GB2235741A

GB2235741A - Improved bore seal

Info

Publication number: GB2235741A
Application number: GB9016796A
Authority: GB
Inventors: Raymond E Latham
Original assignee: Reflange Inc
Current assignee: Reflange Inc
Priority date: 1989-08-01
Filing date: 1990-07-31
Publication date: 1991-03-13
Also published as: GB9016796D0; CA2022405A1

Abstract

An annular bore seal for sealing between connected first and second coaxially aligned members, each of which is provided with an internal seating surface tapering inwardly from their adjoining ends. The seal comprises: an inner cylindrical surface; annular end surfaces; peripheral sealing surfaces adjacent to and tapering outwardly from the end surfaces; an outer alignment ring surface formed midway between the end surfaces; and annular relieved areas between the alignment ring and the sealing surfaces. The taper angle of the sealing surfaces varies from the taper angle of the seating surfaces. <IMAGE>

Description

IMPROVED BORE SEAL The present invention generally relates to fluid seals. More particularly, the present invention relates to an improved annular seal for sealing the connection between coaxially aligned members, said seal provided with a plurality of alignment surfaces.

There exists a variety of seals or gaskets which are used to seal between flanges or other types of connectors. Such prior art seals may be generally categorized as those sealing elements which seal on the bore and those elements which seal on the face of the connector. In both categories, sealing may be achieved by crushing or yielding the gasket; by elastically loading a flexible-gasket utilizing a soft coating or plating on the seal surface; or by a combination of the two. These seals may or may not be pressure energized as dictated by their relative geometry and location in the connector.

Because of their relatively massive cross sections, some bore seals require considerably more bolt up loading then do face seals. Alternatively, bore seals may be more economical due to lower manufacturing tolerances.

Additionally, many or most bore seals are self centering, whereas face seals are generally extremely sensitive to misalignment. Flexible bore seals are particularly adaptable to high temperature use because they are radically compressed during make-up, resulting in residual seal loading.

Some prior art bore seals include a design having a flange portion oppositely disposed flexible lips and a centrally disposed rib portion. The lips of the seal are provided with annular sealing surfaces which taper outwardly toward the rib portion. Disadvantages, however, exist in the manufacture of such a design.

While this type of seal is basically a bore seal, it incorporates some of the characteristics of a face seal, due to the presence of the rib portion which is normally disposed between the end faces of the connectors with which it is used. As a result, such a design requires higher manufacturing tolerances and is therefore more expensive to manufacture.

One solution to this problem was posed by Latham, as disclosed in U.S. Patent No. 4,214,763. Latham discloses a flexible annular bore seal for sealing between first and second coaxially aligned members. In Latham, each of the first and second coaxially aligned members are provided with an internal frusto-conical sealing surface tapering inwardly toward the adjoining ends.

Disadvantages, however, exist with this design since manufacturing tolerances utilized during manufacture may cause the seal to engage its seat with nonuniform contact pressures during make-up of the connector. Such nonuniformity offers the possibility of a leak path in the seal.

The present invention addresses the above-referenced disadvantages of annular bore seals by providing a seal design which substantially diminishes the possibility of nonuniformity during make-up of the seal. In such a fashion, the present seal design generally allows for the formation of a substantially leak free annular bore seal.

The present invention generally comprises a seal with outwardly tapering peripheral sealing surfaces adjacent each of the annular end surfaces, where the taper angle of each of the sealing surfaces varies slightly from the taper angle of the seating surfaces.

In preferred embodiments, there also exists internal variations in the taper angle of the sealing surfaces themselves. Thus, a reduced portion of the sealing surface is brought in contact with the seating surface preliminary to engagement of the seal.

One or more relief rings are formed along the sealing surfaces. Preferably, these relief rings are parallel to the inner cylindrical surfaces of the coaxially aligned members. The length of these relief rings is variable dependent on the desired application for the seal.

Such a design has a number of advantages. For example, the present design serves to reduce friction between the sealing and seating surfaces which allows slight rotation and movement of the seal during make-up.

This is accomplished since during make-up or engagement of the seal, the connector sealing surface, having a diminished contact area, is able to rotate to a position which allows contact pressure between the sealing surface and the seating surface to be spread more uniformly over the engagement area. After make-up, the connector is held securely in radial compression by conventional boltup flanges. Upon compression, the taper angle of the connector sealing surface substantially conforms to that of the seat. Compression also defines a relief area between the seating and sealing members as determined in part by the dimension of the relief ring(s).

In such a fashion, the seal design of the present invention incorporates the features of a predetermined sealing area and load and accomplishes the benefit of pressure energization, reduced turbulence, and economical manufacturing.

Figure 1 is a perspective view illustrating a clamp type connection incorporating a seal of the present invention.

Figure 2 is a partial, cross section of a clamp type connection incorporating a seal of the present invention.

Figure 3 is a detailed view illustrating the sealing surface of the present invention incorporated in a connector shown in association with a seating surface.

Figure 4 is a detailed view of a preferred embodiment of the present invention illustrating the angular relationship of the sealing surfaces to the seating surfaces prior to make-up of the seal.

Figure 5 is a detailed view of the embodiment illustrated in Figure 4 subsequent to a substantial makeup of the seal.

Figure 1 represents a perspective view of coaxially aligned pipe sections 2 and 12 connected by a pair of flanges 4 and 10, respectively. Flanges 4 and 10 may be attached to the pipe sections 2 and 12 by welding, as illustrated at 3 and 11, or by any other suitable means.

Flanges 4 and 10 may be coupled together by bolts, clamps or other suitable means conducive to the formation of a high pressure seal. As illustrated in Figures 1 and 2, flanges 4 and 10 are preferably held together by a clamp arrangement which includes a pair of "C" clamps 6 and 14 which are interconnected by suitable fasteners 8. In a preferred embodiment of the present invention, prior to connection of flanges 4 and 10 a bore seal 20 is placed in the bore of flanges 4 and 10 so as to establish a sealing connection therebetween.

A detailed view of flanges 4 and 10 may be seen by reference to Figures 3-5. Flanges 4 and 10 are provided with internal or frusto-conical seating surfaces 43 and 73, respectively, tapering inwardly from adjoining end faces 47 and 67 of the flanges. The opposite ends of the frusto-conical seating surfaces 43 and 73 preferably terminate at annular shoulders 41 and 84 at the end of the flange bores 40 and 80.

In a preferred embodiment, the angle of taper between the axis of the flange members 4 and 10 and their respective frusto-conical seating surfaces 43 and 73, as illustrated at "a", is preferably in the range of 15c 200.

Referring to Figures 4-5, seal member 20 generally comprises an inner cylindrical surface 49 and annular end surfaces 42 and 82 at opposite ends thereof. The external sealing surfaces of member 20 are generally separated from taper surfaces 52 and 62 by cylindrical relief rings 48 and 68. As divided by rings 48 and 68, the topical external surface of member 20 defines a sealing surfac# (50, 70) and a lower (52, 62) taper surface. In alternate embodiments, surfaces 48 and 68 may vary from a position parallel to the coaxial members so as to provide a greater relief area as will be further described herein.

In a preferred embodiment, the taper angle "c" of taper surfaces 52 and 62 is greater than the taper angle "a" of the frusto-conical seating surfaces 43 and 73 as measured from the axis of the cylindrical members.

Alternatively, the taper angle "c" of the taper surfaces may be machined at the same taper angle "a" as the sealing surfaces 43 and 73, resulting in the configuration illustrated by dotted lines at 52a and 62a.

Sealing surfaces 50 and 70 are formed with yet a third angle of taper "b". In a preferred embodiment, the taper angle "b" of sealing surfaces 50 and 70 is less than that of both the taper surfaces and of the frustoconical seating surfaces. Preferably, taper angle "b" is approximately 1/20 less than taper angle "a".

Taper surfaces 52 and 62 of member 20 converge to form an alignment ring surface 6 approximately midway between ends 42 and 82. When viewed in cross section as in Figures 3-5, ring surface 6 defines a point.

The position of ring surface 6 relative to ends 42 and 82 may vary as determined by the configuration of flange 4 and 10. A second set of alignment ring surfaces 51 and 61 are defined at the intersection of sealing surfaces 50 and 70 and relief rings 48 and 68. Yet a third set of shoulder ring surfaces 90 and 92 are formed by the intersection of sealing surfaces 50 and 70 and annular end surfaces 42 and 82.

In a preferred embodiment, shoulder ring surfaces 90 and 92 are subtly defined along faces 50 and 70 due to the minimal angle differentiation (1/20) between the surfaces when measured from the axis of the cylindrical members. This minimal angular differentiation prohibits "leaking" of sealing surfaces 50 and 70 at alignment ring surfaces 51 and 61 varies might result in a non uniform sealing surface.

Due to the angular variations between the sealing and seating surfaces, dual dimensional annular relieved areas 54 and 64 are defined between alignment ring surface 6 and shoulder ring surfaces 90 and 92. The displacement of areas 54 and 64 are determined by the angular differentiation between the taper of frustoconical sealing surfaces 43 and 73 and the sealing and taper surfaces of sealing member 20. Additionally, this displacement may be varied by the length of relief rings 48 and 68.

It is understood that as with other flexible type bore seals, the radial dimensions of the external sealing surfaces of seal member 20 will be accentuated prior to installation. However, when the connection is properly made, these sealing surfaces generally assume the position illustrated in Figure 5. Since the areas of these sealing surfaces are predetermined the loading forces used in making up the seal may also be predetermined. It is noted that the distance between the annular shoulder 41 and 84 of the respective flanges is slightly greater than the axial length of the seal member 20. These shoulders 41 and 84, coupled with end surfaces 42 and 82 of the seal member 20 and the alignment ring surfaces, result in self-alignment of the seal as the flanges 4 and 10 are clamped together.

It will also be noted that the diameter of the inner cylindrical surface 49 of the seal 20, when the flanges 4 and 10 are properly connected, is substantially the same as the adjoining bore diameters 40 and 80. This eliminates turbulence and the erosion and corrosion associated with such turbulence. Due to this bore configuration, the pressure internally of the connection exerts additional forces against the seal so that it is also pressure energized Thus, it is seen that the flexible pressure energized bore seal of the present invention is one which offers superior sealing and alignment characteristics.

It is also easily and economically manufactured.

While preferred and alternate embodiments have been described herein, many variations of the invention can be made without departing from the spirit of the invention.

Accordingly, it is intended that the scope of the invention be limited only by the claims which follow.

Claims

WHAT IS CLAIMED IS:

1. An annular bore seal for sealing between connected first and second coaxially aligned members, each of which is provided with an internal frusto-conical seating surface tapering inwardly from the adjoining ends of said first and second members towards the bases thereof, said seal comprising: an inner cylindrical surface; annular end surfaces at opposite ends of said inner surface; frusto-conical outer sealing surfaces adjacent each of said end surfaces and tapering inwardly therefrom, said surface having an inward taper as measured from the axis of said seal in the range of fifteen and twenty degrees, said upper sealing surface having an inward taper less than the taper angle of the lower surface;; a first outer alignment surface formed approximately midway between said end surfaces as defined by the circular intersection of a pair of cones whose axis coincides with said seal axis and whose angle of deflection is substantially that of the taper angle of the lower sealing surface as measured from the axis of the seal; a substantially cylindrical surface between the upper and the lower sealing surfaces; a second alignment surface defined by the circular intersection of the cylindrical surface and the upper sealing surface; an annular relieved area defined between said first and second alignment surfaces, where said relieved areas are comprised of the lower sealing surface tapering inwardly from the first alignment surface.

2. The annular bore seal of claim 1 further including a third alignment surface formed by the intersection of the upper sealing surface and the annular end surfaces.

3. The annular bore seal of claim 1 wherein the taper angle of the sealing surface is in the range of 14 1/20 - 19 1/2"1

4. The annular bore seal of claim 1 wherein the difference in angle of taper between the sealing surface and the taper surface is in the range of 0.250 - 50

5. The annular bore seal of claim 1 wherein the lower sealing surface has a taper angle 1!2 less than the taper angle of the seating surfaces of the first and second coaxially aligned members.

6. The annular bore seal of claim 1 wherein the difference on the angle of taper between the axis of the inner cylindrical surface and the frusto-conical seating surfaces is between 15 - 200.

7. An annular bore seal for sealing between connected first and second coaxially aligned members, where each of which members is provided with an internal frusto-conical seating surface tapering inwardly from the adjoining ends of said first and second members toward the bases thereof, said seal comprising:: an inner cylindrical surface; annular end surfaces defined at opposite ends of said inner surface; frusto-conical sealing surfaces formed adjacent each of said end surfaces and tapering inwardly therefrom, said surfaces having an inward taper as measured from the axis of said seal less than the taper angle of frusto-conical seating surfaces; a first outer alignment surface formed approximately midway between said end surfaces and defined by the circular intersection of lower sealing surfaces; a substantially cylindrical relief surface formed between the upper and lower sealing surfaces; a second alignment surface defined by the circular intersection of the cylindrical relief surface and the upper and lower sealing surfaces; an annular relief area defined between said first and second alignment surfaces.

8. The annular bore seal of claim 7 wherein the taper surface has a taper angle, as measured from the axis of said seal, in the range of fifteen to twenty degrees.

9. The annular bore seal of claim 8 wherein the taper angle of the taper surface, as measured from the axis of the seal, is less than the taper angle of the sealing surface.

10. The annular bore seal of claim 9 wherein the taper angle of the sealing surface is in the range of 15 - 200.

11. The annular bore seal of claim 9 wherein the taper angle of the sealing surface is 1/2 less than the taper angle of the seating surfaces.

12. The annular bore seal of claim 9 wherein the difference in taper angle between the sealing surfaces and the taper surface is in the range 0.25 - .50.