CA1336198C - Metallic sealing rings - Google Patents

Abstract

A metallic sealing ring particularly for sealing flange joints is of open or closed hollow sinuous radial cross-section with each of its axial and faces in-curved to define an axially outward facing deep peripheral groove. Additionally at least one. side wall will usually be curved to form a concave. shallow arcuate profile groove.

Description

W~NGDOC: 15~7d IMPRO~EMENTS RFL~TING TO MET~LLIC SE~LING RINGS
~ND THEIR M~N~IF~CTURE

This invention rela~es to ~net~llic sealirlg rirlgs for sealing the joints t~e.twee.n opposed parallel surfaces such as for instance, and in particuldr, the end fldnges by whic.h pipe lengths are connected tcgether by means such as studs, bolts and nuts, and to the Inanufacture of such rings The. inve.ntion relate.s particularly, but not exclusively, to sealing rings capdble of providing an ilnproved alternati~e. to the use of metallic sealing rings, i e gaskets, which are of solid Inulti-sided radi~l cross-section as currently specified by the Qmerican Petroleuln Institute (~PI) for sealing pipeline fl~nge joints by location in opposed grooves in the flange faces The standard groove cross section is d symmetrical trapezium In such applications ~eakage problems arise from time to tilne and partic.ularly in the conveyance. of gases at high pressure In the main thifi is not primarily due to faulty design of the sealing rings but to the difficulty ;~ ~
; -2 13~6198 of ensuring that Inachining of the joint colnponQnts is ofa sufficiently high standard regardless of where. the.y have. been manufactured.

The. leakage proble.m is particularly acute when the flan~es are intended to be drawn into fdce to face abutment instead of slight spacing or stand-off There are mdny situations where it is essential to ha~e face to face assenlblies In accordance with one aspect of the present invention there is proposed a metallic sealing ring which in rad-ial cross-section is hollow and of sinuous profile.
ha~ing axial end faces sinuously cur~ed so as each to define an axially outward facing deep peripheral grooue, the. interior of the ring profile being in communication with the exterior thereof One or each radial face of the ring may be cur~ed to define a laterally facing shallow arcuate profile groo~e Howe~er this is not satisfactory in all working envirorllnents because there is a tendency when an abnormal or excessi~ely high pressure is applied to the systeln for instance. in d blow-out or explosi~e.
situation for a radially outward groo~e not only to flatten out but to becolne outwardly con~ex tight into a -corne.r fclrlned between adjdc.erlt parts of gronved pipe flanges between which the metallic sealing ring is received, this can CdU5e Inovelllent at the high pressure se.aling are.as c)f the seal which can initiate a leakage probleln, To provide a metallic sealing ring which can function efficiently e.ven when subjected to exce.ssiue.ly high pressure.s as aforesaid, one or each of its side walls is curved to de.fine a radially outwardly directe.d shallow conve.x configuration in the. region of the intended abutment or near abutlnent of the. ~urfaces which are to be. seale.d The radial cross-section may he of close.d hollow forlnation or alterndtively a hollow forlnation which is open on one - and preferably its radially inward -side If the hollow forlnation is closed the ring ~
be formed with a normally radial ve.nt hole, to transn\it operating fluid pressure to the interior of the ring cros6 section so that in this configuration, as in the open configuration, the sea~ is self-energised by the fluid pressure acting on the. interna~ surface. of the cross section of the ring ~

-~ccording to another aspect of the in~ention there is pro~ided a metallic. sealing ring which in radial c.ross-se.ction is hollow, at le.ast one of its radidlly inner and outer side walls being cur~ed to define a conca~e shallnw arcuate groo~e, the interior of the r-ing beiny in c~omlllunication with the exterior In dccordance l~lith ye.t dnother dspect of the present in~ention there is proposed a metallic sealing ring which in radial cross-~ection is hollow dnd has oblique axial end faces and has a profile such that said axial end face.s can be dxially colnpressed towdrds one. another in use, at least at their regions of greatest axial extent, the interior of the ring profile being in comlllunication with the exterior thereof The dimensions of the ring are chosen such that in use the ring is jammed or wedged into the. corners of seal groo~es of tapered profile, in pdrticuldr ~PI stdndard gron~es Qccording to a preferred embodiment the metallic sealing ring in rddial cross-section has, on each dxial side. of a median plane, a respec.ti~e radially outer limb whic.h extends, from its iunction with the other such limb, ~k~liquely in the axially outward and radially inward directions at a relatively small angle to the axial d-irectinn, an end face portion extending, froln the ax-ially outer end of said outer limb obliquely at a gredter dngle tn the axial directiun than dnd in the same sense as the axially outer limt, and an inner limb extending froln the radially inne.r end nf the end face pc-rtion tc-wards the median plane and ha~ing a free end ~ colnpression spring Inay be placed inside. the se.aling ring to inc.rease the sealing load, e.g. in the form of a ring or rinqs of sheet spring Inetdl.

The radial cross-section may be of closed hc-llow forllldtion or preferdbly d hollow forlnat.ion which i~ open on one - and preferably its radially inward - side. If the hollow forlnation is closed the ring will be forlned with a normally radial ~ent hole, to transmit operating fluid pressure to the interior of the ring cross section so that in this configuration, as in the. open configuration, the se.al is self-energised by the fluid pressure acting on the internal surface of the c.ross section of the ring.

One or each radial face of the ring may be cur~ed tc-define a laterally facing arcuate profile groo~e to permit said axial compression. Howe~er, this is not satisfdctory in dll working e.nvironlnents be.cause of the.
abo~e-me.ntioned tendency, when an abnormal or exc~essive.ly high pressure is applied to the systeul, for instance in a blow-out or explo~i~e. situation, for a rddidlly outward groo~e not only to flatten out, but tc become c-utwardly c.on~e.x tight into a corne.r fornled between adjdcent pdrts of grooved pipe fldnges between which the. metallic sealing ring is recei~ed, this can cause Ino~elnent at the hlgh pressure sealing dreds of the seal which can initiate a leakage problem. Therefore, to pro~ide a Inetallic sealing ring which can function efFiciently e~en when subjected to excessi~ely high pre55UreS dS dforesaid, the outer side wall preferably has a radially outwardly directe.d shallow con~ex or dngled configurdtion in the region of the intended abutment or near abutment of the surfaces which are to be sealed, and the inner side wdll is open ~nother object of the present in~ention i~ to pro~ide a seal which is better able to stand up to high pressure and corrosi~e gase.s, particularly those which exist in flanqe joints located at the bottoln of the sea on oil drilling platforms This kind cf application is referred to in the art as a "sour-well" dpplication because of the presence of hydrogen sulphide ~H2S) i , . _ which is very often pre.se.nt in an oil and gas mixture, The hydrogen sulphide subje.cts the se.al dnd flanges to a high de.gree. of corrosion, It is known in the art to coat the fldnges and seals with nickel in orde.r to remove the effects of corrosion the.reby Indintdining dn effective seal between the metallic sealing ring and the flanges, Prior art seals are c.onfigured in such d Wdy that sliding Inovement takes place at the contact point between the metallic sealing ring and the flange, Movelllent nf this kind can lead to scuffing of the nickel coating, This can result in a deterioration in the effectiveness of the seal, It is there.fore another aim of the pre.sent invention to provide a metallic sedling ring which overcolnes or at least alle.viates these problems, and in particular a ne.tallic sealing ring which can provide an effective se.al which is not prone to scuffing, ~ccording to this aspect of the present invention, there.
is provided a metallic. sealing ring which in radial cross-section is hollow, the Ineta~lic sed-ing ring comprising a pair of limbs which are joined together at one end and are contiguous with respectively inwdrdly curved portions at the.ir other end, wherein the inwardly . f .
;

c.ur~ed pnrtionx each extend at least as far as a c.ontact point for contdcting d Xedlillg SUrfdCe.

In a preferre.d embodiment the inwardly cur~ed portions extend beyond the contact points so that their free ends are directed towards the. interior of the xealing ring, In this case, the Inetallic sealinq ring Inay be configured such that the free ends contact one another when the ~eal is under c.olnpression thereby enhancing the effecti~eness of the se~l between the contact points and surface to be sealed, ~ seal according to this aspect of the invention has the adUantdge thdt dS the ule.tdllic sedling ring undergoe.s conlpression, the profile of the seal changes in such a Inanner that sliding ~no~elnent between the contact point of the inwardly curved portion and the surface to be xealed does not occur, Scuffing is therefore elilnindted and so any nickel coating present on the metallic sealinq ring and/or on the surfdce of the Inelllber to be sealed is maintained, the effecti~enexs of the seal thereby beinq Inaintdined, The non-sliding contact between the inwardly cur~ed portions of the Inetdllic xedling ring and the xed~ing xurface is achieved by ~irtue of the fact that the -. ~

inwardly curve.d portions undergo a rolling action under co~npression, That i5 tn say the pnint of the. inwardly curved portion contacting the se.aling surface nlo~es toqether with the. sealing surface as the colnpression takes place, This action will be described in greater detail below with reference to the accnlnpanying drawings, gap must exist betwe.e.n the limbs in seals embndying this aspect of the invention for the. rolling action tn oc.cur ntherwise the rolling action is restricted, The gap is present when the sealing ring is in its relaxed state and during most or all of the compressi~e stages of the sealing ring, ~n an embodinlent where the limbs contact one another at the la~t stage of compre~sion, the contacting of the li.mbs ser~es to push the snft plating or nickel coating of the inwardly curved portions agdinst respective surfaces of the member tc~ be sealed thereby ensuring the -integrity of the seal at the cnntact points, This also ser~es to fill in any surface asperities or irregularities in the surfaces of the Inelnber tn be se.aled, This is achie~ed without restricting the rolling action provided that the lilllbs only contdct one.
another during the last part of the compression mo~ement, Seals embodying this aspect nf the invention c.ould be referred to as "rolling se.als", The fact that the seal performs the rolling action means that apdrt fruln avoiding the. occ.urrence of scuffing, the.
seal also adjusts to accommodate dimensional variations in the grooves, which dilnensional ~ariations Indy re.sult from manufacturing tolerances, In d preferred elnbodilllent of this aspe.ct of the invention, at least part of each limb which is also configured for contacting a sealing surface of a respective groove is c.oated with low friction material, This Inaterial Inay be selected froln silver, gold or PTFE
or other low friction material of which there are many and well known in the art, Embodiments are particularly suited for use in both R
and RX ~,P,I, grovves, When d llletdllic sedling ring enlbodying this aspect of the present inventinn is used in association with such d groove, d non-scuffing seal is established between respective contact points nf the inwardly curved portivns dnd d side of respective oppo~ing grooves, Q sliding seal is established between the portion nf the lilnbs having the low frictivn material and the other side of the grooves, ~Ise of the , ~

low friction Indte.rial reduces the possibility of scuffing which may result from the. sliding movement between the lilnbs and the oute.r sides of the groove, In alte.rnative embodinlents the. inwardly curue.d portions nay e.xtend beyond the contact point so thdt the.ir free ends face one anothe.r, Alternatively, hetween the contact point and the free. end, the sedl Indy be straiqht in profile, In either case., the part of the metallic sealing ring beyond the contact point will serve to strengthen the seal so that the seal can withstand higher colllpression forces, The inwardly curved portions of the metallic sealing ring Inay be of constant radius, although this is not essential, The. limbs may be straight or curued in profile, The lilnbs are preferably joined together by Ineans of a we.ld i oint, Embodiments nf this aspect of the present invention are preferably self-energizing in nature, In the. event thdt metallic sealing rings embodying the invention are configured so that the free end~ nf the inwdrdly curved portions contact one another unde.r compression , . . .

collllnunicatiun Inedns is prnvided fvr connecting the.
interior of the. se.aling ring with the exterinr, This permits e~udlizdtion of pressure. between the. interinr and exterior of the ring so that high pre.ssure ya5 can serve to enhdnce the sedling contdct between the metallic sealing ring and the grooves of the flanges, The collllnunication Inedns Inay be in the forln of openings provided in the inwardly curved portions or may be in the form of groove.s extending along the curved portions at or near to the free ends, For some applications it is desirable and advantdgeous to pre-compress the se.aling ring before it is installed, This can substantidlly enhdnce the perfc-rmance of the sealing ring, Typically, the sealing ring is pre-colnpressed to dpproxilndtely one half of the normal compression to ~e applied in use, The nolllinal full colnpression is typicdlly about 15%, Preferably, the sealing ring consists of two annular half-seals each forlning one axidl half of the rddial cross section of the sealing ring, these half-seals be.ing welded together along a circulllferential weld line or lines, with each half-seal ~eing pressed before welding, to a forln correspondin~ to about one half of the nominal compre.ssion in use, 12 a Some preferred embodiments of the invention are hereinafter described with reference to the accompanying drawings, in which each figure is a radial cross section of a respective sealing ring for use with a pipe flange joint. In the drawings:

Figure 1 illustrates a sealing ring according to a first embodiment of the invention, Figure 2 illustrates a sealing ring according to a second embodiment of the invention, Figure 3 illustrates a sealing ring according to a third embodiment of the invention, Figure 4 illustrates a sealing ring according to a fourth embodiment of the invention, Figure 5 illustrates a sealing ring according to a fifth embodiment of the invention, Figure 6 illustrates a sealing ring according to a sixth embodiment of the invention, Figure 7 illustrates a sealing ring according to a seventh embodiment of the invention, Figures 8 to 10 show rings in accordance with figure 1 ,, .~,, 12b 1 336198 emplaced in a flange joint, Figures 11 to 13 show rings in accordance with figure 1 emplaced in an alternative flange joint Figure 14 shows a seal ring according to an eighth embodiment of the invention Figures 15 shows a seal ring according to a ninth embodiment of the invention Figure 16 shows a seal ring according to a tenth embodiment of the invention Figure 17 shows a seal ring according to an eleventh embodiment of the invention Figures 18 to 20 show the rlng of figure 14 in a flange joint Figure 21 shows a twelfth embodiment which is a modification of the ring shown in figure 14 Figures 22 to 24 show the ring of figure 21 in a flange joint Figure 25 shows a seal ring according to a thirteenth embodiment of the invention 12c I 336198 Figures 26 to 28 show the seal ring of figure 25 in a flange joint Figure 29 shows a further sealing ring Figure 30 shows the ring of figure 29 in a flange joint Figure 31 shows yet another sealing ring Figures 32 and 33 show the ring of figure 31 in a flange joint Figure 34 shows yet another seal ring Figures 35 and 36 show the ring of figure 34 in a flange joint Figures 37 and 38 show a flange joint containing a further seal ring Figures 39 and 40 show respective flange joints similar to that of figure 37 but additionally provided with springs in the sealing ring Figure 41 shows another sealing ring Figures 42 and 43 show the sealing ring of figure 41 in ~W

a flange joint Figure 44 shows a modification of the seal ring according to figure 41 Figures 45 and 46 show the seal ring of figure 44 in a flange joint Figure 47 shows-yet another seal Figure 48 shows yet another ring Figure 49 shows details of a seal ring in accordance with a fourteenth embodiment of the invention, which is a modification of the embodiment shown in figure 21.

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Figs. 1 to 3 illustrate three different configurations of sealing rings to be used as an alternative to a ring section known as "RX" under the American Petroleum Institute, (API), classification. Each ring is hollow but whereas the Fig. 1 ring is open on it radially inward side the rings of Figs. 2 and 3 are closed and formed with vent holes 10 on their radially inner sides. All the rings have circumferential medium weld lines 12, at which two pre-formed half-seals are united in a plane perpendicular to the seal ring axis.

All three rings are of sinuous radial profile and are characterised by having opposite-facing corrugated formations which constitute axially outwardly facing deep peripheral grooves 2 in the axial end faces of the rings.

Additionally, one or each side wall of the ring profile may have a laterally facing shallow arcuate concave profile forming a groove 4. In the case of the ring illustrated in Fig, 1 which has an open profile, the qroove 4 is in the radidlly outer side, The ring illustrated in Fig, 2 which has a closed profile has grooves 4 in both the rdd-ially inner and radidlly nuter sldes, Th~ ring illustrate.d in Fig, 3, which has a closed profile, does nnt have grooves 4 but instead has rectilinear axially extending radially inner and outer walls 6 between the respective sinuous end regions, The grooves 4 provide enhanced resilience and flexibility under colnpre.ssion, The form of seal in Fig, 1, completely open on the inner face with its annular groove aruund the outside diameter, is extreme.ly flexible compared with the form in Fig, 2 whic.h is totally enclosed with the inner dnd outer annular groove.s and the vent hole/holes which nakes it substantially stronger, i,e, requiring Inuch higher clamping loads, The seal of Fig, 3 would be even stronger, because of the lack of the annular gruuves 4, This is to cope with higher pressures, In the illustrate.d rings, the side walls and end regions are interconnected by ubliquely extending rectilinear regions 8, ~lte.rndtively, these regions Inay be of curved cross-section, as shown in broken lines in the drawings, it has been estdblished by test that the curve.d faces are operationally superior, Figs, 4 and 5 show two further ring configurdtinns haviny the same characte.ristics as have been mentioned above but which are intended as ilnproved alternatives to what are known as type "R" ring seals or gaskets according to the ~PI classification and therefore hdve a lower ratio of ax-ial to radial dinlensjons, Silnilarly, Figs, 6 and 7 show two further pussible rinq configurations having the same characteristics as have been Inentioned dbove but which are intended dS illlprOVed alternatives to what are known as type "~X" ring seals or ~dskets dccordin~ to the ~PI cldssificdtion dnd therefore have a stil~ lower ratio of axial to radial dilnensions, In each of Figs, 4 to 7 inclusive also, there are indicated by dashed lines alternative rddiused portions between the deep axial groove formations 2 and the shallow lateral grooves 4, ` `t ~` b In Fiqs 8, 9 dnd 10 stdge.s in the forlllation of d Sedled joint between two groo~ed pipe flanges 20 using a sealing ring with the fig 1 radial configuration are illustrated, in fragmentary cross-section It is to be unde.rstovd thdt each of the fldnges 20 is an annular external flange provided on the end of a pipe In the. axially outwdrdly fdcing surface of the fldnge is a coaxial annular groo~e 22 of trapezoidal cross-section as specified by the ~PI, so that when two such fldnges are. assenlbled face to face., the respective groo~es in their surfaces togethe.r forln an dnnuldr ca~ity of hexagonal cross-section accomrnodating the sealing ring Fiq ~ shows the positions of the flanges dnd sealing ring assembled together with the sealing ring seated in the re.spectiue grooves, be.fore the fldnges hd~e been drawn together, and with the sealing ring in its natural uncolnpressed condition In use, the flanges are brought together, for e.xample by Inedns of bolts or cldlnps, into d stdnd-Off COllfi9UrdtiOn or, dS i] lustrated in the drawings, into face to face c.ontact . . , ~:, .

This colnpre.sses the interposed sedlinq ring. Typicdlly, fc-r compone.nts having the nominal dimensions, the degree of colnpre.ssion is dbout 15~

The grooves 22 are mach-ined into the flange faces Inevitably, Inanufacturing tolerdnces lead to varidtions in the groove dimensions These variations affect the interaction between the. side walls of the. grooves, and the sealing rings trapped betwe.en them, thereby creating a nlajor diff.ic.ulty in establishing d true fdce to face.
set-up with conventional ~PI rings of so~id cross section Fig ~ illustrates the position taken up by the sealing ring when the flanges hdue been brought into fdce to face contact, in a situation in which one or other of the grooves has been Inachined to the upper tolerance.
limit, that is to say, to the maximum internal dilnensions and therefore Ininillluln coulpression of the sealing ring ~s shown in Fig ~, in these conditions the. colnpression of the sealing ring is expressed primarily by lateral contraction of the groove forlnations 2 Fig 10 illustrate~ the position taken up by the sealing rinq under full colnpression, when one or other of the .,.1, q~

grnove.s has been Inachined to the lowRr lilnit of tolerance, that is to say, to the minimum internal grnove diulensions In this xitudtion, the. colnpre.ssion of the. sea3ing ring is expressed primarily by de.flection of its inner lilnbs 14, dxially towdrds one another It will be seen that in this configuration as well as in that illustrated in Fig 9, there is alllple sealing contact betwee.n the sealing ring and the. groove walls The. present seals hdve been designed to have sufficient stre.ngth to cope with the high torque. loadings and pressures associated with OIR equiplnent, yet at the salne time having sufficient flexibility to adjust in dimension to satisfy the variation in groo~e dilnensions due to manufacturing tolerances to which these grooues are Indchined Whe.n the. seal is fitted into the grooves and the flanges cldlnped together, the dia~lleter ~0 of the outer corrugation crest 20 is forcibly reduced in dilne.nsinn and the diameter nI of the inner corrugation crest 2I is forcibly increased in dimension This result~
in an extremely high loading force between the inner ~nd outer didlneters of the seal and the sloping fdces of the grooves This is the reason for the grooves 2 which permit the didlneters ~0 and DI to ddjust lg indepe.nde.ntly to suit e.ither of the sloping faces of the groove The depth of the. annular groove 2 in each of the two annular faces is selecte.d to suit the degree of variation between the two diameters and the variation in the dilne.nsions nf the groove in which the se.dl is to be colllpressed This is in cunjunction with the thickness of Inetdl froln which the sedl is Indnufdctured Briefly, if the groove is too deep it is possible for the metal on the inside of the. sedl to frdcture, whereas if the groove was only a gentle undulation, it would act as a rigid strut which would reduce its flex.ibi~ity to dllnost nil Figs, 11, 12 and 13 illustrate successive. stages in the formation of a spaced or stand-off julnt between pipe.
flanges, again utilising a sealing ring with a configuration as indicated in Fig 1 By colnpdrison with the joint illustrate.d in Figs 8, ~ and 10 the grooves~ in the. flanges are shallower, dnd colnpressivn of the sealing ring and final spacing be.tween the flanges is deterulinRd by dn interposed pressure control ring 24 Fig 11 illustrates the pnsition of the. colnponents before compression while Figs 12 and 13 illustrate the configuration of the se.aling ring unde.r top tolerdnce and bottnm tolerance. conditions effecti~e~y Preferably, but not essentidlly, the control ring 24 is of an internal diameter such as to provide a close fit adjacent the outertnost diamete.r of the. fldnqe grooves and sealing ring It will be see.n that the radially inner fdce of the control ring 24 is dt dll tilnes in contact wi.th the radially outermost portions of the seal ring This ouercolnes any possibility of the sedling be.ing forced outward and being nipped between the fldnges which could CdUS~ it to frdcture The desc.ribed seal rings have be.en found to work e.xtrelnely well dnd to provide more re.lidble se.dling an~
~reater accommodation of groove machining tolerances, than the. solid-section sealing rings which hdve hitherto bee.n used as standard components under ~PI
re~uirelnents, Howe.ver, in solne circulnstances the. recess 4 in the radially outer wall may be blown outwards, under conditions of very high interndl pressure, dnd this can impair the sealing action, as already explained this is due to Inovelnent of the sedl during this redction To avoid the. prob-eln of the groove 4 being fldttened or fc-rce.d outwards into the angle forme.d by the radially outer walls of the grooves in d ioint Indde with fdc.e to face contact, the groove 4 may be omitted, the outer fdce uf the sedling ring being, instedd, rddiused or angled in ross-sec.tion.

~cc~ordingly, Fig, 14 to 17 illustrate two different configurations of sealing rings to be used as an alternatiue to a ring section known as "RX" under the ~merican Petroleum Institute, ~PI, classification; i,e, that is 'R' section dnd BX section rings; and Figs, 18 to 20 illustrate stages in the formation of a sealed joint between two grooved pipe flanges using a sealing ring as illustrate.d in Fig, 14, Edch of the rings shown in figs 14 to 17 in rddial cross-section is hollow but whereas the rings of Fig, 14 dnd Fig, 16 are open on their radially inwdrd side, the rings of Figs, 15 and 17 are closed and are formed with vent holes 10, ~ll the rings dre forlned with we.ld lines 12, ~ll four rings are of sinuous radial profile and are c.haracterised by opposite-facing formdtions 2 which constitute axially outwardly directed de~p peripheral grooves in the axial end faces of the rings.

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~dditionally each ring is characterised in that its radially outward wall is curued to define a radially outwardly dire.cte.d shallow con~e.x configurdtion 26 in the. region of the intended abutme.nt or near abutment of the ~urfdces which are. to be ~edled, ~lso the closed profile ho~low ring~ shown in Fig~, 15 and 17 are formed on their rddidlly inwdrd ~ide with d ShdllOW COllCd~e portion or groo~e 4, In Figs, 18, 19 and 20 stages in the. fornlation of a ~eale.d joint betwe.e.n two qrooved pipe fldnges 20 using d sealing ring with the. Fig, 14 radial configuration are illu5 trated, The~e rings can be u~ed in a stand-off jotnt, but it is essential to incorporate d colnpres~ion control rin~ to pre~e.nt the seal being destroye.d by o~er compres~ion, Fig, 18 illustrates the position of the colnponent~
before the flanges ha~e. be.en drawn together into contact dnd before the sedling rinq i~ colt~pressed, Fig, 19 illustrates the po~ition taken up by the sealing rirtg whert the fldnges hdve bee.n brought to fdce to fdce contact in a situation where. one or other of the flange grooves 22 has been Inachined to the lilnit of upper 2~ 1336198 tolerdnce., whereds Fiq 20 illustrate.s the findl position of the sealing ring under c.ompression when one nr other of the qrooves has be.en Indchined to d bOttOIII
3imit of toleranc.e It will be. seen from these draw-ings that under normal operating c.onditions, the sealing action of the sealing rings illustrated in Figs 14 to 20 is similar to that of the rings illustrated in Figs 1 to 13, Howe.ver, under excessive internal pressure, bec.ause the outermost surfdce of the sealing ring is alreddy convex, the pressure can cause only minimal movement of the sealing ring, insufficient to disturb the sedling contact between the sealing ring and the groove walls ~ Ininor disadvantdge is thdt the absence of the groove or recess in the radially outer wall of the sealing r-ing reduces the c.olnplidnce of the sealing ring to solne extent, so that it is somewhat less able tn ac.commndate large groove Inachining tolerances than the rings illustrated in Figs, 1 to 1~, but provided that the grooves are within tolerance there is no probleln The se.aling rings illustrated in Figs 14 to 20 haue suloothly curved convex e.xte.rndl surfdces ~lternatively, the external surface may form an angle ~t . ~ ~
. .

the. weld line 12 as shown in Fig, 21, which illustrate.s a ring otherwise silnilar to that illustrdte.d in Fig, 14, Figs, 22 tn 24 illustrate the behauiour of this ring whe.n clalnped in grooves of top dnd bottoln tole.rances, analogous to Figs, 8 to 10 and Figs, 18 to 20, Fiq, 21 shows dinlensions in inches of a seal ring equivalent to an RX46 seal, by way of example only, Other seal sizes would have. generally proportionate dimensions, Figs, 25 to 28 are corresponding drawings, illustrating a sealing ring intended for use at higher pressures, in the range 5 to 10 thousand PSI, This ring has a configuration generally reselnbling that of Fig, 15, but with an angle at the external weld line 12, and a relatively deep groove or recess 4 in its radidlly inner surface, ~ sealing ring of this configuration has enhanced ability to accollllllodate tolerances in the nldchined groove dimensions, enhanced inherent restnring force, and enchance.d radial and axial hoop stresse.s in operation, It prouides increased contact and therefore sealing pressure at the contact positions between its inner lilnb 16 and the. grooue walls, The inner groove 4 acts as a colnpression restricting Ineans, to increase the contact load between the seal and the groove, - .1 2s 1336198 Figs 25 to 28 also illustrate vent holes 10 placed in the. side regions of the inner groove or recess 4, instead of at the centre of this recess as illustrated in Fig, 15 By pldcing the vent holes dS shown in Fig 25, the effect of these. on the strength and stiffness of the sealing ring is Ininillti7ed The seals of Figs 14 to 28, because of the absenc.e of groove 4 vn the exterior surfdce, are even stronger than that of Fig, 2, requiring h-ighe.r clamping loads, and ~eing able to cope with higher fluid pressures and rougher machined faces Figs, 29 tn ~3 illustrate further configurations of hollow metal sealing rings, intended primarily but not exclusively to be used in pldce of the solid-section sealing rings currently specified by the ~PI

In Fig, 2~ there is illustrated an alterndtive type BX
ring wherein, instead of the deep grooves 2, the pressure receiving axidl facing part~ 18 of the ring are slightly outwardly convex This sealing ring is of c.losed cross-section, having grooves or recesses 4 in both its radially inner and radially outer faces, to provide the necessdry self-energising spring dctinn dnd dbility to dcc,ollllnoddte.
groove machining tolerances, Fig, 30 shows this sealing ring under colnpre~sinn, Fig, 31 illustrates an alternative RX ring, with a cross-section like dn hour-glass, providing dn drc.uate recess 36 in its radially inner and outer surfaces to provide self-energisdtion and dbility to dccollllnodate groove mac.hining toleranc.es, and conuex arcuate axial end surfdces 34 for engdging the groove wdlls, Fig, 32 ~hows this ring in position in a pair of oppnsed flange grooves, before being subjected to colnpression, and Fig, 33 after compression, In practice. this seal wnrked well, but when subjected to a sudden burst of high pressure it mdy fail, Fig, 34 shcws a further alternative RX sealin-3 ring, of closed kidney-shaped cross-section, providing d convex radially outer surface 31 and a concave radially inner surfdce 32, dnd convex end surfdces 38, Fig, 35 shows the same ring in plac.e between a pair of flange. grooves before colllpression, dnd Fig, 36 after colnpression, This seal tends to suffer (but not a~ badly) from silllildr problelns to thdt of the hour-glds~ one in Fig, ~1, ;, ,.,~ ; ,.~

The rings illustrdted in Figs, 29 to 36 ha~e in co~ on, a close.d cross-sectic\n with a gronve or rece.ss in at ledst one of the rddidlly inner and oute.r surfdces, in particular the radially inner surface, to pro~ide self-energisation under colnpression, and ability to accommodate groove tolerances, Figs, ~7 and ~B illustrate d configuration of sealing ring to be used as an alternati~e to a ring section known as "RX" unde.r the ~Inericdn Petroleum Institute, (~PI), classification, The. ring is hollow and open on its radially inward side, and has a circumferential median weld line 12, at which two pre-formed sheet metal half-seals are unite.d in a Inedidn pldne 50 perpendicular to the seal ring axis, Each half-seal, in profile, consists of three portions, ~n outer lilnb 52 extends froln the weld line obliquely in the radially inward and axially outward directions, at a relati~ely shallow angle tn the dXidl direction, slightly less than the slope of the side surface 54 of a seal groove 22 of trapezoidal cross section Inachined in a flange 20 of a piping component to be jointed and sealed, Froln the nuter end of the li~llb 52, an end face portion 56 extends in the radially inward and axially nutward directions, at a Inuch larger dngle to the dXid i ` , ., , _ dire.ction than the lilnb 52 This furlns dn dxial end face. which in use is opposite. the bottom surface 58 of the ~roove. Froln the radially inner and axidlly outer end of the end face portion 56, inner limb 60 extends obliquely radially and axially inwards and terlllinates in a free. end space.d from the median plane This inne.r lilnb hdS d slope c.orre.sponding to that of the inner surface 62 of the groo~e Fiqure 37 shows the sedling ring in it~ initidl uncompressed condition, and accordingly a gap is shown between the respective flanges 20 In this condition, the axial distance betwee.n the radially inner corners 64 forlned between the inner lilnbs and the end face portions, is great than the axial distance between the radially outer corners 68 forlned between the radially outer ends of the end face. portions, and the oute.r linlbs 52 The. axial distance between the respective uuter angles 68 is substantially equal to or filiqhtly greater than the distance between the respecti~e bases 58 of the groo~es in the clamped condition of the flanqes, shown in Figure 38, The dXidl distance between the radidlly inner corners 64 is approxin~ately 10% greater than the distance between the groo~e bases S8 in the clalnped condition, so that when the flanqes are clamped to~ether the sealinq ring is subjected tn apprcxilnately 10%

~' ''~
... .

colnpression, The length of the end fdce portion 5~
be.tween the corners 64 and 68 -is sonle.what greater than the r~dial e.xtent of the gronve base 58.

Figure 37 shows the sealing ring seated in the. grooves of opposed flanges but w.ith no colnpression dppl-ied to the. sealing ring Qfter the flanges are fully clanlped together, the sealing ring is under colnpression and distc-rted as shown in Figure 3~, Specifically, the rddiused curners of the se~ling ring are rallllned holne into the. corresponding corners of the groo~es ~ecauxe the length of edch end face. portion is gredter than thdt of the groove base, the corners of the se.aling ring are f irlnly wedged into the corners of the qroove, the outer limbs of the sealing ring are pressed outwards onto the outer side surfaces of the grooves, dnd the inner lilnbs of the sealing ring are rotated away frnm the inner groove surfaces, In this c.olnpressed condition the sedl is completely leak-tight, with high sealing loads If it is necessdry to increase the sealing load, a spring or springs 70 of pre.ssed sheet spr-ing nletal can be fitted inside the sedling ring dS shown, by way of exanl~le nnly, in Figures 3~ and 4~, The spring or springs l~lill of course dCt, at ledst prillldrily, ~xidlly between the corners 64 Figures 3g and 40 re~pectively o "

~o shnw two diffe.rent arrangements of axial c.ompre.ssion springs, in the uncolnpre.sse.d conditinn corresponding to Figure 37 In the illustrated ring, the side walls and end regions are interconnected by obliquely extending rectilinear regions 52, ~lternati~ely, these regions may be of cur~ed con~ex cross-section It is to be understood that each of the flanges 20 is an annular external flange provided on the end of a pipe In the. axially outwardly fac.ing surface of the flange is a coaxial annular groo~e 22 of trapezoidal cross-section as specified by the ~PI, so that when two such flanges dre asselnbled face to fdce., the respecti~e groo~es in their surfaces together form an annular ca~ity of hexagonal cross-se.ction accolnlllodating the sedling ring In use, the flanges are brought together, for example. by neans of bolts or clalnps, into d stand-off configuration or, as illustrated in Figure ~8, into face to face contdct In a stand-off applicdtion d spdcer ring is place.d be.tween the flanges outside the. groo~es In the colnpressed condition, the angle adopted by the inner linlbs ~0 will ~ary, dependirlg on the dime.nsional ~ .

tolerances of the mdchined qrooves and nf the sealing ring The se.aling ring is designed to provide c.omplete sealing in grooves of Inaxilnuln tolerdnce. Rec.ause the seal ring is ope.n c-n its radially inner side, it c.an provide ample colnpliance for groove tolerances The present seals have been designed to have. sufficient stre.ngth to cope with the high tor4ue loddings dnd pressures associated with OIR e4uipment, yet at the sanle tilne having sufficient fle.xibility to adjust in dimension to satisfy the variation in groove dimensions due to Inanufacturing tolerances to which these grooves are machined The described seal rings have bee.n found to work extremely well and to provide Inore reliable sealing dnd greater accomnlodation of groove machining tolerances, than the solid-section sealing rings which ha~e hitherto been used as standard components under API

re4uirements, ~Inder excessive internal pressure, hecause the. outermost surface of the sealing ring is already angled or convex, the. pressure can c.ause only minimal movement of the se.aling ring, insufficient to disturb the sealing contact between the se.aling ring and the groove walls.

It Inust be noted thdt these xedls are self-energising, This mearls that once the seals are clamped up and the systeln is pressurised, the fluid unde.r pressure. acts nn the internal faces nf the seals and fnrces the sealing fdces of the sedl. e~e.n Inore firully tu the sloping faces of the. grnc)ve, ensuring that the seal functinns euen mnre securely, The illustrated seals are made by initially pressing two nirror-ilndge half-seals froln she.e.t Inetdl, corresponding respecti~ely tn the upper and lower hal~es of the illustrated sealing rinqs, These pressed hdlf-sedls dre then welded toyether along the circumfe.rential weld line nr lines 12, dfter being Indchined if necessdry, ~fter welding, the sealing ring is, if necessary, polishe.d and plated, In all instances the thickness of the metal of the sealinq ring is ddjusted to suit both the pressure to be applied and the. si~e c-f the radial section, The sealing rings can be Indnufdcture.d in any Ine.tal but fnr almost all applications the rings are intended to be produc.e.d in stdinless steel or the high nickel alloy Incone~ (Trade Mark), ~ nicke~ nr nicke~-r-~ch cnating ~ Inay be dpplied to d~oid corrosion, Incone.l "71~" is ..

''s'q~

particuldrly specified for sub-se.d so-cdllRd "~clur well"
applicaticns but requires an a~ing treatment tc- con~ert it tn the specificdtion appro~ed by the. North ~Inericdn Corrosic~n Engineers, Other coatings such afi sil~er, gold, copper, lead and PTFE Cd~ be use.d for other applicdtions, Each of the fi~e embodiments illustrated in Figs, 41 tn 48 is intended for use as an RX 46 ring seal acc.ording to the ~,P,I, c.lassification, In Fig, 41, d lnetdllic ~edling ring colnprises d pdir of limbs 80, 82 which are joined at one end by a weld 12 Inwardly curved portions 84 dnd 86 are cnntiguous with the other end of each of the limbs 80 and 82 The sides of the lilnbs 80 and 82 are tangentidl with the cur~ed sides of the respecti~e inwardly curued portions 84 and 86, In this elnbodilnent, the inwardly cur~ed portions 84, 86 have. a constant radius and, extend through approximately 250~ so that their free ends are directed inwardly with respect to the metallic sealing ring.
low friction coating 88 iS pro~ided on the lilnbs ~0, 82, extending partly onto the inwardly cur~ed portions 84, 86 The purpose of this codting 88 is to reduce sc:uffing which may occur between the limbs 80, 82 and th~ surface to be sedlRd during colnpression.

~4 1~3619~
The inwdrdly curved portinns 84, 86 ha~e. centre.s of cur~ature. R and R' ~e.ac.h of 6,67 mm) these being space.d by 15 ~ , The laterdl spacing between the centres R, R' and the welded joint 12 is 9.68 mm, The ring itself is of Inconel 718, 1,02 llllll thick, Naturally, these dimensions can be ~aried acc.ording to requirements, Prior tn applying d 0, 25 llllll nickel coating for "sour well" applications, the rings are ~acuum age hardened to increase the spring characteristics dS well dS to increase the corrosion rexistance of the Inconel ~Trade Mark) ring, The ring i5 then polished, VdCUUIII hedt treated for 4 hours at 700~C to anneal the nickel and then re-polished, The low friction coating can then be applied, Fig, 42 illustrates the metallic seali.ng ring of Fig, 41 in position betwe.en npposing groo~es 22, which are machined in opposing annular external flanges 20 pro~ided on the ends of pipes 20, Fig, 42 illufitrates this sealing ring in its natural uncolnpressed condition, In use, the flanges 20 are brnught together, for example. by means of bolts or clamps, into a stand-off configurdtion or, dS
illustrated in Fig, 43, into face to face c.ontact, R~

, ~5 1~36198 ~s the. flanges 20 and are drawn together by the clamps nr studs, the Inetallic sealing ring initially undergoes twn changes in prnfile at t.he same time, This c.an be seen from Fig, 42 the lilnbs ao, 82 of the Inetallic sealing ring contact groove surfaces 54 at respective first contdct points '30, ~s opposing fdce.s of respective. flanges 20 are drawn together, the linlbs 80, 82 of the sealing ring are forced in the direction of arrows ~ and 8 at the first contact pnints '30 respectiuely, ~s the fldnges dnd lilnbs 80, 82 Inove with respect tn nne annther, the first contact points 90 slide on the tdpered faces 54, The presence of the low friction coating serves to reduce or elim~nate scuffing at this point due to the reduct.ion in friction, ~ny scuffing which does occur does not unduly affect the guality of the overall seal provided by the Inetallic sealing ring because the integrity of the seal is naintained by contact between the inwardly curved portions and respective tapered groove faces g2, The configurdtion of the Inetdllic se.aling ring is such that as the flanges 20 are drawn together, the inwardly curved portion 84 rotates or rolls in d clockw-ise direction, and the. inwardly curved portion 86 rolls in an dnticlockwise direction on the groove surfaces, The rad-ii of curvature R, R' move towards nne anothe.r as the - :, seal undergoes c.olnpression, ~s a result of this ro~ling, there is no slip or scuffing between the respective inwdrdly curve.d portions ~4, ~6 and their respe.ctive tapered faces 92 at the contact points 94, Since the inwardly curved portions 34, ~0 underqo this rolling action, no scuffing takes place at the contact point 94 between the nickel coated surface of the metallic. sealing ring and the nickel c.oated surface of the flanges, This qives rise to a relidble seal at the contact points 94 since the nlaintenance of the nickel coating Ineans that the seal can withstand the corrosive elements in the case where the seal is u&ed in sub sea sour well or silnildr applicat.ions, The dimensions of the metallic sealing ring illustrated in Fig, 42 are such that when the sea- is fully compressed within the grooves 22 as illustrated in Fig, 43, the inwardly curved portions ~4, ~6 contact one another in an interferenc.e situation at a point ~6 near to their free. ends, This establishes an additional sedl loading line so that as the flange faces are drawn together until they Ine.et, the free ends are urqed in the.
directic-n of arrows C, C.' and n, D', This action enhances the se.aling line force present at the contdct points ~4, nepending on the precise dimensic)ns of the netallic sedling ring and the fldnges, the profile of , ~ -~336198 the inwardly curved portions 84, 86 in the vicinity nf the c.ontact points 94 may flatten sonlewhat, Neverthe.less, the sedl at the c.ontdct point 94 is maintaine.d without slipping occ.urring, In orde.r to e.nsure thdt the. seal is se.lf-ene.rgi~ing, vent holes 10 are provided in the inwardly c.urved portions 84, 86 for enabling pressure equalizdtion to oc.cur betwe.en the interior and inner e~terior of the seal, ~s an alterndtive to providing the openings 28, radial grooves may be cut in the faces of the inwardly c.urved portions in the vicinity of the additional sealing line 96, Fig, 44 illustrates a further embodiment of the present inve.ntion in which the dilnensions of the Inetdllic seali.ng ring are. such that unde.r full c.ompression ~as illustrdted in Fig, 46) an additiondl seal lodd-ing line is not established ~etween the inwardly curved portions 84, 86, The ndture of the contact points in this metallic sealing ring are the same as those described with refe.rence to Fiqs, 41 to 43, In this elnbodilllent, it is not necessary to prc-vide vent holes or grooves in the inwardly curved portions since. self energizdtion of the seal is maintained ~Iy virtue of the fact th~t the inwardly curved portions do not Ineet when the seal is , ., ~ . ..

fully colnpressed, Figure 45 illustrates the seal in situation prior to compression and Figure. 46 illustrates the. seal in its fully cnlnpressed situation, In thifi embodiment, the radii of curuature R, R' are space.d by 17,8 Illln, The lateral spacing between the points R and the weld joint 12 is 9,65 mm, and the radii of curvature R, R' are each 6,02 Ill~n, Figs, 47 and 48 illustrate two further enlbndinlents of the. present inventinn, In the elnbodilllent illustrated in Fig, 47, the -inwardly c.ur~ed portions 84, 86 extend between respective lilnbs 80, 82 and dS far as the contact puints ~4 for cc-ntacting a se.aling surfac.e of an RX ~,P,I, groove, but the free ends of the inwardly curved portions 84 and 86 beyond the contact point are straight, ~s the Inetallic sealing ring of Fig, 4?
undergoes c.ompression, a non-slip sealing contact will be established at contact points 94 and the free ends will tend to ~e directed inwardly wittl respect to the Inetallic sealing ring d5 the inwardly cur~ed portic,ns 84 and 8~ undergo the rolling action, The elnbodilnent illustrated in Fig, 48 differs frollt the embodiment of Fig, 47 in that the straight free ends of the inwardly cur~ecl portions 84, 86 are directed i :.....

~g outwardly (towards the axis of the ring) when the.
me.tallic sealing ring is in its uncompressed state, The contact pnints g4 of this elnbodilllent neverthele.ss maintain non-slip seals with flanges of the groove (not shown) as the InRtallic sealing r-ing undergoes cc-mpressinn, Modifications may be made to the embodiments described above without de.parting froln the scope of the. present inve.ntion, In particular, the nic.kel coating nee.d nnt be applied to the sealing ring in the event that the seal is to be used in non-corrosive e.nuironments, ~lso, the specific dimensions of the seal can be adiusted depending upon the groove in which the seal is tn be elnployed, It must be nnted that these seals are. self-energising, This u~eans that once the seals are clalnped up and the system is pressurised, the fluid under pressure acts on the internal face.s of the seals and forces the sealing faces of the seal even more firmly to the sloping faces of the groove, ensuring that the seal functions even mnre securely, The illustrate.d seals are made by initially pressing two Inirror-ilnage half-seals froln sheet Inetal, corresponding ,~, - . , respectively tn the uppe.r dnd lowe.r hal~e.s of the.
illustrate.d se.aling rings. These pressed half-seals are the.n welded tuge.the.r along.the circulnferential weld line or l~nes 12, after be.ing machined if necessary, ~fter welding, the sealing ring is, if necessary, polished and plate.d, In all instances the thic.kness of the nletal of the sealing ring is adiusted to suit both the pressure to be applied and the. size of the radial section, The sealing rinqs can be Inanufdcture.d in any Ine.tal but for almost all applications the rings are intended to be produced in stainless steel or the high nickel alloy ~Incone~. (Trade Mark), ~ nickel or nickel-rich coating Bl Inay be applied to auoid corrosion, Inconel "718" is particularly specified for so-called "sour well"
applicationx but requires an aging treatlllent to convert it tn the specification appro~ed by the North ~nlerican Corrosion Engineers, It has bee.n found in practice that for "sour well" use coatings such dS sil~er, lead and PTEE should be duoided whe.re~er possible and that nickel is usually essential to a~oid corrosion, 5~C

41 133619~
With nicksl-coated rings, problelns can arise. if the grooves also have surfac.e.s of nicke], or nickel-ric.h surfaces, for exalnple of Inconel 71~ to avoid corrosion in the grooves ~e.cause of the relative sliding between the tapered sides of the groove and the. surface of the seal ring, and the similarity c-f the materials of these.
surfaces, se.rious scuffinq or galling betwe.en the groove surface and the sealing ring occurs, It has been found that this proble.ln can be. overcolne, and other advantage.s can be obtained, if the sealing ring is shdped before use, to d shape corresponding to that which it would adopt if c.ompressed to a de.gree less than the nolninal degree of colnpression in use. Pre.ferably the ring is or its components are pre-compressed, preferably to about one half of the nolnindl c.olnpression, which is typically about 15%, Preferably, the sealing ring consists of two half-ring~
welded together along a circumferential weld line, for e.xample as shown at 12 in Figure 1, and each of the half-seals is axially compressed after initial pressing to shape and before welding, by ~bout one half of the nominal compression in use ~ ~\ p.~G ~9~ k ,, ,.,,~
~ ~

42 ~33619~
It has been found that pre-c.nmpression of the sealing rings c.an not only reduce. or elilllindte problelns of scuffing or galling between nickel or nickel-rich surfaces but cdn also increase the strength and performance of the. seal irrespectiue of the nature of the seal and groove surfaces.

~ preferred method of manufacture is as follows.

Two mirror-image half seal rings of stainless steel or Inc.onel are pressed to the appropriate c.orrugated cross section corresponding for exalnple to the. upper and lower halves of the seal-ing ring shnwn in Figure 21.
~dditional c.olnpression is then applied so that the findl form of the pressed half seal corresponds to the forrll of the basic sealing ring dS it would be when subjected to one half of the nominal compression in use. Thus for exalnple each hdlf seal Inay be pressed to d profile intermediate between that illustrated in Figure 8 and that illustrated in Figure 1n with the height of the inner corrugat-ion peaks less than that of the outer corrugation peaks. This colnpression can be applied for example by placing the initially pressed half-seal between two fnrlning dies nf the re4uired profile corresponding in particular to the grooves in which the finished seal is tn be used and colnpressing it to dn appropriate extent.

The. pressed half-deforlned half-seals are. then Illachined in the weld area, and are welded together along a circumferential we.ld line or lines for exalnple as shown at 12 in Figure 21, to form the. complete sealing ring The welded sealing ring is fully age-hdrdened dnd then pclished The hardened and polished sealing ring is then nickel-plated, and polished, The nickel plating is then annealed, for example by vacuum heat treatment for about 4 hours at about 700~C

The resulting sealing ring, when used then undergoes 50%
of nolninal colnpression, that is to Sdy about 7-~%
further compression It hds been found that this pre-colllpression, or prelinlinary modification of the sealing ring profile, substantially elilninates scuffing and g~lling be.twe.en the sealing ring and the grooves There Indy remain a smdll risk of sc.uffing on the radially outer surface of the sealing ring during compression, and to elilninate this, the sealing ring ,(l~y have d very light coating of d suitdble low-friction material at least at its nutside surface or on the regions thereof liable to sc.uffing ~lternative.ly, other forms of lubrication may be prc)vided in this region of the. sealing ring, The de.scribe.d method of manufacture leads to a numher of significant advdnt~ges The. contact travel of the sealing ring and the groove is effect-ively halve.d, and this reduction in travel of the groove faces ove.r the surface of the sealing ring reduces or elilnindtes sc.uffing, galling, and failing to seal This advantage is particularly significant when the groove and sealing ring surfaces both colnprise nickel or a high-nickel composition During colnpression of the sealing ring there is a sliding action betwee.n the groove wall and the radially outer surfaces of the sealing ring, particuldrly in the regions identifie.d by reference numeral ~ in the drawings, while, at least in the case of sealing rings having profiles sinlilar to that shown in Figure 1, a rolling action occurs between the inner lilnbs and the groove walls during compression, . ~ . ,.
. ~?. ' .,~, '~
~ . . ~ ~ ~

nue to the aging during Inanufacture, the se.aling ring is made. stronger Ccnsequently, during compression the forc.es on the sealing ring are roughly half-wdy between axial and radial, whereas in a sealing ring made by welding without age hardening, and without pre-compression or pre.-deformation of the half-seal profiles, the. forces on the. sealing ring are essentially axial ~lso due to the aging, hoop stresses during compression are increased, increasing the cuntact load between the inner limbs of the sealing ring and the groo~e. walls, ensuring that the. nickel coating is forced under preasure to fill any surface asperities of the mat-ing faces, The contact pressure is substantidlly greater than in the case of a sealing ring made without aging, so that the sealing perforlnace beconles Inore reliable The enhanced rolling action at the inner limbs of the sealing ring, and reduced sliding in these regions, remo~e. the possibility of scuffing in these regions Figure 4~ shows, by Wdy of exalnple only, d sedl ing ring ha~ing a profile generally resembling that ~hown in Figure 21, but Inanufactured as just describe.d and therefore ha~ing a modified profile in that the axial , 13361g8 distance between the corrugatinn pe.aks adjacent the lnne.r lilnbs i5 less than the. axidl distdncs between the corrugation peaks adjac.ent the outer limbs of the seali~g ring ~y way of exalnple only this drawi~g shnws typical dimensions in inches clearly illustrating the extent to which the inner limbs have been axially Inoved towards one another and rotated towards one another colnpdred with the sealing ring profile illustrated in Figure 21

Claims (13)

1. A seal assembly comprising in combination:
first and second bodies to be sealed, each having a sealing surface and an annular groove in said surface which groove has a V-section radial profile with radially inner side wall and a radially outer side wall which side walls converge away from the sealing surface;
and a seal ring adapted to be inserted in, and to make a sealing contact with said converging side walls of said V-section grooves, said seal ring comprising a resilient ring made of sheet metal and having in radial cross-section a hollow ring profile with respective axial ends, said ring profile comprising;
a radially outer side wall region having respective axial ends;
axially adjacent and continuous with each axial end of the outer side wall region a respective radially outer contact surface region extending obliquely inwardly towards the axis of the ring for making sealing contact with a respective radially outer side wall of a respective said V-section groove;
in each axial end of said ring profile, a curved sinuosity continuous with said oblique contact surface region and defining an axially outwardly facing deep circumferential groove; and radially inwardly of and continuous with each said sinuosity a respective radially inner contact surface region extending obliquely inwardly towards the axis of the ring for making sealing contact with a respective said radially inner side wall of said V-section groove;
at each axial of said ring profile, said radially inner and radially outer contact surface regions converging with one another in an axially outward direction;
and the ring having in its radially inner side at least one aperture permitting communication between the hollow interior of said ring profile and the environment adjacent said radially inner side of the ring; whereby the resilience of the sheet metal seal ring provides sealing pressure between the ring and the groove side walls.

2. The assembly according to Claim 1 wherein the ring further comprises, between and continuous with said inner contact surface regions, a radially inner side wall region forming a substantially closed ring profile, said at least one aperture being provided in said radially inner side wall region.

3. The assembly according to Claim 1 wherein the ring has an annular gap between said inner contact surface regions constituting said aperture.

4. The assembly according to Claim 2 wherein at least one of said radially outer side wall and said radially inner side wall regions is of curved cross sectional profile forming a shallow groove or arcuate concave profile.

5. The assembly according to Claims 1 or 2 wherein said outer side wall region is generally convex.

6. The assembly according to Claim 1 wherein said sinuosity defines, at each said axial end, a respective corrugation peak radially within and without said circumferential groove, the radially inner corrugation peak having a smaller axial height than the radially outer corrugation peak.

7. The assembly according to Claim 1, the seal ring having been pre-compressed by an amount less than its normal degree of compression.

8. The assembly according to Claim 1 in which the ring comprises of, in radial cross-section, two annular half-seal rings abutting and welded together in a plane perpendicular to the axis of the sealing ring.

9. The assembly according to Claim 8, the seal ring having a circumferential weld line between said half seal rings on its radially outer side and a low-friction coating at least on this weld line.

10. The assembly according to Claim 1 wherein said outer wall region is of curved cross-section profile forming a shallow groove of arcuate concave profile.

11. A seal assembly comprising in combination:
first and second bodies to be sealed, each having a sealing surface and an annular groove in said surface which groove has a V-section radial profile with a radially inner side wall and a radially outer side wall which side walls converge away from the sealing surface;
and a V-groove flange seal ring adapted to be inserted in, and to make sealing contact with said converging side walls of said V-section grooves in said bodies to be sealed, said seal ring comprising a resilient ring made of sheet metal and having in radial cross-section a hollow ring profile with respective axial ends, said ring profile comprising:
a radially outer side wall region having respective axial ends;
axially adjacent and continuous with each axial end of the outer side wall region a respective radially outer contact surface region extending obliquely inwardly towards the axis of the ring for making sealing contact with a respective said radially outer side wall of a respective said V-section groove;
at each axial end of said ring profile, an end wall region continuous with and radially inward of said oblique contact surface region;
and radially inwardly of and continuous with each said end wall region a respective radially inner contact surface region extending obliquely inwardly towards the axis of the ring for making sealing contact with a respective said radially inner side wall of a said V-section groove;
at each axial end of said ring profile, said radially inner and radially outer contact surface regions converging with one another in an axially outward direction;
and an inner side wall region axially between and continuous with said inner contact surface regions, at least one aperture being provided in said inner side wall region;
and said outer and inner side wall regions being curved in cross-section to define respective shallow concave arcuate grooves; whereby the resilience of the sheet metal seal ring provides sealing pressure between the ring and the groove side walls.

12. A method of making a V-groove flange seal ring adapted to be inserted in, and to make sealing contact with converging walls of, V-section grooves in bodies to be sealed, said seal ring comprising a resilient ring made of sheet metal and of hollow profile in radial cross-section, said method comprising;

forming two annular half-seals each forming a respective mirror-image axial half of said ring and each shaped to have a radially outer side wall region having respective axial ends;
disposing axially adjacent and continuous with one axial end of the outer side wall region a respective radially outer contact surface region extending obliquely inwardly towards the axis of the ring for making sealing contact with a radially outer side wall of a said V-section groove;
disposing an end wall region continuous with and radially inward of said oblique outer contact surface region; and radially inwardly of and continuous with said end wall region a respective radially inner contact surface region extending obliquely inwardly towards the axis of the ring for making sealing contact with s radially inner side wall of a said V-section groove;
disposing said radially inner and radially outer contact surface regions such that they converge with one another in an axially outward direction towards said end wall region;
axially compressing each half-seal to a degree less than the normal compression in use, and then welding the half-seals together along at least one circumferential weld line to form said hollow profile, said hollow profile having a radially inner side; and providing in the radially inner side of the thus welded ring at least one aperture permitting communication between the hollow interior of said ring profile and the environment adjacent said radially inner side of the ring.

13. The method according to Claim 12 further comprising age-hardening the sealing ring after said welding.