GB2279118A - Pipe joint seal - Google Patents

Abstract

Axially movable metal seal members 18/25 are forced together by end wall 21 from a position shown in fig. 2 to a position shown in fig. 3. In so doing member 18 is twisted and forces leg 25A into sealing engagement with wall 20. A double seal is shown in figs. 4 and 5. Deep sea oil or gas use. <IMAGE>

Description

SEALING ASSEMBLY This invention relates generally to an assembly for sealing between the tubular members of a tubular connection. More particularly, it relates to improvements in an assembly of this type which is made of non-elastomeric, relatively rigid material and disposed within an annular space formed between the members in position to be deformed into sealing engagement with the sides of the space in response to relative longitudinal movement between the end walls of the space.

There are many environments in which seal assemblies made of elastomeric material are unsatisfactory because of their inability to withstand high temperatures and/or the corrosive action of the fluids being controlled. This may be true, for example, when the tubular connector is part of a pipe string disposable at great depth within an oil or gas well.

Hence, in these and similar environments, it has been proposed to use seal assemblies made of metal or other nonelastomeric, relatively rigid materials.

Conventional metal seal assemblies, such as hollow metal O-rings, are not entirely satisfactory for these purposes. Thus, for one thing, the O-ring is difficult to install with the proper interference or precompression between its inner and outer sides and the members with which it is to sealably engage. Furthermore, the tolerance between the O-ring and the sides with which it interferes may not permit large ranges of expansion and contraction between the members without the risk of leakage.

In another less conventional non-elastomeric seal assembly manufactured and sold by the assignee of the present application, a metal ring of generally trapezoidal configuration is installed within an annular space formed between the tubular members having end walls which are movable relatively toward one another, with one end wall being shaped conically to conform to one end of the ring, so that, as the end walls are moved relatively toward one another, the ring is compressed between them to sealably engage with the inner and outer sides of the space. More particularly, a relief or gap formed about the outer side of the ring is partially closed, as the ring is compressed, to cause longitudinally spaced sealing surfaces of the ring to sealably engage oppositely disposed surfaces of the tubular members on the inner and outer sides of the space.

Under anticipated loads, the gap merely closes at least in part to provide a spring force for maintaining the sealing surfaces sealably engaged despite expansion and contraction of the connection.

Although a substantial improvement over a metal O-ring, this type of seal assembly is not entirely satisfactory in the case of heavier loads, because, in that case, the gap is closed and the ring "crushed" by the compressive force of the one end wall to the extent that it is unable to adequately compensate for expansion and contraction. It is therefore amongst the objects of this invention to provide a seal assembly of relatively rigid, non-elastomeric material which is of such construction that, like the assembly described above, it is adapted to be activated by relative movement of the end walls of the space toward one another, but which is able to maintain a tight seal between the tubular members despite expansion and contraction.

This and other objects are accomplished, in accordance with a preferred embodiment, by a ~~~~~~~~~~~~~ seal assembly of the type described comprising a first generally U-shaped ring of relatively rigid, nonelastomeric material having an outer leg disposable adjacent the outer wall, an inner leg adjacent the inner wall and a closed end adjacent one end wall of the space, and a second, substantially flat ring of relatively rigid, non-elastomeric material having one end which is disposable intermediate the open end of the first ring and the other end wall of the space in a position to be moved. More particularly, the outer sides of the legs of the first ring and the inner sides of the second ring have longitudinally spaced, annular bearing surfaces which so are arranged and constructed to slidably engage one another, as the one end of the ring is initially moved into the open end of the first ring, in response to relative movement of the end walls toward one another, and then, in response to continued relative movement of the end walls toward one another to move it further into the open end of the first ring, wedge the outer sides of the legs tightly against the sides of the space and thus produce a couple which twists the second ring whereby a torsional spring force is built into the second ring to maintain the outer sides of the first ring against the sides of the space despite expansion and contraction of the members in either a radial or longitudinal sense.

In the illustrated embodiment, ~~~~~~~~~~~~~~~~ one of the legs of the first ring is longer than the other, the inner and outer sides of the second ring taper toward one another in a direction toward its one end, and the bearing surfaces on the legs are near their outer ends, whereby the second ring is twisted in a direction to move its outer end toward the side of the space on which the shorter leg is disposed. More particularly, the longer leg is disposable on the outer side of the space and the shorter leg is disposable on the inner side of the space.

In an alternative embodiment, the assembly includes a second set of first and second rings with the closed end of the first ring of the second set disposable adjacent the other end wall of the space and its legs facing those of the first ring of the first set, and the outer end of the second ring of the second set being engagable with the outer end of the second ring of the first set to force their inner ends between the legs of the first rings upon relative movement of the end walls of the space toward one another. Thus, the assembly is particularly effective in sealing against high pressure differentials in either axial direction.

In the drawings, wherein like reference characters are used throughout to designate like parts: FIG. 1 is a longitudinal sectional view of a tubular connector having an annular space between the members in which one embodiment of a seal assembly constructed in accordance with the present invention is disposed to seal between the tubular members; FIGS. 2 and 3 are enlarged sectional views of the connector of FIG. 1 with the rings of the seal assembly shown in FIG. 2 prior to activation of the seal assembly and in FIG. 3 upon movement of the end walls of the space relatively toward one another to activate the seal assembly; FIGS. 4 and 5 are longitudinal sectional views of a tubular connector similar to that of FIGS. 1 to 3, but with a seal assembly constructed in accordance with an alternative embodiment of the invention in which the two sets of rings are shown in FIG. 4 prior to activation of the seal assembly and in FIG. 5 upon activation of the seal assembly in response to relative axial movement of the end walls of the annular space toward one another.

With reference now to the details of FIGS. 1 to 3, the over-all tubular connector, which is indicated in its entirety by reference character 10, is shown to comprise tubular members 11 and 12 connected together in coaxial relation, and typically forming part of a pipe string disposed in an oil or gas well, at a depth in which the temperature as well as the pressure contained in the pipe string may be high. In the illustrated embodiment of the connector 10, it also includes a nut 13 received between the tubular members 11 and 12 and having male threads for connection to the female threads of the tubular member 12 in order to draw the tubular member 12 upwardly with respect to the tubular member 11 as they are connected to one another. More particularly, the tubular connector also includes a ring 14 seated upon an internal shoulder 15 of the tubular member 12 and a shoulder 16 on its inner side engagable with a downwardly facing shoulder on the tubular member 11 as the tubular member 12 as the nut 13 is made up.

As best shown in FIGS. 2 and 3, an annular space 17 is thus formed between the members for receiving a seal assembly 18 adapted to seal between the tubular members when activated in a manner to be described. More particularly, this annular space includes an inner side 19 on the outer diameter of tubular member 11 and an outer side 20 on the inner diameter of tubular member 12, an upper end 21 beneath a flange 23 about the tubular member 11 and a lower end 24 at the upper end of the ring 14. As best shown in FIGS. 2 and 3, upon make-up of nut 13 to connect the tubular members to one another, the lower end 24 is moved relatively upwardly with respect to the upper end 23 to shorten the height of the space and, thus, as will be described to follow, thereby activate the seal assembly 18 disposed within the space.

As best shown in FIGS. 2 and 3, the seal assembly 18 includes a first generally U-shaped ring of relatively rigid, non-elastic material, such as metal, having its closed end adjacent the upper end 21 of the space and its open legs facing downwardly toward the end 24 of the space.

The ring 25 is of a radial thickness somewhat less than the width of the space so that its legs are spaced slightly from the sides of the space, and the outer leg 25A is longer than its inner leg 25B.

The seal assembly 18 also includes a second generally flat ring 26 which is also made of a non-elastomeric, relatively rigid material, such as metal, and disposed, prior to activation (FIG. 2) of the seal assembly, intermediate the open ends of the legs of the ring 25 and the lower end 24 of the space. The sides of the upper portion of the ring 26 taper upwardly toward one another to form a relatively narrow upper end 26A, and the inner corner of the lower end of the ring is considerably thinner than the space so that its sides are spaced therefrom, with its relatively flat lower end 26B being supported on the lower end 24 of the space.

During installation, the seal assembly may be supported on the ring 14 within the tubular member 12 as the tubular member 11 is moved axially into a position in which its flange 13 is above the upper end of ring 25, after which make-up of the nut with the tubular member 12 lowers the flange and thus the upper end of the space with respect to its upper end. More particularly, during initial make-up of the nut 13, the lower side of the flange and thus the upper end 23 of the space, is in the upper position with respect to the lower end 24 shown in FIG. 2.

At this time, of course, the upper end 26A of the ring 26 has just moved between the open ends of the legs of the ring 25 and the outer sides of the legs 25A and 25B are spaced from the sides of the space 17.

As the nut 13 continues to be made up, so as to move the end walls 23 and 24 relatively toward one another, the upper end 26A of the ring 26 moves further upwardly into the open ends of the legs 25A and 25B of the ring 25. As this occurs, annular bearing surfaces 30 and 31 about the outer and inner sides, respectively, of the ring 25 slidably engage annular bearing surfaces 32 and 33 on the inner sides of the legs 25A and 25B, respectively, of the ring 25. Thus, the effective greater width of the upper portion of the ring 25, intermediate bearing surfaces 30 and 31, will wedge the leg 25 outwardly and the inner leg 25 inwardly against the sides of the space.

As this occurs, the continuing movement of the larger effective width of the ring between the legs of ring 15 creates a couple due to the longitudinally spaced lines of force exerted on the bearing surfaces 30 and 31 to cause the ring 26 to be twisted in a counterclockwise direction from the position of FIG. 2 to the position of FIG. 3. As the ring 26 is twisted in this manner, the inner side of its lower end is free to swing toward the inner side 19 of the space.

Consequently, a torsional force is built into the ring 26 for maintaining the outer sides of the legs of the ring 25 in tight sealing engagement with the inner and outer sides of the space. Thus, even in the event of relatively large expansions and contractions of the space, whether in a longitudinal direction or a radial direction, the spring force built into the ring will continue to force the legs of ring 25 into tight sealing engagement with the inner and outer sides of the space. As will be understood, although the seal assembly is effective to seal against pressure differentials in either direction, its disposal with its open ends of its legs facing downwardly will provide the most effective seal against the higher pressure normally existing within the tubular connector.

The tubular connection shown in FIGS. 4 and 5, and indicated in its entirety by reference character 30, is basically similar to the tubular connector 10 in that it includes tubular members 31 and 32 which are to be connected to one another, with the tubular member 31 having a flange 33 about its outer side and the member 32 supporting a ring 34 beneath the flange 23 in position to be moved relatively toward and away from one another upon make-up of a nut (not shown) connected to the upper end of tubular member 31. Thus, as in the case of the tubular connector of FIGS. 1 to 3, an annular space 35 is formed between the members to receive a sealing assembly for sealing between the members, as will be described to follow. More particularly, this space includes an outer side 36 within the tubular member 32, an inner side 37 within the tubular member 31, an upper end :38 on the lower end of flange 33, and a lower end 39 at the upper end of the thrust ring 34. Due to the construction of the alternative form of the seal assembly, as will be described to follow, the parts of the connector are of such construction and arrangement as to form a somewhat longer space than is formed in the case of the tubular connector of FIGS. 1 to 3.

In this alternative embodiment of the seal assembly, indicated in its entirety by reference character 40, there is included a pair of U-shaped rings 41 having outer and inner legs 41B and 41A of non-elastic, relatively rigid material, such as metal, as well as a pair of relatively flat rings 42, also of non-elastic, relatively rigid material, such as metal of substantially less width than that of the space. More particularly, the upper ring 41 is arranged with its closed end adjacent the upper end 38 of the space and its legs 41A and 41B facing downwardly, while the lower of the rings 41 is disposed with its closed end adjacent the lower end 39 of the space and its legs 41 and 41B facing upwardly, whereby its open end faces the open end of the upper ring 41. As in the case of the first described embodiment, the outer sides of the legs are spaced from the sides of the space, prior to activation, and the outer legs 41 are longer than the legs 41B.

Each of the second relatively flat rings 42 is also of generally the same shape and size as the ring 30 of the first described embodiment, and, as in the case of that embodiment, is initially disposed with one end opposite the open end of one of the rings 41. Thus, as shown in FIGS.

4 and 5, the rings 42 are arranged opposite one another so that the relatively narrow end of each faces the open end of the legs of one of the rings 41. More particularly, during make-up of the tubular members with one another to form the tubular connector, the relatively flat ends 42B of the rings 42 engage with one another so that, as the tubular members are connected to one another so as to move the ends of the space toward one another, the smaller ends of the rings 41 move into the open ends of the oppositely facing first rings 41.

As the nut of the connector continues to be made up to move the ends of the space relatively toward one another, longitudinally spaced, annular bearing surfaces 43 and 44 about the rings 42 are caused to slidably engage annular bearing surfaces 45 and 46, respectively, on the inner sides of the legs of the ring 41 so as to cause the outer sides of the legs to move against the inner and outer sides of the space. As the ends of the space continue to be moved relatively toward one another, the effectively wider lower portions of the rings wedge the legs of the rings 41 into tight engagement with the inner and outer sides of the space.

As this occurs, the longitudinally spaced lines of force exerted on the ring will exert a couple which causes them to be twisted and thus build a torsion spring force into each for purposes previously described. Thus, as shown in FIG. 5, the upper ring 42 is caused to twist in a counterclock-wise direction, while the lower ring 42 is caused to twist in a clockwise direction. In each case, the inner edges of the ends 42B of the rings 42 are free to move toward the inner side of the space, this movement being permitted by the initial spacing of the inner edges of the ends 42 a substantial distance from the inner side of the space in the position shown in FIG. 4.

As previously mentioned, this embodiment ~ - not only provides redundant sealing capacity, but also provides optimum sealing against a higher pressure in either an upward or downward direction.

It will be understood by those skilled in the art that the particular construction and arrangement of the U-shaped and relatively flat rings making up the seal assemblies may be other than that shown and described. For example, the legs of the U-shaped ring may be of the same or substantially same length, and the sides of the relatively flat ring may be parallel or substantially parallel to one another, with appropriate modifications to their oppositely facing sides to accomplish the purposes of this invention.

Thus, for example, the U-shaped ring could be made of equal length by an appropriate shaping of the sides of the relatively flat ring, and that the sides of the relatively flat ring could be made parallel by appropriate shaping of the inner sides of the legs of the U-shaped ring. However, the arrangement shown is preferred due, among other things, to the simplicity of the construction of the rings.

Claims (5)

1. An assembly for sealing between the inner and outer tubular members of a tubular connector forming an annular space between them having inner and outer walls and end walls which are moveable relatively toward one another, the assembly comprising a first generally U-shaped ring of relatively rigid, non-elastomeric material having an outer leg disposable adjacent the outer wall, an inner leg adjacent the inner wall and a closed end adjacent one end wall, and a second, substantially flat ring of relatively rigid, non-elastomeric material having one end which is disposable intermediate the open end of the first ring and the other end wall of the space in position to be moved into the open end of the first ring upon relative movement of the end walls toward one another, the inner sides of the legs of the first ring and the outer sides of the second ring having longitudinally spaced, annular bearing surfaces which so are arranged and constructed to slidably engage one another, as the one end of the ring is initially moved into the open end of the first ring, and then, in response to continued relative movement of the end walls toward one another, wedge the outer sides of the legs tightly against the sides of the space and produce a couple which causes the second ring to be twisted into a shape which provides a torsional spring force to maintain the outer sides of the first ring against the sides of the space.

2. An assembly as claimed in Claim 1, wherein one of the legs of the first ring is larger than the other, and the inner and outer sides of the second ring taper toward one another in a direction toward its one end, and the bearing surfaces on the legs are near their outer ends, whereby the second ring is twisted in a direction to move its outer end toward the side of the space on which the shorter leg is disposed.

3. An assembly as claimed in Claim 2, wherein the longer leg is disposable on the outer side of the space and the shorter leg is disposable on the inner side of the space.

4. An assembly as claimed in any preceding Claim, including a second set of first and second rings with the closed end of the first ring of the second set disposable adjacent the other end wall and its legs facing those of the first ring of the first set and the outer end of the second ring of the second set being engageable with the outer end of the second set of the first set to force their inner ends between the legs of the first rings upon relative movement of the end walls of the space toward one another.

5. An assembly substantially as hereinbefore described and illustrated in the accompanying drawings.