Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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HYDRAULICALLY INSTALLED TUBE PLUG, TUBE PLUG INSTALLATION
TOOLING, AND INSTALLATION SYSTEM AND METHOD
FIELD OF THE INVENTION
This invention relates to means for hydraulically installing a tube plug
within transfer tubes that are found in boilers, condensers, and other type
heat
exchangers, and relates to plug installation techniques, and their system and
method.
BACKGROUND OF THE INVENTION
The present invention relates generally to tube plugs and plug
installation techniques and more particularly to thimble type plugs and the
use of high
pressure expansion mandrel plug installation tooling and technique to stop
leaks in
tubes found in boilers, condensers and other shell-and-tube type heat
exchangers.
Some types of tube plugs used are tapered fiber (wooden or composite
material) type plugs, one piece tapered metal plugs, two-piece metal tapered
pin and
collar plugs, multi-piece breakaway plugs, explosive plugs and thimble plugs.
The
tapered fiber plugs are usually limited to low pressure and temporary
applications and
in many cases are not compatible with the medium that would come in contact
with
the plug. Tapered metal one piece and two-piece (pin and collar) type plugs
rely on
mechanical methods for setting the plugs in the tubes with little or no
control on the
radial pressure applied to the tube. They are typically installed using a
hammer type
device. There is no way to reliably control and measure the radial force that
these
type plugs exert on the ID of the tube and the surrounding tubesheet ligaments
during
installation. This lack of radial pressure control can result in a tubesheet
ligament
being over stressed (plastically deformed) or not enough pressure applied to
stop the
leak. These forces can vary greatly from plug to plug even when installed by
the
same person using the same installation tools and techniques. One plug can be
too
loose and leak or even fall out, while the next plug can be too tight and
cause
permanent ligament damage which can generate leaks in the surrounding tube-to-
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tubesheet joints. Other potential problems with tapered metal plugs are
described in
Stanley YokeII's book "A Working Guide to Shell-and-Tube Heat Exchangers". It
states Quote: "they create a crevice behind the contact surface between the
plug and
tube, which can lead to crevice corrosion; and the tensile stresses they
generate in
the tubesheet may sensitize it to stress corrosion cracking." A disadvantage
of the
two-piece tapered plug is that it requires a tight friction fit in three areas
to work
properly. One is between the tapered pin (inner piece) and the ring (outer
piece),
second is between the OD of the ring and the ID of the tube and last is the
surface
between the tube OD and the tubesheet hole. Another disadvantage is the outer
ring
needs to have an initial clearance gap between it and the tube ID for the plug
to be
inserted. This requires a substantial deformation of the ring to engage the
tube ID
with sufficient force to create the interfacial pressure needed to hold it in
place and
seal the leak. It is possible that because the shoulder of the ring rests
against the
tube end during installation that the driving force necessary to seat the plug
and
expand it may cause the tube itself to be dislodged from its seat and create
another
leak path. Multi-piece breakaway plugs have a very small effective expansion
range
and therefore must be precisely sized to work properly. A common problem is
when
an undersized plug is selected for use. During installation the breakaway
plugs
become rapidly work-hardened during the expansion process. The resistance and
resulting friction forces will cause the breakaway of the plug parts to take
place
before the necessary radial forces are reached that should hold the plug in
place and
seal the leak. The results are plugs that may loosen and fail during the
operation of
the unit.
Explosive friction fit plugs must be installed by explosive certified
personnel and cannot be used in many applications because of the hazardous
environments that the vessels are located in such as chemical plants and
refineries.
Even if they can be used, it may require whole areas of the plant to be shut
down and
personnel removed from the area for safety reasons during their use. Another
down
side of explosive plugs is the extensive cleanup required to remove the
explosive
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residue from the vessel to prevent plant systems contamination prior to
bringing the
vessel back online.
Thimble type plugs are typically a one piece plug that resembles a thin
tube with a closed end or "blind hole." When installed using mechanical
rollers the
plug must fit snuggly in the tube hole to begin with to prevent it from
spinning during
the initial rolling process. In all of the applications discussed with the
exception of
explosive plugs it has been proven that when the ID of the tube hole being
plugged is
even slightly oval shaped it is difficult to get the plug OD to conform to the
tube ID
and provide a reliable sealing surface.
In the patent to Russell D. Wasson and David A Vossbrinck, U.S. Pat.
No. 5,901,594, issued on May 11, 1999, for High Pressure Expansion Mandrel
with
Cams Engaging Oppositely Directed Ends of an Expandable Segmented Ring, there
is disclosed a high pressure mandrel for joining a metal tube to a wall of a
metal
sheet surrounding an annular bore of the metal sheet. Spaced 0-rings are
disposed
on a shaft of a mandrel that is disposed axially in the metal tube. Outboard
of the 0-
rings, backup rings are respectively disposed on the shaft. Outboard of the
backup
rings are disposed segmented ring assemblies which are also disposed on the
shaft.
Facing opposite ends of each segmented ring assemblies are cam rings. The cam
rings are disposed on the shaft. High pressure fluid by means of a conduit in
the
mandrel shaft provides pressure to the inner wall of the metal tube to expand
the tube
radially outward. Simultaneously, the high pressure fluid urges the 0-rings
outward
toward the associated backup rings and in turn the backup rings are urged
outwardly
toward the associated segmented ring assemblies, respectively. Facing each of
the
segmented ring assemblies are cam rings. Each set of cam rings expand radially
its
associated segmented ring assembly in response to the high pressure fluid.
SUMMARY OF THE INVENTION
According to an aspect of the present invention, there is provided a high
pressure
mandrel assembly for fluidic sealing of a tube plug within the wall of a tube
for a
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tubular vessel including but not limited to heat exchangers, condensers,
evaporators,
boilers, and heaters, said mandrel incorporating components that define an
expansion area subject to high pressure fluid for use for expanding the tube
plug and
biasing it against and sealing the tube of a tubular vessel, said components
of said
mandrel including a shaft, said shaft having an inner end with an increased
diameter
section located within the tube plug during usage, said mandrel at its
opposite end is
located exteriorly of the tube plug and has a threaded segment, a nut provided
for
being accommodated upon said threaded segment of said mandrel shaft, the
remainder of said mandrel shaft between said threaded segment and the
increased
diameter section at its inner end with the exception of a pair of grooves
being of
substantially uniform diameter throughout its length and being of a lesser
diameter
than the increased diameter section at the inner end of said mandrel, a bore
provided
within said mandrel and extending partially along its length for opening into
the
expansion area of the mandrel assembly, and a vent passage separately provided
within said mandrel, and extending from its inwardmost end to that part of the
mandrel maintained externally of the tube plug in which it inserts, so that
pressure
forwardly of the mandrel assembly as it is located within and is pulled from
the tube
plug may be vented so as to release any pressure or suction that may be
generated
thereat during its application and removal; a spacer located upon said mandrel
in its
expansion area and at the location where expansion of the tube plug is to be
attained, a pair of sealing o-rings provided to either side of the spacer,
provided upon
the mandrel, and for furnishing of a sealing of the space between the spacer
and the
tube plug when substantial fluid pressure is applied thereat to force said
plug into an
expanded sealing engagement within the tube plug, each o-ring fitting within
one of
said pair of grooves provided upon said mandrel shaft; a pair of backup rings,
one of
each backup ring being applied adjacent to one of each o-ring upon the mandrel
shaft, each backup ring having a diameter larger than the increased diameter
section
upon the inner end of the mandrel shaft, to provide a sealing engagement with
the
interior of the tube plug when the mandrel assembly is installed therein; cam
means,
one provided adjacent the said backup rings; and said increased diameter
section of
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the mandrel forming a front shoulder, a segmented ring biasing against said
mandrel
front shoulder, and one of said cam means biasing against said segmented ring
during insertion and usage of the expanding mandrel assembly.
According to another aspect, there is provided a tube plug for use for
sealing one or more tubes in a tubular vessel requiring plugging, said tubular
vessel
including one of heat exchangers, condensers, evaporates, boilers, and
heaters,
comprising said tube plug having a tubular length, being opened at one end,
and
closed at its inner end and inserts within the tube of a tubular vessel, the
closed inner
end of the tube plug having a shoulder, an internal shoulder against which an
expanding mandrel may be applied, said tube plug at its open end having a
flange for
biasing against the outer end of the tubes of the tubular vessel, and
furnishing means
to provide control of depth of insertion of the tube plug within the tube to
be sealed.
According to another aspect, there is provided a high pressure mandrel
for fluidic sealing of a tube plug within the wall of a tube for a tubular
vessel including
but not limited to heat exchangers, condensers, evaporators, boilers, and
heaters,
said mandrel incorporating various components that locate an expansion area
subject
to high pressure fluid for use for expanding the tube plug and biasing it
against and
sealing the tube of a tubular vessel in which it locates, said mandrel
including a shaft,
said shaft at one end having an increased diameter section, and locates within
the
tube plug, said mandrel at its opposite end and which generally locates
exteriorly of
the tube plug having a threaded segment, a nut provided for being accommodated
upon said threaded segment of said mandrel shaft, the remainder of said
mandrel
shaft between said threaded segment and the increased diameter section at its
inner
end being of substantially uniform diameter throughout its length.
Some embodiments contemplate the construction of a precision hollow
metal plug, and its method of installation within the tube of a high pressure
boiler,
condenser, or other heat exchangers, in order to close off a particular tube
which due
to corrosive or other effects, may be subject to leaking. The precision hollow
metal
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plug of some embodiments is made with a smooth blind hole formed internally,
and
on its external surface, incorporates a series of concentric ridges and
grooves which
in combination with its plug, is inserted into the tube to be plugged. A
mandrel
assembly with seals on both ends, and an internal passage to allow high
pressure
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fluid, such as water or oil, to pass through it, is inserted into the plug.
High pressure
fluid from a pumping system is injected through the mandrel and into the area
between the mandrel and its seals. The pressurized fluid, which may be subject
to
pressures in arrange of 20,000psi to 60,000psi is conducted to and is
contained
between the seals, and is biased against the internal surface of the plug,
which forces
the plug to expand radially under such pressures and causes the outer surface
of the
plug to come in contact with the inner surface of the tube, to create a
fluidic seal.
When the high pressure fluid used to expand the plug into place is relieved,
by
venting, it leaves a tight interfacial fit between the OD of the tube plug,
and the ID of
the tube that is being sealed.
Some embodiments may provide a plug having unique characteristics
that provides for its pressure fitting against various tubes found in boilers
and
condensers, and which can be plugged in place through the application of very
high
psi to form a seal for a tube that is experiencing leakage, fracture, or other
deterioration.
Some embodiments may provide an engineered thimble type tube plug
made of but not limited to the following materials: high strength steel,
stainless steel,
brass, titanium, and other highly engineered composite materials, that can be
expanded using high pressure hydro-expansion tooling and techniques.
Some embodiments may provide a variation of a thimble type tube plug
with a shoulder or collar that is an integral part of the plug OD used to seat
the plug at
the very end of a tube or annular bore in a metal sheet i.e. tube-sheet and
expanded
in place using high pressure hydro-expansion tooling and techniques.
Some embodiments may provide a variation of a thimble type tube plug
with a consistent OD that will allow the plug to be positioned anywhere along
the
interior length of a tube or annular bore in a metal sheet i.e. tube-sheet and
expanded in place using high pressure hydro-expansion tooling and techniques.
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Some embodiments may provide a variation of a thimble type tube plug
with concentric ridges as an integral part of the plug OD. These ridges
facilitate the
plugs ability to penetrate thin layers of scale and bite into the ID of the
bore or tube
surface that the plug is being expanded into and provide a more complete seal.
Some embodiments may provide a high pressure expansion mandrel
assembly for hydro-expansion of thimble type tube plug that utilizes a
pressurized
medium such as but not limited to distilled water. This high pressure medium
the
expansion mandrel uses is supplied by an adjustable high pressure supply
system
that produces variable and controllable pressures between 201000psi and
60,000psi.
These high pressure supply systems may be engineered to utilize pneumatic
controlled logic or electronic and digital control logic or a combination of
both.
Some embodiments may provide a high press expansion mandrel that
incorporates an axial passageway in the body of the mandrel that provides for
a safe
relief of pressure when the mandrel assembly is used in blind holes such as a
thimble
type tube plug. This passage normally acts as a vent hole when inserting or
extracting the mandrel and prevents a hydraulic lock from taking place in the
blind
hole area behind the mandrel. Under conditions that might cause an undesirable
buildup of high pressure in the blind-hole area behind the mandrel assembly,
this
passageway acts as an overpressure safety vent and prevents the area from
pressurizing.
Some embodiments may provide a high pressure expansion mandrel
that has a short raised step at one end that acts as a stop and retains
various sliding
parts on the mandrel when the parts are under an axial force. The opposite end
of
the mandrel is threaded to accept a nut that when engaged, acts to stop and
retain
various sliding parts on the mandrel when the parts are under an axial force
in the
opposite direction.
Some embodiments may provide a high pressure expansion mandrel
that incorporates a cam surface as an integral part of the short raised step
on the end
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of the mandrel shaft body. This integrated cam surface mates up with one side
of a
segmented ring assembly disposed on the mandrel shaft and works with a sliding
cam ring disposed on the same mandrel shaft on the opposite side of the same
segmented ring assembly. In response to high pressure being applied to the
sliding
cam ring, pressure is applied to the sliding segmented ring which moves in an
axial
direction up against the fixed integral cam surface. The forces created by the
opposing cam surfaces act on the segmented ring assembly cause it to expand
radially, until it comes in contact with the plug or tube inner surface. The
resulting
forces facilitate centering and maintaining alignment of the mandrel assembly
in the
axial bore.
Some embodiments may provide a high pressure expansion mandrel
which incorporates removable center land area (spacer) to facilitate removal
and
replacement of worn parts on the mandrel from the primary (threaded end) of
the
mandrel shaft. This spacer when in place helps locate and position the sealing
components of the expansion mandrel assembly which define the expansion zone
area.
Some embodiments may provide a high pressure fluid supply system to
provide fluid under high pressure to hydraulically radially expand tubes and
thimble
type tube plugs.
Some embodiments may provide a high pressure fluid supply system
that is portable and able to operate in hazardous environments using only a
supply of
compressed air to both control and power its pumping system.
A benefit of some embodiments is the use of a mandrel that has an
inward threaded end, that may be secured in threaded engagement with a
previously
installed plug, to facilitate the removal of a plug when further servicing or
tube
replacement may be required.
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Non-limiting examples of embodiments of the invention will now be
described with reference to the drawings, in which:
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a front elevational view of a tube plug according to an
embodiment of the invention;
FIG. 1A is an axial section view of the tube plug taken upon the line A-A
of FIG. 1;
FIG. 2 is an exploded view of the high pressure expansion mandrel
showing a variety of component parts of an embodiment of the present
invention;
FIG. 3 is a side view of the high pressure expansion mandrel located
within a tube plug as shown in FIG. 1, with all shown being inserted into a
tube
located one of the tubes found in boilers, condensers, and the like;
FIG. 3A is a sectional view of the high pressure expansion mandrel, as
located in a tube plug, and shown within the tube being plugged, taken along
the line
A-A of FIG. 3; and
FIG. 4 is a schematic view of the high pressure fluid supply system
showing the relationship of the various components of an embodiment of the
present
invention.
DESCRIPTION OF EMBODIMENTS
In referring to the drawings, and in particular to FIG.1, the tube plug 1 is
a cylindrical housing member that can be made of but not limited to the
following
materials: high strength steel, stainless steel, brass, titanium, and other
highly
engineered composite materials, that can be expanded using high pressure hydro-
expansion tooling and techniques. It is sized for insertion within the end
portion of a
tube or an annular bore in a metal sheet i.e. tube-sheet, for a boiler,
condenser, and
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other type heat exchanger. A portion of the outer surface of the plug 1 may or
may
not have concentric ridges and grooves 2 to grip the inside of the tube and
create a
seal, and may or may not have a flange 3 located at one end to control the
depth of
plug insertion into the tube. The plug 1 has an axial blind bore 4 comprising
a
smooth portion 5 which may or may not communicate with smaller diameter
threaded
portion 6. This threaded portion 6 when included is used for attaching various
plug
extraction tools (not shown) and can be used for attaching internal plug
support
structures (not shown) in various versions of the plug.
Now referring to FIG. 2. The hydraulic expansion apparatus for setting
the tube plug 1 in place includes a mandrel assembly 7 made up of the
following
components. The components are made of appropriate high strength materials
such
as but not limited to, steel, stainless steel, titanium, high strength metal
alloys, plastic
ceramics and can vary depending on the application and any special
environmental
needs. A mandrel shaft 8 made of an appropriate high strength material and has
an
increased diameter section 9 at one end which has a beveled surface 10 on the
inboard side where it joins with the reduced diameter portion of the shaft 11
and a
threaded section 12 at the opposite end of the shaft. It should be noted that
the
mandrel 8 is generally formed of a uniformed diameter along it length except
for its
end 9, so that the components mounted thereon can be slid off and replaced
when
required.
Outboard of the threaded section 12 is a suitable high pressure
connector 13 capable of joining the shaft to a 20,000psi to 60,000psi variable
pressure fluid supply in the operation of the mandrel assembly 7 for the
expansion of
the tube plug 1. 0-ring 14 and a polyurethane backup ring 15 sit in a recess
16
formed in the shaft 8 outboard of the threaded section 12 of the shaft 8.
Suitable
annular grooves 17a and 17b are formed in the reduced section of the shaft 11.
Seated in the grooves 17a and 17b respectively are 0-rings 18a and 18b made of
a
suitably soft material. Outboard and adjacent to 0-rings 18a and 18b are
polyurethane backup rings 19a and 19b made of a resilient composition that are
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considerably harder than the 0-rings 18a and 18b but will deform in a plastic
manner
when placed under extremely high pressure. These backup rings 19a and 19b are
of
a slightly larger diameter than the increased diameter section 9 on the
mandrel shaft
8 to better enable them to fill the annular extrusion or expansion gap for the
mandrel
assembly 7 as defined by the outer surface of the increased diameter section 9
on
the mandrel shaft 8 and the inner wall of the tube plug 5. The backup rings
19a and
19b tend to prevent destructive deformation to the 0-rings 18a and 18b,
respectively
by acting as a barrier between the 0-rings 18a and 18b and other components
disposed on the mandrel shaft 8 outboard of the backup rings 19a and 19b.
A spacer 20a made of an appropriate high strength material with an ID
slightly larger than the OD of the reduced diameter section 11 of the mandrel
shaft 8
to allow it to slide freely in an axial direction on the mandrel shaft 8.
Spacer 20a has
a small diameter cross bore 20d to facilitate the free flow of pressurized
fluid through
and around the spacer. This allows for the removal of the pressure spacer 20a
from
the mandrel shaft 8 which facilitates the installation and removal of various
components that are disposed on the mandrel shaft 8 between the groove 17b
location and the increased diameter section 9 of the shaft. The OD of the
pressure
spacer 20a should be slightly less than the increased diameter section 9 of
the
mandrel shaft 8. The spacer 20a is disposed on the mandrel shaft 8 between
grooves 17a and 17b to provide separation for 0-rings 18a and 18b and to
assist
them in maintaining their desired position in the grooves 17a and 17b when
inserting
and removing the mandrel assembly 7 axially in and out of the tube plug 1.
Outboard of the backup rings 19a and 19b are segmented ring
assemblies 22a and 22b. The segmented ring assemblies 22a and 22b, comprise,
respectively four to eight equal sized segments, more or less, made of a high
strength steel alloy and held together by elastic bands or 0-rings 23a and
23b. The
number of segment pieces for each ring assembly is dependent on the size of
the
application. The elastic bands or 0-rings 23a and 23b rest in grooves formed
respectively in the outer annular face of the segment pieces that form the
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rings 22a and 22b. The ID of the segmented ring assemblies 22a and 22b is a
diameter that allows them to slide along the reduced section 11 of the mandrel
shaft
8. The OD of the segmented assemblies 22a and 22b should be slightly less than
the increased diameter section 9 of the mandrel shaft 8. On each side of the
segmented ring assemblies 22a and 22b are oppositely directed beveled cam
surfaces 24a and 24b.
Cam rings 21a, 21b, and 21c are annular members that are made of a
an appropriate high strength material with an ID that allows them to slide
freely on the
reduced diameter section 11 of the mandrel shaft 8 and an OD slightly less
than the
increased diameter section 9 of the mandrel shaft 8. Each cam ring 21a, 21b
and
21c has one end face thereof that is perpendicular to the axis of the mandrel
shaft 8.
Each cam ring 21a, 21b and 21c has an opposite beveled end face 25a, 25b and
25c
respectively. The cam rings 21a, 21b and 21c are disposed on the mandrel shaft
8
with one inboard of the segmented ring assembly 22a and one inboard and
outboard
of the segmented ring assembly 22b with their beveled end facing its
associated
segmented ring assembly, conforming to or matching the beveled surface
confronting
therewith.
Outboard of cam ring 21c are disposed annular spacers 20b and 20c
made of an appropriate high strength material with an ID slightly larger than
the OD
of the reduced diameter section of the mandrel shaft 11 to allow it to slide
freely in an
axial direction on the mandrel shaft 8. The OD of the spacers 20b and 20c
should be
slightly less than the increased diameter section 9 of the mandrel shaft 8.
Spacer
20b has a small diameter cross bore 20e to facilitate the free flow of venting
fluid
through and around the spacer. The spacers assist in positioning the
components on
the mandrel shaft 8 between groove 17a and the threaded section 12 of the
mandrel
shaft 8. Outboard of the spacer 20c is a locking nut 26 that is secured in
threaded
engagement with the threaded section 12 of the mandrel shaft 8 and limits the
axial
travel of the components on the mandrel shaft 8 in the direction of the
locking nut 26.
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Now referring to FIGS. 1, 2 and 3.The tube plug 1 is inserted axially into
a tube 27 which is disposed in a bore of a metal sheet 28 i.e. a tube sheet.
The high
pressure expansion mandrel assembly 7 is inserted axially into the blind hole
bore 4
of the tube plug 1. As the mandrel assembly 7 enters the tube plug 1, the 0-
ring 18b
seals against the smooth bore 5 of the tube plug 1. Air or liquid that may be
trapped
between this sealing point in the blind hole area 4 of the tube plug 1 is
vented through
an axial bore or vent passage 29 in the mandrel shaft 8 which intercepts a
cross bore
30 located out board of 0-ring 18a and the opposite end of the expansion zone
31.
The expansion zone 31 is defined as the area between the sealing points of 0-
rings
18a and 18b. This venting action prevents a hydraulic lock condition from
taking
place when inserting or removing the mandrel assembly 7 into or from a blind
bore
such as the one in a tube plug 1. A suitable fluid such as but not limited to
distilled
water from a high pressure pump system capable of supplying fluid at variable
and
controllable pressures between 20,000pi and 60,000 psi is supplied via a
suitable
umbilical connection, is injected into the plug 1. These high pressure supply
systems
may be engineered to utilize pneumatic controlled logic or electronic and
digital
control logic or a combination of both. The fluid enters the mandrel shaft 7
via an
axial bore 32 in the center of the mandrel shaft 7 which terminates at the
intersection
of a cross-bore 33 in the expansion zone 31 area which is located between 0-
rings
18a and 18b. The fluid under pressure is contained in the annular extrusion or
expansion gap in the expansion zone 31 located axially between 0-rings 18a and
18b on the mandrel assembly 7. The contained pressurized fluid pushes the 0-
rings
18a and 18b and causes them to leave the grooves 17a and 17b respectively and
slide along the mandrel shaft 8 in an axial direction outward. The 0-rings 18a
and
18b come in contact with the backup rings 19a and 19b respectively and cause
them
to slide in an axial direction outward on the mandrel shaft 8. As the backup
rings 19a
and 19b come in contact with the cam rings 21a and 21b they move them in an
axial
direction outward and into contact with the segmented rings 23a and 23b
respectively. The segmented ring 23a is moved further outward in an axial
direction
until it comes in contact with the beveled surface 10 of the increased
diameter section
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9 of the mandrel shaft 8. Concurrently the segmented ring 22b is moved in an
axial
direction outward and as it comes in contact with the cam ring 21c it moves
cam ring
21c in an axial direction outward until cam ring 21c comes in contact with
spacer 20b.
As the fluid pressure increases the axial movement of the components cause the
beveled surfaces 25a, 25b, and 25c of cam rings 21a, 21b, and 21c respectively
along with the beveled surface 10 of the mandrel shaft 8 to engage with the
oppositely directed conforming walls of the segmented rings 22a and 22b
respectively. This action causes the segmented ring assemblies 22a and 22b to
expand radially during the radial expansion of the extrusion gap which is
taking place
concurrently under the force of the high pressure fluid. As the segmented
rings 22a
and 22b expand radially they remain in contact and parallel to the axis of the
tube
plug 1 and form a barrier to prevent the softer material of the backup rings
19a and
19b from extruding in an axial direction outward. As the high pressure fluid
continues
to enter the annular gap in the expansion zone 31 through the port 33, it
expands the
tube plug 1 radially. As pressure increases the plug 1 goes into plastic
deformation
until it makes contact with the interior of tube 27. Additional pressure
stresses the
tube 27 and tube sheet ligament 28 but always within the ligaments elastic
range. As
the plug wall expands, the ridges 2 on the plug 1 0.D penetrate the inner wall
of the
tube 27 slightly, interlocking with the tube 27 and thereby creating multiple
interlocking sealing rings between the tube plug 1 and the tube 27. When
pressure is
released the tubesheet 28 material returns to its original shape and position
and the
result is a tight interfacial fit between the O.D. of the tube plugl and the
I.D. of the
tube 27.
Now referring to FIG. 4 which is a schematic of a high pressure fluid
supply system 34 showing the relationship of the components used to generate
and
control the fluid used to expand the tube plug in FIG.1. Fluid is taken from a
reservoir
and supplied through a shutoff valve 36, particulate filter 37, and one-way
check
valve 38 to an air-over-hydraulic pump 39. Low pressure compressed air between
80psi and 160psi is supplied to the unit as read on inlet air pressure gauge
40. This
30 air is supplied to two regulators 41 and 42. Regulated pressure from one
regulator
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42 is indicated by pressure gauge 43 as the air is routed to a normally closed
air pilot
valve 44. The regulator 42 will govern the maximum available output pressure
of the
hydraulic pump 39 by controlling the inlet air pressure. Air pressure from the
second
regulator 41 is indicated on a pressure gauge 45 as it is supplied to a
normally open
air pilot valve 46 and to a manually operated 3-way air valve 47. The system
is
activated when the operator selects the open position of air valve 47 and thus
supplies regulated air to the normally open air pilot valve 46 closing it and
to an air
pilot operator 48. Air pilot operator 48 activates a normally closed air valve
49 which
in turn opens and directs regulated air to activate a normally closed air
pilot valve 44.
The air pilot valve 44 opens and directs regulated air to the air side of the
hydraulic
pump 39 causing the pump 39 to operate. The hydraulic pump 39 begins to pump
fluid past the outlet check valve 50 to the manual relief valve 51 and the
high
pressure out conduit 52. When the manual relief valve 51 is closed and the
high
pressure out conduit 52 is restricted, system output pressure will increase
and will be
indicated on the output pressure gauge 53. When the operator closes the 3- way
air
valve 47 the pressurized air to the air pilot valve 46 and the air pilot
operator 48 is
terminated. This causes the air valve 49 and air pilot valve 44 to return to
their
normally closed positions which shuts off the supply of pressurized air to
hydraulic
pump 39 which causes the hydraulic pump 39 to cease cycling. With the
pressurized
air removed from air pilot valve 46, it returns to the open position and
relieves the
pressure trapped in the high pressure out conduit 52 and returns the fluid to
the
reservoir 35.
Variations or modifications to the subject matter of this invention may
occur to those skilled in the art upon review of the invention described
herein. Such
variations are intended to be encompassed within the scope of any claims to
patent
protection issuing hereon. The specific description of the invention as set
forth in the
specification, and as depicted in the drawings, are set forth for illustrative
purposes
only.
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