GB2278163A

GB2278163A - Metal seal ring

Info

Publication number: GB2278163A
Application number: GB9410269A
Authority: GB
Inventors: Timothy Nicholson; Carl A Perry
Original assignee: ADVANCED PROD Inc
Current assignee: ADVANCED PROD Inc
Priority date: 1993-05-21
Filing date: 1994-05-20
Publication date: 1994-11-23
Also published as: GB9410269D0; BE1008953A4; FR2705422A1; DE4417579A1; JPH0755004A

Description

2278163 1 METALLIC SEAL RING The present invention relates to a metallic

seal ring used primarily for high temperature and high pressure sealing applications. More particularly, this invention relates to a metallic seal comprising a metal spring and an annular metal jacket.

Spring energized metal C-rings are well known in the art. In general, such prior art metal seals comprise a toroidal spring enclosed in a "CII-shaped or 11U11-shaped resilient metal case or jacket. Examples of such metal spring energized seal rings are represented by the metal seals sold under the trademark EnerRing by Advanced Products of North Haven, Connecticut (U.S.A.).

The performance of the prior art spring energized metal

C-ring is satisfactory for applications requiring significant amounts of "spring-back" (defined as the amount a seal will rebound after the seal has been compressed between sealing cavities or glands). The metal energizing spring installed within the C-ring jackets greatly enhance the initial (unpressurized) contact sealing stresses as well as providing a more effective seal at all other conditions of pressure and temperature as compared to a less complicated metal "CII-shaped C-ring having no energizing metal spring.

However, a major drawback to the well known prior art metal spring energized C-ring is that the metal energizing spring is or could be exposed to the environment being sealed because the metal jacket only partially encloses the metal energizing spring. Some examples of such situations where the prior art C-rings are disadvantageous are combustion chamber seals and seals used in highly corrosive applications. Such exposure to harsh environments leads to deleterious effects on the metal energizing spring. Moreover, such harsh environments greatly shorten the useful life of the metal spring energized C-ring seal and

2 compromise the ability of the metal spring energized C-ring to maintain required contact sealing stresses and good spring-back over the desired life of the seal. The ability to maintain required spring-back is particularly important where the distances between the sealing surfaces vary due to large variations in pressure and temperature.

In addition, solid jacket metal 0-rings (i.e., circular cross-section without springs inside) which are resilient, all-metal seals are also known in the prior art and are represented by the metal seals sold under the trademark Metal-O-Rings (MOR) by Advanced Products of North Haven, Connecticut (U.S.A.). These seals have proved to be effective in a very broad range of extreme- environment applications. Because the Metal-O-Ring under compression deforms to conform to the mating flange surfaces, it is one of the most effective seals in compensating for such flange conditions as waviness or minor deficiencies in flatness or parallelism. However, this non-spring loaded seal is not satisfactory where spring-back and re-installation of the same seal is required.

Metal seals of the type described herein are often used in expensive and elaborate instrumentation and equipment. The costs (both labour and otherwise) required to repair a damaged or defective metal seal can be extremely high. There is a long-felt need to provide metal seals which are longer lasting in order to reduce expensive repairs as well as to avoid expensive damage to equipment caused by faulty seal.

According to the present invention there is provided a metallic seal comprising a metal spring and an annular metal jacket wherein the annular metal jacket is completely surrounding and enclosing said metal spring thus forming a spring energized metal 0-ring seal.

According to the present invention there is also provided a sealing device comprising a sealing cavity and a spring energized metal 0-ring seal as defined above, 3 wherein the O-ring seal is resiliently compressible under a compression force in said sealing cavity to engage said sealing cavity at at least two locations and wherein said metal O-ring seal exhibits spring back subsequent to 5 release of said compression force.

According to the present invention there is furthermore provided an axial crush seal comprising a shaft, a sealing cavity and a spring energized metal O-ring seal as defined above, wherein the metal O-ring seal is resiliently compressible under a compression force in said sealing cavity and in that said metal O-ring seal exhibits spring back subsequent to release of said compression force.

In a preferred embodiment of the present invention the metal seal comprises a fully enclosed annular tubing of a desired cross sectional diameter which is shaped to a desired, preselected dimension. A helical spring, is disposed within and completely enclosed by the tubing.

Contrary to the "open" C-shaped or U-shaped jacket associated with prior art metal seals of this type, the present invention utilizes a closed tubing or jacket to totally surround the inner spring.

The metal seal of the present invention employing a closed jacket surrounding a spring has many features and advantages relative to the prior art open jacket type seals. For example, the present invention assures that the metallic energizing spring element of the metal spring energized O-ring maintains its integrity regardless of the outside environment since the outside (corrosive or otherwise harsh environment) environment does not come into contact with the spring, thus economic savings are achieved through much longer life of the total seal assembly. The spring energized O-ring of this invention also provides significant features over the prior art closed, spring-less O-rings by providing improved spring-back and allowing for re-installation of the seal ring.

4 The above-discussed and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description and drawings, wherein:

Figure 1A is a perspective view of a metal spring energized c-ring in accordance with the prior art;

Figure 1B is a perspective view of a metal 0-ring in accordance with the prior art;

Figure 2 is a perspective view of a metal spring energized 0-ring in accordance with the present invention; Figure 3 is a cross-sectional elevation view of the 0ring of figure 2 along the line 3-3 of Figure 2; Figure 4 is a partial cross-sectional elevation view of the 0-ring of Figure 2 under compression; and Figure 5 is a cross-sectional elevation view of an alternative embodiment of the 0-ring of Figure 2; Figure 6a is a cross-sectional elevation view of the 0-ring of Figure 2 shown without compression so that either the shaft or gland assembly may move up or down freely to a desired position; and Figure 6b shows the 0-ring of Figure 6a with the gland assembly in the tightened or crushed state after the desired position has been reached; and Figure 7 a is a cross-sectional elevation view of the 0-ring of Figure 2 along the line 3-3 of Figure 2 shown without compression so it can be moved vertically within a casing or hole until it reaches the desired position; Figure 7b is a cross-sectional elevation view of the 0ring of Figure 7a under compression after positioning at the desired vertical location.

Referring to Figure la, herein labelled prior art, a metal spring energized c-ring in accordance with the prior art is generally shown at 10. This prior art metal spring energized c-ring 10 comprises a "C"shaped metal jacket 12 and helical metal spring 14 received by jacket 12. Jacket 12 has a "C" or I1Ull shape and is dimensioned to receive and retain inner spring 14. An open space 16 is defined between the circumferential edges 18, 20 of the "open" jacket 12. It will be appreciated that in the completed C-ring seal 10, open space 16 of "C"shaped jacket 12 allows the environment (which may be corrosive) that is being sealed off to reach the inner helical spring 12. This adversely affects the life and function of helical spring 12 in certain applications and thus shortens the life and function of the entire metal spring energized C-ring seal.

Referring now to Figure 1B, herein labelled prior art, a metal 0-ring in accordance with the prior art is generally shown at 40. This prior art metal 0-ring is comprised of the desired variety of stainless steel or other suitable metal formed to the desired 0-ring shape.

However, unlike the spring energized C-ring of Figure 1A, spring-back is poor and this metal 0-ring under compression deforms to conform to the mating flange surfaces and does compensate for such flange conditions as waviness or minor deficiencies in flatness or parallelism. Because of these qualities, metal 0-rings 40 of the type shown in Figure 1B have limited usefulness in assembly and disassembly applications (i.e., applications requiring repeated use); and in applications that require springback because of wide temperature variations.

Referring now to Figure 2, a preferred embodiment of a metal spring energized oring in accordance with the present invention is shown generally at 22. 0-ring 22 compriseE a metal annular tubing or jacket 24 which completely encloses a helical or inner metal spring 26.

Spring 26 is selected to the proper parameters, such as coil diameter, length, material and temper is installed within the aforementioned tubing (jacket). A preferred metal spring 26 is by one formed from a material having high strength and elongation properties such as a high carbon spring steel or an alloy such as a chromium nickelcobalt alloy characterized by the Aerospace Materials 6 Specification No. 5839 and sold under the tradename ELGILOY in the U.S.A.. Another suitable high strength, high fatigue resistant material is the high nickel alloy such INCONEL X750 manufactured by Inco Alloys International. Metal tubular jacket 24 is preferably comprised of a suitable high strength metal with significant corrosion resistance for the application. Preferably, high nickel alloys such as INCONEL are used.

Spring energized O-ring seal 22 may be manufactured 10 using known and conventional methods. For example, spring 26 is positioned within the metal tube 24 such that the ends are offset to the seam of the enclosing metal tubing. Tubing 24 is then welded or otherwise closed by various means including but not limited to resistance welding, TIG welding, MIG welding, etc. Various means can be used to protect the integrity of the enclosed metal spring during the fastening of the ends of the tubing together. For example, in the case of resistance welding, the metal spring can be coated with non-electrically conductive material capable of withstanding the elevated temperature experienced with the welding process. Any other suitable method may be employed to protect the integrity ofthe metal energizing spring. The weld is then appropriately finished to blend with the rest of the surface of the metal spring energized O-ring seal. It will be appreciated that the jacket may be comprised of any suitable metal such as nickel alloys. Spring type and material can be of any other suitable structure or design to comply with the required application for this invention. For example, for a 0.5 inch outside diameter metal tube with a.050 inch wall (0.400 inch inside diameter), the spring utilized may have a wire diameter of 0.38 inch to.050 inch and the coil diameter of the spring would match the tube inside diameter of 0.4 inch.

Referring now to Figure 4, a sealing cavity or gland 32 is shown having inserted therein a metal seal 22 in 7 accordance with this invention. In Figure 4, metal seal 22 is under an oppressive load and has resiliently deformed to provide sealing engagement to at at least two locations 30 in cavity 32. In accordance with a significant feature of this invention, seal 28 exhibits improved spring-back such that the seal 22 will substantially regain its original shape upon removal of the compressive load.

In Figure 5, an alternate embodiment of the present invention is shown at 221. metal seal 221 differs from seal 22 primarily in that the cross-sectional outer shape of jacket 241 is "U" shape as opposed to the circular crosssectional shape of jacket 24.

Axial crush seals are seals loaded in the longitudinal or axial direction for the purpose of deforming radially against a sealing surface. This effects a high pressure seal in the axial direction. This type of application can be utilized effectively in such areas as oil field tools. For effective use in such an application, the spring energized O-ring when installed into a cavity, must have sufficient diametrical clearance to slip over a shaft while being placed vertically in the desired location. Once the assembly has reached the desired location, the cavity is closed axially, squeezing the spring energized O-ring. The spring energized O-ring deforms, causing the ID of the 0- ring to decrease and the OD of the O-ring to increase. The spring prevents the O-ring seal from buckling and thus produces greater radial load. As the seal is crushed, the OD bears on the cavity ID thus exerting more stress in the inward direction, closing the ID onto the shaft being sealed. The cavity continues to be closed or squeezed until the sealing stresses are satisfactory to effect the requires high pressure seal. Examples of the present invention being used for the aforementioned applications are depicted in Figures 6A-B and 7A-B discussed hereinafter.

8 Another area of application for spring energized 0 rings is for use in combustion chambers and the sealing of hot exhaust. Head gaskets used on internal combustion engines, leak and cause problems in the range between 150.000 to 300.000 km of operation. The new industrial target of current technology is to design a head gasket or in this case, a combustion chamber seal that will last as long as a 1.500.000 km. In the past, spring energized c rings have been used with limited success. A major problem with this type of seal is that the energizing spring is exposed to the products of combustion and such exposure reduces the spring's effectiveness. In addition, the spring can get extremely hot, which again could reduce considerably the strength of the spring. A completely encapsulated spring energized metal O-ring in accordance with this invention will eliminate such problems.

Still another application highly suitable to the use of spring energized O-rings of this invention is as a nuclear reactor head seal. Currently seals in use for this purpose are vented O-rings. The higher contact sealing stresses along this invention desirable for this purpose.

Referring now to Figure 6a, a sealing cavity or gland is shown having inserted therein a metal seal 22 in accordance with this invention and a cover 52 shown in the non-tightened or non-crushed condition. It will be noted that either the gland assembly 54 or the rod, shaf t or piston 56 can be moved to the desired position. Once that position has been reached, the cover 52 is tightened so that seal 22 is compressed or crushed to form a tight seal at at least two points 58 (see Figure 7b). When the cover 52 is released, the spring-back in seal 22 will allow the energized metal O-ring seal of the present invention to return to the relaxed condition as seen in Figure 6a.

Referring now to Figure 7a and 7b, still another application of the use of the spring energized metal 0 ring seal in accordance with the present invention is shown 1 9 as used in an oil-field environment. A borehole 70 is drilled into the earth 72. A borehole-casing 74 is placed into the borehole 70. Cement or other filler 76 is placed in the space 78 to make sure that the borehole-casing 74 is held rigidly in place. An oil-field tool or similar apparatus 80 is lowered through casing 74. Tool 80 includes a gland assembly 82. Spring energized metal O-ring seal 22 in accordance with this invention is shown in Figure 7a in the relaxed or non-crushed condition within gland assembly 82. Spring energized metal O-ring seal 22 is thus able to be raised or lowered in the borehole-casing 74 with virtually no damage until the desired vertical position is reached. In this way, metal O-ring seal 22 is not exposed to any wear until ready for use. When the desired position is reached, element 84 is tightened (by pulling element 84 upwardly since element 84 is axially arranged within tool 80) to crush metal O-ring seal 22 to effect a rigid seal against the ID of the borehole-casing 74 and the OD of the gland 86 (see Figure 6b). When element 84 is released, the springback in seal 22 will allow the energized O-ring seal of the present invention to return to the relaxed condition as seen in Figure 7a for removal or to allow apparatus 80 to be moved to another vertical position.

a

Claims

1. A metallic seal comprising a metal spring and an annular metal jacket, wherein the annular metal jacket is completely surrounding and enclosing said metal spring thus 5 forming a spring energized metal O-ring seal.

2. The seal as claimed in claim 1, wherein said metal spring comprises a helical spring.

3. The seal as claimed in claim 1 and 2, wherein said metal jacket has a circular cross-section.

4. The seal as claimed in claim 1 or 2, wherein said metal jacket has a U-shaped cross-section.

5. A sealing device comprising a sealing cavity and a spring energized metal O-ring seal as claimed in any one of the claims 1 to 4, wherein the O-ring seal is resiliently compressible under a compression force in said sealing cavity to engage said sealing cavity at at least two locations and wherein said metal O-ring seal exhibits spring back subsequent to release of said compression force. 20

6. The sealing device as claimed in claim 5 wherein said sealing cavity forms a portion of a combustion chamber.

7. The sealing device as claimed in claim 5 wherein said sealing chamber forms a portion of a head gasket for an internal combustion engine.

8. The sealing device as claimed in claim 5 wherein said sealing chamber forms a portion of a nuclear reactor head seal.

9. An axial crush seal comprising a shaft, a sealing cavity and a spring energized metal O-ring seal as claimed in any one of claims 1 to 4, wherein the metal O-ring seal is resiliently compressible under a compression force in said sealing cavity and in that said metal O- ring seal exhibits spring back subsequent to release of said compression force.

c 1 11

10. The axial crush seal as claimed in claim 9, wherein the sealing cavity is disposed over the shaft.

11. The axial crush seal as claimed in claim 9, wherein the sealing cavity is disposed within said shaft.

12. The axial crush seal as claimed in claim 11, wherein said shaft comprises a borehole casing.

13 The metallic seal substantially as described hereinbefore with reference to the Figures 2 to 7 in the accompanying drawings.

14. The sealing device substantially as described hereinbefore with reference to the Figures 2 to 7 in the accompanying drawings.

15. The axial crush seal substantially as described hereinbefore with reference to the Figures 2 to 7 in the accompanying drawings.