Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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A PIG FOR DETECTING AN OBSTRUCTION IN A PIPELINE
The present invention relates to an obstacle monitoring pipeline pig used
in chE:cking the interior of a pipeline for obstacles which might impede the
movement of subsequently used pipeline inspecting devices in the pipeline.
A number of caliper pigs are on the market that provide internal pipe
measurements but they are expensive to operate. These existing pigs monitor
all re:;trictions along a pipeline, regardless of size, and will normally
collect a
signifiicant amount of data that requires interpretation by a technician or
computer programs.
It is an object of the present invention to provide an obstacle monitoring
pig which would be of a simple structure permitting relatively low
manufacturing costs, monitoring only major obstacles of a predetermined
minimum magnitude and providing a simple operation.
The obstacle or barrier monitoring pig of the present invention (BM P) is
shown
diagrammatically in the attached simplified, diagrammatic drawing, it being
understood that this is merely an exemplary representation which may be
modified to a substantial degree without departing from the gist of the
present
invention. In the drawings,
FigurE: 1 is a simplified section of the pig of the present invention shown
as it passes through a section of a pipeline; and
FigurE; 2 is a simplified sectional view taken along the section line II-II of
Figure 1.
The inventive BMP is provided with supporting rubber rings 10, 1 1, 12
connected in series one after the other and comprised of a front ring 10 with
a bumper 13, an intermediate ring 1 1 and a rear ring at the back end of the
pig. A, centrally disposed, cylindric holder 20 concentric with the rings 10-
12
is fixedly secured to the front supporting ring 10, to the intermediate
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supporting ring 1 1 and to the rear ring 12, to maintain the three rings 10-12
at a constant spacing.
A segmented, generally disk-shaped resilient member 14 has a number
of segments 14a separated from each other along a generally radial line of
separation 14b. The member 14 is concentric with the rings 10 - 12. It is
dispoaed between the front support ring 10 and the intermediate support ring
1 1 for a free axial displacement along the pig. The resilient member 14 has a
smallE:r outside diameter than the inside diameter of the pipeline 15. The
memk>er 14 thus defines an annular void space 21 between its outer surface
and the inner surface of the pipeline wall.
The radial width of the void 21 is predetermined and depends on the
operational requirements of particular application. It generally correspond to
the maximum tolerable size of restriction at the inner surface of the pipeline
15. Ftear ends of a number of links 22 are pivotally connected to a front face
of the segments of the resilient member 14. The front ends of the same links
22 are: pivotally connected to a sleeve 16 which is slidable in axial
direction on
the central holder. A suitable spring or the like mechanism is adapted to
resiliently hold the sleeve 23 at a predetermined resting position relative to
the
centr<~I holder 20 such that the first and second switches 17, 18 are
inactive.
The pig is propelled through the pipeline - typically - by a pressure
differE:ntial at the front and rear ends of the pig, moving from the left to
the
right ~of Figure 1. If an obstacle is encountered at the wall of the pipeline,
which is radially in excess of the width of the void 21, the respective
segment
14a of the resilient member 14 is deflected by a force which is proportional
to
the size of the obstacle. Since the pig continues its movement, the segment
14a of the resilient member 14 pulls the sleeve 23 via the respective link 22
against the resilient force holding the sleeve in the resting axial position.
The
sleevE: 23 is displaced by a predetermined distance which is sufficient to
activate the mechanism (not shown in detail) of the first switch 17. As a
result, emission of an appropriate signal takes place indicating that a
relatively
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small obstacle, for instance, a partly closed valve, has been encountered.
Eventually, the resilient member runs over the obstacle, whereby the axial
pull
on the: sleeve 23 is no longer active so that the sleeve 23 returns back to
its
original position where both switches 17, 18 are again inactive.
If the obstacle encountered is more substantial, the resilient member 14
is displaced along the central holder 20 to a greater axial distance,
activating
the second switch 18 to provide a signal of a more substantial obstacle having
been encountered.
A deformable barrier ring 19 made, for instance, of a malleable, relatively
thin sheet metal, has the same diameter as the resilient member 14. It is
mounted at the rear end of the pig. Its purpose is to double check a negative
indication by the switches 17, 18. If any of the switches malfunctions and
fails
to activate indication of an obstacle, then such obstacle inevitably deforms
the
ring 19 thus providing information that in fact there had been failure to
monitor
an obstacle. If no signal of an obstacle is received and -after the completed
run of the pig- the check ring 19 will not be deformed to confirm that indeed
no obstacle is present in the inspected section.
Whenever the BMP detects a restriction, time may be recorded and
saved for analysis at the end of the BMP run. At the end of the inspection
run,
the information recorded may be fed to a computer that will correlate the time
the restrictions were encountered with other BMP tracking information and
pipeline geographic position. The positioning will only provide the operator
with an approximation of the restriction location.
As the BMP is designed to only detect large restrictions that are
associated with partially closed valves or some other fitting problems, the
accuracy will provide the operator with sufficient information to determine if
there are any restrictions and if a restriction has been identified, eliminate
it
before running other inspection tools.
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As mentioned above, a number of different modifications of the overall
arrancaement shown can be made without departing from the scope of the
present invention.
