7 is a sectional view taken along the line VII-VII in FIG.

FIG. 8 is an exploded perspective view of the same structure.

FIG. 9 is a longitudinal sectional view showing a main part of the first seal member.

FIG. 10 is a perspective view showing a main part of a second seal member.

FIG. 11 is a perspective view showing a third seal member.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Low temperature fluid transport pipe, 1a ... Flange joint part (leakage point), 2 ... Cover member, 3 ... Seal pressing body, 4 ... First seal member, 5 ... Second seal member, 5a ... Braided packing,
5b ... Expanded graphite tape, 6 ... Third seal member, 6a ...
One end side part, 6b ... Other end side part, 7 ... Cover body, 8 ... Staffin box forming body, 8a ... Staffin box,
9: flange, 9 ': fastening seal surface (divided surface of cover member), 17: cover body portion (divided portion of cover body), 1
8: a part of the staffin box forming body (a divided part of the staffin box forming body), 18 ': a non-fastened sealing surface (a divided surface of the cover member).

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tomichi Shiomi 1 at 541, Shimouchi Shinto shrine, Mita City, Hyogo Prefecture Nippon Pillar Industry Co., Ltd. Mita Plant , U)

Claims (3)

(57) [Claims] 1. A state in which a fluid leakage point in a low-temperature fluid transport pipe is surrounded by a circumferentially divided tubular cover member, and a sheet-shaped first seal member is interposed between the divided surfaces of the cover member. An annular string-shaped second seal member is filled in a compressed state between opposing peripheral surfaces of the cover member and the low-temperature fluid transport pipe, and the first seal member, the second seal member, Between the first seal member and one of the divided surfaces of the cover member, and the other end portion is pressed between the first seal member and the second seal member.
Leakage in a low-temperature fluid transport pipe characterized in that a sheet-like third seal member is interposed between the cover member and the second seal member while being passed between the seal members. Fluid diffusion prevention structure. 2. A cover member comprising: a pair of flanges for fastening between divided surfaces thereof via a first seal member;
A pair of circumferentially divided staffin box forming bodies which form an annular shape by fastening the flange and which can form a stuffing box for filling the second sealing member with the cryogenic fluid transport pipe, and a tube by fastening the flange. And a circumferentially divided cover body capable of surrounding a fluid leakage point of the low temperature fluid transport pipe, and each divided portion of the cover body is made of a metal plate made of a low temperature resistant metal. The flange and each divided portion of each staffin box forming body are made of a non-sheet metal made of low temperature resistant metal that is welded to each divided portion of the cover body, and each staffin box forming body includes 2. The low temperature flow according to claim 1, wherein the circumferentially divided annular seal pressing body is attached so as to be clamped so as to press the second sealing member in the axial direction of the cryogenic fluid transport pipe. Leakage fluid diffusion preventing structure in the transport pipe. 3. A three-layer structure in which a first seal member has a metal foil interposed between expanded graphite sheets, and a second seal member is spirally wound around a cord-like braided packing and an outer peripheral surface thereof. 3. The cryogenic fluid transport according to claim 1 or 2, wherein the third seal member is an expanded graphite sheet having a fine corrugated cross section. Leakage fluid diffusion prevention structure in pipe.