Note: Descriptions are shown in the official language in which they were submitted.
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METHOD AND APPARATUS FOR PUSHING A DUAL DIAMETER PIG INTO
A PIPELINE
This invention is in the field of pipelines, and in particular with pipeline
pigs that are
pushed into a pipeline for various purposes as are well known in the art.
BACKGRQUND
Pipeline pigs are of various designs and are used for a variety of purposes.
One type of
pig is inserted into pipelines and pushed though pipelines to clean the
pipeline. Other
pigs may be used for batching or separating different products that are being
transported
in the pipeline by sealing to the walls of the pipeline and moving along the
pipeline with
the products. Still others are used to inspect the pipeline.
In certain pipelines, pumping stations are located at intervals along the
line, and efficient
pipeline design calls for a smaller diameter pipe connected to the output of
the pumping
station and a larger diameter pipe connected to the suction of the pumping
station. Thus
when moving downstream from one pumping station to the next, at a mid-point
between
the two pumping stations the pipeline transitions from, for example, a 36"
diameter pipe
to a 48" diameter pipe.
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In order to clean these dual diameter pipelines, dual diameter pigs have been
developed
that have an expanded diameter suitable for operations to clean the larger
diameter pipe,
and a compressed diameter suitable for operations to clean the smaller
diameter pipe.
When the pipeline transitions from the smaller to the larger diameter pipe,
the pig
automatically expands. Various means for providing such expandable pigs are
known,
for example as disclosed in United States Patent Number 5,457,841 to Minton.
The dual
diameter pigs are launched into the smaller pipe portion of the pipeline at a
pig trap
located at a pumping station.
At the pumping station the pipeline comes out of the ground and an access port
is
provided to allow the pig to be pushed into the pipeline. A diverter conduit
and valves
are provided such that product can continue to flow through the pipeline while
the pig
trap is isolated from the flow and drained. Once drained a door covering the
port is
opened and the pig is pushed into the trap, the door is closed and valves are
operated to
direct pipeline flow through the pig trap and thus carry the pig down the
pipeline.
Since the pig is launched into the smaller pipe at the output of the pumping
station, it
must be compressed to its smaller size. The pig trap will have a diameter
equal to the
diameter of the smaller pipe. For example with dual diameter pipeline having a
36"
smaller pipe and a 48" larger pipe, the pig will have corresponding compressed
and
expanded diameters, and the pig trap will have a 36" diameter. A conical
reducer is
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typically used to compress the pig for insertion into the trap. The reducer
will have a
smaller end with a 36" diameter opening fixed to the 36" pig trap opening, and
tapering
outward to a larger open end with about a 48" opening. The pig is placed into
the
48"opening and forced through the reducer into the 36" pig trap. Such a pig
launching
operation is generally described in United States Patent Numbers 5,296,039 to
Cooper
and 5,769,955 to Kozisek.
Such pigs for this size of pipeline are quite large, typically eight feet or
more in length,
and are quite heavy as well, making them awkward to maneuver into the trap,
and
requiring considerable force to push through the reducer. The pigs typically
have a solid
core against which a force can be exerted to force the pig through the reducer
into the
trap. The is operation is complicated by the fact that once the gig trap is
open, petroleum
fumes are released and pose a fire hazard which require that operations
include
appropriate safety precautions. Often pigs are maneuvered into place by a
loader or
backhoe vehicle, and then pushed through the reducer into the trap by the
vehicle as well,
however operating internal combustion vehicles in proximity to the open pig
trap presents
a fire hazard. Alternatively it is known to rig a hydraulic cylinder to push
the pig into
the trap, however because of the length of the pig, such hydraulic cylinders
must have a
very long stroke of 10 - 12 feet, and so are costly and awkward to position
and transport.
SUMMARY OF THE INVENTION
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It is an object of the present invention to provide an apparatus for pushing a
dual diameter
pig into pipeline that overcomes problems in the prior art.
The present invention provides, in a t"trst embodiment, an apparatus for
pushing a dual
diameter pig through a conical reducer attached to a pig trap and into a
pipeline. The
apparatus comprises a frame configured to support a pig longitudinally such
that the pig
can move forward along the frame, and having a front end adapted for
attachment to the
pig trap. At least one leg supports the frame such that a vertical position of
the frame can
1U be adjusted to align a front end of a pig supported on the frame with an
open end of the
conical reducer. An extendable actuator is supported on the frame such that
the actuator
is rearward of, and substantially aligned with, a pig supported on the frame,
and an
actuator control is operative to extend the actuator such that a front end
thereof moves
forward with respect to the frame and into contact with a central portion of a
rear end of a
pig supported on the frame, and is operative to retract the actuator. A lock
is operative to
selectively lock the actuator to the frame at a plurality of lock locations
between the front
end of the frame and the rear end thereof, and the lock locations are
separated by a
distance that is less than a stroke of the actuator.
The present invention provides, in a second embodiment, a method for pushing a
dual
diameter pig through a conical reducer attached to a pig trap and into a
pipeline. The
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method comprises attaching a front end of a frame to the pig trap and
supporting a pig
longitudinally on the frame such that the pig can move forward along the
frame;
supporting the frame on at least one leg and adjusting a vertical position of
the frame to
substantially align a front end of the pig with an open end of the conical
reducer;
supporting an extendable actuator on the frame such that the actuator is
rearward of, and
substantially aligned with, the pig and locking the actuator to the frame at a
first lock
location; extending the actuator such that a front end thereof moves forward
with respect
to the frame and into contact with a central portion of a rear end of the pig,
and pushes
the pig partially into the conical reducer; retracting the actuator and
unlocking the
actuator from the frame; moving the actuator forward to a second lock location
where the
front end thereof is in proximity to the rear end of the pig and locking the
actuator;
extending the actuator and thereby pushing the pig farther into the conicai
reducer; and
repeatedly retracting the actuator and unlocking the actuator from the frame,
moving the
actuator forward to further forward lock locations and locking the actuator to
the frame,
and extending the actuator, until the pig is located in the pig trap.
The method and apparatus of the invention uses a shorter actuator, such as a
hydraulic
cylinder, to push the pig through the reducer. By movably mounting the
actuator to a
frame, the actuator can be extended and retracted a number of times to push
the pig
through the required length of travel, rather than using a very long actuator
to push the
required length with a single stroke of the actuator.
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DESCRIPTION OF THE DRAWINGS:
While the invention is claimed in the concluding portions hereof, preferred
embodiments
are provided in the accompanying detailed description which may be best
understood in
conjunction with the accompanying diagrams where like parts in each of the
several
diagrams are labeled with like numbers, and where:
Fig. 1 is a schematic perspective view of an embodiment of an apparatus of the
invention for pushing a dual diameter pig through a conical reducer into a pig
trap
and into a pipeline showing a dual diameter pig supported on the apparatus;
Fig. 2 is a perspective view of the embodiment of Fig. 1 with the pig removed
showing the stroke distance of the actuator;
Figs. 3 -7 are schematic side views showing the steps of a method of the
invention
for launching a dual diameter pig.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS:
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Figs. 1 and 2 schematically illustrate an apparatus 1 for pushing a dual
diameter pig 3
through a conical reducer 5 attached to a pig trap 7 and into a pipeline 9, as
schematically
illustrated in Figs. 3 - 7. The apparatus comprises a frame 11 configured to
support the
pig 3 longitudinally such that the pig 3 can move forward in direction F along
the frame
11. The front end of the frame 11 can be adapted for attachment to the pig
trap 7 by links
or other means which will be well known in the art. The frame 11 can be
attached
directly to the pig trap 7, or to the conical reducer 5 which is attached to
the pig trap 7, or
otherwise substantially fixed with respect to the pig trap 7 such that the
forces exerted by
the apparatus 1 will move the pig 3 into the conical reducer 5, and not move
the apparatus
1 away from the pig trap 7. In the illustrated embodiment the conical reducer
5 is fixed
by welding or the like to the front end of the frame 11 of the apparatus 1,
such that the
apparatus is attached to the pig trap 7 by the flange 13 on the conical
reducer 5. The
flange 13 is configured to match up with a corresponding flange on the pig
trap 7, such
that when the flanges are connected by bolts or the like, the apparatus is
properly aligned
for insertion of the pig 3 into the trap 7.
Legs 15 support the frame 11 such that the vertical position of the frame 11
can be
adjusted to align the front end of the pig 3 with an open end of the conical
reducer 5. In
the illustrated embodiment, the frame 11 comprises right and left side rails
17 extending
substantially from the front end to the rear end of the frame 11, and oriented
substantially
parallel to, and equidistant from, the axis RA of the conical reducer 5. The
frame 11
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further comprises a trough 19 configured to support the pig 3 between the side
rails 17.
The pig 3 is supported on the frame 11 such that a central axis PA of the pig
3 is
substantially aligned with the axis RA of the conical reducer 5.
An extendable actuator 21 is supported on the frame 11 such that the actuator
21 is
rearward of, and substantially aligned with the pig 3 supported on the frame
11. A lock
23 is operative to selectively lock the actuator 21 to the frame 11 at a
plurality of lock
locations 25 between the front end of the frame 11 and the rear end thereof.
As
illustrated in Fig. 2, the lock locations 25 are separated by a distance LD
that is less than
the stroke S of the actuator to allow the actuator to be extended to move the
pig forward
by the stroke distance S, and then retracted to allow movement forward to a
next lock
location 25, as described below.
In the illustrated embodiment, the extendable actuator 21 is attached to cross-
member 27
extending from one side rail 17 of the frame 11 to the opposite side rail 17.
The
extendable actuator 21 is attached to the cross-member 27 at a location such
that the axis
AA of the actuator 21 is substantially aligned with the axis RA of the conical
reducer 5
when the apparatus 1 is attached to the pig trap 7, and aligned with the
central axis PA of
the pig 3, as illustrated in Fig. 3. The lock 23 is operative to lock right
and left ends of
the cross-member 27 to corresponding right and left side rails 17.
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In the illustrated embodiment, the right and left ends of the cross-member 27
engage
grooves 29 along the corresponding right and left side rails 17, and are
movable along the
corresponding right and left side rails 17. Conveniently the side rails 17 are
channel
shaped to provide the grooves 29. The lock locations 25 are defined by rail
apertures 31
defined by the side rails 17, and the illustrated lock 23 comprises a pin 33
in an end of the
cross-member 27 passing through a rail aperture 31 that is aligned when the
cross-
member 27 is at a lock location. Alternatively the cross-member 27 could slide
along the
top of the side rails 17 and be pinned or otherwise locked to the side rails
17 by other
mechanisms as are known in the art.
An actuator control 35 is operative to extend the actuator 21 such that a
front end 37
thereof moves forward with respect to the frame 11 and into contact with a
central
portion of a rear end of the pig 3 as it is supported on the frame 11, and is
operative to
retract the actuator 21. The front end 35 of the actuator 21 has moves with a
range equal
to the stroke distance S illustrated in Fig. 2.
Conveniently the extendable actuator 21 comprises a hydraulic cylinder
connected
through the actuator control 35 to a hydraulic power supply 39 by hoses 41 of
a length
sufficient to allow the hydraulic power supply 39 to be located at a
sufficient distance
from the pig trap to reduce a fire hazard presented by operating the power
supply in
proximity to petroleum fumes from the pig trap.
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The illustrated apparatus further includes a drive operative to move the cross-
member 27
along the side rails 17. A link drive chain 40 is laid out and fixed along the
top of the
bottom flange of the right and left side rails 17. A corresponding sprocket is
rotatably
mounted at the right and left ends of the cross-member 27, and is conveniently
driven by
a hydraulic motor connected to the hydraulic power supply 39. The illustrated
embodiment further rnmprises an operator platform 43 attached to the cross-
member 27
such that an operator can occupy the platform 43 and move along the side rails
17 with
the cross-member 27 while manipulating the actuator control 35 to push the pig
3 into the
trap 7. A lever mechanism can be incorporated as well and connected to the
pins 33 that
lock the cross-member 27 to the side rails 17 to allow the operator to
conveniently
remove the pins 33 from the rail apertures 31 to allow the cross-member to
move, and
also allow re-insertion at the next lock location 25.
The method of the invention for pushing a dual diameter pig 3 through a
conical reducer
5 attached to a pig trap 7 and into a pipeline 9 is schematically illustrated
in Figs. 3 - 7.
The method comprises attaching the front end of the frame 11 to the pig trap
7, either
directly or by attachment to the conical reducer 5 which is itself attached to
the pig trap 7.
The pig 3 is placed longitudinally on the frame 11 such that the pig 11 can
move forward
in direction F along the frame 11, and a vertical position of the frame 11 is
adjusted if
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necessary to substantially align a front end of the pig 3 with an open end of
the conical
reducer. The extendable actuator 21 is moved into position rearward of the pig
3 and is
locked to the frame at a first lock location, illustrated in Fig. 3.
The actuator 21 is extended into contact with a central portion of a rear end
of the pig 3
and pushes the pig 3 partially into the conical reducer 5, as illustrated in
Fig. 4. The
actuator 21 is then retracted and unlocked from the frame 11, moved forward to
a second
lock location illustrated in Fig. 5 where the front end thereof is in
proximity to the rear
end of the pig 3, and locked to the frame in the second lock location, and
extended again,
thereby pushing the pig 3 farther into the conical reducer as illustrated in
Fig. 5. The pig
is pushed completely into the pig trap 7 by repeatedly retracting the actuator
21 and
unlocking the actuator 21 from the frame 11, moving the actuator 21 forward to
further
forward lock locations and locking the actuator 21 to the frame 11 and
extending the
actuator 21, until the pig 3 is located in the pig trap 7, as illustrated in
Fig. 7.
The apparatus 1 uses a relatively compact actuator 21, and frame 11 that is
relatively easy
to set up and transport. Safety is improved by using a hydraulic power pack,
or other
actuator power source that can be located a safe distance from the petroleum
fumes at the
open mouth of the pig trap 7_ The conical reducer 5 can be fixed to the
apparatus 1, as
illustrated, or can be otherwise made available at each location where the
apparatus 1 will
be used. Once the apparatus 1 is set up, the pig can be lifted on to the
apparatus 1 by a
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loader vehicle, crane, or the like, which can then be removed prior to
launching the pig 3.
The foregoing is considered as illustrative only of the principles of the
invention.
Further, since numerous changes and modifications will readily occur to those
skilled in
the art, it is not desired to limit the invention to the exact construction
and operation
shown and described, and accordingly, all such suitable changes or
modifications in
structure or operation which may be resorted to are intended to fall within
the scope of
the claimed invention.
