Note: Descriptions are shown in the official language in which they were submitted.
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NUCLEAR REACTOR END FITTING MOCK-UP ASSEMBLY
The present invention relates to a mock-up assembly for simulating as found
nuclear reactor end fitting conditions suitable for use in testing, training
and proving
of tools to be used in the reactor environment.
BACKGROUND
The end fittings for a CANDUTM nuclear reactor form part of the primary heat
transfer system of the reactor. The end fittings are connected with pressure
tubes that
run through the reactor core and carry fuel bundles. Within the reactor core,
the
pressure tubes are surrounded by calandria tubes spaced therefrom by garter
springs.
Heavy water is circulated into and out of the reactor through the end fittings
and the
pressure tubes which contain fuel bundles. The end fittings also provide
connection
points for a fuelling machine to lock onto for the insertion and removal of
fuel into the
pressure tubes of the fuel channel. Each end fitting has a closure plug to
maintain
water pressure in the channel and the closure plug is removed by the fuelling
machine
creating an opening through which a new fuel bundle carried by the fuelling
machine
is inserted into the fuel channel and spent fuel bundles are removed at the
opposite
end of the reactor. In a CANDUTM nuclear reactor there may be as many as 480
fuel
channels having opposite ends connected to an end fitting. =
In the past, the nuclear reactor industry has developed various mock-up
devices for testing various aspects of the as found reactor design in a non-
radioactive
mock-up site or building located near the reactor. At these mock-up sites,
tool testing
and proving can be performed prior to the tool being used in the radioactive
environment of the nuclear reactor. One such mock-up assembly that has been
developed for testing tooling to be used with the end fittings is a 3 x 3
array mock-up
of end fittings.
The 3 x 3 array mock-up of end fittings typically has one target end fitting
surrounded by eight dummy end fittings. The target end fitting has the same
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geometry as the as found end fittings in the nuclear reactor and is mounted in
a lattice
tube within the mock-up in the same manner as the as found end fitting in the
nuclear
reactor. The target end fitting is used to test new tooling for purposes of
fuelling the
reactor, fuel channel inspection, fuel channel replacement, tool training and
tool
proving associated with any operation to be performed on a fuel channel. The
dummy
end fittings provide the representative end fitting geometry to the target end
fitting in
the reactor environment and are available to react the tooling forces
associated with
the tools used on the target end fitting. In some instances tooling may clamp
onto
adjacent dummy end fittings needed to react the tooling. Usually, testing
instructions
for the tooling may relate to a full 360 degrees about the target end fitting,
and hence
the target end fitting is typically located in the central site of the 3 x 3
array with
dummy end fittings located in the other eight sites surrounding the target end
fitting.
In this mock-up assembly, two opposing face plates or support walls,
representing inner and outer tube sheets of the calandria, each have nine
aligned
openings interspaced by a lattice tube extending between each of the aligned
openings
and connected to each of the face plates. The lattice tubes are adapted to
support the
eight dummy end fittings and the target end fitting. Each lattice tube has two
axially
spaced bearings located in the tube for receiving in sliding free floating
relation
between these bearings a leading end portion of the dummy end fitting or
target end
fitting. The mock-up assembly further includes an external clamping assembly
located on the outside of one of the end plates for clamping to the dummy end
fitting
so as to restrain the dummy end fitting axially. While this arrangement is
able to
provide a mock-up that accounts for as found pressure tube creep, this mock-up
requires many components to be assembled in setting up the mock-up including a
full
length lattice tube that extends between the face plates, internal lattice
tube bearings,
and an external clamping mechanism.
It would be desirable to be able to provide a mock-up assembly for end
fittings
that does not require the use of internal bearings, lattice tubes that span
the space
between the end plates, and an externally mounted clamping assembly while
still
providing for axial positioning of the dummy end fitting.
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BRIEF DESCRIPTION
The present invention relates to a mock-up assembly for simulating as found
nuclear reactor end fitting conditions suitable for use in testing, training
and proving
of tools to be used in the reactor environment.
In accordance with an aspect of the present invention there is provided a
mock-up assembly for simulating as found nuclear reactor end fitting
conditions. The
assembly comprises a front support wall and a rear support wall mounted in
spaced
apart fixed relation with each other. The front support wall has a plurality
of spaced
apart front circular openings extending therethrough wherein the front
openings
represent as found end shield outer tube sheet bores of the nuclear reactor.
The
assembly further comprises a plurality of dummy end fittings each adapted to
pass
through a corresponding one of the front openings of the front support wall.
The
assembly further comprises a plurality of cylindrical sleeves, one for each of
the
dummy end fittings, being secured to the rear support wall, extending forward
from
the rear support wall toward the front support wall, and being spaced in non-
contacting relation away from the front support wall. Each sleeve is mounted
with its
longitudinal axis aligned with a corresponding one of the front openings for
receiving
in axial telescopic positional relation a corresponding one of the dummy end
fittings
extending through the corresponding one of the front openings.
This use of the cylindrical sleeve mounted to the rear wall and extending
forward from the rear wall towards the front wall and being spaced in non-
contacting
relation with the front wall provides a sleeve that does not extend the full
distance
between the first and second support walls. Moreover, with the sleeves being
adapted
to receive telescopically in axially telescopic positional relation a
corresponding
dummy end fitting there is no requirement for a bearing to be used inside a
lattice tube
that would extend between the first and second support walls. Accordingly, the
structure of the present invention is simplified compared to previous mock-up
assemblies.
It is also envisaged that the telescopic arrangement between each cylindrical
sleeve and its corresponding dummy end fitting can be such that the
cylindrical sleeve
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has an outer diameter which is less than the inner diameter of the dummy end
fitting
or alternatively the cylindrical sleeve has an inside diameter that is greater
than the
outside diameter of the dummy end fitting.
The mock-up assembly may further comprise a locking device located
between the front and rear support walls. The locking device is attached to
both of the
sleeve and its corresponding dummy end fitting so as to fix the axial
telescopic
positional relation of the sleeve with its corresponding dummy end fitting. It
is also
envisaged that the locking device may further fix the angular relationship
between the
sleeve and its corresponding dummy end fitting.
The locking device is readily accessible between the front and rear support
walls permitting the fixing of the axially telescopic positional relation or
displacement
between the dummy end fitting and its corresponding sleeve. By locking the
axially
relative position of the sleeve and its corresponding dummy end fitting, the
dummy
end fitting can be positioned externally of the front support wall in and as
found
nuclear reactor end fitting condition. Moreover, the relative axial position
between
different dummy end fittings in the mock-up assembly, allows each of the dummy
end
fittings to be in a correct axial position that simulates the as found end
fitting creep
conditions in the reactor. Further, the locking device may result in the
angular
relationship between the sleeve and its corresponding end fitting being fixed
thereby
accommodating for variable positions of the feeder tubes on the dummy end
fittings
of different reactor designs.
It is envisaged that the locking mechanism may take on several different
embodiments. For example, the locking mechanism could comprise a pipe clamp
surrounding the sleeve with a spring lock or screw type lock extending
radially
through the sleeve into engagement with an outer surface of the dummy end
fitting
telescopically received within the sleeve. This engagement may comprise an
interference fit or there could be a corresponding dimple or hole in the
sleeve through
which the lock would pass. Alternatively, the pipe clamp could be mounted
about the
outside wall of the dummy end fitting and dummy end fitting could pass over
the
sleeve. It is further envisaged that the locking device may comprise a
threaded bolt
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mechanism passing through the sleeve for engagement with one of the series of
apertures extending linearly along the dummy end fitting portion that slides
within the
corresponding sleeve.
In a preferred aspect of the mock-up assembly, one of each said sleeve and its
corresponding dummy end fitting has a leading edge surface portion, a tubular
portion
extending back from the leading edge surface portion, and at least one guide
slot in the
tubular portion extending longitudinally back from the leading edge surface
portion.
The locking device may be mounted to the tubular portion and may have a
locking mechanism adjustably moveable along the guide slot for engaging the
other
one of each said sleeve and its corresponding dummy end fitting for fixing the
relative
axial telescopic position of the sleeve with its corresponding dummy end
fitting.
The other of each said sleeve and its corresponding dummy end fitting may
have a protrusion adapted to slide along the guide slot restricting relative
angular
displacement between the sleeve and its corresponding dummy end fitting and
permitting telescopic movement between the sleeve and its corresponding dummy
end
fitting.
The rear support plate may comprises at least one rear circular opening
representing an as found end shield inner sheet bore which is axially aligned
with a
corresponding one of the front circular openings. The assembly may further
comprise
a lattice tube extending between the rear circular opening and the aligned
front
circular opening, and a target end fitting adapted to pass through the aligned
circular
front opening for reception in the lattice tube.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the nature and objects of the present invention
reference may be had by way of example to the accompanying diagrammatic
drawings in which:
Figure 1 is a perspective view of a mock-up assembly for simulating as found
reactor end fitting conditions in accordance with the present invention.
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Figure 2 is an enlarged perspective view of a first end of the mock-up
assembly shown in Figure 1.
Figure 3 is a perspective view of the dummy lattice tube partial sleeve of the
present invention.
Figure 4 is a plan view of the dummy lattice tube partial sleeve of the
present
invention.
Figure 4A is an end view of Figure 4.
Figure 5 is a perspective view of the dummy end fitting of the present
invention.
Figure 6 is a sectional side view showing the interconnection between the
dummy lattice tube partial sleeve and the dummy end fitting of the present
invention.
DETAILED DESCRIPTION
Referring to Figure 1 there is shown a mock-up assembly 10 for simulating as
found nuclear reactor end fitting conditions. The mock-up assembly 10
comprises
two spaced apart base platforms 12 each having base framing 14 for supporting
a
corresponding 3 X 3 end fitting assembly 16. The support frame sections 14 of
the
mock-up assembly 10 are interconnected by an axially extending weldment 18. It
should be understood that any number of end fittings may be utilized within
the realm
of the present invention, such as, for example, 4 X 4, 3 X 6, and 4 X 8 end
fittings.
Also, it should be appreciated that the distance between the end fitting
assemblies
represents the distance across the calandria core of the nuclear reactor being
simulated
by the mock-up assembly. The 3 X 3 end fitting assemblies 16 are also
vertically
adjustable by means of a vertical guide post 104 and three screw jacks 106
(only one
of which is shown) for vertically lifting the framing 14 relative to the base
platform
12. The screw jacks are operable by a single motor and gear box (not shown).
Referring now to Figures 1 and 2, each of the 3 X 3 end fitting assemblies
comprise a front support wall 20 and a rear support wall 22. Walls 20 and 22
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comprise rectangular plates in the embodiment shown. The front support wall 20
is
spaced apart from the rear support wall 22 by four tube sheet spacer bars 24
located in
the corners of the walls 20, 22. Each spacer bar 24 has threaded end portions
that
pass through the support walls 20, 22 and are secured in place by nuts 26. The
front
support wall 20 and the rear support wall 22 simulate the locations of the
inner and
outer tube sheets of the calandria of a nuclear reactor.
Each of the front support wall 20 and the rear support wall 22 each
respectively comprise front and rear circular openings 28, 30. The front and
rear
circular openings 28, 30 are aligned relative to each other and represent
respectively
the outer and inner tube sheets boars of a nuclear reactor.
Extending outwardly of the front support wall 20 are a plurality of dummy end
fittings 32 and a single target end fitting 34. The target end fitting 34 is
centrally
located to the dummy end fittings 32. It should be understood that the
relative
positioning of the target end fitting 34 with the dummy end fittings 32 may
vary and
that more than one target end fitting may be utilized.
The target end fitting 34 has a target end fitting bellows 36 and is received
within a full lattice tube 38 extending completely between the front support
wall 20
and the rear support wall 22. The target end fitting is mounted in position
relative to
the front support wall 20 by positioning assembly 108 attached to each of the
front
support wall 20 and the target end fitting 34. The lattice tube 38 carries
journal
bearings allowing the target end fitting 34 to be mounted within the lattice
tube. The
target end fitting 34 has an inner portion (not shown) extending within the
lattice tube
38 that is connected to a pressure tube that in turn extends within a
calandria tube 40
spanning the gap between the 3 X 3 end fitting assemblies 16. As shown in
Figure 1,
the calandria tube 40 has a bell shaped end portion 42 held in place with the
end
fitting assemblies 16 by a calandria tube insert 44 within the rear support
wall 22
representing the inner lattice tube sheet. The target end fitting has external
and
internal surface geometries that correspond to those of the as found end
fitting being
simulated. As a result of these internal and external surface geometries,
testing of
tooling may be performed on the target end fittings 32 for the purposes of
fueling the
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reactor, fuel channel inspection, fuel channel replacement, tool training and
tool
proving associated with any operation to be performed on a fuel channel. The
target
end fitting 34 has the same geometry as the as found end fittings in the
nuclear reactor
being simulated.
Surrounding the target end fitting 34 are eight dummy end fittings 32.
Dummy end fittings 32 are representative of the external end fitting geometry
relative
to the target end fitting in the reactor environment and are available to
react the forces
associated with tools used on a target end fitting. That is tooling may clamp
onto the
adjacent dummy end fittings to provide the end fittings needed to react the
tooling
being tested on the target end fitting 34. It should be understood that while
the a
dummy end fitting 32 may have internal and external surface geometries
corresponding to those of the as found end fitting being simulated, in the
preferred
embodiment, the dummy end fittings 32 have an external geometry for that
portion of
the dummy end fitting 32 that extends forward out from the front support wall
20 of
the mock-up assembly 10 that corresponds to the as found dummy end fitting
being
simulated. The dummy end fitting 32 does not require its internal geometry
corresponds to the internal geometry of the as found end fitting under
simulation
because the dummy end fitting 32 is not used with the tooling in the same
manner as
the target end fitting is to be used. Further, the geometry of the dummy end
fitting 32
positioned between the front and rear support walls 20, 22 is not required to
correspond that of the as found end fitting located at this position because
the dummy
end fitting is used to react the tooling located outside of the front support
wall. In the
preferred embodiment, that portion of the dummy end fitting positioned between
the
front and rear support walls 20, 22 is of uniform cylindrical shape for
telescopic
reception in sleeve 60 as discussed in more detail hereinafter.
Referring now to Figure 5, there is shown a perspective view of one of the
dummy end fittings 32. It will be noted that this dummy end fitting has a
closure end
face 46 and a main tubular portion 48 which carries at one end thereof the
feeder
mount 50. The dummy end fitting 32 includes a leading end portion 52 of
uniform
diameter and cylindrical shape having two sets of paired apertures 54, 56 and
58. The
paired apertures 54, 56 and 58 are located in various different angular
positions about
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the dummy end fitting and are also located axially at different locations
along the
length of the dummy end fitting 32. Each one of the pairs of apertures 54, 56,
and 58
are spaced apart axially along the dummy end fitting 32. One set of paired
apertures
54, 56 and 58 is shown in Figure 5. The other or second set of paired
apertures are
located diagonally opposite the shown pairs and are not visible in Figure 5.
These
apertures 54, 56 and 58 are made in the dummy end fitting 32 so as to
represent
various lengths of end fittings for differing reactor environments. The
purpose of the
aperture sets 54, 56 and 58 is subsequently described.
Referring now to Figures 2, 3, and 4 there is shown a plurality of cylindrical
sleeves 60 which functions as a dummy lattice tube. Sleeve 60 is mounted to
the rear
support wall 22 by a lugs 62 screwed into the rear support wall 22. The sleeve
60
includes a rim or rims 64 over which the ear of the lugs 62 fit so as to
secure the
sleeve relative to the rear support wall 22. The sleeve 60 has finger flanges
76 that
pass through and engage a corresponding rear circular opening 30 in the rear
support
wall 22. In this manner, the sleeve 60 is held in axial alignment with the
front circular
opening 28 of the front support wall. As shown in Figures 1 and 2, the sleeve
60
extends from the rear support wall 22 towards the front support wall 20 and is
spaced
in non-contacting relation away from the support wall 20.
As further shown in Figures 1 and 2, the dummy end fittings 32 are shown to
be telescopically received within the sleeve 60. In this regard, leading end
portion 52
of the dummy end fitting 32 has a uniform diameter and cylindrical shape which
is
not of reduced diameter which reduced diameter is joined with a pressure tube
as is
present in an end fitting used in a nuclear reactor environment. The inside
diameter of
the sleeve 60 is slightly greater than the outside diameter of the dummy end
fitting 32
along end portion 52. As shown in Figure 2, the dummy end fitting 32 passes
through
the front circular opening 28 into the area 100 between the front and rear
support
walls 20, 22 and is moveable axially and telescopically into and relative with
the
sleeve 60.
Also as shown in Figure 2 each of the dummy end fittings has a dummy
bellows 66 surrounding the dummy end fitting 32 adjacent the front end of the
front
support wall 20.
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This telescopic arrangement of the dummy end fitting 32 within the sleeve 60
eliminates the need for a lattice tube to extend completely between the front
support
wall 20 and the rear support wall 22 and eliminates the use of bearings in the
lattice
tube. The axial telescopic positional relation between the sleeve 60 and the
dummy
end fitting 32 allows for the positioning of the fittings 32 on the mock-up
assembly 10
in locations corresponding to as found nuclear reactor end fitting conditions.
Referring to Figures 2 through 5, the relative positioning and locking of
dummy end fitting 32 with the sleeve 60 is shown. Each of the sleeves 60 has
associated with it a corresponding dummy end fitting 32. Each sleeve 60 has a
tubular portion 68 extending back from the leading edge portion 70 of the
sleeve 60
towards the rear support wall 22. The tubular portion has two diametrically
opposed
guide slots 72 that are cut through the sleeve 62 and extend back from the
leading
edge surface portion 70 towards the rear support wall 22. The slots 72 do not
extend
the complete length of the sleeve 62.
Each of the dummy end fittings 32 has a protrusion extending there from in
the form of a fastener or a socket head cap screw 74. In Figure 6, the socket
head cap
screw 74 is threadably secured within one of the apertures of the sets of
apertures 56.
It should be appreciated that while Figure 6 and the description relate to
screw 74
threadably secured within one of the apertures 56, the screw 74 could also be
fastened
to one of either of apertures 54 or 58 depending on the nuclear reactor design
that is
being simulated by the dummy end fitting 32. The aperture that the socket head
cap
screw 74 is located in is the aperture 56a of the aperture set 56 furthest
away from the
end portion 52 of the dummy end fitting 32. The socket head cap screw 74 is
surrounded by a spacer or washer 78 such that the washer 78 and the socket
head cap
screw 74 are received within the guide slots 72. During the assembly of the
dummy
end fitting 32 with the sleeve 60, the dummy end fitting 32 is passed through
the front
circular opening 28 in the front support wall 20. The socket head cap screw 74
and
the washer 78 are then inserted into the aperture 56 furthest from the end 76
of the
dummy end fitting 32. Thereafter, the dummy end fitting is rotated to align
the cap
screw 74 and washer 78 with the guide slot 72. The end fitting 32 may then be
telescopically inserted into the sleeve 60 in proper angular positioning. This
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arrangement of the guide slot 72 and the socket head cap screw 74 and washer
78
combination restricts the angular displacement or rotation of the dummy end
fitting 32
relative to the sleeve 60.
A locking device 80 is located between the front and rear support walls and is
attached to the sleeve 60. The locking device has a fastener or a shoulder
screw 82
that is adapted to be rotated and secured into the leading aperture 56b found
in the
dummy end fitting 32. The shoulder screw 82 comprises a screw having a pin
like
portion that has a threaded end that passes into the aperture 56b of the dummy
end
fitting 32. The pin portion passes through a circular shoulder 84 mounted on
the end
of a threaded shaft 86. Circular shoulder 84 may be welded or formed as part
of the
threaded shaft 86. The threaded shaft 86 extends along a narrowing slot 88
which is a
continuation of the guide slot 72. The sleeve 60 has a cross slot 90 adjacent
the
junction 102 between the narrowing slot 88 and the guide slot 72. A slot nut
92 is
captured in cross slot 90. In Figure 6 the two slot nuts 92 are tightened snug
in
opposite directions against different fore and aft surfaces of the
corresponding cross
slot 90that the nut is in. The combination of the shoulder screw 82, shoulder
84,
threaded shaft 86 and captured slot nut 92 allows for adjustment in the length
of the
threaded shaft 86 along the narrowing slot 88 and the guide slot 72 thereby
allowing
for adjustment of the relative axial position of the shoulder screw 82 in the
guide slot
72. Since the threaded portion of the shoulder screw 82 is fastened in the
aperture 56
of the dummy end fitting 32 closest to its leading end portion 52, the
relative axial
position of the dummy end fitting 32 with respect to the sleeve 60 and with
respect to
the front support wall 20 is adjustable with the adjustment of nuts 92. This
adjustment allows for changes in axial displacement of the dummy end fitting
relative
to the front support wall so as to represent as found creep conditions
associated
between the end fitting and the end shield of the nuclear reactor.
The head of the shoulder screws 82 acts to fix the corresponding dummy end
fitting 32 with the sleeve 60 in an axial telescopic positional relation.
Furthermore,
the locking device 80, or shoulder screw 82, passing through the guide slot 72
fixes
the angular position relation between the sleeve 60 and its corresponding
dummy end
fitting 32. The protrusion in the form of socket head cap 74 and washer 78
extending
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from the dummy end fitting into the guide slot 72 restricts relative angular
rotation of
movement and the locking device further fixes such relative angular rotational
movement.
The assembly of the dummy end fitting 32 to the sleeve 60 comprises the steps
of initially passing the dummy end fitting 32 through one of the front
circular
apertures 28. Next, two screws 74 and corresponding washer 78 are inserted
into
opposing apertures 56a in each of the opposing pairs of apertures 56. The
apertures
56 are chosen to represent the desired simulated nuclear reactor environment.
Alternatively another aperture pair 54 or 58 may be chosen to represent other
as found
nuclear reactor environments. Once both screws 74 are inserted, the dummy end
fitting 32 is rotated so as to align the screw head with corresponding guide
slots 72.
The dummy end fitting 32 is then slid telescopically within the sleeve 60 with
the
relationship between the screw 74 and the guide slot 72 restricting angular
movement
between the dummy end fitting 32 and the sleeve 60. The dummy end fitting 32
is
slid axially relative to the sleeve 60 until the dummy end fitting 32
approximates the
desired location within the sleeve 60 to represent the as found creep
conditions in the
nuclear reactor end fitting under simulation. At this time two locking device
80 are
attached to the dummy end fitting 32 and the sleeve 60. The distance between
the
shoulder screw 82 and the nut 92 of each locking device 80 is adjusted along
the
threaded shaft 86 allowing the nuts 92 to enter corresponding cross slots 90
as the
shoulder screws 82 are threaded into corresponding opposing apertures 56b of
the
dummy end fitting 32. Thereafter the nuts 92 are adjusted to be lock against
different
opposite walls of the cross slot 90 as shown in Figure 6. With the snug nuts
92
locked into position in the cross slots 90, the dummy end fitting 32 is
secured with the
sleeve 60 both in an axial telescopic position and angular position by the
locking
devices 80.
It should be understood that the foregoing relates to a preferred embodiment
for the present invention and that other locking mechanisms may be used. For
example, a pipe clamp surrounding the sleeve 60 may also have shoulder screws
that
pass through the guide slot 72 into the aperture 56. Moreover, a continuous
slot or
guide slot 72 may not be required as a plurality of apertures may be drilled
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longitudinally along the sleeve to affect the similar results of the guide
slot 72.
Further, it should be understood that the parts may be reversed whereby the
locking
mechanism may be attached to the dummy end fitting and the dummy end fitting
may
have the guide slot and apertures may be provided in the sleeve. It is
envisaged that
this may occur when the sleeve is telescopically received within the dummy end
fitting. With the use of the pipe clamp, the pipe clamp may have a series of
apertures
through which screws pass and pass through both the sleeve and the dummy end
fitting. Then the dummy end fitting may be moved with the pipe clamp along the
sleeve to the desired axial location and then the pipe clamp can be clamped
and
tightened to prevent any further axial movement.
While there have been described herein what are considered to be preferred
and exemplary embodiments of the present invention, other modifications of
these
embodiments falling within the scope of the invention described herein shall
be
apparent to those skilled in the art.
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