U.S. patent number RE30,802 [Application Number 06/014,654] was granted by the patent office on 1981-11-24 for method of securing a sleeve within a tube.
This patent grant is currently assigned to Combustion Engineering, Inc.. Invention is credited to George D. Rogers, Jr..
United States Patent |
RE30,802 |
Rogers, Jr. |
November 24, 1981 |
Method of securing a sleeve within a tube
Abstract
A method is disclosed for securing a repair sleeve within a
tubular fluid conveying conduit. The sleeve is positioned within
the tube so that it extends coextensive with a region of degraded
tube wall and partially beyond the axial extremes of the degraded
area. A radially outwardly directed force is then applied to the
tubular sleeve from within along a portion of the sleeve at each
end, extending beyond the degraded area. The force is sufficient to
cause outward plastic deformation of both the sleeve and the tube
resulting in an interference mechanical joint therebetween.
Inventors: |
Rogers, Jr.; George D.
(Enfield, CT) |
Assignee: |
Combustion Engineering, Inc.
(Windsor, CT)
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Family
ID: |
26686334 |
Appl.
No.: |
06/014,654 |
Filed: |
February 22, 1979 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
670932 |
Mar 26, 1976 |
04069573 |
Jan 24, 1978 |
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Current U.S.
Class: |
29/421.1; 138/98;
29/402.09; 29/523; 29/890.036 |
Current CPC
Class: |
B21D
22/105 (20130101); B21D 26/041 (20130101); B21D
26/045 (20130101); B21D 39/04 (20130101); F16L
55/163 (20130101); B21D 39/203 (20130101); Y10T
29/49361 (20150115); Y10T 29/49805 (20150115); Y10T
29/4994 (20150115); Y10T 29/49732 (20150115) |
Current International
Class: |
B21D
22/00 (20060101); B21D 26/02 (20060101); B21D
39/04 (20060101); B21D 39/20 (20060101); B21D
22/10 (20060101); B21D 39/08 (20060101); B21D
26/00 (20060101); F16L 55/163 (20060101); F16L
55/162 (20060101); B23P 017/02 () |
Field of
Search: |
;29/421R,157.3C,157.4,41D,402,41R,523,234 ;138/97,98 ;156/94
;72/370,54,58,59 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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801888 |
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Jan 1951 |
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DE |
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1083774 |
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Dec 1960 |
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DE |
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Primary Examiner: Gilden; Leon
Attorney, Agent or Firm: Kochey, Jr.; Edward L.
Claims
What is claimed is:
1. A method of securing a coaxially disposed tubular sleeve within
a fluid conduit comprising the steps of:
a. inserting said sleeve into an open end of said conduit;
b. positioning said sleeve in a desired axial position with respect
to said conduit;
c. applying a radially outwardly directed uniform force from within
said sleeve along a selected axial portion thereof having a
magnitude sufficient to cause said portion of sleeve to expand
outwardly into contact with the inner wall of said conduit.Iadd.,
but not sufficiently to permanently increase the outer diameter of
said fluid conduit.Iaddend.; and
d. applying .[.an.]. .Iadd.a second .Iaddend.additional radially
outwardly directed uniform force .Iadd.controlled .Iaddend.through
a limited distance from within said sleeve along said selected
portion having a magnitude sufficient to cause said portion of
sleeve and the wall of said conduit in contact therewith to
concurrently radially outwardly expand a predetermined and limited
distance.
2. A method of repairing a metal tube having a degraded wall
section comprising the steps of:
a. inserting an open ended tubular metal sleeve into an open end of
said tube, said sleeve being of a length greater than the axial
extent of said degraded wall section;
b. positioning said sleeve at a location in which said sleeve is
entirely coextensive with and each end extends axially beyond the
degraded area of said tube;
c. applying a radially outwardly directed uniform force from within
a selected portion of a first end of said sleeve having a magnitude
sufficient to cause said portion of sleeve to expand outwardly into
substantially circumferentially uniform contact with the inner wall
of said conduit, but not sufficient to permanently increase the
outer diameter of said tube;
d. applying an additional radially outwardly directed uniform force
from within said selected portion of the first end of said sleeve
having a magnitude sufficient to cause said portion of sleeve and
wall of said tube in contact therewith to concurrently radially
outwardly expand a predetermined and limited distance;
e. applying a radially outwardly directed uniform force from within
a selected portion of the other end of said sleeve having a
magnitude sufficient to cause said portion of sleeve to expand
outwardly into substantially circumferentially uniform contact with
the inner wall of said tube, but not sufficient to permanently
increase the outer diameter of the tube; and
f. applying an additional radially outwardly directed uniform force
from within said selected portion of the other end of said sleeve
having a magnitude sufficient to cause said portion of sleeve and
wall of said tube in contact therewith to concurrently radially
outwardly expand a predetermined and limited distance.
3. A method of securing a coaxially disposed tubular sleeve within
a fluid conduit comprising the steps of:
a. inserting said sleeve into an open end of said conduit;
b. positioning said sleeve in a desired axial position with respect
to said conduit; and
c. applying .[.a.]. .Iadd.an unopposed .Iaddend.radially outwardly
directed uniform force from within said sleeve along a selected
axial portion thereof having magnitude sufficient to cause said
portion of sleeve to outwardly expand .Iadd.by confining a
pressurized hydraulic fluid within said sleeve along said selective
sleeve portion, and thereafter supplying an additional
predetermined and controlled fixed volumetric quantity of hydraulic
fluid to cause a limited expansion of said conduit
.Iaddend.including .[.applying the force.]. .Iadd.controlling the
application of the force by internally limiting the distance of
application .Iaddend.through .[.a.]. .Iadd.the
.Iaddend.predetermined and limited radial distance .[.thereby
also.]. .Iadd.including .Iaddend.causing said conduit to
.Iadd.permanently .Iaddend.expand a limited distance.
4. A method of repairing a metal conduit having a degraded wall
section comprising the steps of:
a. inserting an open-ended tubular metal sleeve having a length
greater than the axial extent of the degraded wall section into an
open end of said conduit;
b. positioning said sleeve at a location in which said sleeve is
entirely coextensive with and each end extends axially beyond the
degraded area of said conduit;
c. applying a radially outwardly directed uniform force from within
a selected portion of a first end of said sleeve having a magnitude
sufficient to cause said portion of sleeve to radially outwardly
expand including applying the force through a predetermined and
limited distance thereby causing said conduit in contact therewith
to expand a limited distance; and
d. applying a radially outwardly directed uniform force from within
a selected portion of the other end of said sleeve having a
magnitude sufficient to cause said portion of sleeve to radially
outwardly expand including applying the force through a
predetermined and limited distance thereby also causing said
conduit in contact therewith to expand a limited distance. .Iadd.
5. The method according to claim 1 or 2 wherein:
a. the step of applying a radially outwardly directed uniform force
along said selected sleeve portion includes supplying a pressurized
hydraulic fluid within said sleeve along said selected sleeve
portion to a predetermined pressure level; and
b. the step of applying the additional radially outward directed
uniform force includes supplying additionally a predetermined fixed
volumetric quantity of hydraulic fluid to cause the predetermined
and limited expansion of said sleeve and conduit portions.
.Iaddend..Iadd. 6. The method according to claim 4 wherein: the
step of applying a radially outwardly directed uniform force along
said selected sleeve portion includes confining a pressurizable
hydraulic fluid within said sleeve along said selected sleeve
portion, and thereafter supplying an additional predetermined and
controlled fixed volumetric quantity of hydraulic fluid to cause
the limited expansion of said conduit. .Iaddend..Iadd. 7. A method
according to claim 3 or 4 wherein: the step of supplying the
radially outwardly directed uniform force along said selected
sleeve portion through a predetermined and limited radial distance
includes:
a. compressing an elastomer within said sleeve adjacent said
selected sleeve portion through a limited axial distance to cause a
limited radial expansion of said elastomer and thereby cause the
limited expansion of said conduit. .Iaddend.
Description
BACKGROUND OF THE INVENTION
The invention relates generally to a method and apparatus for
securing a tubular sleeve coaxially within a fluid conduit.
There exists, in a variety of embodiments, fluid conduits which
themselves are surrounded by a fluid environment. One such example
is that of a tube and shell heat exchanger wherein a first fluid is
contained within the fluid conduit and a second fluid surrounds the
exterior of the conduit such that heat exchange between the two
fluids is effected. Such fluid conduits may from time to time
develop leaks due to rupturing of the conduit wall, which may occur
due to initial imperfections or through subsequent deterioration of
the conduit. The resulting leak permits fluid communication between
the first and second conduits which may not always be tolerable.
Such would be the case if the two fluids in combination reacted
violently or if one fluid would introduce some undesirable property
to the second fluid. An example of this latter problem arises in
the steam generating heat exchangers associated with pressurized
water nuclear steam supply wherein the fluids are at substantially
different pressures and one fluid contains radioactivity while the
other does not. For these reasons, continued, large amounts of
fluid communication between the two fluids through a leak in the
tube must be prevented.
When the fluid conduits are readily accessible, a variety of
techniques may be employed to repair the ruptured conduit directly
or to install a sleeve device or a plug into the conduit which
stops the leak or completely isolates the entire conduit from a
fluid source. However, in some environments, including that of a
nuclear heat exchanger, it may be difficult for reasons of
inaccessibility or biological hazard to effect such repairs. In
such instances, techniques have been developed for plugging the
fluid conduits from a remote location and thus totally removing
them from service. Either rolling, explosive expansion and/or
welding have been used to secure plugs in the tube ends. Rolling
and welding are rather difficult to apply as remote operation and
explosive expansion has emerged as the most viable means of
plugging tubes by remote operation.
A serious drawback to plugging both ends of a heat exchanger tube
is that eventually as more and more tubes are plugged the capacity
of the steam generator becomes less and less. Plugging requires
removing an entire tube from operation when in general only a small
localized zone of the tube is involved in the leak. Attempts have
been made to install sleeving within the tube to isolate the
portion of the tube which has degraded thereby stopping the leak.
Previous sleeving development work has been primarily concerned
with obtaining an absolutely leak proof joint by brazing, arc
welding, explosive welding, or some other means. All of these
metallurgical bonding techniques have problems which are not
immediately amendable except in very closely controlled laboratory
situations. This is due to the need for cleanliness, close
fittings, heat application and atmosphere control.
SUMMARY OF THE INVENTION
The present invention relates to a method of forming an
interference mechanical joint for securing a coaxially disposed
tubular sleeve within a conduit. The tubular sleeve is first
inserted into an open end of the conduit and moved to the desired
location therein. A radially outwardly directed force is then
applied from within the tube along a selected axial portion
thereof. The magnitude of the force is sufficient to cause the
portion of the sleeve to which it is applied to expand outwardly
into contact with the inner wall of the conduit and to continue
expanding a predetermined amount to expand the surrounding conduit,
resulting in the desired interference mechanical joint.
One particularly advantageous application of the invention permits
repair of a metal tube having a degraded wall section. A tubular
metal sleeve is selected having a length greater than the axial
extent of the degraded wall section. The sleeve is positioned
within the tube with a portion extending beyond the degraded
section at each end. An interference mechanical joint is then
formed at each end of the sleeve/tube in the portion of the tube
extending beyond the degraded section. The sleeve, so mounted
isolates the degraded section from flow within the tube and further
substantially increases the axial strength of the tube in this
region.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view showing a tubular sleeve secured with a
fluid conduit in a manner according to the principles of the
invention;
FIG. 2 illustrates a hydraulic apparatus for applying a radially
outwardly directed force to a portion of the interior wall of the
sleeve/tube according to the invention; and
FIG. 3 illustrates a mechanical apparatus for performing the same
function as the apparatus of FIG. 2 by applying a compressive force
to an elastomeric material.
DETAILED DESCRIPTION OF THE INVENTION
Referring first to FIG. 1, a sleeve 10 is shown positioned within a
fluid conduit 12 having a region of degradation 14 in the exterior
wall thereof. This figure shows the joint of the invention at an
intermediate stage on the right side and, on the left side, after
it has been secured within the tube by application of internal
radially extending pressure on the interior wall of the sleeve.
FIGS. 2 and 3 illustrate two alternate embodiments of apparatus
which permit remote application of the necessary internal force
upon the sleeve to cause the sleeve and the tube to expand
outwardly to form an interference mechanical joint.
Referring back now to FIG. 1, the method of securing the repair
sleeve 10 within the tube 12 will be described in greater detail.
The outer diameter of the repair sleeve is somewhat smaller than
the inner diameter of the tube being repaired permitting the sleeve
to be easily inserted within the tube and moved axially therealong
to a desired position with the ends thereof extending beyond the
degraded area which it is desired to isolate from the fluid flow
within the conduit. As pointed out above, upon close inspection of
FIG. 1 it will be noted that the joint 16 on the right side
illustrates an intermediate step in the securing of the sleeve
within the tube wherein the sleeve has been expanded into contact
with the inner wall of the tube, however, the tube wall itself has
not yet been expanded to form the final interference mechanical
joint as illustrated by the joint 18 on the left end.
Once the sleeve is positioned in the desired location within the
tube suitable means are used to apply a radially outwardly directed
force from within the tubular sleeve, first at one end and then at
the other end of the tube to cause the sleeve to expand radially
outwardly first, into contact with the inner wall of the tube and
then to further expand along with the tube resulting in a
mechanical interference. Because the sleeve and the tube have
essentially equivalent elastic constants and, accordingly the outer
tube is stressed to the same level as the sleeve, a slight
mechanical clearance may exist between the sleeve and the tube at
the joint. As a result, the joint will not obtain absolute leak
tightness but will limit the leakage thereby to a very small amount
estimated at less than 100 cc's per minute. The sleeve will provide
mechanical strength in the axial direction capable of preventing
separation of the tube in the degraded area should the tube wall
fail completely.
In a typical application, a 3/4 inch outside diameter Inconel 600
tube of the type commonly used in a nuclear steam generator having
a wall thickness of 0.048 inch is provided with a 5/8 inch outside
diameter having a 0.032 inch thickness wall also made from Inconel
600. The sleeve length is selected so that it extends beyond the
degraded area by an amount required to provide for inaccuracies in
axial location. Internal pressure is then applied to a limited
portion of one end of the sleeve to cause expansion of the sleeve
and the tube together to form the desired interference mechanical
joint. Internal pressures of 14,000 to 15,000 psig are necessary in
order to obtain the desired expansion of the tube and sleeve
described above as will be described more fully hereinafter in
connection with apparatus for imparting the necessary radially
directed pressure.
Turning now to FIG. 2, hydraulic apparatus 20 is shown for applying
the radially outwardly directed force necessary to cause the
expansion joint. The apparatus is shown positioned adjacent to the
end of a sleeve 10 which has been positioned in the desired axial
location within the outer tube 12. The apparatus comprises a center
mandrel 22 having a fixed stop 24 and a movable stop 26. The fixed
stop 24 comprises a radially enlarged section of the mandrel which
is sized to fit closely with the inner diameter of the sleeve 10.
The movable stop 26 comprises an annular ring having an outer
diameter the same as that of the fixed stop and an inner diameter
permitting a close tolerance sliding fit on the outer diameter of
the mandrel. The end of the mandrel extending into the sleeve is
provided with a threaded nut 28 which engages mating threads 30 on
the mandrel and which is used to adjust, within limits, the
position of the movable stop 26 axially with respect to the mandrel
22. The fixed and the movable stop along with the section 32 of the
mandrel extending therebetween and the interior wall 34 of the
sleeve 10 cooperate to define an annular chamber 36 in fluid
communication with the inner wall of the sleeve. A pair of opposed
"U"-cup seals 38 are positioned about the mandrel within the
chamber 36 and are situated with their flat annular surface 40
abutting the fixed stop and the movable stop and their "U"-shaped
cross section in fluid communication with the annular chamber. The
"U"-cup seals 38 are the primary hydraulic fluid sealing elements
and act positively with pressure, i.e., as internal pressure is
increased, their sealing effect increases. The mandrel is provided
with an axially extending hydraulic passageway 40 through the
center thereof which terminates within the mandrel adjacent to the
annular chamber 36. A second passageway 42 substantially
perpendicular to the first extends from the end of the first
passageway through the mandrel wall to provide fluid communication
between the first hydraulic passageway and the annular chamber 36.
A suitable hydraulic fitting 44 at the end of the mandrel connects
to a tube 46 supplying a suitable hydraulic fluid from a positive
displacement pump 48. A predetermined fixed volumetric input of
hydraulic fluid controlled by control means 50 following
application of an initial set pressure, determines the maximum
diameter of expansion of the joint. As an example, for the 3/4 inch
O.D. tube and 5/8 inch O.D. sleeve described above the pressure
required to plastically expand the sleeve into contact with steam
generator tube I.D. is 6000 to 7000 psig. The pressure is then
increased while applying the fixed volumetric input to a peak of
14,000 psig to 15,000 psig to expand both tubes to the final
configuration. For a one inch long expanded zone in the above
example a final volumetric input of 1 cc results in a final
diameter expansion of the outer tube of 0.025.+-.0.005 inch.
In order to obtain a good seal at the outer surface 52 of the
"U"-cup seals, the interior wall 34 of the sleeve 10 is provided
with a smooth surface, usually 16 micro inch RMS or better is
sufficient to provide a good substantially leakproof seal while the
hydraulic pressure is being applied. It has also been found that to
prevent damage to the seals during assembly it is desirable to
provide lead in chambers and a seal lubricant to improve ease of
assembly.
Referring now to FIG. 3, a mechanical expanding apparatus 54 is
shown wherein an annular elastomer plug 56 is caused to expand
within a sleeve 10 thereby causing expansion of the sleeve and tube
to form the desired interference mechanical joint. The apparatus
comprises an elongated mandrel 58 threaded at one end 60 and having
an adjusting nut 62 engaging said end for adjusting the axial
position of a movable stop 64. The movable stop comprises an
annular ring whose inside diameter and outside diameter are in
relatively close tolerance engagement with the mandrel 58 and the
inner wall 34 of the sleeve 10, respectively. A fixed stop 66
identical in structure to the movable stop is positioned on the
mandrel 58 axially spaced from the movable stop 64 to define an
annular chamber within which the annular elastomer plug 56 is
retained. The fixed stop 66 is maintained in the desired position
within the sleeve 10 by means of an elongated reaction tube 68
which is held in a fixed position by means external to the tube and
not shown in the drawing. The reaction tube has a central opening
70 therethrough through which the mandrel extends. Once the mandrel
assembly is inserted into a sleeve/tube arrangement in the desired
position as shown in FIG. 3 a hydraulic ram or other mechanical
means not shown but represented by arrow 72 is used to pull upon
the mandrel and force the movable stop or piston 64 and mandrel
toward the stationary stop or piston 66. The axial motion increases
pressure on the elastomer plug 56 which, when confined, acts
similar to a fluid in exerting uniform outwardly directed pressure
on the sleeve and tube.
The permissible axial movement of the mandrel, and as a result the
total expansion of the elastomer 56 is limited to a predetermined
amount by a mechanical stop comprising an enlarged diameter section
74 upon the mandrel which defines an annular shoulder engages a
hard stop 76 comprising a second annular shoulder provided in the
fixed reaction tube 68.
For the 3/4 inch O.D. tube and 5/8 inch O.D. sleeve described above
a mandrel 58 having a shaft diameter of 5/16 inch has been used
with a urethane plug having an I.D. of 5/16 inch and an O.D. 9/16
inch to fit within the sleeve. A typical material for the plug is a
cast urethane such as a product of the Acushnet Co., available
under the trade name of Elastocast Urethane.
With this material axial forces (72) of around 3,000 lbs. are
required to obtain a forming pressure on the elastomer plug of
15,000 psi. The diametral clearances between the stops or pistons
64, 66 and the sleeve inner wall 34 and the mandrel are on the
order of 0.001 inch to prevent extrusion of the elastomer at the
high forming pressures obtained.
It will be obvious to one skilled in the art that two or more
hydraulic chambers and elastomeric expanders may be assembled on a
common mandrel and accordingly have the capability of forming more
than one expansion joint in one operation. While such arrangements
are not shown or described in detail herein they are intended to
fall within the scope of the invention.
Further, while this preferred embodiment of the invention has been
shown and described, it should be understood that it is merely
illustrative and that changes may be made without departing from
the scope of the invention as claimed.
* * * * *