JP5719529B2 - Union joint and seal structure of union joint - Google Patents

Description

  The present invention relates to a union joint and a seal structure of a union joint.

2. Description of the Related Art Conventionally, union-type assembly pipe joints are known in which components are connected by being sandwiched between union nuts and union screws. The “union type” refers to a connection method in which components are connected by being sandwiched between a union nut and a union screw.
A union joint is a union screw attached to one end of the pipe to be connected, a union collar to the other end of the pipe, a packing is held between the opposing faces of the union screw and the union collar, and the union nut is straddling the two. It is a joint while fitting and connecting. When connecting or disconnecting, it is only necessary to turn the union nut, and there is no need to turn the pipe.

The details of the union joint will be described with reference to FIG. FIG. 7 is an upper half sectional view of a union joint 71 according to a conventional embodiment. In the union joint 71, smooth seal surfaces 7221 and 7321 are formed on the opposing surface portions 722 and 732 of the union screw 72 made of a metal member and the union collar 73, respectively. On the other hand, a packing 75 is fitted between the sealing surfaces 7221 and 7321. Here, as the union nut 74 is tightened, the packing 75 comes into surface contact with the seal surface, and the surface pressure of the contact surface increases, thereby improving the sealing performance of a fluid such as gas or water.
Further tightening strongly the union nut 74, packing 75 between the Yu anion screw 72 and the union flange 73 becomes very thin crushed by pressing between their sealing surfaces 7221,7321. If the packing 75 is within the elastic deformation range when it becomes thin in this way, the packing 75 can seal between the seal surfaces 7221 and 7321 with elasticity.

  As such a union joint, there exists a union joint etc. which are mentioned by patent document 1, for example.

JP 2001-56077 A

  However, in the conventional union joint 71, the packing 75 is disposed between the seal surface 7221 of the union screw 72 and the seal surface 7321 of the union collar 73, and the union nut 74 is screwed into the screw portion of the union screw 72. Tighten and compress packing 75. At this time, since the packing 75 is compressed on the entire surface, a large tightening torque is required for tightening the union nut 74, and this tightening is performed using a normal tightening tool.

  Further, the packing 75 that is normally used is made of rubber or the like, and since the compression force at the time of use is large, the elasticity is lost over time, and the sealing performance is often deteriorated. However, unless it is tightened with such a torque, good sealing performance cannot often be obtained in the initial stage of installation.

As described above, since a large torque is required for tightening, there is room for improvement in workability such that when the packing 75 has a large diameter size, a weaker person cannot tighten the union nut 74 to a torque necessary for tightening. was there.
Further, since the required torque is not tightened, the seal surface pressure at the seal surfaces 7221 and 7321 is low, and as a result, the fluid may leak.

  In addition, a technique for thinning the packing 75 has been considered, but the packing is easy to bend and is difficult to handle. In particular, a hard material such as non-asbestos packing has a problem of breaking due to breakage.

  Therefore, the present invention has been proposed in view of the above points, and the object of the present invention is to improve the reliability of the function of the union joint in addition to the simplicity of pipe connection work by the union joint, and the small torque. It is an object of the present invention to provide a sealing structure that can provide sufficient sealing performance.

In order to solve the above problems, the present invention is closed and Union thread, the opposite surface to the end face have a flange portion radially outer periphery to have a facing surface in a closed-to the end face of the male screw portion radially outer periphery Union A union nut having a collar, a female thread part that can be screwed into the male thread part of the union screw, and a radially inner circumferential collar part that is hooked on the collar part of the union collar, and between the opposing surface parts of the union screw and the union collar A union joint including a seal surface of the formed union screw and a packing sandwiched between the seal surface of the union collar , wherein the facing surface portion of the union screw includes the seal surface of the union screw and the union A seal surface of the screw and a partially opposing surface of the union screw adjacent in the radial direction, and the opposing surface portion of the union collar includes the seal surface of the union collar, and the union Adjacent the sealing surface and the radial direction of the flange, and said union has a union flange portion facing surface axially protruding from the sealing surface of the flange, the sealing surface of the union screw and the union flange sealing surface It is a union joint which has the hollow part which reduces the clamping pressure area of packing compared with the case where the whole area of packing is contacting at least one seal surface of.

  The union joint according to the present invention is configured to have a recess that reduces the clamping area of the packing, so that the clamping area on the seal surface with the packing is in contact with the entire area of the conventional packing. Compared to this, it can be greatly reduced. For this reason, it can be tightened with a small tightening torque, and the surface pressure of the seal surface can be increased. That is, it is not necessary to compress the entire packing surface as in the prior art, and as a result, tightening of the union nut does not require a large tightening torque as in the prior art. Therefore, the fluid sealing performance can be greatly improved by increasing the surface pressure. Therefore, even when the size of the union joint (packing) is large, it is possible to cope with it sufficiently. Further, it is possible to sufficiently cope with the packing which is harder than rubber or the like without breaking at the time of tightening.

  On the other hand, when returning a tightened union nut, the overall clamping area is small despite the large surface pressure. As a result, the frictional resistance of the contact surface is reduced and the return torque when returning the union nut The union nut can be easily returned by hand. In addition, the fluid held in the recess also acts as a lubricating effect when returning the union nut, and an effect of contributing to a reduction in return torque can be obtained.

  Further, since it can be tightened with a weaker tightening torque than conventional ones, a person with weak force can easily use it. The fact that it can be easily tightened with a light force is extremely advantageous in terms of work efficiency.

  Further, since the packing having the same size as the existing packing used conventionally can be used, it becomes easy to handle.

  In addition, in the seal structure of the union joint according to the present invention, even if the same packing as the conventional one is used, it is sufficient that the force that needs to be applied when performing the sealing operation is sufficient. There is no need to use it.

It is an upper half sectional view of the union joint concerning a 1st embodiment of the present invention. It is an expanded sectional view of the part enclosed with the dashed-two dotted line of FIG. It is the elements on larger scale in the upper half sectional view of the union joint concerning a 2nd embodiment of the present invention. It is the elements on larger scale in the upper half sectional view of the union joint concerning a 3rd embodiment of the present invention. It is the elements on larger scale in the upper half sectional view of the union joint concerning a 4th embodiment of the present invention. It is the elements on larger scale in the upper half sectional view of the union joint concerning a 5th embodiment of the present invention. It is upper half sectional drawing of the union joint which concerns on the conventional embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view of the upper half of the union joint 1 according to the first embodiment of the present invention. This figure shows a state where the union nut 4 is tightened with a standard tightening torque. As shown in FIG. 1, the union joint 1 according to the present embodiment includes a union screw 2 having a male screw portion 23 on the outer periphery in the radial direction, a union collar 3 having a flange portion 31 on the outer periphery in the radial direction, and a male screw of the union screw 2. A union nut 4 having a female thread portion 43 that can be screwed to the portion 23, and a radially inner circumferential flange portion 41 that is hooked on the flange portion 31 of the union collar 3, and an opposing surface portion 22 between the union screw 2 and the union collar 3. , 32 and the packing 5 sandwiched between the seal surface 221 of the union screw 2 and the seal surface 321 of the union collar 3.

The union screw 2 is a substantially hollow cylindrical member having a large diameter portion and a small diameter portion. A pipe can be inserted into the hollow so as to be connected to the pipe end, and the opposing surface 22 is provided on the end face opposite to the side connected to the pipe end.
The facing surface portion 22 of the union screw 2 further includes a sealing surface 221 facing the packing 5, and a partially facing surface 222 adjacent to the sealing surface 221 in the radial direction and facing the partially facing surface 322 of the union collar 3. doing.
Further, the union screw 2 has a male screw portion 23 that is screw-coupled with the union nut 4 on the radially outer periphery of the large-diameter portion near the seal surface 221. This screw connection is indicated by reference numeral 60.

The union collar 3 is a substantially hollow cylindrical member. As with the union screw 2, another pipe can be inserted into the hollow and connected to the pipe end, and the flange 31 on the axial outer periphery and the side connected to the pipe end And an opposing surface portion 32 on the opposite end surface.
The facing surface portion 32 of the union collar 3 further includes a sealing surface 321 that faces the packing 5, and a partially facing surface 322 that is adjacent to the sealing surface 321 in the radial direction and faces the partially facing surface 222 of the union screw 2. doing.
The packing 5 is held or pinched between the seal surface 221 of the union screw 2 and the seal surface 321 of the union collar 3.

In this embodiment, the union nut 4 uses a hexagonal nut having a hexagonal column shape. On the inner surface on the opening side, a female screw portion 43 is cut for the screw coupling 30 with the male screw portion 23 on the outer periphery of the union screw 2. Further, an inner peripheral flange 41 that is caught by the outer peripheral flange 31 of the union collar 3 is formed on the inner surface of the opening side.
The union nut 4 is mounted on the union collar 3 so as to be able to tighten and loosen the nut, and the flange 31 provided on the union collar 3 prevents mutual union with the union collar 3. ing.
When the union nut 4 and the union screw 2 are screw-coupled, for example, the union nut 4 is tightened with the union screw 2 held by a flat wrench with a spanner.

  In addition, the union screw 2, the union collar 3, and the union nut 4 which comprise the union joint 1 are manufactured with a metal material, for example, are manufactured with casting, stainless steel, or brass. In some cases, it is also possible to manufacture and use a resin such as PE. It is also possible to use stainless steel such as SUS304 material in order to avoid the influence of rust generation at the packing 5 installation part.

In this embodiment, the packing 5 is held in a normal shape, that is, an annular packing 5 having a substantially uniform thickness between the seal surface 221 of the union screw 2 and the seal surface 321 of the union collar 3 and tightened. As a result, the seal surfaces 221 and 321 are sandwiched.
The role of the packing 5 is to attach between the union screw 2 and the union collar 3 that are in contact with each other to prevent leakage of gas, liquid, etc. from between the union screw 2 and the union collar 3, and from the outside It has a role to prevent the intrusion of foreign matter, and is to stably operate the union joint 1.
The material of the packing 5 is an exercise seal material used to give the structure of the union joint 1 airtight and watertight, and the material used for the packing 5 is independent depending on conditions such as temperature, pressure, and resistance. Used in combination. Generally used as a fluororesin packing such as polytetrafluoroethylene and joint sheets (for example, a sheet reinforced with aramid fibers mainly composed of expanded graphite using oil-resistant rubber as a binder) Non-asbestos packing or the like obtained by punching a pressure-rolled sheet) is used. Since they are harder than rubber or the like, the tightening torque is also increased to ensure sealing performance. Moreover, it is also possible to use what has the elastic performance which has the sealing performance of fluids, such as gas and a liquid, between the sealing surfaces 221 and 321. FIG. For example, rubber materials, resin materials, and composite / synthetic resin materials such as rubber and polytetrafluoroethylene are also used depending on the usage environment. For example, nitrile rubber that is oil-resistant rubber, fluororubber that is heat- and oil-resistant rubber, exercise Examples thereof include urethane having excellent performance.

  In addition, in this embodiment, what was formed in cyclic | annular form as the packing 5 was illustrated, However, What is necessary is just to have a sealing function at the time of pinching, and is not limited to cyclic | annular form. For example, it may be formed in a U-shaped cross section, a plurality of holes having an arbitrary shape penetrating from the outer peripheral surface to the inner peripheral surface in the circumferential direction, or spaced at one end and the other end in the circumferential direction. In addition, the cutouts having an arbitrary shape may be alternately formed, or the cutouts having an arbitrary shape may be formed to face each other so as to be symmetrical.

  In addition, it is obvious that the packing 5 should be used with an appropriate tightening torque that will not be destroyed. What is the strength of the safety factor with respect to the tightening torque used for the packing 5? Is a design matter that can be appropriately set as necessary.

  Next, the hollow part 6 of the union joint 1 according to the first embodiment will be described based on FIG. 1 or FIG. FIG. 2 is an enlarged cross-sectional view of a portion surrounded by a two-dot chain line in FIG.

  Here, the hollow portion 6 will be described. In the first embodiment, the recessed portion 6 that reduces the clamping area of the packing 5 is formed on the seal surface 221 of the union screw 2. By forming the dent 6, the clamping area when the packing 5 is clamped can be reduced compared to the conventional case, and the seal surface pressure can be increased with a small tightening torque.

Specifically, as described above, the facing surface portion 22 of the union screw 2 is a portion facing the seal surface 221 facing the packing 5 and the partial facing surface 322 of the union collar 3 adjacent to the sealing surface 221 in the radial direction. And an opposing surface 222. Here, the seal surface 221 is further configured as follows. That is, the sealing surface 221 of the union screw 2 has a first surface portion 221a having a recess portion 6, adjacent to the first face 221a and the radial direction, a second face 221b located axially outer side of the first face 221a The second surface portion 221b is configured to be able to contact the packing 5.

With the above-described configuration, in the union joint 1 according to this embodiment, the union nut 4 is tightened, and the male screw portion 22 of the union screw 2 and the female screw portion 43 of the union nut 4 are screwed together. When the screw is engaged, the packing 5 is screwed while being pressed, and finally the packing 5 is sandwiched between the second surface portion 221b of the union screw 2 and the seal surface 321 of the union collar 3 and comes into partial surface contact. Specifically, the entire surface of one axial surface 5 a of the packing 5 is in contact with the seal surface 321 of the union collar 3, whereas the other surface in the axial direction of the packing 5 is in contact with the second surface portion 221 b of the union screw 2. Only a part of 5b is in contact. That is, by providing the hollow portion 6, the clamping area on the other surface 5 b in the axial direction of the packing 5 is reduced. Therefore, the surface pressure of the contact surfaces (seal surfaces) 221b and 5b increases, and the sealing performance is improved.
On the other hand, the partial facing surface 222 of the union screw 2 and the partial facing surface 322 of the union collar 3 are opposed to each other with an interval.

  In addition, although the clamping area of the 2nd surface part 221b of the union screw 2 and the packing 5 is small compared with the clamping area of the sealing surface 321 of the union collar 3, the clamping pressure area of the 2nd surface part 221b and the packing 5 is small. As for, it is the pinching area of the magnitude | size which can pinch so that when the union nut 4 is tightened strongly, the packing 5 may incline and the function as a packing is not impaired. In other words, the union screw 2 having the recessed portion 6 needs to have an area where the areas of the first surface portion 221a and the second surface portion 221b constituting the seal surface 221 of the union screw 2 satisfy the above conditions.

  Further, the axial height from the first surface portion 221a having the hollow portion 6 to the second surface portion 221b (the axial size of the surface 221c to be described later) also functions as a packing when the packing 5 is clamped. It is necessary to have a size in the axial direction enough to tighten the packing so as not to damage it.

  The first surface portion 221a and the second surface portion 221b having different axial heights are continuous surfaces, and the surface 221c extending in the axial direction between the surfaces 221a and 221b is a surface substantially parallel to the axial direction. An inclined surface may be used. In the present embodiment, the first surface portion 221a, the second surface portion 221b, and the surface 221c form a right-angled step portion. The first surface portion 221a having the recessed portion 6 and the second surface portion 221b adjacent to the first surface portion 221a through the stepped portion, and the second surface portion 221b is located on the inner side in the axial direction from the first surface portion 221a. The union joint 1 is configured to be able to contact the packing 5.

As described above, the union joint 1 according to the present embodiment has the depression area 6 that reduces the clamping area of the packing 5 on the sealing surface 221 of the union screw 2, so that the clamping area between the packing 5 and the sealing surface 221 is reduced. However, as compared with the case where the entire area of the packing is in contact as shown in FIG. 7 showing the conventional embodiment, it can be greatly reduced. For this reason, it can be tightened with a small tightening torque, and the surface pressure of the seal surface 221 can be increased. That is, it is not necessary to compress the entire packing surface as in the prior art, and as a result, tightening of the union nut 4 does not require a large tightening torque as in the prior art. Therefore, the fluid sealing performance can be significantly increased by increasing the surface pressure. Therefore, internal fluid leakage can be suppressed and high sealing performance can be maintained.
In other words, in the present embodiment, the packing 5 is not uniformly compressed over the entire surface, but is locally compressed by a predetermined compression allowance, that is, an amount sufficient for sealing. Yes. Therefore, compared with compressing the entire surface by a predetermined amount, the required force is extremely small. Even in such local compression, if the compression allowance is appropriate, extremely high sealing performance can be obtained.
As a result, even when the size of the union joint 1 (packing 5) is large, it is possible to cope with it sufficiently.

  On the other hand, when the tightened union nut 4 is returned, the entire pinched area is small in spite of the large surface pressure. As a result, the frictional resistance of the contact surface is reduced and the union nut 4 is returned. The return torque is also reduced, and the union nut 4 can be easily returned by hand. In addition, the fluid held in the depression 6 also acts as a lubricating effect when the union nut 4 is returned, and an effect of contributing to a reduction in return torque can be obtained.

  Moreover, since it can be tightened with a tightening torque weaker than in the prior art, even a person with weak power can easily use the union joint according to the present embodiment. The fact that it can be easily tightened with a light force is extremely advantageous in terms of work efficiency.

  Further, the packing 5 is easy to handle because a packing having the same size as the existing packing used conventionally can be used. In particular, compared to conventional packings such as fluororesin packing and non-asbestos packing that had to be careful not to exceed the allowable tightening surface pressure because the material is harder than rubber. Can be tightened with less tightening torque. Therefore, the possibility of breaking such a hard packing due to breakage was improved.

  In the seal structure of the union joint 1 according to the present embodiment, even if the same packing as the conventional one is used, it is sufficient that the force that needs to be applied when performing the sealing operation is sufficient. There is no need to use etc.

  Moreover, the hollow part 6 is opening to the radial inside. Therefore, the sealing performance can be improved according to the magnitude of the fluid pressure.

  The present invention is not limited to the above-described embodiments, and various changes and modifications can be made without departing from the technical scope of the present invention.

As shown in FIG. 3, in the second embodiment, one axial surface of the first surface portion 221a of the union screw 2 that faces the other axial surface 5b of the packing 5 with a gap is directed radially inward. It is also possible to adopt a configuration in which the inner diameter increases as the taper increases. In this embodiment, the 1st surface part 221a (or dent part 6 itself) which has the hollow part 6 is formed in inclined surface shape (tapered shape), and the 2nd surface part 221b adjacent to the 1st surface part 221a and radial direction outer side is packing. The union joint 1 is configured so as to be able to come into contact with 5.
For this reason, the fluid interface formed in the gap between the first surface portion 221a and the other axial surface 5b of the packing 5 facing the first surface portion 221a becomes a meniscus shape due to the surface tension. Is prevented from leaking out of the union joint 1. That is, a taper seal of fluid is formed between the first surface portion 221 a and the packing 5.
In addition, by configuring the taper seal portion, even when fluid is about to leak, the taper seal portion exerts an action of attracting the fluid to the second surface portion 221b side where the gap is gradually narrowed. For this reason, it is possible to prevent the fluid from leaking outside the union joint 1. In addition, the fluid volume increases due to centrifugal force, temperature rise, etc., or some other action may cause the meniscus of the taper seal part to move radially outward. In equilibrium, outflow of fluid to the outside of the union joint 1 is prevented. Therefore, the union joint 1 having high sealing performance and high reliability can be provided.

In addition, as shown in FIG. 4, it is possible to form a plurality of depressions 6 in the radial direction and / or the circumferential direction on the seal surface 221. That is, a plurality of first surface portions 221 a and second surface portions 221 b are formed in the radial direction and / or circumferential direction on the seal surface 221, and the plurality of second surface portions 221 b come into contact with the packing 5, and the union collar 3 and the clamping pressure You may make it the structure made.
By forming in this way, the surface 5b on the other side in the axial direction of the packing 5 that faces the seal surface 221 of the union screw 2 is any surface (for example, an uneven surface). The union joint 1 can appropriately correspond to the position of the seal surface pressure in accordance with the shape of the packing.

  In the said embodiment, although the hollow part 6 was provided in the union screw 2, the structure provided in the union collar 3 is also possible. For example, FIG. 5 is a partially enlarged view of the upper half cross-sectional view of the union joint according to the fourth embodiment of the present invention. As shown in FIG. 5, the recess 6 is formed on the seal surface 321 of the union collar 3. ing.

In the union joint 1 according to the fourth embodiment, the facing surface portion 32 of the union collar 3 includes a sealing surface 321 facing the packing 5, and a partially facing surface 222 of the union screw 2 adjacent to the sealing surface 321 in the radial direction. And a partial facing surface 322 facing each other. Here, the seal surface 321 is further formed as follows. That is, the sealing surface 321 of the union collar 3 has a first surface portion 321 b having a recess portion 6, adjacent the first surface portion 321 b and the radial direction, and the second is located in the axially outer side of the first surface portion 321 b has a surface portion 321 a, the second surface portions 3 21 a is configured to be contact with the gasket 5.

With the configuration as described above, in the union joint 1 according to the present embodiment, the union nut 4 is tightened to press the packing 5, and finally the packing 5 is connected to the second surface portion 321 a of the union collar 3 and the union. It is pinched between the seal surface 221 of the screw 2 and comes into partial surface contact. Specifically, while the other axial surface 5b entire gasket 5 on the sealing surface 221 of the union screws 2 are in contact with one surface axially of the packing 5 in the second surface portion 321 a of the union collar 3 Only a part of the surface of 5a abuts. In other words, the provision of the depression 6 reduces the other clamping area in the axial direction of the packing 5. Therefore, the contact surface (sealing surface) 321 a, the surface pressure of 5a increases, the seal performance is improved.
On the other hand, the partial facing surface 222 of the union screw 2 and the partial facing surface 322 of the union collar 3 are opposed to each other with an interval.

  FIG. 6 is a partially enlarged view of the upper half cross-sectional view of the union joint according to the fifth embodiment of the present invention. In this embodiment, the seal surfaces 221 and 321 of both the union screw 2 and the union collar 3 are provided. It is also possible to employ a configuration in which the depressions 6 and 6 are provided. As a configuration, the first embodiment and the fourth embodiment described above are combined, and the operational effects of the union joint 1 according to the present embodiment are the same.

  Moreover, not only 5th Embodiment but the structure which combines other embodiment suitably can also be taken.

  INDUSTRIAL APPLICABILITY The present invention can be used for butt piping of inner pipes and connection of inner pipes and gas appliances. Union joints are used in many general piping facilities including nuclear power plants, and the range of use is wide.

DESCRIPTION OF SYMBOLS 1 Union joint 2 Union screw 22 Opposite surface part 221 Seal surface 221a 1st surface part 221b 2nd surface part 221c surface 222 Partially opposed surface 3 Union collar 32 Opposed surface part 321 Seal surface 321a 2nd surface part 321b 1st surface part 322 Partially opposed surface 4 5 Packing 5a One surface in the axial direction 5b The other surface in the axial direction 6 Recessed portion

Claims (4)

And Union thread to have a facing surface in a closed-to the end face of the male screw portion radially outer periphery,
And Union collar to have a facing surface in a closed-to the end face of the flange portion in the radial direction outer circumference,
A union nut having a female thread part that can be screwed into a male thread part of the union screw, and a radially inner circumferential collar part that is hooked on the collar part of the union collar;
A packing to be clamped between the sealing surface and the union flange sealing surface of the union screws to be formed between the opposing surface of the union collar and the union screw,
Union fittings including
The opposing surface portion of the union screw is
A sealing surface of the union screw;
A seal surface of the union screw and a partially opposed surface of the union screw adjacent in the radial direction;
The facing surface portion of the union collar is
A sealing surface of the union collar;
A seal surface of the union collar which is adjacent to the seal surface in the radial direction and protrudes in the axial direction from the seal surface of the union collar;
A union having a recess that reduces the clamping area of the packing compared to the case where the entire area of the packing is in contact with at least one sealing surface of the sealing surface of the union screw and the sealing surface of the union brim Fittings. The seal surface of at least one of the seal surface of the union screw and the seal surface of the union collar is:
A first surface portion having the recess,
A second surface portion that is adjacent to the first surface portion in the radial direction and is located on the inner side in the axial direction from the first surface portion;
The union joint according to claim 1, wherein the second surface portion can contact the packing.   The union joint according to claim 1 or 2, wherein the recess is open radially inward. And Union thread to have a facing surface in a closed-to the end face of the male screw portion radially outer periphery,
And Union collar to have a facing surface in a closed-to the end face of the flange portion in the radial direction outer circumference,
A union nut having a female thread part that can be screwed into a male thread part of the union screw, and a radially inner circumferential collar part that is hooked on the collar part of the union collar;
A packing to be clamped between the sealing surface and the union flange sealing surface of the union screws to be formed between the opposing surface of the union collar and the union screw,
In a seal structure of a union joint in which the seal surface is sealed by the sandwiched packing,
The opposing surface portion of the union screw is
A sealing surface of the union screw;
A seal surface of the union screw and a partially opposed surface of the union screw adjacent in the radial direction;
The facing surface portion of the union collar is
A sealing surface of the union collar;
A seal surface of the union collar which is adjacent to the seal surface in the radial direction and protrudes in the axial direction from the seal surface of the union collar;
A union having a recess that reduces the clamping area of the packing compared to the case where the entire area of the packing is in contact with at least one sealing surface of the sealing surface of the union screw and the sealing surface of the union brim Joint seal structure.

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