CA2229771A1

CA2229771A1 - A pig for detecting an obstruction in a pipeline

Info

Publication number: CA2229771A1
Application number: CA 2229771
Authority: CA
Inventors: Donald D. Savard
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-02-18
Filing date: 1998-02-18
Publication date: 1999-08-18

Abstract

An obstacle Monitoring Pig for preliminary inspection of a section of a pipeline travels through the section and determines if there are any restrictions that might damage other pigs that require the full bore of the pipe. A
disk-shaped segmented resilient member 14 is mounted in the body of the pig.
Its outside diameter is smaller by a spacing 21 than the inside diameter of the pipeline 15. The spacing is set at the maximum tolerable size of the obstacle encountered. The displacement of the member 14 is transmitted to a switch system activating the indication of an obstacle having been encountered. A
non-resiliently deformable checkup disk 19 is provided at the rear end of the pig, to double check that a no-signal passage through the pipe is not due to failure of the switching system.
The device is structurally simple thus providing low manufacturing and operation costs and simple operation.

Description

_2_ 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-is fixedly secured to the front supporting ring 10, to the intermediate 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 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.

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.

Claims

1. A pig for detecting an obstruction in a pipeline, comprising, in combination:
(a) support means for supporting a body of the pig in a sliding engagement with the interior of the pipeline;
(b) a resilient, generally disk-shaped member for contacting an obstruction, said member being disposed in the body and mounted for axial movement relative to the body, the member having an outer diameter smaller than the inside diameter of the pipeline to define therewith a generally annular void having a predetermined radial clearance;
(c) holding means for resiliently holding said member at a predetermined resting position relative to the body, but permitting a temporary axial displacement of the member towards the rear end of the body when the member engages an obstruction in the pipeline; and (d) switch means operatively associated with the member to actuate signal generating means when the member is displaced rearwards a predetermined axial distance from the resting position.

2. The pig of claim 1, wherein the member is a segmented disc-shaped member comprising a plurality of segments separated from each other by a generally radial separation line.

3. The pig of claim 1 or claim 2, further comprising a check ring having a diameter generally equal to that of the member but made from a permanently deformable material such as a highly malleable sheet metal.

4. The pig of any one of claims 1 - 3, wherein the switch means comprises two switches disposed at an axial spacing from each other, whereby a relatively small obstacle can result in actuation of one of said switches, and a relatively large obstacle can result in actuation of the other one of said switches.