CA1280456C - All metal seal for pressure sealing - Google Patents
All metal seal for pressure sealingInfo
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- CA1280456C CA1280456C CA000516292A CA516292A CA1280456C CA 1280456 C CA1280456 C CA 1280456C CA 000516292 A CA000516292 A CA 000516292A CA 516292 A CA516292 A CA 516292A CA 1280456 C CA1280456 C CA 1280456C
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Abstract
ALL METAL SEAL FOR PRESSURE SEALING
ABSTRACT
A sealing connection (10) is disclosed which incorporates a metal-to-metal seal. The pin (22) extends to an end or snout having an outer annular frusto-conical primary sealing surface (36) and an inner frusto-conical secondary sealing surface (38). The line of intersection between the cones on which primary and secondary sealing surfaces lie on the pin define a hypothetical male sealing circle (40) of predetermined diameter. The box (24) defines a sealing pocket (32). The sealing pocket also includes an outer annular frusto-conical primary sealing surface (44) and an inner frusto-conical secondary sealing surface (46). The line of intersection between the cones on which the sealing surfaces of the box lie defines a hypothetical female sealing circle (48) having a diameter slightly less than the male sealing circle (40). This insures that the primary sealing surface on the male pin contacts the primary sealing surface on the female box and deflects the male end inward to form an effective metal-to-metal seal between the primary sealing surfaces when the pin engages the pocket. The primary sealing surface of the male member forms an angle relative to the center line less than the angle between the primary sealing surface of the female member and center line.
ABSTRACT
A sealing connection (10) is disclosed which incorporates a metal-to-metal seal. The pin (22) extends to an end or snout having an outer annular frusto-conical primary sealing surface (36) and an inner frusto-conical secondary sealing surface (38). The line of intersection between the cones on which primary and secondary sealing surfaces lie on the pin define a hypothetical male sealing circle (40) of predetermined diameter. The box (24) defines a sealing pocket (32). The sealing pocket also includes an outer annular frusto-conical primary sealing surface (44) and an inner frusto-conical secondary sealing surface (46). The line of intersection between the cones on which the sealing surfaces of the box lie defines a hypothetical female sealing circle (48) having a diameter slightly less than the male sealing circle (40). This insures that the primary sealing surface on the male pin contacts the primary sealing surface on the female box and deflects the male end inward to form an effective metal-to-metal seal between the primary sealing surfaces when the pin engages the pocket. The primary sealing surface of the male member forms an angle relative to the center line less than the angle between the primary sealing surface of the female member and center line.
Description
B-2~102 ~2~
ALL METAL SEAL FOR PRESSURE SEALING
TECHNICAL FIELD
This invention relates to sealing connections, and in particular to a self-sealing threaded connection for use in high pressure environments such as found in the petroleum industry.
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ALL METAL SEAL FOR PRESSURE SEALING
TECHNICAL FIELD
This invention relates to sealing connections, and in particular to a self-sealing threaded connection for use in high pressure environments such as found in the petroleum industry.
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2 1~ 5~
BACKGROUND OF THE INVENTION
The threaded connection of pipe to form a pipe string or line is common. Often, some type of sealing will be required in the connection to prevent high pressure material within the pipe from entering the thread area or passing to the exterior of the pipe. In other applications, the exterior of the pipe may have the high pressure environment from which the threads and interior of the pipe must be protected. One common use of such threaded connections is in the petroleum industry where long strings of pipe extend down hole into high pressure, hot and often corrosive environments.
Many prior seals have been formed in threaded connections with the use of a sealing element, such as an O-ring or compression seal. While these can be effective in certain circumstances, they have several disadvantages. Initially, it is difficult to assure that the operator places the seal element in the proper position as each threaded connection is made up. This is particularly so in the petroleum industry. The sealing elements may also be damaged while the connection is being made up and their service life is often quite short, particularly in hostile environments, requiring frequent replacement.
As noted, O-rings have previously been used to form the seal element. In a typical application, a first pipe section will have an end known as a pin or stinger which has a male thread. This end will be made up with an end of a second pipe which has a box with female threads for receiving the male threads of the first pipe. One or more O-rings will be positioned in annular grooves on either the pin or ~ 3 ~2~3~45~;
box to seal between the two pipe members. However, in higher pressure environments, these O-rings tend to extrude out from the grooves along the annular space between the two pipe elements, destroying the integrity of the seal.
In an effort to overcome the disadvantages of a separate seal element, attempts have been made to design a self-sealing threaded connection. One example is disclosed in U.S. Patent No. 3,489,437, issued January 13, 1970 to Duret. Other examples are disclosed in U.S. Patent No. 2,258,066 to Oyen; U.S.
Patent No. 2,793,059 to Woodling; U.S. Patent No~
BACKGROUND OF THE INVENTION
The threaded connection of pipe to form a pipe string or line is common. Often, some type of sealing will be required in the connection to prevent high pressure material within the pipe from entering the thread area or passing to the exterior of the pipe. In other applications, the exterior of the pipe may have the high pressure environment from which the threads and interior of the pipe must be protected. One common use of such threaded connections is in the petroleum industry where long strings of pipe extend down hole into high pressure, hot and often corrosive environments.
Many prior seals have been formed in threaded connections with the use of a sealing element, such as an O-ring or compression seal. While these can be effective in certain circumstances, they have several disadvantages. Initially, it is difficult to assure that the operator places the seal element in the proper position as each threaded connection is made up. This is particularly so in the petroleum industry. The sealing elements may also be damaged while the connection is being made up and their service life is often quite short, particularly in hostile environments, requiring frequent replacement.
As noted, O-rings have previously been used to form the seal element. In a typical application, a first pipe section will have an end known as a pin or stinger which has a male thread. This end will be made up with an end of a second pipe which has a box with female threads for receiving the male threads of the first pipe. One or more O-rings will be positioned in annular grooves on either the pin or ~ 3 ~2~3~45~;
box to seal between the two pipe members. However, in higher pressure environments, these O-rings tend to extrude out from the grooves along the annular space between the two pipe elements, destroying the integrity of the seal.
In an effort to overcome the disadvantages of a separate seal element, attempts have been made to design a self-sealing threaded connection. One example is disclosed in U.S. Patent No. 3,489,437, issued January 13, 1970 to Duret. Other examples are disclosed in U.S. Patent No. 2,258,066 to Oyen; U.S.
Patent No. 2,793,059 to Woodling; U.S. Patent No~
3,856,337 to Ehm; U.S. Patent No. 4,398,756 to Duret et al.; and U.S. Paten$ No. 4,489,963 to Raulins.
However, none of these prior sealing designs has proven totally satisfactory. Therefore, a need exists for a self-sealing threaded connection which will work reliably within the desired applications.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, a sealing connection is provided-for connecting a first member to a second member- with the passages through each of the members being connected. Each of the members has an elongate central axis. The first member has a male end. ~he male end tor snout) has an annular outer frusto-conical sealing surface facing radially outward from the central axis of the first member. The male end further has an annular inner frusto-conical surface facing radially inward toward the central axis of the first member. The minimum diameter of the outer sealing surface and the maximum diameter of the inner surface generally coincide. The intersection of the cone which contains the outer sealing surface and the cone which contains the inner surface defines a hypothetical male sealing circle of predetermined radius about the central axis of the first member The second pipe has a female sealing pocket. The female sealing pocket has an annular outer frusto-conical sealing surface facing radially inward toward the central axis of the second member. The sealing pocket also includes an annular inner frusto-conical ~5 surEace facing radially outward from the elongate axis of the second member. The minimum diameter of the ouker sealing surface of the sealing pocket and the maximum diameter of the inner surface of the sealing pocket generally coincide. The intersection of the cone which contains the inner surface and the cone which contains the outer sealing surface defines a hypothetical female sealing circle of second predetermined radius about the central axis of the second member.
~ 5 ~2~45~
The h~pothetical male sealing circle on the undeformed male end has a larger radius than the hypothetical female sealing circle. Structure is provided to urge the male outer frusto-conical sealing surface into contact with the female outer frusto-conical sealing surface, deflecting the male end radially inward and forming a seal therebetween.
In accordance with another aspect of the present invention, the outer frusto-conical sealing surface of the second member extends at an angle relative to the central axis of the second member be~ween about 10 and 45. The outer frusto-conical sealing surface on the male end extends at an angle from the center axis of the first member less than the angle of the frusto-conical sealing surface of the second member to ensure contact between the sealing surfaces. The inner frusto-conical surface of the first member extends at a lesser angle relative to its central axis than the inner frusto-conical surface of the second member to prevent contact between the inner surfaces prior to a seal being formed between the outer sealing surfaces.
~ 6 5~
BRIEF DESCRIPTION OF THE DRAWINGS
For a more complete understanding of the present invention, reference is now made to the following detailed description, taken in conjunction with the accompanying drawings, in which:
FIGURE 1 is a vertical cross-sectional view of a threaded connection between a first and second pipe;
FIGURES 2a and 2b illustrate a portion of the threaded connection illustrating how the male end of the pin contacts the female sealing pocket, with the male end being deflected radially inward against the sealing pocket to form a seal;
FIGURE 3 is a partial cross-sectional view of the end of the pin illustrating the configuration of the frusto-conical surfaces at the end;
FIGURE 4 is a partial cross-sectional view of the box i~lustrating the sealing pocket and the frusto-conical surfaces thereon;
FIGURE 5 is a partial cross-sectional view of the male threads;
FIGURE 6 is a partial cross-sectional view of the female threads; and FIGURES 7a-7c illustrate the sealing action of the sealing elements.
DETAILED DESCRIPTION
Referring now to the drawings, wherein like reference characters designate like or corresponding parts through several views, FIGURE 1 illustrates a sealing connection 10 forming a first embodiment of the present invention. The sealing connection 10 is made between a first pipe 12 and second pipe 14.
Both pipes 12 and 14 have a uniform thickness 16 along subst~n~ially their entire length and each has a central axis 13 or 15. The pipes define passages 18 and 20 therethrough which form a continuous passage for the flow of fluids and the like when the sealing connection 10 is made.
At the end of the pipe 12 illustrated, a male member or pin 22 is formed. Similarly, the illustrated end of the second pipe 14 defines a female member or box 24. In the usual case, pipe 12 will have a female member at its opposite end, and pipe 14 a male member at its opposite end for constructing a pipe string.
Preferably, but not necessarily, the pin 22 has a tapered male thread 26 which extends along most of the pin 22, except for an unthreaded male end or snout 28. As can be seen, the tapered threads taper radially inwardly toward the snout 28.
The box 24 has mating tapered female threads 30 formed on its inner surface which taper radially inwardly and terminate at a sealing pocket 32 formed in the box 24. It will be understood that, while the embodiment of the invention disclosed herein has tapered male and female threads 26 and 30, other mating thread configurations, as well as other structure for making up the seal, such as clamps, 8 ~8~5~
bolts etc. can be used while employing the advantages of the present invention.
With reference now to FIGURES 3 and 7a-c, the male end 28 of pin 22 can be seen to define an exterior cylindrical surface 34 which extends substantially parallel to the center axis 13 of the first pipe 12. The cylindrical surface 34 can be seen to merge into the male tapered threads 26 at one end thereof. However, the opposite end joins with an outer annular frusto-conical primary sealing surface 36. An inner annular frusto-conical secondary sealing surface 38 is also provided.
The secondary sealing surface 38 lies radially within the primary sealing surface 36. As can be seen, the minimum diameter of the primary sealing surface 36 is merged into the maximum diameter of the secondary sealing surface 38. Ideally, it would be preferred to have surfaces 36 and 38 intersect at a fixed angle. However, due to limitations in materials and cutting tools, there will always be a transition zone 37 between the surEaces 36 and 38, as best seen in FIGURES 7a-7c. Transition zone 37 preferably has a constant radius of curvature Rs.
If it were possible to form the surfaces 36 and 38 to intersect at a fixed angle, as illustrated by lines 100 and 102 in FIGURES 7a-7c, the circle defined by the intersection between the surfaces 36 and 38 would define a hypothetical male sealing circle 40 at a radius R1 from the center axis 13.
Hypothetical male sealing circle 40 corresponds to the circle of intersection between the cones on which surfaces 36 and 38 lie. The male sealing circle 40 would define the furthest extent of the pin 22 into the box 24 if it were possible to reduce Rs to zero.
With reference now to FIGURES 4 and 7a-c, the structure of the sealing pocket 32 of box 24 will be described in greater detail. The sealing pocket 32 defines an interior cylindrical surface 42 which extends generally along the center axis 15 of the second pipe 14. The edge of the cylindrical surface 4~ adjacent the end of the box 24 merges into the female tapered threads 30~ The opposite end of the cylindrical surface 42 transitions into an outer annular frusto~conical primary sealing surface 44 which generally faces radially inward. An inner annular frusto-conical secondary sealing surface 46 extends from the radially innermost portion of the primary sealing surface ~4 toward the center axis 13. Again, if it were possible, the surfaces 44 and ~6 would intersect at a fixed angle. However, a transition zone 45 is necessary which preferably has a constant radius of curvature Rp If it were possible to form surfaces 44 and 46 to intersect at a fixed angle, as illustrated by lines 104 and 106 in P'IGURES 7a~7c, the circle of intersection between surfaces 44 and 46 would define a hypothetical female sealing circle 48 have a radius from center axis 15 of R2. ~ypothetical female sealing circle 48 corresponds to the circle of intersection between the cones on which surfaces 44 and 46 lie. Preferably, Rs is longer than Rp so sealing contact between the pin 22 and pocket 32 is avoided within the transition zone 45. In one connection formed of 4130 steel, a radius Rs of 0.041" and a Rp of 0.031" proved satisfactory. A difference in radius of at least 0.010" is recommended as the tolerance in each of the cutting tools forming zones 37 and 45 is about ~8~5~i 0.005". For other types of materials or cutting techniques, the difference between Rs and Rp Should be sufficient to prevent bottoming out in spite of unavoidable variations in dimensional tolerances.
In the preferred embodiment, the diameter of the male sealing circle 40 when the male end is undeformed is larger than the diameter of the hypothetical female sealing circle 48 by the value ~R. The value of ~R will depend on the materials and dimensions of the pipes, and the function of the threaded connection. For a reusable threaded connection/ the value ~R is chosen so that neither the snout nor the sealing pocket will be plastically de~ormed as the seal is made between sealing surfaces 36 and 44. For example, a diameter difference ~R of O . nos inches for pipe made of 4130 steel with a four inch O.D. has proven satisfactory. With reference to FIGURES 2a and 2b, it can be seen that this assures that the primary sealing surface 36 on the pin 22 will contact the primary sealing surface 44 in the box 24 as the threads are made up. Further rotation of the first pipe into the second pipe will then cause the end 28 of pin 22 to deflect radially inward toward the now coincident center axes 13 and 15, while the box 24 will expand radially outward to a lesser degree at surface 44 due to the greater wall thickness relative to end 28, with a tight, virtually line contact metal-to-metal seal being formed between the primary sealing surfaces 36 and 44. If it were possible to form the materials of the connection with Rs and Rp approaching zero, the line of sealing contact would be between male sealing circlP 40 and a portion of surface 44. As actually constructed, the ~2~ 5~
seal contact will be virtually a line contact between portions of surfaces 36 and 44.
The outer annular frusto-conical prima-ry sealing surface 44 preferably lies at an angle to the center axis 15 of ~etween about 10 and 45, with the embodiment illustrated having an angle of about 30. To use an angle less than 10 would increase the risk of plastic deformation of the materials. To use an angle of more than 45 would increase the force necessary to make up the seal to an undesirable level. The outer annular frusto-conical primary sealin~ surface 36 also preferably lies at an angle to the center axis 13 in the same range as surface 44, but at an acute angle less than the angle of 1S surface 44. With the radius R1 of the undeformed hypothetical male sealing circle 40 greater than the radius R2 of the hypothetical female sealing circle 48, and taking into account average production tolerances and pin angular deflection upon sealing, the angle of surface 36 is preferably about 21~o less than the angle of surface 44. This angle dif~erence should be sufficient to consistently assure that line contact sealing will occur (as shown in Figs. 7b ~nd/or 7c) between the pin and the box even accounting for manufacturing tolerances and pin deflection. In the embodiment illustrated (see Fig.
3), the surface 36 lies at an angle of 271/2 to axis 13.
~he angles of intersection of surfaces 38 and 46 with axis 13 and 15 are selected so that surface 38 will not contact surface 46 as the primary seal is made between surfaces 36 and 44. Pre~erably the angle of intersection of surface 38 with its axis is 12 ~ 4 S~;
smaller than the angle of intersection of surface 46 with its axis to avoid such contact. In the-embodiment illustrated, the angles of surface 38 and surface 46 with their respective axes are 69D and 70, respectively, (or 21 and 20, respectively, relative to planes perpendicular to their axes as shown in FIGURES 3 and 4).
As the first pipe is threaded ever tighter into the second pipe, the radially inward deflection of the end 28 of the pin 22 simply increases the effectiveness of the seal between the primary sealing surface 36 and primary sealing surface 44. As torque is applied, the radius difference ~R will decrease as the end 28 and sealing poc3cet 32 deflect, as best seen in FIGURE 7b. While there will normally be a small gap between the secondary sealing surfaces 38 and 45, as seen in FIGURE 2b, due to their geometry, if sufEicient torque is applied, the end 28 and sealing pocket 32 can be so deformed as to create a Second seal between the secondary sealing surfaces 38 and 46 as best seen in FIGURE 7c. Preferably, the pipes 12 and 14 will be formed of materials, and the dimensions o~ the male end 28 and sealing pocket 32 will be such that the end 28 and sealing poclcet 32 are only elastically deformed when the joint is made up, permitting multiple use of the connection.
However, limited plastic deformation can be designed into the connection.
The primary seal between surfaces 36 and 44 is primarily for resisting bursting pressures from inside the pipes. Use of the secondary seal between surfaces 38 and 46 will provide added resistance to collapse pressures from without.
" 13 4~
As best seen in FIGURES 5 and 6, the tapered male and female threads 26 and 30 are pre~erably buttress threads. The engagement faces 50 a~d 52 of the threads which are in contact as the threaded connection is made up are preferably tilted at an angle of 3 from a plane perpendicular to the respective center axes 13 and 15 of the pipes and tilted in the direction of motion of the pin 22 as it is threaded into the box 24. The trailing faces 54 and 56 are preferably formed at an angle of about 10 relative to a plane perpendicular to the center axes 13 and 15 in the direction of movement of the pin 22 as it is unthreaded from the box 24. The height 58 of each tooth 60 on the male thread 26 is preferably less than the length of the tooth along the center axis 13. Similarly, the depth 62 of the helical groove 64 in the female threads 30 is also less than the length of the groove 64 along the center axis 15.
As can be seen, connection 10 is disclosed which is capable of multiple reuses while providing an effective metal-to-metal seal between the pin ~2 and box 24, without the need of any additional sealing members. While an effective seal is formed by the threaded connection 10, it can clearly be supplemented with other sealing techniques such as O-rings or compression seals. In addition, the make up force to form the sealed connection need not be supplied by a threaded engagement, but can be supplied by any suitable technique, such as clamps, bolts, etc.
Although a single embodiment of the invention has been illustrated in the accompanying drawings and ~lf~ 5~
described in the foregoing detailed description, it will be understood the invention is not limited to the embodiment disclosed, but is capable of ~umerous rearrangements, modifications and substitutiDns of parts and elements without departing from the spirit of the invention.
However, none of these prior sealing designs has proven totally satisfactory. Therefore, a need exists for a self-sealing threaded connection which will work reliably within the desired applications.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, a sealing connection is provided-for connecting a first member to a second member- with the passages through each of the members being connected. Each of the members has an elongate central axis. The first member has a male end. ~he male end tor snout) has an annular outer frusto-conical sealing surface facing radially outward from the central axis of the first member. The male end further has an annular inner frusto-conical surface facing radially inward toward the central axis of the first member. The minimum diameter of the outer sealing surface and the maximum diameter of the inner surface generally coincide. The intersection of the cone which contains the outer sealing surface and the cone which contains the inner surface defines a hypothetical male sealing circle of predetermined radius about the central axis of the first member The second pipe has a female sealing pocket. The female sealing pocket has an annular outer frusto-conical sealing surface facing radially inward toward the central axis of the second member. The sealing pocket also includes an annular inner frusto-conical ~5 surEace facing radially outward from the elongate axis of the second member. The minimum diameter of the ouker sealing surface of the sealing pocket and the maximum diameter of the inner surface of the sealing pocket generally coincide. The intersection of the cone which contains the inner surface and the cone which contains the outer sealing surface defines a hypothetical female sealing circle of second predetermined radius about the central axis of the second member.
~ 5 ~2~45~
The h~pothetical male sealing circle on the undeformed male end has a larger radius than the hypothetical female sealing circle. Structure is provided to urge the male outer frusto-conical sealing surface into contact with the female outer frusto-conical sealing surface, deflecting the male end radially inward and forming a seal therebetween.
In accordance with another aspect of the present invention, the outer frusto-conical sealing surface of the second member extends at an angle relative to the central axis of the second member be~ween about 10 and 45. The outer frusto-conical sealing surface on the male end extends at an angle from the center axis of the first member less than the angle of the frusto-conical sealing surface of the second member to ensure contact between the sealing surfaces. The inner frusto-conical surface of the first member extends at a lesser angle relative to its central axis than the inner frusto-conical surface of the second member to prevent contact between the inner surfaces prior to a seal being formed between the outer sealing surfaces.
~ 6 5~
BRIEF DESCRIPTION OF THE DRAWINGS
For a more complete understanding of the present invention, reference is now made to the following detailed description, taken in conjunction with the accompanying drawings, in which:
FIGURE 1 is a vertical cross-sectional view of a threaded connection between a first and second pipe;
FIGURES 2a and 2b illustrate a portion of the threaded connection illustrating how the male end of the pin contacts the female sealing pocket, with the male end being deflected radially inward against the sealing pocket to form a seal;
FIGURE 3 is a partial cross-sectional view of the end of the pin illustrating the configuration of the frusto-conical surfaces at the end;
FIGURE 4 is a partial cross-sectional view of the box i~lustrating the sealing pocket and the frusto-conical surfaces thereon;
FIGURE 5 is a partial cross-sectional view of the male threads;
FIGURE 6 is a partial cross-sectional view of the female threads; and FIGURES 7a-7c illustrate the sealing action of the sealing elements.
DETAILED DESCRIPTION
Referring now to the drawings, wherein like reference characters designate like or corresponding parts through several views, FIGURE 1 illustrates a sealing connection 10 forming a first embodiment of the present invention. The sealing connection 10 is made between a first pipe 12 and second pipe 14.
Both pipes 12 and 14 have a uniform thickness 16 along subst~n~ially their entire length and each has a central axis 13 or 15. The pipes define passages 18 and 20 therethrough which form a continuous passage for the flow of fluids and the like when the sealing connection 10 is made.
At the end of the pipe 12 illustrated, a male member or pin 22 is formed. Similarly, the illustrated end of the second pipe 14 defines a female member or box 24. In the usual case, pipe 12 will have a female member at its opposite end, and pipe 14 a male member at its opposite end for constructing a pipe string.
Preferably, but not necessarily, the pin 22 has a tapered male thread 26 which extends along most of the pin 22, except for an unthreaded male end or snout 28. As can be seen, the tapered threads taper radially inwardly toward the snout 28.
The box 24 has mating tapered female threads 30 formed on its inner surface which taper radially inwardly and terminate at a sealing pocket 32 formed in the box 24. It will be understood that, while the embodiment of the invention disclosed herein has tapered male and female threads 26 and 30, other mating thread configurations, as well as other structure for making up the seal, such as clamps, 8 ~8~5~
bolts etc. can be used while employing the advantages of the present invention.
With reference now to FIGURES 3 and 7a-c, the male end 28 of pin 22 can be seen to define an exterior cylindrical surface 34 which extends substantially parallel to the center axis 13 of the first pipe 12. The cylindrical surface 34 can be seen to merge into the male tapered threads 26 at one end thereof. However, the opposite end joins with an outer annular frusto-conical primary sealing surface 36. An inner annular frusto-conical secondary sealing surface 38 is also provided.
The secondary sealing surface 38 lies radially within the primary sealing surface 36. As can be seen, the minimum diameter of the primary sealing surface 36 is merged into the maximum diameter of the secondary sealing surface 38. Ideally, it would be preferred to have surfaces 36 and 38 intersect at a fixed angle. However, due to limitations in materials and cutting tools, there will always be a transition zone 37 between the surEaces 36 and 38, as best seen in FIGURES 7a-7c. Transition zone 37 preferably has a constant radius of curvature Rs.
If it were possible to form the surfaces 36 and 38 to intersect at a fixed angle, as illustrated by lines 100 and 102 in FIGURES 7a-7c, the circle defined by the intersection between the surfaces 36 and 38 would define a hypothetical male sealing circle 40 at a radius R1 from the center axis 13.
Hypothetical male sealing circle 40 corresponds to the circle of intersection between the cones on which surfaces 36 and 38 lie. The male sealing circle 40 would define the furthest extent of the pin 22 into the box 24 if it were possible to reduce Rs to zero.
With reference now to FIGURES 4 and 7a-c, the structure of the sealing pocket 32 of box 24 will be described in greater detail. The sealing pocket 32 defines an interior cylindrical surface 42 which extends generally along the center axis 15 of the second pipe 14. The edge of the cylindrical surface 4~ adjacent the end of the box 24 merges into the female tapered threads 30~ The opposite end of the cylindrical surface 42 transitions into an outer annular frusto~conical primary sealing surface 44 which generally faces radially inward. An inner annular frusto-conical secondary sealing surface 46 extends from the radially innermost portion of the primary sealing surface ~4 toward the center axis 13. Again, if it were possible, the surfaces 44 and ~6 would intersect at a fixed angle. However, a transition zone 45 is necessary which preferably has a constant radius of curvature Rp If it were possible to form surfaces 44 and 46 to intersect at a fixed angle, as illustrated by lines 104 and 106 in P'IGURES 7a~7c, the circle of intersection between surfaces 44 and 46 would define a hypothetical female sealing circle 48 have a radius from center axis 15 of R2. ~ypothetical female sealing circle 48 corresponds to the circle of intersection between the cones on which surfaces 44 and 46 lie. Preferably, Rs is longer than Rp so sealing contact between the pin 22 and pocket 32 is avoided within the transition zone 45. In one connection formed of 4130 steel, a radius Rs of 0.041" and a Rp of 0.031" proved satisfactory. A difference in radius of at least 0.010" is recommended as the tolerance in each of the cutting tools forming zones 37 and 45 is about ~8~5~i 0.005". For other types of materials or cutting techniques, the difference between Rs and Rp Should be sufficient to prevent bottoming out in spite of unavoidable variations in dimensional tolerances.
In the preferred embodiment, the diameter of the male sealing circle 40 when the male end is undeformed is larger than the diameter of the hypothetical female sealing circle 48 by the value ~R. The value of ~R will depend on the materials and dimensions of the pipes, and the function of the threaded connection. For a reusable threaded connection/ the value ~R is chosen so that neither the snout nor the sealing pocket will be plastically de~ormed as the seal is made between sealing surfaces 36 and 44. For example, a diameter difference ~R of O . nos inches for pipe made of 4130 steel with a four inch O.D. has proven satisfactory. With reference to FIGURES 2a and 2b, it can be seen that this assures that the primary sealing surface 36 on the pin 22 will contact the primary sealing surface 44 in the box 24 as the threads are made up. Further rotation of the first pipe into the second pipe will then cause the end 28 of pin 22 to deflect radially inward toward the now coincident center axes 13 and 15, while the box 24 will expand radially outward to a lesser degree at surface 44 due to the greater wall thickness relative to end 28, with a tight, virtually line contact metal-to-metal seal being formed between the primary sealing surfaces 36 and 44. If it were possible to form the materials of the connection with Rs and Rp approaching zero, the line of sealing contact would be between male sealing circlP 40 and a portion of surface 44. As actually constructed, the ~2~ 5~
seal contact will be virtually a line contact between portions of surfaces 36 and 44.
The outer annular frusto-conical prima-ry sealing surface 44 preferably lies at an angle to the center axis 15 of ~etween about 10 and 45, with the embodiment illustrated having an angle of about 30. To use an angle less than 10 would increase the risk of plastic deformation of the materials. To use an angle of more than 45 would increase the force necessary to make up the seal to an undesirable level. The outer annular frusto-conical primary sealin~ surface 36 also preferably lies at an angle to the center axis 13 in the same range as surface 44, but at an acute angle less than the angle of 1S surface 44. With the radius R1 of the undeformed hypothetical male sealing circle 40 greater than the radius R2 of the hypothetical female sealing circle 48, and taking into account average production tolerances and pin angular deflection upon sealing, the angle of surface 36 is preferably about 21~o less than the angle of surface 44. This angle dif~erence should be sufficient to consistently assure that line contact sealing will occur (as shown in Figs. 7b ~nd/or 7c) between the pin and the box even accounting for manufacturing tolerances and pin deflection. In the embodiment illustrated (see Fig.
3), the surface 36 lies at an angle of 271/2 to axis 13.
~he angles of intersection of surfaces 38 and 46 with axis 13 and 15 are selected so that surface 38 will not contact surface 46 as the primary seal is made between surfaces 36 and 44. Pre~erably the angle of intersection of surface 38 with its axis is 12 ~ 4 S~;
smaller than the angle of intersection of surface 46 with its axis to avoid such contact. In the-embodiment illustrated, the angles of surface 38 and surface 46 with their respective axes are 69D and 70, respectively, (or 21 and 20, respectively, relative to planes perpendicular to their axes as shown in FIGURES 3 and 4).
As the first pipe is threaded ever tighter into the second pipe, the radially inward deflection of the end 28 of the pin 22 simply increases the effectiveness of the seal between the primary sealing surface 36 and primary sealing surface 44. As torque is applied, the radius difference ~R will decrease as the end 28 and sealing poc3cet 32 deflect, as best seen in FIGURE 7b. While there will normally be a small gap between the secondary sealing surfaces 38 and 45, as seen in FIGURE 2b, due to their geometry, if sufEicient torque is applied, the end 28 and sealing pocket 32 can be so deformed as to create a Second seal between the secondary sealing surfaces 38 and 46 as best seen in FIGURE 7c. Preferably, the pipes 12 and 14 will be formed of materials, and the dimensions o~ the male end 28 and sealing pocket 32 will be such that the end 28 and sealing poclcet 32 are only elastically deformed when the joint is made up, permitting multiple use of the connection.
However, limited plastic deformation can be designed into the connection.
The primary seal between surfaces 36 and 44 is primarily for resisting bursting pressures from inside the pipes. Use of the secondary seal between surfaces 38 and 46 will provide added resistance to collapse pressures from without.
" 13 4~
As best seen in FIGURES 5 and 6, the tapered male and female threads 26 and 30 are pre~erably buttress threads. The engagement faces 50 a~d 52 of the threads which are in contact as the threaded connection is made up are preferably tilted at an angle of 3 from a plane perpendicular to the respective center axes 13 and 15 of the pipes and tilted in the direction of motion of the pin 22 as it is threaded into the box 24. The trailing faces 54 and 56 are preferably formed at an angle of about 10 relative to a plane perpendicular to the center axes 13 and 15 in the direction of movement of the pin 22 as it is unthreaded from the box 24. The height 58 of each tooth 60 on the male thread 26 is preferably less than the length of the tooth along the center axis 13. Similarly, the depth 62 of the helical groove 64 in the female threads 30 is also less than the length of the groove 64 along the center axis 15.
As can be seen, connection 10 is disclosed which is capable of multiple reuses while providing an effective metal-to-metal seal between the pin ~2 and box 24, without the need of any additional sealing members. While an effective seal is formed by the threaded connection 10, it can clearly be supplemented with other sealing techniques such as O-rings or compression seals. In addition, the make up force to form the sealed connection need not be supplied by a threaded engagement, but can be supplied by any suitable technique, such as clamps, bolts, etc.
Although a single embodiment of the invention has been illustrated in the accompanying drawings and ~lf~ 5~
described in the foregoing detailed description, it will be understood the invention is not limited to the embodiment disclosed, but is capable of ~umerous rearrangements, modifications and substitutiDns of parts and elements without departing from the spirit of the invention.
Claims (17)
1. A sealing connection for sealingly connecting a passage in a first member with a passage in a second member, each of said members having an elongate central axis, comprising:
a male portion on said first member, the male portion having a male end, the male end having an annular outer frusto-conical sealing surface facing radially outward from the central axis of the first member, the male end further having an annular inner frusto-conical surface facing radially toward the central axis of the first member, the minimum diameter of the outer sealing surface generally coinciding with the maximum diameter of the inner surface, the intersection of the cones on which the surfaces of the male end lie defining a hypothetical male sealing circle of predetermined diameter centered on the central axis of the first member;
a female portion on said second member, the female portion having a sealing pocket, the sealing pocket having an annular outer frusto-conical sealing surface facing radially toward the central axis of the second member, the sealing pocket further having an inner frusto-conical surface facing radially outward from the central axis of the second member, the minimum diameter of the outer sealing surface of the sealing pocket and the maximum diameter of the inner surface of the sealing pocket generally coinciding, the intersection of the cones on which the surfaces of the sealing pocket lie defining a hypothetical female sealing circle of second predetermined diameter centered on the central axis of the second member; and means for urging the sealing surfaces of said first and second members into engagement, the male sealing circle being of larger diameter than the female sealing circle when the male circle is undeformed so that the male outer frusto-conical sealing surface contacts the female outer frusto-conical sealing surface, deflecting the male end radially inward and forming a seal between the sealing surfaces.
a male portion on said first member, the male portion having a male end, the male end having an annular outer frusto-conical sealing surface facing radially outward from the central axis of the first member, the male end further having an annular inner frusto-conical surface facing radially toward the central axis of the first member, the minimum diameter of the outer sealing surface generally coinciding with the maximum diameter of the inner surface, the intersection of the cones on which the surfaces of the male end lie defining a hypothetical male sealing circle of predetermined diameter centered on the central axis of the first member;
a female portion on said second member, the female portion having a sealing pocket, the sealing pocket having an annular outer frusto-conical sealing surface facing radially toward the central axis of the second member, the sealing pocket further having an inner frusto-conical surface facing radially outward from the central axis of the second member, the minimum diameter of the outer sealing surface of the sealing pocket and the maximum diameter of the inner surface of the sealing pocket generally coinciding, the intersection of the cones on which the surfaces of the sealing pocket lie defining a hypothetical female sealing circle of second predetermined diameter centered on the central axis of the second member; and means for urging the sealing surfaces of said first and second members into engagement, the male sealing circle being of larger diameter than the female sealing circle when the male circle is undeformed so that the male outer frusto-conical sealing surface contacts the female outer frusto-conical sealing surface, deflecting the male end radially inward and forming a seal between the sealing surfaces.
2. The sealing connection of Claim 1 wherein the sealing surface on the female pocket forms an angle of between about 10° and 45° relative to the central axis of the second member; and the outer sealing surface on the male end forming an angle relative to the central axis of the first member less than the angle of the female sealing surface.
3. The sealing connection of Claim 1 wherein said male end has an exterior cylindrical surface centered about the central axis of the first member and said sealing pocket has an interior cylindrical surface centered on the central axis of the second member, the interior cylindrical surface having a slightly greater diameter than the exterior cylindrical surface to avoid interference as the seal is made up.
4. The sealing connection of Claim 1 wherein the inner surfaces of the male end and female sealing pocket form a stop and a secondary seal subsequent to formation of the primary seal as said urging means further deflects the male end.
5, The sealing connection of Claim 1 wherein mating threads on said first and second members form said means for urging the sealing surfaces into engagement.
6. The sealing connection of Claim 1 wherein the inner surface of the male end intersects the central axis of the first member at a smaller acute angle than the angle of intersection of the inner surface of the female pocket with the central axis of the second member.
7. The sealing connection of Claim 1 wherein the difference in the predetermined diameters of the sealing circles is selected to form a seal between the sealing surfaces without plastic deformation of the male end and female pocket.
8. The sealing connection of Claim 1 wherein said male end and female pocket each form a transition zone between the inner and outer surfaces, the transition zones having a constant radius with the radius of the transition zone on the male end being greater than the radius of the transition zone of the female pocket.
9. A sealing connection for sealingly connecting a passage in a first member with a passage in a second member, each of the members having an elongate central axis, comprising:
a pin formed on said first member, said pin including male threads, said male threads merging into an exterior cylindrical surface centered on the central axis of the first member, an outer annular frusto-conical primary sealing surface being formed at the other end of the exterior cylindrical surface and extending radially inward toward the central axis of the first member at an angle of less than about 45° and greater than about 10° relative to the central axis of the first member, the minimum diameter of the primary sealing surface generally coinciding with the maximum diameter of an inner annular frusto-conical secondary sealing surface extending radially inward of the primary sealing surface toward the central axis, the minimum diameter of the secondary sealing surface merging with the inner surface of the first pipe, the intersection of the cones on which the sealing surfaces of the pin lie defining a hypothetical male sealing circle having a predetermined diameter centered on the central axis of the first member;
a box formed on the second member, said box defining female threads, said female threads merging into an interior cylindrical surface centered about the central axis of the second member, the opposite end of the interior cylindrical surface mating with the maximum diameter of an annular frusto-conical primary sealing surface extending radially inward toward the central axis of the second member at an angle greater than the angle of the outer sealing surface on the pin, the minimum diameter of the primary sealing surface coinciding with the maximum diameter of an annular frusto-conical secondary sealing surface extending radially inward toward the central axis of the second pipe and positioned radially inward of the primary sealing surface, the minimum diameter of the secondary sealing surface coinciding with the inner diameter of the second pipe, the intersection of the cones on which the sealing surfaces of the box lie defining a hypothetical female sealing circle having a predetermined diameter centered on the central axis of the second member; and the diameter of the male sealing circle on the undeformed pin being greater than the diameter of the female sealing circle so that the male primary sealing surface contacts the female primary sealing surface as the threads are made up, the end of the pin being deflected radially inward to form a seal between the primary sealing surfaces.
a pin formed on said first member, said pin including male threads, said male threads merging into an exterior cylindrical surface centered on the central axis of the first member, an outer annular frusto-conical primary sealing surface being formed at the other end of the exterior cylindrical surface and extending radially inward toward the central axis of the first member at an angle of less than about 45° and greater than about 10° relative to the central axis of the first member, the minimum diameter of the primary sealing surface generally coinciding with the maximum diameter of an inner annular frusto-conical secondary sealing surface extending radially inward of the primary sealing surface toward the central axis, the minimum diameter of the secondary sealing surface merging with the inner surface of the first pipe, the intersection of the cones on which the sealing surfaces of the pin lie defining a hypothetical male sealing circle having a predetermined diameter centered on the central axis of the first member;
a box formed on the second member, said box defining female threads, said female threads merging into an interior cylindrical surface centered about the central axis of the second member, the opposite end of the interior cylindrical surface mating with the maximum diameter of an annular frusto-conical primary sealing surface extending radially inward toward the central axis of the second member at an angle greater than the angle of the outer sealing surface on the pin, the minimum diameter of the primary sealing surface coinciding with the maximum diameter of an annular frusto-conical secondary sealing surface extending radially inward toward the central axis of the second pipe and positioned radially inward of the primary sealing surface, the minimum diameter of the secondary sealing surface coinciding with the inner diameter of the second pipe, the intersection of the cones on which the sealing surfaces of the box lie defining a hypothetical female sealing circle having a predetermined diameter centered on the central axis of the second member; and the diameter of the male sealing circle on the undeformed pin being greater than the diameter of the female sealing circle so that the male primary sealing surface contacts the female primary sealing surface as the threads are made up, the end of the pin being deflected radially inward to form a seal between the primary sealing surfaces.
10. The sealing connection of Claim 9 wherein said threads are tapered buttress threads.
11. The sealing connection of Claim 9 wherein the exterior cylindrical surface of the pin is smaller in diameter than the interior cylindrical surface of the box to avoid interference as the threads are made up.
12. The sealing connection of Claim 9 wherein the male sealing circle of the undeformed pin has a diameter in excess of the diameter of the female sealing circle so that the material of the pin and box is elastically deformed as the seal is formed.
13. The sealing connection of Claim 9 wherein the inner sealing surface of the pin intersects the central axis of the first member at a smaller angle than the intersection of the inner sealing surface of the pocket and the central axis of the second member to prevent engagement of the inner sealing surfaces until the outer sealing surfaces are sealingly engaged as the threads are made up.
14. The sealing connection of Claim 9 wherein said pin and pocket each form a transition zone between the inner and outer sealing surfaces thereof, the zones each having a constant radius, with the radius of the zone on the pin being greater than the radius of the zone on the pocket to maintain a line seal between the outer surfaces of the members.
15. A member having a male threaded end for engagement with a female threaded end of another member and a female threaded end for engagement with the male threaded end of a third member, said member having a center axis and including:
a generally uniform diameter portion extending between the male and female threaded ends and defining a passage therethrough;
the male threaded end having a male threaded portion, the male end further defining a snout having an outer annular frusto-conical primary sealing surface having a maximum diameter approximately the same diameter as the minimum diameter male thread and extending toward the center axis of the pipe at an angle between about 10°and 45°, the snout further having an inner annular frusto-conical secondary sealing surface positioned radially inward of the primary sealing surface with the minimum diameter of the primary sealing surface generally coinciding with the maximum diameter of the secondary sealing surface to form a transition zone of constant radius, the cones on which the sealing surfaces of the male threaded end lie intersecting at a male sealing circle of predetermined diameter centered on the center axis of the member, the secondary sealing surface extending radially inward to intersect the inner surface of the member;
the female threaded end defining female threads, said female end further defining a sealing pocket having an outer annular frusto-conical primary sealing surface having a maximum diameter generally equal to the minimum diameter female thread, said primary sealing surface extending radially inward at an angle relative to the center axis of the member greater than the angle of the primary sealing surface of the male threaded end, said sealing pocket defining an inner annular frusto-conical secondary sealing surface positioned radially inward of the primary sealing surface, the minimum diameter of the primary sealing surface generally coinciding with the maximum diameter of the secondary sealing surface to form a transition zone of constant radius less than the radius of the transition zone on the male threaded end, the cones on which the sealing surfaces of the female threaded end lie intersecting at a female sealing circle of predetermined diameter, said secondary sealing surface extending radially inward at an angle relative to the center axis of the member to merge with the inner surface of the member, the female sealing circle having a diameter slightly less than the male sealing circle of the undeformed male threaded circle.
a generally uniform diameter portion extending between the male and female threaded ends and defining a passage therethrough;
the male threaded end having a male threaded portion, the male end further defining a snout having an outer annular frusto-conical primary sealing surface having a maximum diameter approximately the same diameter as the minimum diameter male thread and extending toward the center axis of the pipe at an angle between about 10°and 45°, the snout further having an inner annular frusto-conical secondary sealing surface positioned radially inward of the primary sealing surface with the minimum diameter of the primary sealing surface generally coinciding with the maximum diameter of the secondary sealing surface to form a transition zone of constant radius, the cones on which the sealing surfaces of the male threaded end lie intersecting at a male sealing circle of predetermined diameter centered on the center axis of the member, the secondary sealing surface extending radially inward to intersect the inner surface of the member;
the female threaded end defining female threads, said female end further defining a sealing pocket having an outer annular frusto-conical primary sealing surface having a maximum diameter generally equal to the minimum diameter female thread, said primary sealing surface extending radially inward at an angle relative to the center axis of the member greater than the angle of the primary sealing surface of the male threaded end, said sealing pocket defining an inner annular frusto-conical secondary sealing surface positioned radially inward of the primary sealing surface, the minimum diameter of the primary sealing surface generally coinciding with the maximum diameter of the secondary sealing surface to form a transition zone of constant radius less than the radius of the transition zone on the male threaded end, the cones on which the sealing surfaces of the female threaded end lie intersecting at a female sealing circle of predetermined diameter, said secondary sealing surface extending radially inward at an angle relative to the center axis of the member to merge with the inner surface of the member, the female sealing circle having a diameter slightly less than the male sealing circle of the undeformed male threaded circle.
16. The member of Claim 15 wherein said threads are tapered and a cylindrical transition surface is formed between the smallest diameter threads and the maximum diameter of the primary sealing surfaces.
17. The member of Claim 15 wherein the male sealing circle has a diameter only sufficiently greater than the female seal circle diameter to ensure an effective seal without substantial plastic deformation of the member.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000516292A CA1280456C (en) | 1986-08-19 | 1986-08-19 | All metal seal for pressure sealing |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000516292A CA1280456C (en) | 1986-08-19 | 1986-08-19 | All metal seal for pressure sealing |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1280456C true CA1280456C (en) | 1991-02-19 |
Family
ID=4133758
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000516292A Expired - Fee Related CA1280456C (en) | 1986-08-19 | 1986-08-19 | All metal seal for pressure sealing |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1280456C (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102032401A (en) * | 2010-12-29 | 2011-04-27 | 海盐管件制造有限公司 | Metal-to-metal sharp angle seal welding pipe joint |
-
1986
- 1986-08-19 CA CA000516292A patent/CA1280456C/en not_active Expired - Fee Related
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102032401A (en) * | 2010-12-29 | 2011-04-27 | 海盐管件制造有限公司 | Metal-to-metal sharp angle seal welding pipe joint |
| CN102032401B (en) * | 2010-12-29 | 2012-10-31 | 海盐管件制造有限公司 | Metal-to-metal sharp angle seal welding pipe joint |
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