Note: Descriptions are shown in the official language in which they were submitted.
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METHOD AND APPARATUS FOR DETERMINING BENDS IN A PIPELINE
Background of the Invention
1. Field of the Invention
The present invention relates to bend detector used
to map out a pipeline system conveying materials such as
oil, natural gas, water and the like. More particularly,
the present invention relates to a bend detection
apparatus used in conjunction with a pipeline pig
assembly.
2. Prior Art
When pipeline systems are laid, most of the
necessary bends are provided by manufactured or standard
pipe elbows. Slight bends or elbows are usually
generated while the pipeline is being laid. However,
lS older pipeline systems generally do not have alignment
sheets showing the locations of the standard elbows. On
the newer pipeline systems, any repairs that have been
made may render a current alignment sheet either
incomplete or inaccurate. Precise location of any sharp
bend is necessary before various maintenance operations,
such as the use of corrosion tools, can be initiated.
There are three general types of standard bends or
elbows commonly used for pipeline systems. The sharpest
bend is a 90- 1-1/2 radius bend, wherein the pipe curves
90 along an arc whose radius is 1-1/2 times the diameter
of the pipe. The other two bends are a 90 3 radius bend
and a 45- 1-1/2 radius bend. More shallow bends can be
made on site during the laying of the pipeline.
Pipeline caliper pigs used to inspect pipeline
systems are well known. These pipeline pigs are used to
detect ovality, serious dents and the like within the
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interior surface of the pipeline. However, some pipeline
pigs and various curvature sensing apparatus are unable
to negotiate the sharp bends of factory elbows.
A preliminary search was conducted and the following
prior art patents were uncovered.
U.S. Patent Patentee Issue
Date
3,496,644 Short Feb. 27, 1970
3, 718,978 Van Koevering et al. March 6, 1973
3, 755,908 Ver Nooy Sept. 4, 1973
3, 780,442 Gresho Dec. 25, 1973
3,789,511 Groom et al. Feb. 5, 1974
3, 821,856 Rapp July 2, 1974
3, 882,606 Kaenal et al. May 13, 1975
3,886,665 Lowen June 3, 1975
A pipeline survey vehicle is disclosed in the patent
to Van Koevering et al. A motor propelled vehicle is
inserted into a pipeline for sensing deflection in a
vertical plane. The Van Koevering vehicle is an
essentially bullet-like sled with a gravity operated
steering means. A bend is detected by means of a
plurality of gauge elements which come into contact with
the interior surface of the pipeline.
A standard pipeline caliper pig is disclosed in U.S.
Patent No. 3,755,908 to Ver Nooy. The caliper pig is
inserted into a pipeline to locate deviations along the
interior of the pipe such as dents, ovality and the like.
In U.S. Patent No. 3, 789,511 to Groom et al., an
apparatus for sensing a curvature in a conduit is
disclosed. The Groom patent is used to determine the
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curvature and strain of a pipeline as it is being laid on
marine bottoms. This apparatus comprises a pair of
pivotally interconnected rigid components which are
subsequently connected to a traction unit which pulls the
apparatus through the conduit. Strain gauges are used in
conjunction with a rod which passes through the pivotal
interconnection to determine the curvature of the
pipeline.
A method and apparatus for measuring curvature and
variations in pipelines is disclosed in U.S. Patent No.
3,882,606 to Kaenel et al. The Kaenel apparatus
comprises an instrumented pig carrying an array of
sensing wheels. As the pig travels down a length of the
pipeline, the rotation of the sensing wheels is encoded
as a function of the axial distance traveled.
A monitoring apparatus for measuring the varying
radii of curvature along the axis of a bore is disclosed
in U.S. Patent No. 3,886,665 to Lowen. The monitoring
apparatus comprises an elongated or tubular body member
having a roller assembly mounted at each end. The Lowen
apparatus is used for indicating the length of the offset
over the chord length.
In light of the above, and as will more fully
appear hereinafter, the prior art does not disclose the
means for detecting bends in a pipeline in the manner
disclosed and claimed in the present invention. No prior
art device discloses an apparatus used in conjunction
with a pig assembly that is system propelled. No prior
art patent discloses a bend detector having a broad range
of maneuverability and capable of traversing through
abrupt bends without buckling in the pipeline.
A . ' ' .
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Summary of the Invention
An object of the present invention is to provide a
pipeline pig for locating and recording manufactured
bends in a pipeline system. Another object of the
present invention is to provide a pig assembly to detect
field generated bends whose angles are too sharp for the
passage of servicing tools. A further object of the
present invention is to provide a mechanical bend
detection apparatus that provides accurate and consistent
readings.
It is contemplated that the bend detector of the
present invention can be used simultaneously with a
gauging system or detector in which case the two
detectors can have drums which are synchronized from the
same odometer. Therefore, it is a still further object
of the present invention to offer a benchmark system
which will provide footage correlations between bends and
line anomalies.
The present invention comprise6 a pair of pipeline
pigs pivotally connected to each other in a tandem
relation6hip. Each pig comprises a central body having
hemispherical cups attached to the front and rear
portions of the body. The forward pig is provided with a
circular metal plate attached to its rear end behind the
rear cup. The rear pig is also provided with a circular
metal plate attached to its front end ahead of and
adjacent the front cup.
The pivotal connection of the two pigs comprises a
universal joint having two yoke members wherein the yoke
portions themselves are pivotally interconnected to a
central member so as to oscillate about a pair of
mutually perpendicular axes lying in a plane generally
perpendicular to the axis of the pipeline. These two
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mutually perpendicular axes are defined by pivot pins
which are rigidly connected together to form a cross.
The ends of the yoke members opposite from the ends which
are connected to the central member are defined as
collars terminating in flanges. The flanges of the yoke
members are attached to metal plates on the pigs. The
collars and the central member have been bored out to
form an axially aligned passageway. The central member
has been provided with a hollow sleeve that is received
in the central bore thereof. The innermost ends of the
holes in the collars are provided with teflon (or similar
plastic) inserts.
A plastic wrapped cable passes through the teflon
inserts and is anchored at one end to the rear plate
attached to the rear pig. The other end of the cable is
attached to an arm which is connected to an actuator
shaft which operates a stylus. The cable is tautly
anchored to the rear plate resulting in pull areas at the
ends of the hollow sleeve. These pull areas refer to the
bending action of the cable against the sleeve ends. A
pull exerted by the cable causes the actuator shaft to
move longitudinally rearward.
When the pig assembly goes around an internal bend,
the sleeve rotates against the cable as the forward pig
pivots with respect to the rear pig. This pull action
exerted on the cable causes the stylus to move to the
right (in reference to the drawings) against a recording
drum. The movement of the stylus is registered as a
deflection on a chart and will indicate the degree of the
bend. A sharper bend, such as a 90 1-1/2 radius length,
would leave a longer recording mark than a less sharp
bend. Slight bends may or may not be registered. A
longer sleeve will register smaller bends.
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Brief Description of the Drawings
Figure 1 is a side elevational view of a pipeline
pig assembly constructed in accordance with the present
invention;
Figure 2 is an enlarged side elevational view of the
bend detector apparatus of the preEent invention;
Figure 3 is a side elevational view of the pig
assembly of Figure 1 shown as transversing through a bend
in a pipeline system;
Figure 4 is an enlarged view of Figure 3 showing the
details of the bend detector;
Figure 5 is a further enlarged view of the bend
detector similar to that shown in Figure 3 but
representing the relative positions of the elements when
traversing a bend which is not in a horizontal or
vertical plane;
Figure 6 is side elevational view of the universal
joint embodied in with the present invention showing
certain parts being cut away;
Figure 7 is a cros~-sectional view (on a reduced
scale) taken along section line 7-7 of Figure 6; and
Figure 8 is a portion of a typical bend detection
chart made by the device of the present invention.
Detailed Description of the Prçfe~rç~_ mbodiments
Referring to the drawings in detail, Figures 1 and 3
show a pipeline pig assembly 10 which includes the bend
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detector of the present invention. Pig assembly 10
comprises a forward pig element 12 and a rear pig element
14 which are pivotally interconnected at 16 in a tandem
relationship. The pivotal interconnection 16 forms a
portion of the bend detector whose details will be
disclosed hereinafter. The forward pig 12 comprises a
cylindrical central body or housing 18, which is
longitudinally disposed, having a forward drive cup 20
attached to its front end and a rear cup 22 attached to
its rear portion. The forward cup is necessary for
propelling the pig assembly through the pipeline;
however, the rear cup is principally to support the
central body 18 in a substantially axial position.
The rear pig 14 also comprises a cylindrical central
body 26 having a forward cup 28 and a rear cup 30. Cups
20, 22, 28 and 30 are essentially hemispherical in shape
and constructed of plastic or similar material, such as
urethane, rubber, neoprene or other similar flexible
material. The cups 28 and 30 on the rear pig element 14
are provided essentially to support the rear pig element
in a substantially axial position and need not
necessarily be cups as such.
The rear pig 14 is also provided with a pair of
odometer wheels 32 disposed directly behind forward cup
28 and extending radially outward to contact the interior
surface of a pipeline section 36. The odometer wheels 32
are connected to recording means (not shown) housed in
the interior of housing 18 and are used to determine the
distance traveled by pig assembly 10 through the
pipeline system.
Although housings 18 and 26 are shown as cylindrical
central bodies, the operation of the pig assembly 10 is
not limited to the above shapes or locations in the
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pipeline section. Pig assembly 10 is system propelled;
in that, the assembly is inserted into a pipeline system
and is moved through the pipeline by means of drive cup
20. As shown, the drive cup is solid (imperforate)
whereas the other cups 22, 28 and 30 are provided with a
plurality of holes or bypass ports 34. The cups 22, 28
and 30 provide a means for axially supporting the pig
elements 12 and 14 in a pipeline 36. The bypass ports 34
allow fluid to pass through the other cups and into the
drive cup 20 thereby propelling assembly 10 through the
pipeline 36. The bypass ports also eliminate the excess
friction (generally caused by fluid pressure pushing the
cup material outwardly against the pipe wall) between the
surface of the pipeline and the cups 22, 28 and 30
thereby preventing buckling of pig assembly 10 in the
pipeline 36.
Referring now to Figures 1-5, the rear cup 22 is
disposed between a front mounting flange 40 and a rear
mounting flange 42. The forward pig element 12 is
provided with a circular metal mounting plate 46 which is
connected to the rear cup 22 by means of a plurality of
studæ 44. The front ends of studs 44 are bolted or
threadably connected to mounting flanges 40 and 42, and
the rear ends of the studs are bolted to mounting plate
46.
The front cup 28 of the rear pig 14 is also disposed
between a pair of mounting flanges 50 and 52. The
mounting flange 52 serves as a rear mounting plate, whose
purpose will be disclosed hereinafter.
As best shown in Figures 2, 4, 5, 6, and 7, the bend
detector 16 (which is the pivotal connection of the two
pigs 12 and 14) comprises a universal joint having two
yoke members 60 and 62 having their yoke portions 64 and
. . ~, ,,
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66 pivotally interconnected by means of a central member
69 which consists of two pivot pins 68 and 70 which are
rigidly connected to each other in the form of a cross.
The yoke flange or collar 72 of member 60 is bolted to
the plate 46 of the forward pig. The yoke flange or
collar 74 of member 62 is bolted to the rear mounting
plate 52 of the rear pig.
~ eferring to Figures 2, 4, 5, 6, and 7, the
universal joint is provided with an axially aligned
passageway 76 which is bored substantially at right
angles through the center of the cross 69 formed by the
pivot pins 68 and 70 for receiving a plastic wrapped
cable 80. The pivotal connection, formed by the pins 68
and 70, has thus been bored out for receiving a hollow
rod or sleeve 82 in the passageway 76. The cable 80,
therefore, actually passes through the sleeve 82. The
ends of the sleeves extend at right angles to the plane
of the pivot pins. Sleeve 82 is provided with a pair of
cover nuts 86 at each end for securing it to the joint.
The yoke collars 72 and 74 have each been provided with
central openings 90 which form the ends of the cable
passageway. The central openings 90 have been provided
with teflon* inserts 92.
As shown, the cable 80 passes through inserts 92 and
is firmly anchored at one end to the mounting plate 52 at
* trade mark
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a point 94 (Figures 2, 4 and 5). The other end of the
cable is tautly attached to an arm 96 in order to
eliminate any slack in cable 80 as it passes through the
universal joint. The arm 96 is provided with a plurality
of anchor or return springs 98 attached to the mounting
flange 42. The arm is pivotally connected at 100 to an
actuator shaft 102 which operates a stylus rod 104. The
pivotal connection 100 is merely for the sake of
convenience and has no function in the present invention
other than as a connection.
The tautness of cable 80 results in a "pull areas"
at the ends 83 of the sleeve 82. As best shown in Figure
5, the pull areas refer to the turning action of the
sleeve against the cable 80 when the forward pig 12
pivots or turns with respect to the rear pig 14. The
combination of the taut cable 80 and the sleeve 82
changes the pivot axis of a common universal joint to a
type of lever having two possible pivot points at its
ends 83. (One pivot point in Figure 4 and two pivot
points in Figure 5).
As best shown in Figures 3 and 4, the forward pig 12
turns or pivots with respect to rear pig 14 as the entire
pig assembly goes around an internal bend in the pipeline
36. A pull exerted by the cable 80 pulls back arm 96
thereby moving the actuator shaft 102 and stylus rod 104
longitudinally rearward. The above pull causes a stylus
(not shown but mounted at the end of stylus rod 104) to
move to the right against a recording drum (not shown)
housed inside the housing 18 of the forward pig element
12. After the pig assembly 10 passes completely through
a bend, the springs 98 assists in returning arm 96 back
into the position shown in Figure 2.
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Referring to Figure 8, a portion of a chart 110 is
shown that has been produced by the action of the stylus
104 against the internal recording drum. A straight line
112 shows the distance traveled through pipeline 36 as
recorded by odometer wheels 32. The first vertical line
114 indicates a relatively shallow bend such as though
generated in the field during the laying of the pipeline
36. The second vertical 116 indicates a 90 1-1/2 radius
length manufactured bend and the third vertical line 118
indicates a 90 3 radius length bend. The last vertical
line 120 indicates a 45- 1-1/2 radius length bend.
A modification (not shown) of the passageway 76
provides a means for indicating whether the bend is a
right turn or a left turn. The passageway is bored
horizontally through the central area 69 so that it is 5-
(or some other small angle) off-to the left or the right
from a true longitudinal axis. The above 5- variation
creates a preloaded tension on the cable which will not
show up on the chart when the pig assembly is traversing
a straight section of pipeline. A6suming, for example,
that the angular offset is towards the left
(counterclockwise), when the pig assembly goes through a
right turn bend, the cable 80 continues to be taut and
the deflections will be the same as shown at lines 114,
116, and 118. However, if the pipe goes through a left
turn bend, this action initially tends to create a slight
slack (not shown) in the cable 80 which causes the
springs 98 to pull the stylus towards the left so as to
produce a slight dip 122 in straight line 118. Thus, the
3C occurrence of dips 122 represent left turn bends, and
those without dips represent right turn bends.
