Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1336198
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
-
1336198
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
~
-
4 1336198
~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
1336198
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
1336198
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 , . _
1336198
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 .
;
1336198
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
-
. ~
1336198
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,
1336198
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
, ~
1336198
1 1
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
, . . .
12 1336198
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,
1336198
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
1336198
12
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.
,~
- 13 - 1336198
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
14 1336198
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
1336198
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
1336198
16
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
. . , ~:,
.
17 1336198
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~
18 1336198
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
1336198
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
1336198
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
21 1336198
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.
.~
1336198
22
~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
. ~ ~
. .
1336198
24
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
26 1336198
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,
;, ,.,~ ; ,.~
27 1336198
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 ` ,
., , _
28 1336198
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%
~' ''~
... .
29 1336198
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
"
1336198
~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
~ .
31 1336198
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.
32 1336198
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~
1336198
33
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
- :,
1336198
36
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
37
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
, ., ~ . ..
38 1336198
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 :.....
1336198
~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
,~, - . ,
1336198
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.
1336198
43
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
1336198
44
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,
. ~ . ,.
. ~?. ' .,~, '~
~ . . ~ ~ ~
1336198
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
46
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
