JP4893100B2 - Pressure vessel seal structure - Google Patents

Description

The present invention relates to a seal structure for sealing an opening such as a pipe connection part or a drain of a pressure vessel that encloses and accumulates a high-pressure fluid.
Here, the fluid is air; an inert gas such as helium, argon or nitrogen; a gas such as flammable gas such as hydrogen, propane gas or natural gas; and a liquid such as liquefied propane gas or liquid nitrogen; Includes mixed fluids.

  Pressure vessels that contain and store high-pressure fluids are currently available in a variety of shapes, sizes, and materials, and there are various internal pressures that can be sealed. The sealing pressure is high, and some of the pressure ranges from 500 to 700 atmospheres.

  These pressure vessels usually have openings such as pipe connections and drains, and these openings are pipe connection members attached to the openings to prevent leakage of the internal high-pressure fluid. (Hereinafter, also simply referred to as a piping member) or a sealing structure is provided between other members such as a sealing member.

  The most common sealing structure is to insert an annular packing (O-ring, V-ring, C-ring, etc.) made of a soft material into a predetermined packing groove or sealing surface, and squeeze it tightly around the entire circumference. In this system, the internal fluid is sealed by filling a gap between the opening and another member attached to the opening.

  Here, the soft material refers to a material whose hardness is smaller than the material of the pressure vessel opening and the material of other members (piping members, sealing members, etc.) attached thereto. When the material of the opening of the pressure vessel and other members is steel, examples of soft materials include metals such as copper and copper alloys, polymer materials such as rubber and resin, and polymer materials such as glass fiber and carbon fiber. And composite materials in which reinforcing materials such as these are mixed.

  Various types of seal structures using annular packings of pressure vessels have been proposed so far. For example, the seal structures described in the following Patent Documents 1 to 3 have been devised in terms of structure in order to enhance the sealability of the seal portion, but are the same in that an annular packing made of a soft material is used.

Although this method depends on the packing material and tightening force, it is basically unsuitable for containers with extremely high pressure, and guarantees sealing (sealability) against very high internal pressure. I can't. Furthermore, in the case of packing made of rubber or resin, since it deteriorates with time, regular maintenance such as replacement is required.
JP 2002-349796 A JP 11-013995 A JP 2000-291887 A

  The object of the present invention is to provide a seal that does not cause leakage even at a very high internal pressure, which is difficult to seal with conventional packing techniques. An object of the present invention is to provide a pressure vessel sealing structure having performance.

  Another object of the present invention is to provide a pressure vessel sealing structure that does not use a packing (or gasket), and thus eliminates maintenance such as replacement of the packing.

  As shown in FIG. 8, many conventional pressure vessel seal structures using an annular packing have a female threaded portion 4 on the inner surface of the opening 2 of the pressure vessel 1 and a pipe connection member or seal attached to the opening. A male screw portion 14 is provided on the outer peripheral surface of the mating member 11 such as a member (the surface facing the inner surface of the container opening), and the packing 21 is subjected to tightening force (compression force in the screwing direction) by screwing these screws. It is a system that generates high contact surface pressure and seals. In the figure, reference numeral 12 denotes a through hole when the mating member is a pipe connecting member. When the counterpart member is a sealing member, there is no through hole.

  However, with this packing method, if the tightening force by the screw decreases due to deformation of the mating member due to an increase in internal pressure, looseness or sag of the screw (aging over time), or deterioration of the packing material itself, the packing is immediately There is also a problem that the contact surface pressure is reduced, and the worst is leakage.

  This problem is not solved even if the seal structure does not use a packing made of a soft material, as long as the structure uses only the tightening force of the screw as the force for pressing the seal surface.

  In other words, if a structure other than the tightening force of the screw, that is, the compressive force in the screwing direction (screw axial direction), can be used, even if the screw is loosened or sagged, the sealing performance will be improved. A seal structure with less influence can be obtained.

  From this point of view, the present inventors have focused on introducing a radial fitting force into the pressure vessel seal structure. Specifically, a sealing surface is provided on the inner surface of the opening of the pressure vessel that has the female screw and the outer surface of the other member that is attached to the opening that has the male screw, facing the inner surface. When the diameter of the seal surface provided on the outer peripheral surface of the member is slightly larger than the diameter of the inner surface seal surface of the pressure vessel opening opposite to the outer surface and the two seal surfaces are fitted together in the radial direction, the seal is sealed over the entire circumference. The surface adheres uniformly with high contact surface pressure.

  The close contact between the seal surfaces in this case is that the diameter of the seal surface of the other member with male thread (hereinafter also simply referred to as the male screw member or other member) as the inner member is larger than the diameter of the seal surface of the pressure vessel as the outer member. This is due to the fit (tightening). That is, the contact surface pressure of the sealing surface is generated by the energy of the sealing surface of the male screw member whose diameter is reduced by the fitting margin to return to the original diameter. This surface pressure acts in a direction perpendicular to the seal surface, and thus in a substantially radial direction. At this time, if the diameter of the male screw member is within the range of elastic deformation, the elastic deformation energy (elastic recovery force) is used for generating the surface pressure, and the contact surface pressure is not attenuated over a long period of time. . Therefore, a seal structure that is not easily affected by the tightening force of the screw can be obtained. In particular, if the male screw member and the container opening are made of a metal such as steel, the elastic deformation energy is very large and the generated contact surface pressure is also very large, so that excellent sealing performance can be obtained.

The present invention based on the above knowledge is a seal structure between the pipe connection portion of the pressure vessel and the inner surface of the opening of the drain and the outer peripheral surface of the other member attached to the opening, and the inner surface of the opening of the pressure vessel is at least One female screw portion and at least one seal surface A, and the outer peripheral surface of the other member has at least one male screw portion and at least one seal surface B that are screwed into the female screw portion, and the seal surface B is a screw-in shaft. Is a conical surface, a curved rotating surface, or a cylindrical surface whose diameter decreases in the screwing direction, and the sealing surface A has a shape facing the sealing surface B, and the male screw and the female screw portion are screwed together. The seal surfaces A and B are configured so as to be in close contact with each other by fitting, and the inner surface of the opening of the pressure vessel acts as a screw stopper. Both with one torque shoulder, comprises at least one torque shoulder also corresponding outer peripheral surface of the other member, and, both sealing surfaces A and B are metal is steel or soft plated steel, sealing surface B The pressure container is characterized in that the fitting margin, which is the difference in diameter between the seal surfaces before fastening at the center of the seal, is 0.1 to 2% of the diameter of the seal surface B before screwing. This is a seal structure.

The curvature rotator surface means a surface formed by rotating around an axis having a curvature curve, that is, a rotator surface having a curved surface. When the sealing surface B is a curvature rotator surface, the curved surface may be concave or convex. The curved surface may be a curved surface having two or more inflection points.
The pressure vessel sealing structure of the present invention can also be applied to the case where the sealing surface A of the pressure vessel and the sealing surface B of the other member are fitted by shrink fitting, in addition to fitting by screwing. Shrink fitting is a method in which a pressure vessel, which is an outer member, is expanded at a high temperature and the diameter of the opening is expanded, and another member is inserted therein, cooled, and the vessel is contracted and fitted. . Even when fastening by this method, tightening with screws is necessary to prevent other members from falling off .

  In the present invention, when the pressure vessel is fastened to the other member by screwing or shrink fitting, the sealing surfaces A and B are configured to be in close contact with each other by fitting (tightening). That is, the diameter of the seal surface B provided on the outer peripheral surface of the other member that enters the inside is slightly larger than the diameter of the seal surface A of the pressure vessel opening located on the outer side. Has undergone elastic deformation due to reduced diameter. Due to the elastic recovery force that the elastic deformation tries to return to, the close contact over the entire circumference of the seal surfaces A and B is obtained.

  Further, the thickness of the other member at the central position of at least one sealing surface B of the other member is not less than 1/22 and not more than 1/6 of the diameter of the other member at the same position before fastening. Is preferred.

When the sealing surface B is a conical surface tapered in the screwing direction (more precisely, a truncated cone surface) or a curvature rotator surface, the taper angle or the maximum tangent angle is relative to the central axis of the cone or curvature rotator. Is preferably in the range of 1 to 25 °. This central axis is equal to the rotational central axis of the container opening having a rotating body shape, and is equal to the screwing direction when the inner surface of the opening has a threaded portion . Both the seal surface A and the seal surface B are metal.

  According to the present invention, even when the pressure vessel is fastened to the other member by screwing, the male screw member is hardly affected by a decrease in tightening force (slack or sag), and stably has a very high sealing performance. A seal structure that can be exhibited is obtained. This effect is more surely obtained particularly when the sealing surface is a tapered surface having a gentle slope.

  In addition, if the pressure vessel can be heated, the seal structure of the present invention can be fitted with a seal surface by shrink fitting, in which case a cylindrical surface can also be applied to the seal surface, and excellent sealing performance Can be secured.

  In addition, since packing made of soft material is not used, there is no concern about surface pressure drop due to aging deterioration often seen in rubber packing, etc., sealing performance is demonstrated over a long period of time, and maintenance such as replacement of packing is unnecessary. Become.

Hereinafter, various aspects of the present invention will be described in more detail with reference to the accompanying drawings.
The seal structure of the pressure vessel according to the present invention can be applied to openings of various pressure vessels from large to small. Since the present invention relates to a pressure vessel seal structure, that is, a seal structure of the opening thereof, the structure, shape, purpose of use, etc. of the vessel itself are not particularly limited.

The material of the container is not particularly limited as long as it can withstand the pressure of the fluid sealed in the container and satisfies other required characteristics such as corrosion resistance. Typically, it is a metal, especially steel, but glass, ceramic, plastic, or a composite material combining these materials can also be used. However, as described above, since the sealing surface of the sealing surface is secured by utilizing the elastic deformation energy and its recovery force in the present invention as described above, the sealing surface on the container side from the metal that can exhibit high elastic deformation energy. that make up the a. For the same reason, that make up the metal also sealing surface B of another member.

  1, 2 and 3 are schematic views showing a sealing structure according to the present invention. In FIG. 1, the sealing surface B (13) of the other member 11 has a conical surface (that is, a tapered surface) whose diameter decreases in the screwing direction (the lower direction in the figure) with the screwing axis (the chain line in the figure) as the rotation axis. ). The angle of the cone surface with respect to the screwing axis is indicated by θ. FIG. 2 shows a mode in which the sealing surface B (13) is a cylindrical surface (that is, θ = 0 °). In FIG. 3, the sealing surface B (13) of the other member 11 is a conical surface whose diameter decreases in the screwing direction, as in FIG. The aspect made into the opening part inner surface of a pressure vessel is shown.

  As shown in FIGS. 1, 2, and 3, the opening 2 of the pressure vessel 1 having the sealing structure according to the present invention has a female screw portion 4 on the inner surface thereof, and the other member 11 attached to the opening 2. (Piping connection member, sealing member, etc.) have a male screw portion 14 on the outer peripheral surface thereof facing the female screw portion 4 of the container opening. About this thread part, it is the same as that of the conventional seal structure using the packing 21 shown in FIG. Similarly to FIG. 8, when the mating member is a pipe connecting member, the through hole 12 is provided, and when the mating member is a sealing member, there is no through hole.

  In the present invention, as means for ensuring the sealing performance, the inner surface of the container opening 2 has a seal surface A indicated by 3 in addition to the female screw portion 4 instead of packing, and the outer peripheral surface of the other member 11 is , 13 has a sealing surface B. The seal surface B (13) of the other member is a conical surface, a rotating curvature surface, or a cylindrical surface whose diameter decreases in the screwing direction with respect to the screwing shaft. The container-side seal surface A (3) has a shape facing the seal surface B, and the seal surfaces A and B are configured to be in close contact with each other when the other member is screwed to the pressure vessel. . That is, the sealing surfaces A and B are in a position where they are opposed to each other after fastening, and have an appropriate fitting margin.

  The fitting margin is a difference in diameter between the seal surface A of the opening 2 of the pressure vessel 1 and the seal surface B of the other member 11 attached to the opening 2 and having a diameter larger than that of the seal surface A. When the other member 11 is attached to the opening 2 of the pressure vessel 1, the contact surface pressure is generated on the seal surface B by elastic deformation energy that the seal surface B of the other member 11 whose diameter has been reduced tends to return to the original diameter. This surface pressure acts in a direction perpendicular to the seal surface, that is, substantially in the radial direction, and the contact surface pressure is not attenuated over a long period as long as the diameter of the seal surface B of the other member 11 is within the range of elastic deformation. . Furthermore, since the pressure inside the pressure vessel presses the sealing surface B of the other member 11 toward the outside, even if the pressure inside the vessel increases, the surface pressure applied to the sealing surface is maintained, and high sealing performance is exhibited. The

  In order to fit and fasten the other member 11 having the sealing surface B having a fitting margin to the sealing surface A of the opening 2 of the pressure vessel 1, the sealing surface is tapered as in the examples of FIGS. In the case where it is attached, the female screw part 4 is provided in the opening 2, and the male screw part 14 is provided on the outer peripheral surface of the other member 11 at a portion facing the female screw part. It can be fitted to the seal surface A. As another method, the pressure vessel 1 is expanded to a high temperature, and the sealing surface A of the other member 11 is screwed into the sealing surface A of the opening 2 thus expanded, and then the vessel is cooled to open the opening. Shrink fitting that shrinks and fits 2 can also be used. In this case, when the pressure vessel 1 is large, it is not necessary to heat the entire vessel, and it is only necessary to expand at least the vicinity of the opening 2 at a high temperature. Even when fastening by the shrink fitting method as described above, it is necessary to provide a threaded portion to prevent the other member 11 from falling off.

  As in the example of FIG. 2, when the sealing surface B (13) is a cylindrical surface (that is, θ = 0 °) and has a shape that is difficult to be screwed in, the shrink-fitting method may be used. The shape of the sealing surfaces 3 and 13 may be any of a cylindrical surface, a conical surface, and a rotating surface of curvature when the pressure vessel and other members are fastened by shrink fitting.

  When the sealing surface is a conical surface or a curved rotator surface, the taper angle or average tangential angle with respect to the screwing direction (the central axis of the conical surface or the curved rotator surface) is, for example, as shown in FIG. 4 (θ = 60 °). On the other hand, if the pressure is too large, the influence of fluctuations in the tightening force of the screw on the surface pressure of the seal surface increases, and the contact surface pressure is significantly reduced when an internal pressure is applied. Therefore, this angle θ is preferably 30 ° or less, and more preferably in the range of 1 to 25 °.

  If the fitting margin, which is the difference in diameter between the sealing surface B of the other member 11 and the sealing surface A of the opening 2 of the pressure vessel 1, is increased so as to cause permanent deformation, the contact surface pressure of the sealing surface is impaired. Therefore, the deformation of the other member 11 and the container opening 2 after fastening should be set so that both remain in the elastic deformation region.

  The desirable range depends on the material and dimensions, but when the other member 11 and the container opening 2 are both steel, they are 0.1 to 2% of the diameter of the sealing surface B (13) of the other member 11. It is better to be within the range. The diameter of the reference seal surface B is the diameter at the center of the seal surface B when the other member 11 is screwed to the pressure vessel 1.

  When the sealing surface shape is a conical surface or a curved rotating body surface, the fitting margin of the sealing surface can be controlled by a torque shoulder that serves as a screw stopper. When the torque shoulder 15 provided on the outer peripheral surface of the other member 11 is in contact with the torque shoulder 5 provided on the inner surface of the opening 2 of the container 1, the difference in the diameter of the seal surface fits into each other. Management becomes easy. Even when the seal surface shape is a cylindrical body, it is preferable to provide a torque shoulder because positioning is facilitated by providing a torque shoulder.

  For example, in the example shown in FIG. 1 and FIG. 2, the torque shoulder 5 is disposed on the end face of the opening 2 of the pressure vessel 1 and the other member 11 is screwed in the screwing direction so as to abut the same as in FIG. A torque shoulder 15 is provided on the inner end face of the flange portion corresponding to the rear screw head. In the aspect shown in FIG. 3, the tip end surface of the other member 11 becomes the torque shoulder 15, and the torque shoulder 5 is formed on the inner surface of the opening 2 of the pressure vessel 1 so as to come into contact therewith.

  Both the torque shoulders 5 and 15 are preferably substantially perpendicular to the screwing shaft. The torque shoulders in the examples of FIGS. 1, 2 and 3 are all surfaces that are substantially perpendicular to the screwing shaft, but are slightly inclined from the surfaces that are substantially perpendicular to the screwing shaft as long as they function as screwing stoppers. Also good. The contact area of the torque shoulder is sufficient if it serves as a stopper, and may be a relatively small area.

  The position of the torque shoulder is not limited to the position described above. That is, the torque shoulder includes the tip position of the other member 11 (position in FIG. 3), between the screw portion and the seal surface, in the screw (in other words, between two-stage screws), and behind the screw portion (in FIG. 1). (Position) may be provided anywhere.

  The same can be said for the seal surface, and the seal surface B provided on the other member 11 will be described. The most peripheral surface of the threaded portion and the intermediate surface of the threaded portion (in other words, between the two-stage screws). It may be provided anywhere on the outer peripheral surface behind the threaded portion. As can be seen, the threaded portions can also be provided at two or more locations. That is, two or more of the thread portion, the seal surface, and the torque shoulder can be provided.

  7A to 7Q, some possible combinations of the seal surface 13, the threaded portion 14, and the torque shoulder 15 in the case where the other member 11 is a pipe connecting member (that is, having the through hole 12). Indicates. The auxiliary second sealing surface and the second shoulder may be provided anywhere, but the adjacent sealing surfaces are not so good because each surface pressure decreases.

  The fitting margin and the thickness of the seal surface are greatly related to the magnitude of the contact surface pressure generated on the seal surface. In addition, the magnitude of the contact surface pressure generated on the sealing surface greatly affects the sealing performance and seizure resistance. That is, if the contact surface pressure is too large, seizure is likely to occur during screwing, but if the contact surface pressure is too small, the sealing performance is insufficient. In the shrink-fitting method, there is no fear of seizure, and it is sufficient if the fit is within the elastic deformation range.

  It is quite difficult to control the surface pressure of the sealing surface that does not cause seizure and can provide sufficient sealing performance at the stage of tightening by screwing. That is, since the range of the fitting margin satisfying such conditions is considerably narrow, there is a possibility that the manufacture becomes difficult and the yield is extremely lowered.

  Problems that may occur in the manufacturing process can be solved by reducing the thickness of the seal surface on the side of the other member (that is, the male screw member) having the male screw. Therefore, it is preferable that the thickness of the other member at the position of at least one sealing surface B is smaller than the thickness at the position of the male screw portion.

  If the sealing surface of the male screw member is made thin, the contact surface pressure generated does not become excessively large even if the fitting margin is somewhat increased, so that the occurrence of seizure can be avoided. Further, as described above, the internal pressure applied by the pressurized fluid in the container acts on the inner side of the seal surface and works in a direction in which the seal surface of the male screw member is more closely attached. The contact pressure does not decrease extremely. This effect becomes more remarkable as the sealing surface of the male screw member is thinner, and a very high sealing performance is obtained.

  As the thickness of the sealing surface of the male screw member is as thin as described above, it is more effective, but if it is too thin, the portion of the reduced sealing surface will buckle and collapse due to the fit, and the sealing surface Will not contact evenly over the entire circumference, causing leakage. Therefore, if the thickness of at least one seal surface B of the male screw member 11 is thicker than 1/22 of the seal surface diameter, which is within the range of plastic buckling, although it depends on the size of the fit, Such buckling collapse usually does not occur. Of course, in order to draw out the increase effect of the contact surface pressure due to the internal pressure as much as possible, it is obvious that it should be as close to 1/22 as possible within the range not exceeding 1/22.

  The seal surface diameter of the seal surface B is the diameter of the male screw member at the center of the seal surface. The thickness of the sealing surface B of this male screw member is preferably 1/6 or less of the diameter of the sealing surface. If the thickness of the seal surface B is larger than this, seizure due to the fitting margin is likely to occur at the time of screwing, and the effect of increasing the seal surface contact surface pressure due to the internal pressure of the container becomes difficult to work. Thus, it is preferable that the thickness of the sealing surface B of the other member (male screw member) 11 is considerably reduced to 1/6 to 1/22 of the diameter of the portion.

  There is no particular guideline for the upper and lower limits of the diameter of the opening, but if the opening is too large or too small, very high machining accuracy is required. Therefore, in reality, it is considered to be in the range of about 20 mm to 500 mm. Of course, it can be applied to dimensions outside this range if the manufacturing technology and manufacturing cost allow.

  When the other member is a pipe connecting member having the through-hole 12, in any of the examples shown in FIGS. 7A to 7Q, basically, the inner diameter of the through-hole in the portion provided with the seal surface Is increased, the sealing surface B indicated by 13 can be made to have an appropriate thickness. However, since a rapid change in the diameter of the through hole causes erosion and the like, it is better not to change the inner diameter so much. Therefore, as shown in a, b, c, e, m, n, o, p, q in FIG. It is desirable to secure a predetermined seal surface thickness by thinning and to make the diameter of the through hole uniform.

  On the other hand, when the other member 11 is a sealing member having no through hole, as shown in FIGS. 1 to 4 (when there is no through hole 12 in the figure), the sealing surface B (13 ) Is provided at or near the front end of the other member 11, and the center portion is scraped off so that a necessary thick lip portion is formed around the end surface of the other member 11. This boring is applicable also when another member has the penetration steel 12, as shown in FIGS. In this way, a recess is formed on the end face of the other member leaving the necessary thickness. The depth of the recess may be such that the thickness of the seal surface B at the center of the seal surface B is in the above range. However, it is of course not preferable that the thickness of the male screw portion is made as thin as the sealing surface by making it too deep.

  Naturally, the sealing surfaces A and B of the pressure vessel 1 and the other member 11 are required to be smooth surfaces with small surface roughness in order to ensure sealing performance. When the seal surface is made of metal, it is desirable that the surface roughness be approximately Ra of 3.2 μm or less, although it depends on the applied surface treatment and lubricant. In order to further improve the sealing performance, one or both sealing surfaces may be plated with a soft material such as copper or tin, or a polymer or oil-based lubricant may be used.

Next, the effect of the present invention will be verified more specifically.
The pressure vessel seal structure according to the present invention shown in FIGS. 2 to 4 and the conventional pressure vessel seal structure of the packing system shown in FIG. 8 are tightened with a male screw member, which is another member, and then the internal pressure is determined by finite element analysis. An increasing simulation was performed to compare the contact surface pressures of the seal surfaces. As described above, the embodiment shown in FIG. 4 is an example that is not very desirable in that the taper angle of the seal surface is too large.

  Table 1 (analysis conditions) and Table 2 (material constants) show the specifications of the models used in this analysis. In Table 1, the seal surface diameter, the margin for fitting, and the seal surface thickness of the male screw member are all values at the center of the seal surface of the male screw member.

  The tightening conditions were all set until the screw stopper (torque shoulder) contacted. For the prior art (FIG. 8), tightening was completed when the packing thickness decreased by 1 mm.

A finite element analysis in which the internal pressure was gradually applied to 1000 atmospheres (100 MPa) was performed on each model that had been tightened.
FIG. 5 shows the relationship between the amount obtained by integrating the contact surface pressure of the sealing surface in the tightening process in the sealing direction (hereinafter simply referred to as contact surface pressure) and the tightening axial force. All of the seal structures of the present invention have a higher contact surface pressure than the prior art and have a gentler slope of the diagram, so that it can be seen that the seal structure is more stable than the prior art against fluctuations in the tightening axial force.

  FIG. 6 shows the relationship between the contact surface pressure and the working internal pressure during the internal pressure loading process. In the seal structure of the prior art, the contact surface pressure becomes zero near the internal pressure = 60 MPa, whereas in any of the seal structures of the present invention, the contact surface pressure remains even if the internal pressure is increased to 100 MPa. . Furthermore, more contact surface pressure remains in the embodiment of FIGS. 2 and 3 which is within the desired scope of the present invention than the embodiment of FIG. 4 which is within the scope of the present invention but is not desirable. I understand.

  As shown by these analysis results, the seal structure of the present invention has a much larger contact surface pressure of the seal surface than the conventional technology, and is more stable even if the tightening axial force fluctuates or a large internal pressure is applied. Yes.

The schematic diagram of the typical seal structure of this invention. The schematic diagram of the typical seal structure of the aspect of the shrink-fitting system of this invention. The schematic diagram of another aspect of the seal structure of this invention. The schematic diagram of the seal structure of another mode of the present invention. The figure explaining the analysis result of the relationship between the integral amount to the sealing direction of the contact surface pressure of a sealing surface, and a fastening axial force in a male screw member fastening process. The figure explaining the analysis result of the relationship between the amount of integrals in the sealing direction of the contact surface pressure of the seal surface in the process of internal pressure loading, and a working internal pressure. The schematic diagram which shows the various aspects of the seal structure of this invention. The schematic diagram which shows the various another aspect of the seal structure of this invention. The schematic diagram of the soft packing type seal structure of a prior art.

Explanation of symbols

  1: pressure vessel, 2: opening of pressure vessel, 3: seal surface A, 4: female screw portion, 5: torque shoulder of vessel, 11: other member (male screw member), 12: through hole, 13: seal surface B , 14: male thread portion, 15: torque shoulder of another member, 21: packing (O-ring), θ: taper angle of the seal surface with respect to the screwing direction

Claims (4)

A seal structure between a pipe connection part of a pressure vessel and an inner surface of an opening of a drain and an outer peripheral surface of another member attached to the opening, wherein the inner surface of the opening of the pressure vessel has at least one female screw part and at least one seal. The outer surface of the other member has at least one male screw portion and at least one seal surface B, and the seal surface B has a screwing shaft as a rotation axis and a diameter in the screwing direction. Is a conical surface, a curved rotating body surface, or a cylindrical surface, and the sealing surface A has a shape facing the sealing surface B, the male screw and the female screw portion are screwed together, and the sealing surfaces A and B are fitted together. And at least one torque shoulder in which the inner surface of the opening of the pressure vessel acts as a screwing stopper. For example, comprise at least one torque shoulder also corresponding outer peripheral surface of the other member, and, both sealing surfaces A and B are metal is steel or soft plated steel, prior to fastening at the center of the sealing surface B A sealing structure for a pressure vessel , wherein the fitting margin, which is the difference in diameter between the two sealing surfaces , is 0.1 to 2% of the diameter of the sealing surface B before screwing.   2. The pressure vessel sealing structure according to claim 1, wherein the sealing surfaces A and B are configured to closely contact each other by shrink fitting.   The thickness of the other member in the central portion of at least one sealing surface B of the other member is 1/22 or more and 1/6 or less of the diameter of the other member at the same position before fastening. 3. The pressure vessel seal structure according to 2. Sealing surface B is conical body surface or curvature rotational body surface, the tangent angle of the taper angle or average is within the range of 1 to 25 ° with respect to the center axis of the cone or curvature rotating body, according to claim 1 to 3 The pressure vessel seal structure according to any one of the above.

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