GB2180903A

GB2180903A - Bi-directional metal-to-metal seal

Info

Publication number: GB2180903A
Application number: GB08622038A
Authority: GB
Inventors: Charles Edward Jennings
Original assignee: Vetco Offshore Industries Inc
Current assignee: Vetco Inc
Priority date: 1985-09-23
Filing date: 1986-09-12
Publication date: 1987-04-08
Also published as: NO863724L; NO863724D0; GB8622038D0; GB2180903B

Abstract

Bi-directional metal-to-metal seal (10) comprising a ring with a pair of oppositely acting sealing elements (20 or 22) integral with the outer periphery of the ring. In one embodiment, two pairs of such sealing elements (20 and 22) are located on each end of the ring (as viewed in cross section) and are of a thickness to be resilient (springy) and deflectable when inserted in an interference fit relationship into a cylindrical wall or bore to be sealed. The first sealing element (24) has a curved outer surface (26) and with an opening (30) facing the main flow path of pressure fluid. The curved outer surface rolls inward against the cylindrical wall (42) while being inserted into the cylinder, partially closing the opening (30) but still allowing the pressure fluid to enter and urge the curved surface against the cylindrical wall. The second sealing element (32) also has a curved outer surface (36) and is of a thickness to be flexible and springy and likewise deflectable (rollable) into the cylindrical surface (26) in an interference fit relationship. The second sealing element (32) has a wall 34 which is open towards a second fluid under pressure so that the seal elements are operable in two directions. The latter sealing elements are similar but oppositely arranged for sealing against leakage, between the two pairs and in either direction of flow through the pipe or flow path. <IMAGE>

Description

SPECIFICATION Bi-directional metal-to-metal seal Background of the invention This invention relates to metal-to-metal seals for sealing joints of pipe and the like against leakage and is particularly directed to a bi-directional metal-tometal seal for sealing such joints against leakage in the event a reversal offlowofthefluid underpressure occurs in the flow path. This invention is also directed to the use of a plurality of such seals as a cluster of seals held in a retainer as an assembly so that the entire assembly of seals may be installed or removed at the same time. The latter assembly is especially useful in flowline connections in the oil and gas industry.

The use of metal-to-metal seals for sealing joints of pipe and the like against leakage of various types is old. See, for example, thefire-resistant metal-tometal seal as disclosed in the U.S. Patent No.

4,471,965toJennings, et al, and especiallythose having pressure-responsive lips such as shown in the U.S. Patent Nos. 2,405, 1 52to Kitchenmann; 3,455,562 to Burtis; the French Patent 1,356,218 of the Cadillac Gage Company; and the U.K. PatentApplication 2,000,234A of Panigati; all of which were sited in the Jennings, et al, patent.

None of the foregoing seals, however, were effectiveto seal a flow path in two directions in the event of a reversal oftheflowoffluid under pressure in the flow path. Also, none of the patents disclosed a metal-to-metal seal which could be inserted and removed without galling or scoring the sealing surface which the seal engaged, nor do any of the patents disclose an assembly of a cluster of seals which may be installed or removed all at the same time. As itwill be apparent to those skilled in the art, the use of such an assembly is particularly advantageous in installing and removing multiple seals used in flowline connectors where a plurality offlowlines (individual pipe lines) terminate at a common pointto be con nected, usually below the surface ofthe water in subsea well systems.

Summary ofthe invention The bi-directional metal-to-metal seal of this invention comprises a ring (cylindrical sleeve), having a boreofsubstantiallythesamediameterofthe pipeor flow path to be sealed, with a pair of oppositely acting sealing elements located on, and integral with, the outer periphery of the ring. In one embodiment, two pairs of such sealing elements are located on each end of the ring (as viewed in cross section) and are of a thickness to be resilient (springy) and deflect able when inserted in an interference fit relationship into a cylindrical wall or bore to be sealed. The first or outer of the sealing elements is curved somewhat cylindrical with a curved outer surface and with an opening facing the main flow path of pressure fluid.

The curved outer surface rolls inward againstthe cylindrical wall being inserted into the cylinder, clos ing the opening but still allowing the pressure fluid to enter and urge the curved surface against the cylindr ical wall. The second or inner sealing element ofthe same pair of sealing elements also has a curved outer surface and is of a thickness to be flexible and springyand likewisedeflectable (rollable) intothe cylindrical surface in an interference fit relationship.

The second sealing element has a surface which is open towards opposite direction from the first sealing element and toward a second fluid under pres sure so thatthe sealing elements are operable intwo directions. In the embodiment having two pairs of sealing elements, the sealing eiements a re similar but oppositely arranged for sealing against leakage, between the two pairs and in either direction offlow through the pipe orflow path.

In the embodiment having two pairs of bidirectional sealing elements, there is a center area of larger diameter than the sealing elements for retention in a retainer so that a clusterofsuch seals can be retained as an assembly of seals. The retainer itself is provided with a peripheral metallic seal which also rolls when inserted into a cylinder in an interference fit relationship to energize the seal in intimate contact with the cylindrical wall. This latter seal comprises a pair of semi-cylindrical sealing elements with curved outer surfaces and openingswhich are open to fluid which will urge the sealing elements into closer contact in the cylindrical wall on response to fluid pressure.Thus, an assembly comprising a plurality of bidirectional ring seals and a bi-directional peripheral seal may be inserted as a unit between flowlineterminals comprising a plurality of flow paths such as used in connecting a subsea well to a production tree.

It will be apparentto those skilled in the artthatthe rolling action of the sealing elements against the cylindrical wall allows entry and withdrawal ofthe bi-directional seal without scoring or galling, thereby allowing the seal to be used morethan oncewithout further machining of either the seal or the cylindrical surface.

Description of drawings Figure 1 a cross-sectional view of the ring having pairs of sealing elements with each pairformingthe bi-directional seal of this invention; Figure2 is a viewofthe bi-directional seal in enlarged over that shown in Figure 1 in the area of the arrow 2; Figure 3 is a view of the seal of Figure 2 showing the rolling reaction of the sealing elements when inserted in a cylindrical bore; Figure 4 illustrates a pair of such bi-directional seals in an arrangementwheretheconceptofsealing in both directions is illustrated together with the peripheral seal;; Figure 5is a perspective view of a retainer for a cluster of such bi-directional seals as an assembly so that a plurality offlowlines may be sealed orthe seals removed all atthe same time; Figure 6and Figure 7illustratethe bi-directional seal ofthis invention as partofa clusterorassembly being inserted in a flowline.

Detailed description In the cross-sectional view ofthe two pairembodi- ment ofthe bi-directional metal-to-metal seal 10, as shown in Figure 1, it can be seen thatthis embodiment comprises a ring having a bore 12 of the diameter of the pipe orflow path to be sealed. The ring comprises a base 14 having, in cross-section, a thick central portion 16 for resistance against external pressure and a pair of sealing elements 20 and 22 at each end. Both pairs of sealing elements are integral with the base 14 are formed to be springy (deflectable). The first, or outer, sealing element 24 of one pair, comprises a relatively thin walled curvedsemi- cylinder with a curved outer surface 26 and a central cavity 30 opening toward the path of flow of fluid.

The second or inner sealing element 32 of the pair 20 is essentially a straight, angularly disposed, wall 34with a curved outersurface36 and with the central portion l6definingacavity40openingintheop- posite direction from cavity 30, i.e.,towards the cen- terofthe ring so asto be actuated bythe leakage of fluid flowing from the opposite direction from the fluid flowing into the first cavity 30 of another seal.

The element 32 is also formed to be springy (deflectable).

As can be seen, the other pair of sealing elements 22 are identical but oriented to operate in the opposite direction. The reference numerals applied to pair 22 are the same as those applied to the pair 20 sincotheirfunction is the same but oppositely acting.

The element to be sealed, whether a termination of a flowline or a pipe is itself provided with a cylindrical surface shown as a counterbore 42 of slightly less diameterthantheouterdiameterofthesealingel- ements at their outermost curved surfaces 26 and 36, so thatwhen the elements are inserted into the counterbore an interference fit exists and the sealing elements deflect (energized). As shown in the enlarge ment pair20 in Figure 2 and 3,there is a slight curved inward deflection (roll) ofthe sealing elements in the direction indicated by the arrows 44 and 46. As also shown in Figure 3, the counterbore 44 is provided with a conical outer guide surface 50 to facilitate insertion.The amount of rolling deflection ofthe elements is exaggerated in Figure 3 to illustrate the energizing ofthe sealing elements but, as shown,the openings 30 and 40 remain open to pressure fluid to be also energized thereby. The sealing elements may be inserted and withdrawn for the counterbore without scoring or galling of either surface and this is attributed to the deflection and rolling phenomenon.

Figure 4 is a schematic illustration of the cluster of seals assembled in a retainer 52 as shown in Figure 5.

This retainer 52 is a pair of plates 54 and 56 with a plurality of bores 60 which correspond in number and sizetotheflowlines and held together by any suitable means, such as bolts 62. The arrangement of the retainer is shown more clearly in Figure 4 but for simplicity only two seals 10 and two flowlines are shown. Thus,while Figure 4 is schematic, both Fig ures 4 and 5 should be viewed together to understand how the retainerfunctions.

Two bi-directional seals 10 are held in the retainer 52 (two plates 54 and 56) and inserted into two flowl inetern#inals64and 66.

To hold the bi-directional seals 10 in the retainer 52, each seal is provided with a peripheral centrally located radially opening groove 70 into which a split ring 72 is inserted. This split ring 72 cooperates with two steps 74formed on the periphery of each bore 60 in the retainer plates 54 and 56 which, when brought together, form one groove for the split ring 72,thus holding each seal within the plates 54 and 56. These plates 54 and 56 are also provided with a pair of steps 76 on their outer periphery which, when the plates are brought together, form a groove to receive a rad ially inwardly directed profile 80 on a peripheral seal 82.

This peripheral seal 82 comprises, in addition to the profile 80, a pairof sealing elements 24a similar to the outer sealing elements 24, previously descri bed, and a second radially outwardly directed profile 84 to be received as a pair of steps 86 formed in the flowline terminals 64 and 66 which, when brought together, form a groove. Thus, the peripheral seal 80 is held in place bythe retainerandflowlineterminals 68 and 66. These sealing elements 24a cooperate with peripheral grooves 90 in the flowlineterminals and are oppositely facing so that when the seal assembly is brought between the two flowlineter- minals, the outer periphery is sealed against leakage in both directions.These sealing elements 24a also deflectand roll in the grooves 90 in the same manner as sealing elements 24 in groove42. Finally,tocom- plete the description of Figures 4 and 5, each terminal 64 and 66 is provided with counterbores 42 and guide surface 50 as previously described.

Under normal circumstances, when the flowline terminals are brought together, the fluid under pressure intheflowlines is sealed against leakage. This is represented by the solid line arrows 92. However, should one line pull a vacuum, orshould leakage occur at one seal 10, then the pressure between the seals, being the higher pressure, would tend to flow into the otherflowline. This flow is represented by the dotted line arrows 94. However, this flow is stopped bythe second sealing elements 32 operating in a direction opposite to the first sealing elements 24 sealingtheflowlineagainstthispossibility.

Itshould be apparentto those skilled in the artthat considerable separation of the flow line terminals can be tolerated without leakage between the flowlinesoroutthe peripheral seal due to the nature of these seals.

The next Figures 6 and 7 illustrates a seal assembly or cluster positioned between two facing flowline terminals with the appropriate number of metal-tometal seals 10 and with the peripheral metal-to-metal seal 82 held in the retainer 52. The terminals are formed to reserve the metal-to-metal seals 10 and the peripheral metal-to-metal seal 82 as described in connection with Figure 4 and need not be described further at this point. These Figures do show one ex ampleofthe mannerinwhichtheflowlineterminals are brought together, sealed, and connected. Thus, the cluster is first inserted into one of the terminals, such as 64. Thereafter, the otherterminal 66 is brought into position to receive the other end ofthe metal-to-metal seals and when the faces ofthetwo flowline terminals 64 and 66 are broughttogether, the clamping device 100 is actuated. As shown, the clamping device is located on the flowline terminal 66 and comprises a hydraulic actuator 102 which movesacammingring 104 urging dogs 106 into a profile (grooves) 118 on theflowlineterminal 64to releasablyconnectthetwoflowlineterminals together.It is to be noted that in the embodiments of theflowline terminals 64 and 66 shown in Figures 6 and 7, the steps 86 in theflowlineterminals of Figure 4were omitted and replaced by a movable latch 112 to latch the profile 84 of the peripheral seal 82. This latch is functionally the same as the steps 86. In this mannerthe individual flowlines,terminating at their respective terminations, are isolated from each other and, in the event ofthefailure ofanyoneflowline,the sealing elements ofthe otherflowlines remain sealed against the leaking fluid in the manner discussed above.

Finally, it should also be apparentthat only one pair of sealing elements such as 20 or 22 may be used with other types of seals where the design of the elementto be sealed dictates such a change.

As stated before, these sealing elements are capable of being removed and reinserted for repair and maintenancewithoutgalling orscoringthewalls against which the sealing elements react.

As an example of a typical seal constructed in accordance with this invention for a three inch flowline, the length of the ring is approximately3.25 inches (8.26 cms), the outer diameter of the two sealing elements on each end is approximately4 inches (10.l6cms) to engagethe cylindrical boreofapp- roximately 3.995 inches (10.15 cms) to form the interference fit with the two sealing elements. The outer diameterofthe ring inthethickerportion 16 is approximately4.250 inches (10.80 cms) and the metal-tometal seal itself is made of a low yield strength material such as 80 K material &num;4130.

Claims

1. A metal-to-metal seal comprising a cylindrical ring having a bore therein and having bi-directional sealing elements on the outer periphery of said ring; each bi-directional sealing element comprising; a first sealing element of flexible, springy material, engageable in a cylindrical bore in interference fit relationship and, thus energized thereagainst, said first sealing element having curved outer surface and open toward a first flow path offluid pressure and pressure assisted by said fluid pressure against said cylindrical wall, a second sealing element of flexible, springy material also engaging said cylindrical wall in interference fit relationship and energized thereby, said second sealing element having a surface facing away from said firstflow path ofpressurefluid and energizable by fluid from a second direction to seal said flow path in two directions.

2. The metal-to-metal seal as claimed in Claim 1, wherein said first and second sealing elements roll against said cylindrical surface as said sealing elements are made engageable in said cylindrical bore.

3. The metal-to-metal seal as claimed in Claim 1, further including a second bi-directional sealing element on the outer periphery of said ring, said first sealing element of this second bi-directional sealing element being offlexible, springy material, engageable in a second cylindrical bore in interference fit relationship and, thus, energized thereagainst, said first sealing element of this second bidirectional sealing element being curved and open toward the flow path of fluid pressure which would react against said second sealing element of said first bi-directional sealing element and pressure assisted by the latterfluid pressure against said second cylindrical wall;; a second sealing element of this second bidirectional sealing element of flexible, springy material also engaging said second cylindrical wall in interference fit relationship and energized thereby, said second sealing element having a surface facing toward said first flow path of pressure fluid and end ergizable by fluid to seal said flow path in two directions.

4. The metal-to-metal seal as claimed in Claim 3, wherein said first and second sealing elements of said second bi-directional seal roll against said second cylindrical surface as the latter sealing el- ements are made engageable in said second cylindrical bore.

5. The metal-to-metal seal as claimed in Claim 2, wherein both bi-directional sealing elements are integral with said ring.

6. The metal-to-metal seal as claimed in Claim 3, further having means to connect said seal to a re tainerforinsertion intosaidfirstandsecondcylindri- cal bores.

7. A metal-to-metal seal comprising a base with an inner bore, tapered and thickened between pairs of sealing elements on each end; said tapered, thickened portion having means for connecting said seal to a retainer for holding said seal as said sealing elements are inserted into a bore in interference fit relationship so as to be deflected and energized against said bore; said sealing elements having means reacting against the flow of pressurized fluid in opposite dir- ections so that such pressurised fluid is sealed and isolated, irrespective of the direction of the flow of such pressurized fluid.

8. A metal-to-metal seal assembly of metal-tometal seals as claimed in claim 7, comprising a plurality of such metal-to-metal seals in a retainerto be inserted in a similar number of cylindrical surfaces to isolate a plurality of flow paths in a flowline.

9. The metal-to-metal seal assembly as claimed in Claim 8further including a peripheral seal forsealing the periphery of said retainer against leakage when said peripheral seal is inserted in cylindrical surface in said flowline.

10. A metal-to-metal fluid seal for isolating fluids subjected to pressure comprising; an annular metal sealing element having a base; a sealing lip on said base of curved cross sectional configuration and having a curved sealing face; a sealing surface between said base and said first sealing lip and having a curved sealing face; a metallic, cylindrical surface against which said sealing lip and sealing surface press in an interference fit relationship when in functional position therewith, said cylindrical surface having an axial dimension sufficient to assure continuous contact thereofwith said sealing lip and sealing surface.

11. The fluid seal as claimed in Claim 10 wherein said sealing lip is responsive to fluids subjected to pressure from one source and said sealing surface is responsive to fluids subjected to pressure from a second source; both fluids assisting the sealing lip and sealing surface to engage said cylindrical surface.

12. Thefluid seal as claimed in Claim 11 wherein said sealing faces react against said cylindrical surface by a rolling action when pressed into said interference fit relationship.

13. A metal-to-metal seal, substantially as herein before described with reference to the accompanying drawings.

14. A metal-to-metal fluid seal for isolating fluids subjected to pressure, substantially as hereinbefore described with reference to the accompanying drawings.