Note: Descriptions are shown in the official language in which they were submitted.
CA 02855113 2014-06-25
PIPE PIG
FIELD
[0001] Pipe pigs.
BACKGROUND
[0002] Pipe pigs are known that are self-propelled and that are smart, in that
they carry and may be
controlled by electronics. However, some pipes have tight bends, for example
in headers in heat
exchangers, and this makes it difficult for some smart pigs to get around the
bends. Conventional pigs
are configured to fit centrally within pipes, either occupying the entire
cross section of a pipe, or with
symmetrical legs contacting the interior surface of the pipe. Although wheeled
pigs are known, the
symmetrical arrangement limits the wheels to a small size relative to the
internal diameter of the pipe.
SUMMARY
[0003] A new pipe pig is disclosed. The pipe pig is provided with linked
segments, each segment
having a size in cross section smaller than an internal dimension of a pipe
which the pipe pig is
configured to enter; the pig having a biasing element for biasing the linked
segments away from a
straight line alignment, so that adjacent segments are biased into contact
with opposite sides of the
pipe.
[0004] In an embodiment, an intermediate segment and another segment are
linked by a
connector that pivots about a first axis associated with the intermediate
segment. In a further
embodiment, a further segment is also connected to the intermediate segment by
a connector that
pivots about the first axis. The connectors may comprise further pivotal
elements that pivot about axes
perpendicular to the first axis. The intermediate pig segment may comprise an
intermediate wheel
rotatable around the first axis, the intermediate wheel configured to contact
a first portion of an internal
surface of the pipe when in use. The segments connected to the intermediate
segment may comprise
respectively first and second flanking wheels rotatable around respective axes
parallel to the first axis
and configured to contact a portion of the internal surface of the pipe
opposite to the first portion when
in use. At least one of the intermediate wheel, first flanking wheel and
second flanking wheel may be a
hub driven wheel. The second flanking wheel may be connected to tow a battery
pack. A video camera
may be mounted on the first flanking wheel and the video camera may have a
field of view directed
away from the intermediate wheel.
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[0005] A new pipe pig is disclosed. In an embodiment, the pipe pig is provided
with linked wheels, and
at least a central wheel of the linked wheels is pivotally linked to adjacent
wheels through a spring
loaded connection that biases the central wheel out of straight line alignment
with the adjacent wheels.
The pipe pig may be used to negotiate tight bends in a pipe and carry sensing
electronics.
[0006] In an embodiment of a pipe pig, the pipe pig includes a body formed of
connected wheels, the
connected wheels including at least an intermediate wheel and a first flanking
wheel and a second
flanking wheel, each of the connected wheels having an axis about which the
wheel rotates, and the
axes of each of the connected wheels being parallel to each other, the first
flanking wheel being
connected to the intermediate wheel by a first hinged link and the second
flanking wheel being
connected to the intermediate wheel by a second hinged link and the first
hinged link and the second
hinged link being connected by a tensioner that biases the connected wheels
away from a straight line
alignment of the axes of the connected wheels.
BRIEF DESCRIPTION OF THE FIGURES
[0007] There will now be described embodiments of a pipe pig with reference to
the figures by way of
example, in which like reference characters denote like elements, and in
which:
[0008] Fig. 1 is a schematic diagram of an articulated pig with linked
segments biased away from a
straight line alignment, in a pipe.
[0009] Fig. 2 is a schematic diagram of an embodiment of the articulated pig
of Fig. 1 in which a
connector connecting a segment on one side of an intermediate segment connects
to the intermediate
segment at an axial pivotal connection.
[0010] Fig. 3 is a schematic diagram of an embodiment of the articulated pig
of Fig. 2 in which
connectors connecting a segment on both sides of an intermediate segment
connect to the intermediate
segment at an axial pivotal connection.
[0011] Fig. 4 is a schematic diagram of embodiment of the articulated pig of
Fig. 3 in which the
segments comprise large wheels.
[0012] Fig. 5 is a drawing of a torsion spring as an example biasing element,
drawn schematically as a
spiral.
[0013] Fig. 6 is a perspective view of an embodiment of a smart pig.
[0014] Fig. 7 is a side view of a single wheel showing an axle configuration
of a smart pig.
[0015] Fig. 8 is a perspective view of a wheel and connecting link arrangement
for the smart pig of Fig.
1.
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[0016] Fig. 9 is a side view of an embodiment of a smart pig in operation in a
pipe.
[0017] Fig. 10 is a side view of a second embodiment of a smart pig.
[0018] Fig. 11 is a side view of the smart pig of Fig. 4 together with a towed
package.
DETAILED DESCRIPTION
[0019] Referring to Fig. 1, a pipe pig 100 is formed of connected segments
102, 104 and 106. The
diagram is schematic and although each segment is depicted as circular and all
the same size, for the
purposes of this diagram the segments can be taken to have any shape and can
have different sizes. The
pig 100 is depicted within a pipe 170 having an internal dimension, here a
diameter (ID) 172. The
segments are smaller in cross section than the internal diameter of the pipe
so that each of the
segments, if taken separately from the rest of the pig, could be positioned
within the pipe without
touching the internal surface of the pipe. For non-round pipes, the segments
need only be smaller than
an internal dimension of the pipes. The segments are connected by connectors
110 and 116. The
segments are biased using biasing element 174 which biases the segments away
from a straight-line
alignment thus biasing adjacent segments into contact with opposite sides of
the pipe. Arrows 182, 184
and 186 indicate the general direction of bias. The biasing element here is
depicted schematically as a
spring connecting segments 102 and 106, but is not limited to what is
depicted. Further examples of
biasing elements will be given later.
[0020] Referring to Fig. 2, an embodiment of the pipe pig of Fig. 1 is shown
in which the connector 110
pivots about an axis 176 associated with segment 104. In this figure, arrows
182 and 186 show the
general directions the biasing element biases segments 102 and 106 relative to
segment 104 if elements
of the pig other than the pivot and the biasing element are relatively rigid.
[0021] Referring to Fig. 3, an embodiment of the pipe pig of Fig. 2 is shown
in which connector 116 also
pivots about axis 176.
[0022] Referring to Fig. 4, an embodiment of the pipe pig of fig. 2 is shown
in which the pig segments
comprise wheels. The wheels as depicted are sufficiently large that each wheel
substantially comprises
the outer diameter of the respective pig segment as viewed from a direction
aligned with an axis of the
wheel, but smaller wheels could be used. In the embodiment depicted the
connectors between
segments are pivotally connected to the segments at the same axes the wheels
rotate around. In
another embodiment, the connectors could be pivotally connected but not at the
same axes as the
wheel. In another embodiment, the connectors could be not pivotally connected.
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[0023] Referring to Fig. 5, an example biasing element 174 is shown comprising
a torsion spring
disposed at a pivot 176 between two arms 110 and 116. The torsion spring may
be adjustable for
example by providing a disk (not shown) attached to one of the arms at the
pivot, the attitude of the disk
being adjustable, and connecting the torsion spring between the disk and the
other arm. Other examples
of biasing elements include: A spring connecting points on the two arms; a
leaf spring connecting the
pivot and points on the arms to push on the pivot relative to the arms; a
piston between the arms, which
may contain a gas or a fluid pressurized by a gas or a spring; a cable between
points on the arms, the
cable tightened for example by a coil spring attached to a reel; or active
biasing elements which may
include for example, in an embodiment where a motor drives a wheel relative to
one of the arms, a
brake to brake the other arm relative to the wheel.
[0024] Referring to Figs. 6-8, a pipe pig 10 is formed of connected wheels 12,
14 and 16. The connected
wheels include at least an intermediate wheel 14 and a first flanking wheel 12
and a second flanking
wheel 16. Although a three wheeled pipe pig is shown, any number of wheels
could be connected
together providing there are three or more and each wheel may house a separate
set of electronics.
Each of the connected wheels 12, 14, 16 has an axis (respectively A, B, C)
about which the wheel
rotates.
[0025] The axes A and B preferably lie in the same plane, and when the wheels
are aligned in respect of
the alignment of joint 24 the axes And B are parallel to each other. The axes
B and C preferably lie in the
same plane, and when the wheels are aligned in respect of the alignment of
joint 30 the axes B and Care
parallel to each other. The term parallel used here means functionally
parallel, and likewise for being in
the same plane (coplanar). Some degree of axial misalignment is permitted
without the pipe pig losing
its functionally. In addition, in a group of more than three wheels, only
three wheels are required to
provide a force against the pipe wall to provide traction. In a group of six
wheels, the wheels may be
grouped into two groups of three, both of which groups may have independent
traction and other
functionality. When there are two groups of three in series, the groups may be
connected by a swivel
joint that allows the two groups of wheels to rotate relative to each other
about the axis of a pipe in
which they are operating.
[0026] Wheel 12 is connected to wheel 14 by a hinged link 20 formed of
connecting arms 21 and 22
that are hinged together by a joint 24 having an axis D that is perpendicular
to the axes A and B and that
lies on a line connecting the centers of the wheels 12 and 14. Wheel 16 is
connected to wheel 14 by a
hinged link 26 formed of connecting arms 27 and 28 that are hinged together by
a joint 30 having an axis
E that is perpendicular to the axes C and B and that lies on a line connecting
the centers of the wheels 16
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and 14.. The hinged link 20 and the hinged link 26 are connected by a
tensioner (biasing element, not
shown) that biases the connected wheels 12, 14 and 16 away from a straight
line alignment of the axes
of the connected wheels. The tensioner thus forces the wheels 12, 14 and 16
into a V-shape. If there are
five wheels in the pipe pig 10, each intermediate wheel being biased out of
straight line arrangement by
a tensioner, then the wheels form a W shape.
[0027] The wheels 12, 14 and 16, or others if present, may have any suitable
diameter but preferably
have a diameter more than half the ID of a pipe 170 that the pipe pig is going
to be used in and less than
the ID of the pipe. The wheels 12, 14 and 16 may each have a smooth rounded
traction surface 36 since
that has been found to assist in frictional engagement of the wheel with the
inner surface of a pipe. The
traction surfaces 36 may have a radius of curvature in a plane that includes
the wheel axis that is close to
but less than the radius of curvature of the pipe the pipe pig is intended to
be used in. In a preferred
embodiment the wheels may be about 3 inches in diameter with a curved outer
surface for more surface
area in contact with a pipe interior wall, for use in a pipe of 4 inch
internal diameter. It is preferred that
the wheels have as much traction as possible with the interior of the pipe.
Smooth rounded traction
surface 36 may be made of a soft material to enhance traction. Preferably, for
larger diameter pipes
larger diameter power wheels are used, as larger wheels have more contact
surface area allowing more
traction to pull larger units.
[0028] The hinged links 20 and 26 rotate relative to each other about the axis
B of the intermediate
wheel 14. One of the hinged links 20 and 26, here hinged link 26, may lie on
top of the other hinged
link. An arrangement may also be provided with the hinged links 20 and 26 on
opposite sides of the
intermediate wheel 14, but this makes it harder to run wires between the
wheels and it is better to have
the hinged links connect to the intermediate wheel on the same side of the
wheel. The hinged links may
also be provided on both sides of each wheel. In such an embodiment, where
there are hinged links on
each side of the wheels, the hinged links on one side need not meet between
the wheels.
[0029] The outer or upper hinged link, link 26 in Fig. 6 and Fig. 8, may
connect to a central shaft or axle
40 shown in Fig. 7. The inner hinged link 20 may be connected, for example by
a friction fit
supplemented with suitable connectors, to an outer shaft 42. The central shaft
40 may be journalled
within the outer shaft 42. The hinged links 20, 26 may thus rotate relative to
each other about the axis
B. The outer shaft 42 may be journalled within an electromagnet 44. By
including a suitable magnet in
the outer shaft 42, for example a permanent magnet, energizing the
electromagnet 44 may cause the
wheel 14 to rotate about the shafts 40, 42, and the wheel 14 will thus
function as a hub driven wheel or
CA 02855113 2014-06-25
wheel with a hub motor. Electrical energy may be supplied to the electromagnet
44 through a cable 46
that runs along the hinged links 20, 26.
[0030] Fig. 9 shows an embodiment in which the hinged links connect on the
same side of all wheels.
This embodiment is shown in a pipe 170.
[0031] A further embodiment of a pipe pig is shown in Fig. 10 with wheel pairs
50, 52, 54, 56 and 58
and connecting links 51, 53, 55 and 57. In an embodiment with paired wheels,
there are at least 6
wheels (3 pairs). The connecting links on either side of a pair of wheels both
may connect to an axle
connecting the wheels in a pair. One or both wheels of a pair of wheels may be
a hub driven wheel. Any
one or more or all of the pairs of wheels may have one or more hub motors. A
tensioner may be
provided between each pair of connecting links. Each connecting link may end
with a yoke that engages
an axle of the wheels. The tensioner may comprise a coil spring that lies
between adjacent yokes of
respective connecting links and is fastened to each link to resist relative
rotation of the connecting links
about the axle between the pair of wheels. In another embodiment, the
tensioner may comprise a leaf
spring anchored to one connecting link at an axle between a pair of wheels and
pressing against the
other connecting link that connects to the same axle. The tensioner is set so
that the pipe pig in the
resting state occupies a width greater than the pipe ID for which the pipe pig
is intended to be used. In
the embodiment of Fig. 10, the wheel diameter is less than half the ID of the
pipe that the pig is to be
used in. In a preferred embodiment, both wheels in a pair may be individually
driven and controlled to
cause the pair of wheels to twist, allowing the pig to be oriented within the
pipe, for example to
negotiate a "T" intersection in the pipe or to go around a 180 degree bend. In
a preferred embodiment,
all wheels are driven and controlled. More wheels allow more total driving
force, useful for example to
pull sensor instruments such as an eddy current and/or non-destructive testing
(NDT) unit through the
pipe.
[0032] In the embodiment of Fig. 11, a pipe pig 10 has its rearward flanking
wheel 16 connected to tow
a battery pack 60. In an embodiment the battery pack may be mounted on a pig
segment having wheels.
In the embodiments of Figs. 6 and 11, the pipe pig 10 may have a video camera
62 mounted on the
flanking wheel 12 with the video camera 62 having a field of view directed
away from the intermediate
wheel 14. Video cameras for pipe pigs are known. Any suitable video camera may
be used. The video
camera may deliver video to a memory carried by the pipe pig or to a tether if
the pipe pig is run with a
tether or sent wirelessly to a remote server or transmitted along the pipe
walls. The pipe pig may also
carry any conventional sensor used in pipe inspection, for example to detect
corrosion or pipe thickness
variation. Signals from the sensor may be stored or communicated as with the
video data.
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[0033] Preliminary embodiments have been made using parts (motors, wheels and
electronic
components) sourced from Japan, but for mass production could be made in
several countries.
[0034] Immaterial modifications may be made to the embodiments described here
without departing
from what is covered by the claims. In the claims, the word "comprising" is
used in its inclusive sense
and does not exclude other elements being present. The indefinite articles "a"
and "an" before a claim
feature do not exclude more than one of the feature being present. Each one of
the individual features
described here may be used in one or more embodiments and is not, by virtue
only of being described
here, to be construed as essential to all embodiments as defined by the
claims.
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