Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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PIPE END SEALING TOOL
FIELD OF THE INVENTION
This invention relates to a pipe end sealing tool, such as a pipe end plug.
The
tool may be utilised to seal the end of a pipe or tube to permit, for example,
the
pressure integrity of the pipe to be tested.
BACKGROUND OF THE INVENTION
In many industries there is a requirement to pressure test pipes, tubes, pipe
modules, pipelines and the like. For example, in the oil and gas industry,
some
process plant is assembled from modules, which are welded together on site.
The
pipe weldments in these modules must be pressure tested prior to shipping to
site.
The first step in the pressure testing process is the sealing of the open end
of the
tubing. At present, this is achieved by one of: welding a cap on to the
tubing;
inserting an isolation plug into the end of the tubing; or by sliding a
mechanical cap
over the end of the tubing.
Welding a cap on to the tubing is expensive and time consuming.
Furthermore, once the test is complete, the cap must be cut off.
The use of an internal isolation plug requires provision of a plug with a
locking mechanism and seal. This requires a straight length of pipe to
accommodate
the plug, and thus may require a straight spool to be welded to the pipe to
accommodate the plug. Furthermore, steel pipe tends to be supplied in standard
outside diameters, but internal diameters may vary. Accordingly, internal
plugs
must be dressed or sized to suit the particular internal diameter of the
tubing under
test. This is particularly important for the plug locking mechanism, where an
incorrect sizing selection may reduce the ability of the plug to resist the
test pressure
load, which load will tend to eject the plug from the tubing if not resisted.
In the case
of self-energised plugs in which the test pressure energises the plug sealing
and lock
mechanisms, the loads generated by the test pressure are transferred to the
tubing,
causing peak hoop stress at the seal and lock contacts. Accordingly, the tube
end
must be assessed for each application, to ensure that the tubing wall will
accommodate the anticipated hoop stress.
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The use of externally mounted mechanical caps removes the dressing
requirement for each tubing bore, as pipe is normally specified by outside
diameter,
but as the cap seals engage the outer wall surface of the tubing, and thus
encompass a
larger area, the ejection load experienced by a cap is greater than that
experienced by
a corresponding plug. Caps also tend to be heavier and require even longer
lengths
of straight pipe than a corresponding plug. Furthermore, the cap locks and
seals
create localised stresses on the tubing wall, such that the tubing wall
condition must
always be carefully assessed.
SUMMARY OF THE INVENTION
According to the present invention there is provided a pipe end sealing tool
comprising:
a body;
a seal mounted on the body and adapted to apply a radial sealing pressure to a
wall of a pipe end to be sealed; and
a lock mounted on the body and adapted to engage a wall of the pipe end,
whereby a radial load applied to the pipe wall by the lock is adapted to
support the
opposing sealing pressure, the seal and the lock positioned so that the seal
pressure
and lock load are substantially balanced such that the pipe wall does not
experience
significant radial stresses.
According to another aspect of the present invention there is provided a
method of sealing an end of a pipe, the method comprising:
providing a tool comprising a seal and a lock, both mounted on a tool body;
locating the tool on the end of a pipe;engaging a wall surface of the pipe end
with the lock; and
applying a radial sealing pressure to a wall surface of the pipe end with the
seal, whereby a radial load applied to the pipe wall by the lock supports the
opposing
sealing pressure, the seal and the lock positioned so that the seal pressure
and lock
load are substantially balanced such that the pipe wall does not experience
significant
radial stresses.
Thus, the load applied to the pipe outer diameter by the lock is supported by
the seal pressure, and vice versa. This avoids the problems experienced with
conventional internal plugs and conventional externally-mounted caps, in which
the
sealing pressure and lock loads act in a common direction, placing potentially
large
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unbalanced loads on the pipe wall. Also, the separation of the sealing and
locking
arrangements facilitates provision of a more compact arrangement, and
embodiments
of the invention have been produced which are approximately half the length of
a
conventional plug or cap.
The seal may take any appropriate form, and in one embodiment the seal
comprises a compression seal. Radial movement of a sealing surface of the seal
and a
sealing pressure may be produced by axial compression of the seal. The seal
may
comprise an elastomeric seal element. In one embodiment, an annular seal
element is
provided on a mandrel or core between opposing compression faces, the faces
being
relatively movable to compress the element and induce radial expansion of the
element.
The seal may be self-energised. Once a minimum pressure differential is
achieved across the seal, the internal pipe pressure will tend to maintain the
seal in the
energised configuration, independently of the status of the seal actuation
system, such
that the seal is fail-safe.
The lock may take any appropriate form. Lock members may be provided and
be adapted to be selectively urged into engagement with the wall of the pipe.
The
lock may comprise a taper lock. A lock member may comprise an inclined surface
and be operatively associated with a relatively movable cooperating member
with a
corresponding inclined surface. The lock member may feature teeth or some
other
surface configuration for gripping the pipe wall surface.
The lock may be configured such that an ejection load on the tool serves to
increase the grip of the lock on the pipe wall surface, that is the lock may
be self-
energised. The ejection load path through the tool may be arranged to bypass
the lock
actuation system. This may facilitate avoiding overloading of the system and
ensure
that the self-energising feature is effective in the event of an actuating
system failure.
The seal and lock may be actuated separately, or may be actuated by a
common actuation system or arrangement. The seal and lock may be actuated by
any
appropriate mechanism, for example by bolts, torque, or by induction. In one
embodiment, one or both of the seal and lock are fluid actuated, and may be
hydraulically actuated, although pneumatic actuation may also be utilised.
The lock may be energised or actuated prior to energising or actuating the
seal,
ensuring that the tool is locked to the pipe end before pressure is applied
across the
tool.
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The tool may feature a fill/vent port, and this port may extend through a tool
core. Where the tool is intended to be utilised in horizontal applications,
the port may
be configured, for example by provision of an internal elbow, to provide a
high point
vent.
The tool may comprise a dual seal feature, whereby a volume between two
seals can be pressurised and monitored to allow the integrity of the seal to
be verified
before pressurising the pipe.
The various features and options listed above may have utility independently
of the aspects of the invention described above, and may form separate aspects
of the
invention. In particular, the self-energising seal and lock features, and the
fail-safe
seal and lock features, may form separate aspects of the invention.
According to a further aspect of the present invention there is provided a
pipe
end sealing tool comprising:
a body;
a seal mounted on the body and adapted to apply a sealing pressure to an inner
wall of a pipe end to be sealed; and
a lock mounted on the body and adapted to engage an outer wall of the pipe
end, whereby load applied to the pipe wall by the lock is adapted to support
the
opposing sealing pressure, the seal and the lock positioned so that the seal
pressure
and lock load are substantially balanced such that the pipe wall does not
experience
significant radial stresses.
According to a further aspect of the present invention there is provided a
method of sealing an end of a pipe, the method comprising:
providing a tool comprising a seal and a lock, both mounted on a tool body;
locating the seal within a pipe end and the lock externally of the pipe end;
engaging an outer wall surface of the pipe end with the lock; and
applying a sealing pressure to an inner wall surface of the pipe end with the
seal, whereby load applied to the pipe wall by the lock supports the opposing
sealing
pressure, the seal and the lock positioned so that the seal pressure and lock
load are
substantially balanced such that the pipe wall does not experience significant
radial
stresses.
According to a further aspect of the present invention there is provided a
pipe
end sealing tool comprising:
a body;
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a seal mounted on the body and adapted to apply a sealing pressure to an inner
wall of a pipe end to be sealed, wherein the seal is adapted to be self-
energised; and
a lock mounted on the body and adapted to engage an outer wall of the pipe
end, whereby a radial load applied to the pipe wall by the lock opposes the
sealing
5 pressure.
According to a further aspect of the present invention there is provided a
method of sealing an end of a pipe, the method comprising:
providing a tool comprising a seal and a lock, both mounted on a tool body;
locating the seal within a pipe end and the lock externally of the pipe end;
engaging an outer wall surface of the pipe end with the lock; and
applying a sealing pressure to an inner wall surface of the pipe end with the
seal, wherein the seal is adapted to be self-energised and whereby load
applied to the
pipe wall by the lock opposes the sealing pressure.
According to a further aspect of the present invention there is provided a
pipe
end sealing tool comprising:
a body;
a seal mounted on the body and adapted to apply a radial sealing pressure to a
wall of a pipe end to be sealed, wherein the seal is adapted to be self-
energised; and
a lock mounted on the body and adapted to engage a wall of the pipe end,
whereby a radial load applied to the pipe wall by the lock opposes the sealing
pressure.
According to a further aspect of the present invention there is provided a
method of sealing an end of a pipe, the method comprising:
providing a tool comprising a seal and a lock, both mounted on a tool body;
locating the tool on the end of a pipe;
engaging a wall surface of the pipe end with the lock; and
applying a radial sealing pressure to a wall surface of the pipe end with the
seal, wherein the seal is adapted to be self-energised and whereby a radial
load
applied to the pipe wall by the lock opposes the sealing pressure.
According to a further aspect of the present invention, there is provided a
pipe
end sealing tool comprising:
a body;
a seal mounted on the body and adapted to apply a sealing pressure to an inner
wall of a pipe end to be sealed; and
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a lock mounted on the body and adapted to engage an outer wall of the pipe
end, wherein at least one of the seal and the lock is fluid actuated and
whereby load
applied to the pipe wall by the lock opposes the sealing pressure.
According to a further aspect of the present invention, there is provided a
method of sealing an end of a pipe, the method comprising:
providing a tool comprising a seal and a lock, both mounted on a tool body;
locating the seal within a pipe end and the lock externally of the pipe end;
engaging an outer wall surface of the pipe end with the lock; and
applying a sealing pressure to an inner wall surface of the pipe end with the
seal, wherein at least one of the seal and the lock is fluid actuated and
whereby a load
applied to the pipe wall by the lock opposes the sealing pressure.
According to a further aspect of the present invention, there is provided a
pipe
end sealing tool comprising:
a body;
a seal mounted on the body and adapted to apply a radial sealing pressure to a
wall of a pipe end to be sealed; and
a lock mounted on the body and adapted to engage a wall of the pipe end,
wherein at least one of the seal and the lock is fluid actuated and whereby a
radial
load applied to the pipe wall by the lock opposes the sealing pressure.
According to a further aspect of the present invention, there is provided a
method of sealing an end of a pipe, the method comprising:
providing a tool comprising a seal and a lock, both mounted on a tool body;
locating the tool on the end of a pipe;
engaging a wall surface of the pipe end with the lock; and
applying a radial sealing pressure to a wall surface of the pipe end with the
seal, wherein at least one of the seal and the lock is fluid actuated and
whereby a
radial load applied to the pipe wall by the lock opposes the sealing pressure.
BRIEF DESCRIPTION OF THE DRAWING
The figure is a sectional view of a pipe end sealing tool in accordance with a
preferred embodiment of the present invention, the top half of the figure
illustrating
the tool in a fitting and retrieval configuration, and the lower half of the
figure
illustrating the tool in an energised configuration.
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DETAILED DESCRIPTION OF THE DRAWING
The drawing illustrates a pipe end sealing tool 10 in accordance with a
preferred embodiment of the present invention. The figure shows the tool 10 in
section, the upper half of the figure illustrating the tool 10 in a fitting
and retrieval
configuration, while the lower half of the figure illustrates the tool 10 in
an activated
or energised configuration. The tool 10 may be utilised to close and seal the
end of
any appropriate pipe or tube, and is ideally suited for use in testing
prefabricated pipe
spools and the like, as used in the oil and gas industry. The tool is shown
mounted on
the end of a length of plain pipe 12, in this example the pipe being the end
of a pipe
spool.
The tool 10 comprises a body 14 providing mounting for a compression seal
16, adapted to engage the inner pipe wall 18, and a taper lock 20, adapted to
engage
the outer pipe wall 22.
The compression seal 16 comprises an annular rubber seal element 24.
Mounting for the element 24 is provided by a mandrel or core 26. The core 26
is in
two parts, the element 24 being mounted on a flanged sleeve 28 which is
threaded to a
carrier 30. A fill/vent port 32 extends through the carrier 30, to allow the
interior of
the pipe to be pressurised and vented.
While the inner end face and inner diameter of the element 24 are contained
by the flanged sleeve 28 mounted on the carrier 30, the outer end face of the
element
24 is contained by a face of a ported body member 34. A carrier flange 36 and
a
body member flange 38, provided with co-operating seals 40, 42, define a
chamber 44
into which pressure may be introduced such that the carrier 30 acts as a
piston to
move the core 26 outwards relative to the body member 34 and the pipe end, to
axially compress and radially expand the seal element 24.
The taper lock 20 comprises lock members or segments 50 adapted to engage
the outer pipe wall 22. In an initial fitting and retrieval configuration, the
teeth on the
inner surface of the lock segments 50 are lifted clear of the pipe wall 22 by
sprung
pins 52, to facilitate fitting and removal of the tool 10 from the pipe end.
The end
face of each lock segment 50 engages a piston sleeve 54 which co-operates with
stepped outer faces of the body member 34. Seals 56, 58 create a chamber 60 to
which pressurised hydraulic fluid may be supplied via the body member ports
62, to
move the piston sleeve 54 and lock segments 50 relative to the body member 34.
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An outer sleeve or casing 64 is threaded to the body member 34 and features a
taper face 66 for co-operating with corresponding lock segment taper faces 68.
Thus,
when pressurised hydraulic fluid is introduced to the chamber 60, relative
movement
between the taper faces 66, 68 urges the lock segments 50 into locking contact
with
the outer pipe wall 22.
In use, the tool 10 is located on the end of a pipe 12 to be pressure tested.
The
pipe wall is accommodated in the annular volume between the seal element 24
and the
lock segments 50. Steel pipe is supplied in standard outside diameters, such
that the
components adapted to co-operate with the outer pipe wall 22 may be sized with
a
degree of accuracy and confidence. However, variations in pipe wall thickness
and
configuration, which give rise to less predictable inner pipe wall dimensions,
are
relatively easily accommodated by the clearance provided by the non-energised
seal
element 24.
To actuate or energise the tool 10, a source of pressurised hydraulic fluid is
coupled to the body member ports 62, and pressurised fluid supplied to fill
the
chambers 44, 60, as shown in the lower half of the figure. The actuation
arrangement
is configured such that the lock segments 50 will be energised to grip the
outer pipe
wall 22 before the seal element 24 is fully energised, and comes in to contact
with the
inner pipe wall 18. This ensures that the lock arrangement 20 is actuated
prior to the
generation of a seal, ensuring that the tool 10 is securely locked on the pipe
end 12
before any pressure can be applied across the tool 10.
It will be noted that the actuated lock segments 50 and the energised seal
element 24 are positioned on opposing sides of the pipe wall. Accordingly, the
loads
applied to the pipe wall by the lock members 50 and the seal element 24 are
balanced,
the pressure forces created by the energised seal element 24 being supported
by the
energised lock members 50, and vice versa.
Once activated, the load path of the internal test pressure self-energises the
tool 10, such that the isolation will be maintained, independently of the
integrity of
the actuation system. In particular, the internal test pressure which acts on
the tool
core 26 generates a force on the compression seal relative to the test
pressure times
the ratio of the pipe bore cross sectional area divided by the seal element
cross
sectional area. This load generates a rubber pressure in the seal element 24
which is
higher than the pressure being isolated.
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Furthermore, the ejection load path through the tool 10 passes through the
body member 34 and the outer casing 64 to pull on the taper of the lock
segments 50,
so increasing the grip of the lock 20. This load path bypasses the hydraulic
actuation
system, to both prevent over pressurising the system and to ensure that the
loss of the
actuation system would not effect the self-energisation feature.
Those of skill in the art will recognise that the above described pipe end
sealing tool 10 provides a quick and reliable method of temporarily capping
open
pipes and tubes. The relative locations of the seal 16 and lock 20 allow the
tool 10 to
be relatively compact, typically half the length of a conventional mechanical
plug or
mechanical cap. Furthermore, the relative locations of the seal 16 and lock 20
allow
the internal seal and external locking loads to balance, such that the pipe
wall does not
experience significant radial stresses. Furthermore, the tool 10 may be
actuated
quickly and easily using hydraulic fluid, but once differential pressure is
applied
across the tool, both the seal 16 and the lock 20 are self-energised.
It is believed that tools made in accordance with embodiments of the
invention, such as the tool 10 described above, will be capable of isolating
pressures
in excess of 350 bar.
Those of skill in the art will appreciate that the above described tool 10 is
merely exemplary of the present invention, and that various modifications and
improvements may be made thereto without departing from the scope of the
invention. For example, many of the advantages of the invention may be
achieved in
a tool in which a seal is mounted externally on a pipe, and a lock is provided
internally.
