U.S. patent application number 12/877513 was filed with the patent office on 2011-03-10 for seal.
Invention is credited to Horace P. Halling.
Application Number | 20110057394 12/877513 |
Document ID | / |
Family ID | 42830849 |
Filed Date | 2011-03-10 |
United States Patent
Application |
20110057394 |
Kind Code |
A1 |
Halling; Horace P. |
March 10, 2011 |
SEAL
Abstract
A seal is inserted into a space to be sealed. First and second
end portions of the seal are engaged with first and second end
surfaces of the space. The seal is compressed between the first and
second end surfaces. The compression strains the seal. The strain
includes the rotation of a cross-section of the seal so as to bias
the seal into engagement with a surface forming one of an inboard
surface and an outboard surface of the space.
Inventors: |
Halling; Horace P.; (Durham,
CT) |
Family ID: |
42830849 |
Appl. No.: |
12/877513 |
Filed: |
September 8, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11610220 |
Dec 13, 2006 |
7810816 |
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12877513 |
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60749908 |
Dec 13, 2005 |
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Current U.S.
Class: |
277/312 ;
277/628; 277/644; 277/650; 277/651 |
Current CPC
Class: |
Y02T 50/672 20130101;
F01D 9/023 20130101; F01D 11/005 20130101; F16J 15/06 20130101;
F05D 2240/55 20130101; F16L 23/20 20130101; F16J 15/0887 20130101;
Y02T 50/60 20130101 |
Class at
Publication: |
277/312 ;
277/628; 277/644; 277/650; 277/651 |
International
Class: |
F16J 15/02 20060101
F16J015/02 |
Claims
1. A method for sealing a space formed by first and second end
surfaces adjacent inboard and outboard surfaces, the method
comprising: inserting a seal into the space without radial
interference with inboard or outboard surfaces; engaging first and
second end portions of the seal with the first and second end
surfaces of the space; locally compressing the seal between the
first and second end surfaces; and straining the seal to rotate a
cross-section of the seal to bias the seal into engagement with the
inboard and outboard surfaces of the space, the straining including
a terminal portion of the compressing acting to shift the seal into
said engagement with said inboard and outboard surfaces of the
space.
2. The method of claim 1 wherein the straining comprises: exposing
the seal to an operational fluid pressure difference across the
seal in the space, the pressure difference acting to shift the seal
into said engagement with the other one of said inboard and
outboard surfaces of the space.
3. The method of claim 1 wherein: the first and second end surfaces
are base surfaces of first and second channels in first and second
flanges.
4. The method of claim 3 wherein: the first and second end surfaces
are surfaces of first and second flanges, respectively, and the
compressing bottoms said first and second flanges without bottoming
the seal relative to the first and second flanges.
5. The method of claim 1 wherein: the first and second end surfaces
are surfaces of first and second flanges; and with the first and
second flanges bottomed against each other, the seal is not
bottomed.
6. The method of claim 1 wherein: the first and second end surfaces
are surfaces of first and second flanges; and with the first and
second flanges bottomed against each other, engagement regions of
the first and second end portions of the seal with the first and
second end surfaces remain radially spaced apart and radially
non-overlapping.
7. A method for sealing an annular-shaped space, the method
comprising: inserting a seal into the space without radial
interference inboard or outboard; engaging first and second end
portions of the seal with first and second end surfaces of the
space; compressing the seal between the first and second end
surfaces, the compressing bottoming first and second members
respectively having the first and second end surfaces without
bottoming the seal relative to the first and second members; and
straining the seal to rotate a cross-section of the seal to bias
the seal into engagement with the inboard and outboard surfaces of
the space; and shifting the seal into engagement with said inboard
and outboard surfaces of the space.
8. The method of claim 7 wherein: the engaged first and second end
portions are offset normal to a direction of the compressing so as
to provide a force couple to induce the rotating.
9. The method of claim 7 wherein: the seal is a continuous annulus
and the first and second end portions are radially offset from each
other normal to a central axis of the seal.
10. The method of claim 7 further comprising: exposing the seal to
an operational fluid pressure difference across the seal in the
space, the pressure difference acting to increase an engagement
bias of the seal against at least one of the inboard and outboard
surfaces.
11. The method of claim 7 wherein: said cross-section has an
exterior perimeter formed as a rounded-corner trapezoid, and
wherein, in a relaxed condition, the base and top of the trapezoid
have off-longitudinal normals.
12. The method of claim 11 wherein: the engaging is along first and
second diagonally opposite said rounded corners; and a combination
of the compressing and an operational pressure difference brings
the third and fourth said rounded corners into respective
engagement with the inboard and outboard surfaces.
13. The method of claim 7 wherein: said cross-section has an
exterior perimeter having first and second rounded ends and first
and second sides; the engaging brings a first portion of the first
rounded end into engagement with the first end surface; the
engaging brings a first portion of the second rounded end into
engagement with the second end surface; a combination of the
compressing and an operational pressure difference brings a second
portion of the first rounded end into engagement with the outboard
surface; and the combination of the compressing and an operational
pressure difference brings a second portion of the second rounded
end into engagement with the inboard surface.
14. The method of claim 7 applied with inboard and outboard such
seals to seal between three members: a first member providing the
inboard surface for the inboard seal; a second member providing the
outboard surface for the inboard seal and the inboard surface for
the outboard seal; and a third member providing the outboard
surface for the outboard seal.
15. The method of claim 14 wherein: said first member is a tubing
hanger; said second member is a spacer; said third member is a
wellhead.
16. The method of claim 7 further comprising engineering the seal,
the engineering comprising: determining a desired seal response to
a fluid pressure difference across the seal in the space, the
desired response including an increase in engagement bias of the
seal against at least one of the inboard and outboard surfaces; and
selecting at least one parameter of shape and orientation of the
cross-section to provide the desired response.
17. A sealed joint comprising: a first end surface; a second end
surface; a seal compressed between the first and second end
surfaces and having first and second end portions respectively
contacting the first and second end surfaces, the first and second
end portions offset transverse to a direction of the compression;
and a lateral surface, the seal compressively engaged to the
lateral surface and not an opposite lateral surface.
18. The joint of claim 17 wherein: the lateral surface is an
outboard surface.
19. The joint of claim 17 wherein: first and second flanges
respectively having the first and second end surfaces are bottomed
relative to each other without the seal being bottomed relative to
the first and second flanges.
20. The joint of claim 17 wherein: the seal has a circular annular
platform; the seal has a cross-section having an exterior perimeter
formed as a trapezoid with rounded corners.
21. The joint of claim 17 wherein: the seal has a circular annular
platform; the seal has a cross-section having an exterior perimeter
formed having first and second parallel sides and first and second
rounded ends.
22. A method for sealing a space formed by first and second end
surfaces adjacent inboard and outboard surfaces, the method
comprising: inserting a seal into the space without radial
interference inboard or outboard, the seal having a cross-section
having an exterior perimeter formed as a trapezoid with rounded
corners; engaging first and second of the corners of the seal
cross-section with first and second end surfaces of the space;
compressing the seal between the first and second end surfaces; and
straining the seal to rotate the cross-section of the seal to bias
the seal into engagement with said inboard and outboard surfaces of
the space.
23. A single-element bi-directional sealing ring for sealing
against fluid pressure in an annulus between the facing concentric
surfaces of two bodies, said sealing ring comprising an annular
body member with an inclined trapezoidal cross-section.
24. The scaling ring of claim 23 in which all corners of said
trapezoidal cross-section have a radius feature.
25. The scaling ring of claim 23 in which after the system pressure
and clamping loads are removed, the sealing ring returns
approximately to its original form, so that the joint of which it
is a part may be more easily separated for disassembly.
26. The sealing ring of claim 23 having a cross-section to diameter
ratio sufficient to avoid elastic instability and buckling due to
its displacement and loading during installation and in
operation.
27. The sealing ring of claim 23 in which at least three corners of
said trapezoidal cross-section are rounded.
28. A method for engineering the sealing ring of claim 23, the
method comprising; determining a desired increase in the radial
dimension of the cross-section in proportion to at least one of:
axial compression of the ring; and a defined axial force; and
selecting the inclination angle is defined so as to provide said
increase.
29. The sealing ring of claim 23 formed of a metallic material.
30. The sealing ring of claim 23 formed of a non-metallic
fiber-reinforced composite material.
31. The sealing ring of claim 23 installed between the facing
surfaces of the bodies and longitudinally compressed between planar
surfaces of a support ring and a loading ring.
32. The sealing ring of claim 23 installed between the facing
surfaces of the bodies and longitudinally compressed between the
bodies.
33. The sealing ring of claim 23 installed between the facing
surfaces of the bodies and wherein: the seal cross-section is
shaped and oriented so that an increase in radial span of the
cross-section in response to axial loading eliminates radial
clearances between the seal and facing surfaces and generates
radial compression of the contacting surfaces of the seal
cross-section and said bodies effective to create a barrier to the
passage of fluid.
34. A bi-directional sealing ring for sealing against fluid
pressure in the annulus between the facing cylindrical surfaces of
two concentric bodies, said sealing ring comprising an annular body
member with an inclined triangular cross-section.
35. A bi-directional sealing ring for sealing against fluid
pressure in the annulus between the facing cylindrical surfaces of
two concentric bodies, said sealing ring comprising an annular body
member an inclined cross-section of trapezoidal, triangular, or
obround exterior perimeter so as to have radially offset first and
second longitudinal extremes.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This divisional application claims priority to U.S. patent
application Ser. No. 11/610,220 filed on Dec. 13, 2006, and to U.S.
Patent Application Ser. No. 60/749,908 filed on Dec. 13, 2005, the
disclosures of which are incorporated by reference herein as if set
forth at length.
BACKGROUND OF THE INVENTION
[0002] The invention relates to seals. More particularly, the
invention relates to compression seals.
[0003] A variety of metallic seal configurations exist. Many
metallic seals are commonly held under compression between two
opposed flanges of the elements being sealed to each other. Such
metallic seals may be used in a variety of industrial
applications.
[0004] Many examples of such metallic seals are of an annular
configuration, having a convoluted radial section which permits the
seal to act as a spring and maintain engagement with the flanges
despite changes or variations in the flange separation. Certain
such seals have an S-like section while others have a section
similar to the Greek capital letter sigma (.SIGMA.) with diverging
base and top portions. Other similar seals are formed with
additional convolutions.
SUMMARY OF THE INVENTION
[0005] One aspect of the invention involves a method for sealing a
space. A seal is inserted into the space. First and second end
portions of the seal are engaged with first and second end surfaces
of the space. The seal is compressed between the first and second
end surfaces. The compression strains the seal. The strain includes
the rotation of a cross-section of the seal so as to bias the seal
into engagement with a surface forming one of an inboard surface
and an outboard surface of the space.
[0006] In various implementations, the space may have both said
inboard surface and said outboard surface and the sealing may be
between said inboard and outboard surfaces. The seal may be
inserted into the space in a non-interference relation. The seal
may be exposed to an operational fluid pressure difference across
the seal in the space (e.g., resulting from normal or abnormal
operation of the members being sealed). The pressure difference
acts to increase an engagement bias of the seal against at least
one of the inboard and outboard surfaces. The cross-section may
have an exterior perimeter formed as a rounded-corner trapezoid. In
a relaxed condition, the base and top of the trapezoid may have
off-longitudinal normals. The engaging may be along first and
second diagonally opposite ones of the rounded corners. The
compressing may bring the third and fourth rounded corners into
respective engagement with the inboard and outboard surfaces. The
seal may be engineered so that the actual or abnormal fluid
pressure difference provides a desired increase in the engagement
bias of the seal against at least one of the inboard and outboard
surfaces. The engaged first and second end portions may be offset
normal to a direction of the compressing so as to cause the
rotation (e.g., at different radii for an annular seal of circular
planform).
[0007] The details of one or more embodiments of the invention are
set forth in the accompanying drawings and the description below.
Other features, objects, and advantages of the invention will be
apparent from the description and drawings, and from the
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a plan view of a first seal.
[0009] FIG. 2 is a central longitudinal sectional view of the seal
of FIG. 1.
[0010] FIG. 3 is a partial view of the seal of FIG. 2.
[0011] FIG. 4 is a partial central longitudinal sectional view of a
second seal.
[0012] FIG. 5 is a partial central longitudinal sectional view of
the seal of FIG. 1 in an initial condition of installation.
[0013] FIG. 6 is a stress plot of the seal of FIG. 5 under
compression.
[0014] FIG. 7 is a stress plot of the seal of FIG. 5 under
compression and a first pressure difference.
[0015] FIG. 8 is a stress plot of the seal of FIG. 5 under
compression and a second pressure difference.
[0016] FIG. 9 is a partial central longitudinal sectional view of a
pair of seals in a first wellhead.
[0017] FIG. 10 is a partial central longitudinal sectional view of
a pair of seals in a second wellhead.
[0018] FIG. 11 is a partial central longitudinal sectional view of
a seal having a rounded-corner triangular section.
[0019] FIG. 12 is a partial central longitudinal sectional view of
a seal having a rounded-corner rectangular section.
[0020] FIG. 13 is a partial central longitudinal sectional view of
a seal having an obround cross-section.
[0021] FIG. 14 is a partial central longitudinal sectional view of
a seal having a hollow rounded-corner trapezoidal
cross-section.
[0022] FIG. 15 is a partial central longitudinal sectional view of
a second seal having an obround cross-section in an initial
condition of installation between a pair of opposed flanges.
[0023] FIG. 16 is a view of the seal of FIG. 15 in a compressed
condition of installation.
[0024] FIG. 17 is a view of the seal of FIG. 16 under a first
pressure difference.
[0025] FIG. 18 is a view of the seal of FIG. 16 under a second
pressure difference.
[0026] FIG. 19 is a partial central longitudinal sectional view of
a seal having a round-corner rhomboid cross-section in an initial
condition of installation between a pair of opposed flanges.
[0027] FIG. 20 is a view of the seal of FIG. 19 in a compressed
condition of insulation.
[0028] FIG. 21 is a view of the seal of FIG. 19 under a first
pressure difference.
[0029] FIG. 22 is a view of the seal of FIG. 19 under a second
pressure difference.
[0030] FIG. 23 is a partial central longitudinal sectional view of
a rounded-corner rectangular section seal in an initial condition
of installation.
[0031] FIG. 24 is a view of the seal of FIG. 23 under
compression.
[0032] FIG. 25 is a view of the seal of FIG. 23 as opposed to a
first pressure difference.
[0033] FIG. 26 is a partial central longitudinal sectional view of
a rounded-corner rectangular section seal in an initial condition
of installation.
[0034] FIG. 27 is a view of the seal of FIG. 26 under
compression.
[0035] FIG. 28 is a view of the seal of FIG. 26 exposed to a first
pressure difference.
[0036] FIG. 29 is a view of a seal in an initial stage of
installation.
[0037] FIG. 30 is a view of the seal of FIG. 29 in a compressed
condition.
[0038] FIG. 31 is a view of the seal of FIG. 29 exposed to a
pressure difference.
[0039] FIG. 32 is a view of a vane ring assembly.
[0040] FIG. 33 is a sectional view of the assembly of FIG. 32
showing fore and aft seals.
[0041] FIG. 34 is a partial central longitudinal sectional view of
an arcuate section seal in an initial condition of
installation.
[0042] FIG. 35 is a view of the seal of FIG. 34 in a compressed
condition.
[0043] FIG. 36 is a partial central longitudinal sectional view of
an arcuate section seal in an initial condition of
installation.
[0044] FIG. 37 is a view of the seal of FIG. 36 in a compressed
condition.
[0045] FIG. 38 is a partial, partially longitudinally cutaway view
of a turbine case in an intermediate stage of assembly.
[0046] FIG. 39 is an enlarged view of a seal of the case of FIG.
38.
[0047] FIG. 40 is a transverse cutaway view of the case of FIG.
38.
[0048] FIG. 41 is an enlarged view of the case of FIG. 40.
[0049] Like reference numbers and designations in the various
drawings indicate like elements.
DETAILED DESCRIPTION
[0050] FIGS. 1 and 2 show a seal 20 having a central longitudinal
axis 22. The exemplary seal 20 is of closed circular annular
planform. Other configurations are, however, possible (e.g.,
obround, rounded-corner rectangular, or yet more complex
planforms). The seal also is shown having a transverse centerplane
24. The exemplary seal has a relaxed outer diameter D.sub.O at a
radial outboard extreme 26 and a relaxed inner diameter D.sub.I at
a radial inboard extreme 28. A relaxed seal radial span R.sub.S is
half the difference between D.sub.O and D.sub.I. The seal has a
relaxed height H between first and second longitudinal extremes or
rims 30 and 32. Exemplary R.sub.S is small relative to the
diameters. For example, the exemplary R.sub.S is less than 10% of
D.sub.O. Exemplary R.sub.S and H are of similar orders of magnitude
(e.g., R.sub.S being 50-500% of H). The exemplary rims are radially
offset from each other by a radial offset R.sub.O.
[0051] FIG. 3 shows the seal cross-section as a rounded-corner
trapezoid. The exemplary trapezoid is a regular trapezoid having
lateral symmetry. The trapezoid includes a base 40 (i.e., the
longer of the two parallel sides). The base 40 is at an angle
.theta. off-radial (the half angle of the frustoconical surface
being 90.degree. minus .theta.). The cross-section has a top 42
parallel to the base 40 and spaced-apart by a thickness T. Thus,
surface normals 41 and 43 of the base 40 and top 42 are
off-longitudinal by the same angle .theta.. In the exemplary
configuration, the base 40 forms a convergent/external
frustoconical surface having a half angle of 90.degree. minus
.theta. and the top 42 forms a divergentlinternal conical surface
of similar half angle.
[0052] The seal cross-section includes first and second sides 44
and 46. A rounded corner 48 transitions between the base 40 and
first side 44; a rounded corner 50 transitions between the base 40
and second side 46, a rounded corner 52 transitions between the
first side 44 and top 42; and a rounded corner 54 transitions
between the second side 46 and the top 42. In the exemplary relaxed
condition, the rim 30 falls along the corner 48 relatively near the
base 40; the second rim 32 falls along the corner 54 relatively
near the top 42; the outboard extreme 26 falls along the corner 50;
and the inboard extreme 28 may be represented by the first side 44
or may be along the corners 48 or 52 near the first side 44. A
center 60 of the seal cross-section may be represented by the
centroid or, for the exemplary regular trapezoid, the central
midpoint between the base 40 and top 42. In the exemplary circular
planform seal 20, the center 60 forms a circle along which the seal
cross-section is swept 360.degree. about the axis 22.
[0053] FIG. 4 shows an alternate seal 70 otherwise similar to the
seal 20 but wherein the cross-section is inverted left-to-right
about the center 60 so that the outboard extreme falls along or
near the side 44; the inboard extremity falls centrally along the
corner 50; the base 40 forms an internal surface; the top 42 forms
an external surface; and the first longitudinal extreme 30 (upper
as viewed in FIG. 4) is at a greater radius than the second
longitudinal extreme 32 by the offset R.sub.O.
[0054] FIG. 5 shows the seal 70 installed in an annular space or
compartment 100 defined between longitudinal surface 102,
longitudinal surface 104, and first and second radially-extending
longitudinal end surfaces 106 and 108. The exemplary surface 102
may be along an outboard member 110 and the exemplary surface 104
may be along an inboard member 112 separate from the outboard
member 110 and to be sealed relative thereto. The surfaces 106 and
108 may respectively be along members 114 and 116. The members 114
and 116 may be separate from or integrated with one of the members
110 and 112. For example, the member 114 may be integral with the
outboard member 110 and the member 116 may be integral with the
inboard member 112.
[0055] The seal may initially be longitudinally installed in a
relaxed condition freely without radial interference inboard and/or
outboard (or with very light interference). For example, with the
members 110, 112, and 114 in position and the member 116 remote,
the seal may be longitudinally inserted through the associated open
annular channel end. The member 116 may then be inserted to close
the channel to form the space 100. Among other alternatives where
the members 110 and 112 are not pre-positioned, the seal may be
pre-placed around the member 110 or within the member 112. In this
relaxed installation state, there may be gaps 120 and 122 between
the seal outboard and inboard extremes and the adjacent surfaces
102 and 104. To provide sealing, the members 114 and 116 and their
associated surfaces 106 and 108 are drawn toward each other. The
surfaces 106 and 108 may initially engage the rims 30 and 32.
Because the contact locations 124 and 126 are at different radii
(initially offset by R.sub.O (FIG. 4)), the radial difference
allows the compression by the members 114 and 116 to form a couple.
The couple rotates the seal cross-section (e.g., clockwise about
the center 60 in the view of FIG. 5). The rotation may shift the
contact locations along the seal and the members being sealed. The
shift may alter the radial offset of the contact locations. Under
compression, the contact locations will cease to be single-point
(in section) and will be distributed. Nevertheless, the contact
locations may be represented as medians, averages, peak pressure
locations, and the like. This rotation brings the corner 48 into
compressive engagement with the surface 102 and the corner 50 into
compressive engagement with the surface 104. With this engagement,
the seal may sealingly separate four separate regions 130, 132,
134, and 136 of the space 100. With the exemplary seal, the seal
corners are sufficiently smooth and blunt as are the associated
mating surfaces so that neither the seal nor the mating surfaces
are permanently engraved or similarly deformed by the other (e.g.,
so that the seal and mating surfaces may be reusable).
[0056] FIG. 6 shows stress distribution in the seal and the mating
members in the compressed condition without differential
pressurization of the regions 130, 132, 134, and 136. Depending
upon operational parameters, differences among pressure in the
regions 130, 132, 134, and 136 may augment the sealing and the
particular cross-sectional shape and orientation of the seal may be
configured to take advantage of this. For example, with the
exemplary seal, a pressure in the region 134 above that in the
region 132 may tend to further rotate the seal section clockwise
as-viewed and increase the engagement forces between the seal and
the surfaces 102 and 104. FIG. 7 shows the stress distribution for
such a situation. Sealing engagement between the members 110 and
112 is supplemented by the pressure. Additionally, the contact
location 126 serves as a fulcrum. Accordingly, local compressive
stress in the member 114 is increased thereby increasing sealing at
the contact location 126. Compressive stress at the contact
location 124 is reduced thereby greatly reducing stress in the
member 116. Although local sealing at the contact location 124 may
be reduced, the maintenance of sealing at the radial contact
locations maintains seal integrity. FIG. 8 shows an opposite
pressurization wherein the pressure in the region 132 exceeds that
of the region 134.
[0057] Accordingly, the exemplary seal in the exemplary space can
function effectively as a bidirectional seal. Also, the exemplary
seal could be installed upside-down and still provide bidirectional
sealing, thereby avoiding problems of installer error.
Nevertheless, the seals may be applied to environments (i.e.,
configurations of the space being sealed) where only unidirectional
sealing is necessary or where the seal must be installed in a
particular one of the two orientations.
[0058] The longitudinal resilience of the exemplary seal is
associated more with changes in its cross-sectional orientation
than with changes to its cross-section. This may be distinguished
from certain annular springs and spring seals. To achieve this, the
exemplary seal cross-section is of relatively low aspect or
slenderness ratio. The aspect ratio may be measured in several
ways. One way is to determine the largest linear dimension of the
cross-section (approximately shown by L.sub.MAX in FIG. 4). This is
compared with the largest dimension normal thereto (e.g.,
approximately shown as L.sub.N). Exemplary ratios of L.sub.MAX to
L.sub.N are broadly less than 10:1 and less than 3:1 in the FIG. 4
example. Alternative measurements may be used, especially for
highly regular seals (e.g., length to width ratios of a rectangular
section seal). Another characterization of slenderness may involve
the direct distance between the seal longitudinal extremes (not the
longitudinal distance or height) relative to the maximum dimension
normal thereto. It can further be seen that the exemplary seals of
FIGS. 1-4 are relatively non-convoluted. For example, the length
L.sub.MAX and the line between longitudinal extremes both fall
entirely within the seal rather than passing outside the seal as
would be the case with a C-seal or other such spring seal.
[0059] Exemplary seal materials are metals (e.g., alloys),
optionally coated (e.g., electroplated). Exemplary alloys are
nickel aluminum bronze, stainless steel or other iron-based alloys,
copper, beryllium copper, nickel- or cobalt-based superalloys, and
the like. For example, for the wellhead seal discussed below, an
uncoated nickel aluminum bronze may be used. Alternatively, a
plated superalloy may be used (e.g., silver-plated Alloy 718). In a
turbine nozzle application discussed below, an exemplary material
is a nickel- or cobalt-based superalloy (e.g., Alloy 718 or
Waspaloy (UNS: N07001) coated with an intermetallic, cermet
coating). Alternative materials include metal matrix composites
(e.g., metal matrices including ceramic fibers such as silicon
carbide or alumina). Exemplary matrices may be foamed by spray
deposition (e.g., of a titanium-aluminum-vanadium alloy such as
Ti6Al4V), powder metallurgy, mechanical alloying, liquid metal
pressure forming, stir casting, squeeze casting, and reactive
processing. Non-metallic seal materials may nevertheless be
used.
[0060] Exemplary seal manufacturing techniques may involve one or
more rough stages including rough forming and rough machining and
one or more finish stages including finish machining and polishing.
For small diameter seals, initial machining may be from bar, ring,
or tube stock. For intermediate diameter seals, forging or casting
may be followed by machining. Alternatively, butt-welded rings may
be formed and spin profiled. Large rings may be formed by
close-to-form extruded wire rolling followed by butt welding,
dressing, and critical surface machining/polishing. Nevertheless,
other manufacturing techniques may be used.
[0061] In various examples, the seals may be used in the oil
industry (e.g., wellheads, Christmas trees, and the like). FIG. 9
shows a wellhead assembly 160 similar to that shown in U.S. Pat.
No. 6,164,663 of Turner. The exemplary wellhead assembly 160
includes an aligned pair 162 and 164 of concentric annular seals to
seal between an outer diameter (OD) surface 166 of a tubing hanger
168 and an interior/inner diameter (ID) bore surface 170 of a
wellhead 172. In the example, the inboard seal 162 seals between
the surface 166 and an interior (ID) surface 174 of a spacer ring
176. The outer seal 164 seals between the (OD) surface 178 of the
spacer ring and the wellhead bore surface 170. To provide the
longitudinal compression that in turn causes radial engagement and
sealing, lower longitudinal extremities of the seals 162 and 164
engage respective rim surfaces 180 and 182 of inboard and outboard
support rings 184 and 186, respectively secured/attached to the
tubing hanger and wellhead. Similarly, the upper longitudinal
extremities of the seals 162 and 164 respectively engage lower rim
surfaces 188 and 190 of inboard and outboard legs 192 and 194 of a
U-ring loader. Whereas the '663 patent maintains sealing engagement
by downward biasing of a wedge ring (in the physical place of the
spacer ring 176 and having a wedge surface partially in place of
the illustrated cylindrical surface), sealing may be maintained by
downward bias of the U-ring loader without necessarily having any
bias of the spacer ring or any wedge effect.
[0062] FIG. 10 shows an alternative arrangement which effectively
unifies the FIG. 9 spacer ring 176 and U-ring loader into a single
T-ring loader 200. The support rings are integrated with their
associated tubing hanger and wellhead as a tubing hanger 202 and
wellhead 204.
[0063] Yet other seal sections are possible.
[0064] FIG. 11 shows a seal having a rounded-corner triangular
exterior cross-section.
[0065] FIG. 12 shows a seal having a rounded-corner rectangular
exterior cross-section.
[0066] FIG. 13 shows a seal having an obround exterior
cross-section.
[0067] FIG. 14 shows a seal having an exterior cross-section is of
rounded-corner trapezoidal form but being hollow. Such a seal may
be formed from rough tube stock (e.g., circular cross-section) or
by forming such a tube. The tube is bent into a hoop and its ends
butt-welded to form a hollow metal O-ring. The desired
cross-section may be formed by one or more shaping steps (e.g.,
rolling between shaped rollers). To facilitate the shaping, the
O-ring may be gas-pressurized or liquid-filled (e.g., via drilling
a port and pressurizing/filling and then at least temporarily
closing the port). After shaping, the gas or liquid may be
withdrawn and the port optionally re-closed (e.g., via welding).
Finishing may be as with the other seals. Exemplary uses for such a
hollow seal involve situations of relatively low compression force.
For example, nuclear pressure vessel sealing commonly uses hollow
metal O-ring seals.
[0068] The FIG. 14 seal might offer improved springback and might
be appropriate for use as a replacement seal after a damaged seal
groove has been machined to an oversize condition beyond which the
baseline seal would not provide advantageous sealing. Hollow
section seals may be particularly relevant as replacements for
hollow metal O-ring seals in existing equipment because of
similarities in their general characteristics and avoidance of the
need to completely requalify vessels in which they are used. Solid
section seals may be preferable for future applications (e.g.,
non-retrofit) because, among other things, they are easier to
electroplate than hollow rings. Many existing hollow metal O-rings
have one or more holes through their walls for mounting to the
pressure vessel cover (lid). Fluids migrate into the interior of
the hollow ring during plating, necessitating lengthy interstage
rinsing procedures for their removal (to prevent carry-over from
plating tank to plating tank (e.g., between nickel strike and
silver plating solutions)).
[0069] FIG. 15 shows another obround cross-section seal 300 in a
relaxed condition in an initial stage of assembly between first and
second flanges 302 and 304. Each flange has a mating face 306 in
which a channel 308 is formed. The channel is bounded by an inboard
surface 310, a base surface 312, and an outboard surface 314. In
the exemplary configuration, the two channels are identical and
mate to form the space to be sealed. The obround seal section has a
first side 316 which forms an interior/internal frustoconical
surface of the seal 300. A second side 318 forms an
exterior/external frustoconical surface. In the initial stage of
installation, the first flange channel base 312 may contact an
associated first rounded end 320 of the section. The base of the
channel of the second flange 304 may contact a second rounded end
322. At this initial point of engagement, the seal may be in free
(i.e., non-interfering) relation to the inboard and outboard
surfaces 310 and 314 of both channels.
[0070] Further compression of the flanges to a fully mated
condition will rotate the cross-section of the exemplary seal
(e.g., clockwise as viewed in FIGS. 15 and 16). FIG. 16 shows a
fully engaged condition wherein the seal separates a first region
330 of the combined channel/space from a second region 332. With
the flanges fully mated or bottomed, or when other external
constraint prevents further closure of the flanges, the seal may
advantageously have further longitudinal compressibility relative
to the flanges and an ability for its section to rotate about the
section centerline. For example, the seal section may be oriented
so that the seal does not interfere with at least one of inboard
and outboard surfaces of the combined channel/space. Also, the
sides 316 and 318 also would not be bottomed against channel
surfaces so that the seal itself is not what prevents the further
drawing together of the two opposed surfaces 312 of the
channels.
[0071] The non-bottoming of the seal may have one or more of
several advantages. First, manufacturing tolerances and wear
tolerances of the members being sealed (e.g., the flanges) may be
more easily accommodated. Differential thermal expansion may also
be more easily accommodated (e.g., thermal expansion of the seal
relative to the space being sealed). In some applications, it may
be desirable to provide further flexibility by not having the
flanges bottomed. Non-bottoming flanges could be provided with an
adjustment mechanism to adjust the precompression of the seal. Such
adjustment may also be useful for addressing tolerance issues.
[0072] The effective leveraging or mechanical advantage associated
with rotating the seal cross-section may make the radial contact
loads particularly sensitive to the longitudinal position. This is
exacerbated by any radial tolerance problems. Accordingly, the
adjustment mechanism may be particularly useful where there are
radial tolerance issues or where relatively precise control over
the radial loading is required.
[0073] In the exemplary configuration of FIG. 16, with fully mated
flanges, the seal does not interfere with either of the surfaces
310 or 314 of both channels in the absence of a pressure
difference. FIG. 17 shows a net pressure P in the region 330 above
that in the region 332. This net pressure may further rotate the
seal about its contact location with the second flange 304. This
further rotation may bring the seal first end 320 into engagement
with the outboard surface 314 of the channel of the first flange
302. This rotation may, further, cause disengagement of the seal
from the base surface 312 of the channel of the first flange 302.
However, sealing may be maintained.
[0074] The pressure difference may be reversed. FIG. 18 shows a
pressure P in the region 332 above that in the region 330. The
pressure difference may cause a further rotation about the contact
location with the first flange 302. This further rotation may bring
the seal section second end into sealing engagement with the
inboard surface 310 of the channel of the second flange 304.
[0075] FIGS. 19-20 show a seal 400 having a cross-section
characterized as a rounded-corner rhomboid. Engagement with flanges
402 and 404 may be similar to that of the seal 300 of FIGS.
15-18.
[0076] FIGS. 23-28 contrast an exemplary non-interfering sealing
situation (FIGS. 23-25) with an exemplary singly interfering
sealing situation (FIGS. 26-28). The singly-interfering situation
involves interference at one of an inboard surface and an outboard
surface. Although shown in a space formed by a channel in a single
member, the illustration is equally applicable to spaces formed by
mating channels in each of the two members being sealed. Although
shown with a seal having a generally rectangular cross-section with
small radius of curvature rounded corners, other seal shapes may be
involved. The difference between the two situations is that the
FIG. 23-25 situation has relatively more clearance between the seal
and the channel inboard surface in the initial (relaxed) condition.
With the flanges fully mated and the seal compressed, FIG. 24 shows
clearance between the seal and the inboard surface of the space.
However, in the second situation, during the initial compression of
the seal from the FIG. 26 condition, the seal engages the inboard
surface so as to interfere in the mated FIG. 27 condition.
[0077] In the FIG. 24 situation, an operational pressure difference
P in the region between the seal and second flange above the
pressure in the region between the seal and first flange will cause
the seal section to rotate about its contact location with the
first flange and disengage from the second flange to create a
sealing failure (FIG. 25). However, in the FIG. 27 situation, this
pressure difference (FIG. 28) creates and/or increases sealing
contact between the seal and the inboard surface along the second
flange while maintaining contact between the seal and the first
flange. For an opposite anticipated operational pressure
difference, the channel could be positioned so that the
pressure-induced sealing interference was with the channel outboard
surface.
[0078] FIGS. 29-31 show a seal 600 for sealing a space defined by
mated channels 602 and 604 extending from end faces 606 and 608 of
flanges 610 and 612. The exemplary seal 600 is of near-obround
cross-section with an exterior side 620 and an interior side 622.
An inboard end 624 is essentially round. An outboard end 626 is
slightly off-round, flattened toward the outboard side 620 for
broader mating with the outer surface of the space. FIG. 30 shows
the seal in a compressed, un-pressurized condition wherein the
inboard end 624 of the seal section is accommodated with clearance
at an intersection of the base and inboard surface of the channel
602. The outboard end is accommodated at an intersection of the
base and outboard surface of the channel 604.
[0079] In FIG. 31, the seal 600 is exposed to an internal pressure
greater than an external pressure. The pressure difference rotates
the seal slightly counterclockwise in the particular view about the
inboard end 624. The outboard end 626 bears into firmer engagement
with the outboard surface of the space and may shift out of
engagement with the base surface of the 14 channel 604. For
reference, the seal is shown in an exemplary coupling wherein the
flanges are secured by a clamp 614 such as in a pipe coupling. An
alternative joint is an aircraft engine bleed air duct. As is
discussed further below, a pressure in an interior 616 of the duct
may exceed a pressure in an exterior environment 618.
[0080] FIGS. 32 and 33 show a turbomachine (e.g., turbine) vane
ring 700 (e.g., of a combustor outlet nozzle) comprising a
circumferential array of vane segments 702. Exemplary vane segments
have an inboard platform 704 and an outboard shroud 706. One or
more foils 708 may extend between the platform and shroud. The
exemplary platform is sealed in a front/upstream location to a
first member/structure 710 and at an aft/downstream location to a
second member/structure 712. An exemplary first structure may be a
combustion liner. An exemplary second structure may be a mounting
flange. The first and second structures may be continuous,
un-segmented structures. An exemplary front seal 720 is positioned
in a space 722 defined between the structure 710 and the platform
704. An inboard/forward corner of the exemplary seal 720 engages a
radially-extending surface 730 of the structure 710. An outboard
end of the seal 720 is captured at the junction of a
radially-extending surface 732 and an axially-extending surface 734
of the platform. During installation, before axial compression of
the seal there may be radial clearance between the seal outboard
end and the surface 734. Axially compressive engagement by the
surface 730 may rotate the outboard end into engagement or into
firmer engagement with the surface 734. The exemplary aft seal 750
is positioned in a channel 752 formed entirely in the structure 712
and engages a radially-extending surface 754 of the platform.
[0081] Such seals 720 and 750 may offer increased robustness
relative to thin self-energizing compression spring seals (e.g.,
formed of convoluted sheetmetal rings such as having cross-sections
resembling the letter E or the Greek capital letters sigma
(.SIGMA.) or omega (.OMEGA.)). Surface discontinuities of the vane
ring 700 at junctions between the segments 702 may wear the seal
during operation. For a sheetmetal seal, the thinness of the metal
allows only a slight amount of wear before failure. With the
thicker seals of FIG. 33, more wear (and thus a greater operational
time) can be tolerated.
[0082] FIGS. 34 and 35 show a seal 800 having an arcuate
cross-section. An exemplary cross-section is of an annular segment
having rounded ends. As is discussed below, in distinction to the
seals of FIGS. 1-4, this seal is subject to a greater degree of
flexing of its cross-section relative to rotation of its
cross-section. In this vein, a line representing the maximum
cross-sectional distance and a line connecting the contact
locations of the section may pass outside of the seal. In a relaxed
condition, the arc of the seal is slightly less than 90.degree.
(e.g., 70-85.degree.). The seal 800 is positioned to seal a space
802 formed by a channel in the face 804 of a first flange 806 on
the one hand and an end face 808 in a second flange 810 on the
other hand. The channel has a base surface 812 and first and second
side surfaces 814 and 816. The arcuate cross-section is
characterized by a concave side 820, a convex side 822, and first
and second ends 824 and 826. In the initial relaxed insertion, the
seal may contact the base 812 near the intersection of the convex
surface 822 and the first end 824. In the first end 824 may be
clear of the surface 816 at this point. Similarly, the convex
surface 822 may be clear if the surface 814. The end 826 protrudes
beyond the flange face 804. In the compressed state, the end 824 is
driven outward into engagement with the surface 816. The second end
826 is driven flush with the flange and 804. This may bring the
seal into compressive engagement with the surface 814 (e.g., near a
junction of the convex surface 822 and concave surface 820). FIGS.
36 and 37 show a seal 850 whose cross-section is reversed
(inverted) relative to the seal 800.
[0083] FIGS. 38-41 show use of a segmented seal of cross-section
similar to that of the non-segmented full annulus seals of FIGS.
1-4. The exemplary seal is fainted in two segments each of which
form essentially 180.degree. of the total seal. The exemplary seal
has an upper segment 900 and a lower segment 902. Exemplary uses
are in horizontally split cases (e.g., of steam or gas turbines).
The exemplary turbomachine case 910 includes a section 912 having
an upper case segment 914 and a lower case segment 916. Case
sections 918 and 920 are respectively shown to the left and right
(e.g., fore and aft or upstream and downstream) of the section 912.
The segment 914 has first and second end faces 930 and 932. Each of
these may include a channel 934 for carrying an associated seal for
sealing with the end surface of the adjacent section 918 and/or
920. The exemplary channels 934 have a base surface 940, an inboard
surface 942, and an outboard surface 944. Each segment 900 and 902
has a first end 950 and a second end 952. The exemplary ends 950
protrude slightly from the case split whereas the exemplary ends
952 are sub-flush. When the case is assembled, the end 950 of each
seal is received in the channel of the opposite segment to bear
against the end 952 of the other seal. Engagement between the ends
may create a desired hoop compression. This compression, along with
the sealing effects discussed above for the seals of FIGS. 1-4, may
help maintain the seal in sealing engagement with the outer surface
944, base surface 940, and mating surface of the adjacent case
segment.
[0084] One or more embodiments of the present invention have been
described. Nevertheless, it will be understood that various
modifications may be made without departing from the spirit and
scope of the invention. For example, as noted above, the particular
anticipated pressure differences may influence the selection of
seal cross-sectional shape and orientation. In reengineering,
remanufacturing, or retrofit applications, details of the existing
components to be sealed may influence details of any particular
implementation. Accordingly, other embodiments are within the scope
of the following claims:
* * * * *