CA2231609A1 - Inflatable icepig and method of installing same - Google Patents
Inflatable icepig and method of installing same Download PDFInfo
- Publication number
- CA2231609A1 CA2231609A1 CA 2231609 CA2231609A CA2231609A1 CA 2231609 A1 CA2231609 A1 CA 2231609A1 CA 2231609 CA2231609 CA 2231609 CA 2231609 A CA2231609 A CA 2231609A CA 2231609 A1 CA2231609 A1 CA 2231609A1
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- Canada
- Prior art keywords
- pipeline
- plug
- water
- interspace
- ice
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 238000000034 method Methods 0.000 title claims abstract description 44
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 60
- 230000008569 process Effects 0.000 claims abstract description 33
- 230000008014 freezing Effects 0.000 claims abstract description 17
- 238000007710 freezing Methods 0.000 claims abstract description 17
- 238000009412 basement excavation Methods 0.000 claims abstract description 10
- 239000007788 liquid Substances 0.000 claims abstract description 10
- 239000002689 soil Substances 0.000 claims description 11
- 239000000356 contaminant Substances 0.000 claims description 5
- 238000011144 upstream manufacturing Methods 0.000 claims description 5
- 230000004888 barrier function Effects 0.000 claims description 3
- 238000012423 maintenance Methods 0.000 claims description 3
- 239000002245 particle Substances 0.000 claims description 3
- 238000007789 sealing Methods 0.000 claims description 2
- 238000007689 inspection Methods 0.000 claims 2
- 238000007599 discharging Methods 0.000 claims 1
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 abstract description 12
- 229910052757 nitrogen Inorganic materials 0.000 abstract description 6
- 239000000126 substance Substances 0.000 abstract description 2
- 239000007787 solid Substances 0.000 description 5
- 229920001971 elastomer Polymers 0.000 description 4
- 230000009471 action Effects 0.000 description 3
- 230000008901 benefit Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000002093 peripheral effect Effects 0.000 description 1
- 229920001084 poly(chloroprene) Polymers 0.000 description 1
- 229920002635 polyurethane Polymers 0.000 description 1
- 239000004814 polyurethane Substances 0.000 description 1
- 230000008439 repair process Effects 0.000 description 1
- 238000007790 scraping Methods 0.000 description 1
- 125000006850 spacer group Chemical group 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
- 229920001059 synthetic polymer Polymers 0.000 description 1
- 229920003002 synthetic resin Polymers 0.000 description 1
- 239000000057 synthetic resin Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- F16L55/00—Devices or appurtenances for use in, or in connection with, pipes or pipe systems
- F16L55/10—Means for stopping flow in pipes or hoses
- F16L55/103—Means for stopping flow in pipes or hoses by temporarily freezing liquid sections in the pipe
Landscapes
- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Pipe Accessories (AREA)
Abstract
An ice plug of the type having an annular chamber for clean process water to be frozen to temporarily plug a section of a pipeline is described, in which the supply of clean process water is drawn from a bottom layer of water filling the inspected or repaired pipeline. Also disclosed and claimed is an improved ice plug which carries a reservoir of clean process water which is injected into the annular space limited by a flexible seal disposed between the process water in the annular interspace and the inner wall of the pipeline. An improved method of freezing an ice plug is also disclosed and claimed. It utilized a modified pneumatic excavation tool avoiding the need for the usual jacket around the pipe for liquid nitrogen or the like freezing substance.
Description
_2_ INFLATABLE ICEPIG AND METHOD OF INSTALLING SAME
The present invention relates to an ice plug similar to that described and claimed in co-pending Canadian Patent Application S.N. 2,214,666, filed September 4, 1997 and currently assigned to the present applicant.
Ice plugs or icepigs are used in isolating a portion of a pipeline for testing, maintenance or repair purposes. Briefly, they operate on the principle of creating a solid ice barrier in a pipeline filled with water for the purpose. The pig is brought to a desired location in a pipeline. The exterior of the pipeline section surrounding the pig is then provided with a jacket and a freezing liquid, such as liquid nitrogen is supplied into the jacket to freeze the pipeline section and thus the water in the icepig to provide a solid plug isolating the section of the pipeline.
According to the most recent development in icepigs as set forth in the above co-pending patent application, the overall solid ice plug is replaced with a design where only a peripheral annular portion between the body of the icepig and the inside wall of the pipeline is frozen solid thus reducing the volume of water required to be frozen solid.
The object of the present invention is to provide further improvement in the art of icepigs of the above type. It is also an object of the invention to provide an improved method of isolating a predetermined section of a pipeline using an icepig.
The invention will be described in greater detail with reference to the accompanying drawings. In the drawings:
Figure 1 is a longitudinal section through an icepig of the improved type, showing the inventive way of supplying process water to the annular interspace between the cylindric body of the icepig and the inner wall of the pipeline section;
Figure 2 is a simplified side view somewhat similar to that of Fig. 1 but being on a smaller scale to show an accessory to the icepig for supply of process water into the interspace;
Figure 3 is a diagrammatic representation, on a reduced scale, corresponding to Fig. 1, of the position of the icepig in a state where the icepig has just reached a desired location of the pipeline;
Figure 4 is a view similar to that of Fig. 3 but showing the pig half way through the cycle of filling the interspace with process water;
Figure 5 is a view similar to that of Fig. 3 but showing the icepig in a position where the interspace is filled with process water ready to be frozen;
Figure 6 is a longitudinal section through another embodiment of the icepig;
Figure 7 is a detail of a lower end portion of a pneumatic excavation tool used in the process of plugging the pipeline with an icepig;
Figure 8 is a detail of the outlet of the lower end portion shown in Fig. 7 on enlarged scale; and Figure 9 is a simplified diagrammatic side view of a known pneumatic excavating tool showing the principle of pneumatic excavation.
When working with an icepig, the pipeline section to be isolated is first evacuated of oil or the like and then filled with water as a medium to propel the pig within the pipeline to a desired location. This is done by manipulating water pressure differential at the opposed ends of the pig. The water filling the pipeline, particularly an oilfield pipeline, becomes inevitably contaminated with residual oil droplets or wax particles which impair the freezing process making an emulsion-like substance with the water.
One of the objects of the present invention is to efficiently provide the interspace of the icepig with water virtually devoid of oil or other contaminants which would retard the freezing process, or at least substantially reduce the volume of such contaminants. The water with the reduced content of the contaminants is referred to hereafter at "process water."
In the icepig of the co-pending patent application, the droplets of oil or the like are allowed to rise in water present the interspace and then forced out with the contaminated water by a piston-like mechanism. At the same time, the suction side of the piston draws cleaner process water into the interspace.
The process water is then frozen as described.
Turning now to Figures 1 and 2, the structure of the icepig shown is similar to that of the co-pending patent application.
The icepig includes a cylindrical body 10 having a front end 11 (also referred to as downstream end 11 ) enclosed by an end plate 12. The back end 13 (also referred to as upstream end 13) of the body 10 is open.
According to one feature of the present invention, the back end 13 is equipped with a fitting 14 to which a hose 15 (Fig. 2) supplying process water is connected. The hose 15 supplies process water due to an arrangement, whereby the inlet end of the hose 15 is provided with a polyurethane ballast 16 which maintains the free end of the hose 15 at the lowermost part of the water filled pipeline. Accordingly, water that may enter the hose 15 from the pipeline is taken from that portion which is least likely to contain contaminants such as oil droplets which rise to the upper portion of the water fill. By the same token, the ballast 16 protects the free end of the hose 15.
The body 10 is fixedly secured to two bi-directional discs: a front disc 17 and a rear disc 18. The discs 17, 18 are fastened to the body by rings 19 and 20 and bolts 21, 22, respectively. The term "bi-directional" discs indicates that despite their conical shape, they are designed to permit movement within the pipeline in both directions. In the direction backwards (from the right to the left of Fig. 1 ), they have the tendency to spread out due to the conical configuration, but this merely results in an increased resistance to the reverse movement due to the friction at the inside wall of the pipe and the consequent scraping action, as will be described.
In order to facilitate a smooth passage of the icepig through the pipeline, a carrying front cup 23 is fastened, by an integrally formed flange 24 at a rear end of a hollow rod 25 and the bolts 14, to the downstream ring 19. If desired, the front cup 23, the flange 24 and the hollow rod 25 can be separate items bolted together.
A conically shaped brake ring 26 is made from a suitable synthetic resin, polymer or the like material. Compared with the bi-directional discs 17, 18, the brake ring 26 ring has an enlarged outside diameter. The brake ring 26 is fixedly secured to a sliding collar 27. The size of the outside diameter of the ring 26 is such that, while it can be displaced (at a resistance) in downstream direction it cannot travel backwards (to the left of Fig. 1 ), while, as mentioned above, the bi-directional discs 17, 18 allow the movement rearwards. Such movement, when induced by providing a desired pressure differential, results in the body 10 sliding back through the stationary collar 27. Thus, under the reverse pressure differential conditions, the only stationary portion relative to the pipeline is the brake ring 26 and the collar 27.
The sliding movement of the body 10, of the cup 23 and of the portions fixedly secured to the two, relative to the collar 27 from the initial position of Fig. 3 through the intermediate state of Fig. 4 and to the terminal position of Fig. 5 draws process water coming from the free end of the hose 15, into the annular interspace 28 through a passage 29 which is at first obstructed by the collar 27 (Fig. 1 or 3) but is free (Figs. 4 and 5) when the body 10 slides through the collar 27 in the direction from the state of Fig. 3 to Fig. 4.
The removal of the contaminated water from the interspace 28 takes place via drains 30 into the interior of the hollow cylindrical body 10 and through the open back end out into the pipeline as indicated by arrows in Fig.
4. Eventually, the collar 27 reaches the front position (Fig. 5) and obstructs the drains 30.
At the same time, the conical bi-directional disc 18, scrapes wax and oil from the inside surface of the pipe. As a result, a mixture of the wax, oil and water is forced out from what eventually becomes the outermost extreme of the interspace 28 between the neoprene or the like discs 17, 18 thus further reducing the contamination of process water therein.
When the interspace 28 is filled with clean water, the movement of the body 10 through the collar 27 is stopped and freezing process may be started.
The freezing process is - preferably, but not exclusively - carried out by a method of the present invention described hereafter.
When the icepig travels in the water filled pipeline, the brake ring 26 assumes the position at the rear of the pig as shown in Fig. 1. This is caused by friction at the between the ring 26 and the inside wall of the pipe. In this position, the collar 27 overlaps the clean water inlet 29. The sealing of the closure of the inlet 29 is secured by two 0-rings 31, 32.
At the same time, the drains 30 are open and permit the flow of contaminated water into the centre of the body 10 as shown in Fig. 4. When the body 10 reaches its rearmost position relative to the brake ring 27 (Fig.
5), the collar 27 now overlaps the drains 30. Thus closing the discharge from the interspace 28 which is now filled with relatively clean process water.
Reference should now be had to a second embodiment of the icepig of the present invention. This icepig is designated for use in operations where water in the pipe is too contaminated to provide a reasonably clean process water by the method described above. In Fig. 6 clean water is supplied to the interspace from within the pig. The needed clean process water is stored in the body of the pig and is transferred into an inflatable seal through inlets by a piston which is actuated by a reverse pressure in the pipeline.
_7_ The second embodiment of the icepig comprises a body 40 enclosed at front end by a welded plate 41, with an opening for a flexible piston rod 42.
The rear end is sealed by plate 43 which co-operates with an O-ring 44, fastened to a rear flange 45 of the body 40 by bolts 46. The front end of the body 40 is provided with a carrying bi-directional rubber disk 47 and the rear end with a carrying bi-directional rubber disk 48. Front and rear collars 49, and spacer discs 51 & 52 made from soft rubber provide side support to an inflatable flexible seal 53. The seal 53 is thus held in place by the collars and 50. The front carrying rubber disc 47 is clamped by ring 54 fastened by bolts 55. The front end of the interior of the body 40 is sealed by a piston with piston seals 57. When the icepig is stopped and suitable pressure differential is created, the piston 56 is pushed back by the flexible piston rod 42. This action causes the clean process water stored within the body 40 to flow by inlet 58 into the inflatable seal 53. Vent holes 59 in plate 41 prevent vacuum creation. Eventually, the seal 53 is filled with the process water and the freezing process may be started.
The freezing process is preferably carried out by a pneumatic excavating device. The advantage of this device over the regular excavating with subsequent application of a freezing mantle to the exterior of the pipe is in that the likelihood of mechanical damage to the pipe is virtually eliminated. The use of the method and apparatus of the present invention simplifies the freezing operation to mere excavation followed up by filling the cavity thus created by liquid nitrogen , eliminating the use of a freezing mantle which is expensive to produce and to apply.
The pneumatic excavation may partly be carried out by known devices, for instance by a tool described in US Patent 4,991,321 ( issued February 12, 1991 to T.G. Artzberger, which is incorporated herein by reference.
Figure 9 shows the Artzberger device. It is described in the above patent as including a body 60 connected through a supply line 61 to a source of pressure such as an air compressor. An elongated tube 62 is connected to the _$_ body 60 and actuated by a control valve operatively associated with a trigger 63 to control the flow of air through the tube 62. The normally lower end of tube 62 is secured to a housing 64 which includes a conduit 65 to which the lower end of the tube 62 is connected. The lower end of the conduit 65 is bent inwardly to reach into a larger diameter tube portion 66 which is outwardly flared at a distal end 67, where it carries a nozzle assembly of which only an outwardly projecting part 68, concentric with an open lower end of the tube portion is visible in Fig.9. The nozzle assembly is designed to provide an increased velocity of airflow coming out of the projecting end shown in Fig. 9 and directed toward the soil to dislodge same. At the same time, the opposite end of the nozzle assembly provides aspirating action drawing the dislodged soil away through a flexible conduit 69.
The tool of this type is useful in excavating soil around cables, pipelines etc. as it does not pose the danger of damage to the underground utility lines.
Compared with regular, mechanical excavators, it removes soil from a smaller area around the pipeline or the like.
The icepig freezing method of the present invention makes use of these features and further presents a simple but technologically important supplement to the existing pneumatic excavation tools.
Referring to Figures 7 and 8, the lower end of the Artzberger tool is modified in accordance with the present invention for use in freezing icepigs in pipelines. The parts corresponding to the representation of Fig. 9 are designated with the same reference numbers and letter "A."
The tube 62A delivering the airflow as described in Artzberger, communicates with a conduit 65A which forms a part of a housing 64A. The housing 64A includes a tube portion 66A. Near the distal end 67A of the tube portion 66A, the end portion of the conduit 65A passes through the wall of the tube portion 66A and supports a nozzle assembly 71 having a distribution chamber 73 thereof. The distribution chamber 73 communicates with an _g_ upstream end of a dislodging nozzle 72 of the type increasing the velocity of the incoming airflow. The dislodging nozzle 72 is provided in that part of the nozzle assembly 71 which projects outwardly from the distal end 67A of the tube portion 66A. An aspiration nozzle 74 aimed into the tube portion 66A is disposed at a point opposite to that where the upstream end of the nozzle 72 is located. The purpose of the aspiration nozzle is to generate aspiration resulting in the removal through the tube portion 66A of particles of soil dislodged by the airflow discharged from the dislodging nozzle 72.
It is the feature of the present invention, that at least the dislodging nozzle is so disposed that its axis is generally horizontal while the tube 62A, the main part of the tube portion 66A and the flexible conduit (not shown in Figs. 7, 8) are generally upright.
It is preferred that the overall arrangement of the distal end of the tool be as shown in Figs. 7 and 8. That is to say, the distal section 75 of the tube portion 66A is bent relative to the main portion thereof generally at 90° and the nozzles 72, 74 are coaxial with each other.
In use, the tool of the present invention permits the excavation of soil immediately below an underground pipeline. Combined with the normally vertical excavation by a tool such as described in Artzberger, the present invention permits the formation of a relatively narrow cavity surrounding both sides and the underside of an underground pipeline with minimum soil having been removed. The cavity is ready to be filled with liquid nitrogen covering also the top portion of the pipeline section. The liquid nitrogen, fully surrounding the pipeline section, freezes the pipe and thus the water in the interspace 28 of the icepig. This provides substantial savings compared with known method of freezing icepigs which require a substantial excavation along both sides and under the underground pipe section to permit installation of a mantle for receiving the liquid nitrogen.
It will be appreciated that the above description pertains to the presently preferred embodiments of the present invention. Such embodiments may be modified to a greater or lesser degree without departing from the scope of the present invention.
The present invention relates to an ice plug similar to that described and claimed in co-pending Canadian Patent Application S.N. 2,214,666, filed September 4, 1997 and currently assigned to the present applicant.
Ice plugs or icepigs are used in isolating a portion of a pipeline for testing, maintenance or repair purposes. Briefly, they operate on the principle of creating a solid ice barrier in a pipeline filled with water for the purpose. The pig is brought to a desired location in a pipeline. The exterior of the pipeline section surrounding the pig is then provided with a jacket and a freezing liquid, such as liquid nitrogen is supplied into the jacket to freeze the pipeline section and thus the water in the icepig to provide a solid plug isolating the section of the pipeline.
According to the most recent development in icepigs as set forth in the above co-pending patent application, the overall solid ice plug is replaced with a design where only a peripheral annular portion between the body of the icepig and the inside wall of the pipeline is frozen solid thus reducing the volume of water required to be frozen solid.
The object of the present invention is to provide further improvement in the art of icepigs of the above type. It is also an object of the invention to provide an improved method of isolating a predetermined section of a pipeline using an icepig.
The invention will be described in greater detail with reference to the accompanying drawings. In the drawings:
Figure 1 is a longitudinal section through an icepig of the improved type, showing the inventive way of supplying process water to the annular interspace between the cylindric body of the icepig and the inner wall of the pipeline section;
Figure 2 is a simplified side view somewhat similar to that of Fig. 1 but being on a smaller scale to show an accessory to the icepig for supply of process water into the interspace;
Figure 3 is a diagrammatic representation, on a reduced scale, corresponding to Fig. 1, of the position of the icepig in a state where the icepig has just reached a desired location of the pipeline;
Figure 4 is a view similar to that of Fig. 3 but showing the pig half way through the cycle of filling the interspace with process water;
Figure 5 is a view similar to that of Fig. 3 but showing the icepig in a position where the interspace is filled with process water ready to be frozen;
Figure 6 is a longitudinal section through another embodiment of the icepig;
Figure 7 is a detail of a lower end portion of a pneumatic excavation tool used in the process of plugging the pipeline with an icepig;
Figure 8 is a detail of the outlet of the lower end portion shown in Fig. 7 on enlarged scale; and Figure 9 is a simplified diagrammatic side view of a known pneumatic excavating tool showing the principle of pneumatic excavation.
When working with an icepig, the pipeline section to be isolated is first evacuated of oil or the like and then filled with water as a medium to propel the pig within the pipeline to a desired location. This is done by manipulating water pressure differential at the opposed ends of the pig. The water filling the pipeline, particularly an oilfield pipeline, becomes inevitably contaminated with residual oil droplets or wax particles which impair the freezing process making an emulsion-like substance with the water.
One of the objects of the present invention is to efficiently provide the interspace of the icepig with water virtually devoid of oil or other contaminants which would retard the freezing process, or at least substantially reduce the volume of such contaminants. The water with the reduced content of the contaminants is referred to hereafter at "process water."
In the icepig of the co-pending patent application, the droplets of oil or the like are allowed to rise in water present the interspace and then forced out with the contaminated water by a piston-like mechanism. At the same time, the suction side of the piston draws cleaner process water into the interspace.
The process water is then frozen as described.
Turning now to Figures 1 and 2, the structure of the icepig shown is similar to that of the co-pending patent application.
The icepig includes a cylindrical body 10 having a front end 11 (also referred to as downstream end 11 ) enclosed by an end plate 12. The back end 13 (also referred to as upstream end 13) of the body 10 is open.
According to one feature of the present invention, the back end 13 is equipped with a fitting 14 to which a hose 15 (Fig. 2) supplying process water is connected. The hose 15 supplies process water due to an arrangement, whereby the inlet end of the hose 15 is provided with a polyurethane ballast 16 which maintains the free end of the hose 15 at the lowermost part of the water filled pipeline. Accordingly, water that may enter the hose 15 from the pipeline is taken from that portion which is least likely to contain contaminants such as oil droplets which rise to the upper portion of the water fill. By the same token, the ballast 16 protects the free end of the hose 15.
The body 10 is fixedly secured to two bi-directional discs: a front disc 17 and a rear disc 18. The discs 17, 18 are fastened to the body by rings 19 and 20 and bolts 21, 22, respectively. The term "bi-directional" discs indicates that despite their conical shape, they are designed to permit movement within the pipeline in both directions. In the direction backwards (from the right to the left of Fig. 1 ), they have the tendency to spread out due to the conical configuration, but this merely results in an increased resistance to the reverse movement due to the friction at the inside wall of the pipe and the consequent scraping action, as will be described.
In order to facilitate a smooth passage of the icepig through the pipeline, a carrying front cup 23 is fastened, by an integrally formed flange 24 at a rear end of a hollow rod 25 and the bolts 14, to the downstream ring 19. If desired, the front cup 23, the flange 24 and the hollow rod 25 can be separate items bolted together.
A conically shaped brake ring 26 is made from a suitable synthetic resin, polymer or the like material. Compared with the bi-directional discs 17, 18, the brake ring 26 ring has an enlarged outside diameter. The brake ring 26 is fixedly secured to a sliding collar 27. The size of the outside diameter of the ring 26 is such that, while it can be displaced (at a resistance) in downstream direction it cannot travel backwards (to the left of Fig. 1 ), while, as mentioned above, the bi-directional discs 17, 18 allow the movement rearwards. Such movement, when induced by providing a desired pressure differential, results in the body 10 sliding back through the stationary collar 27. Thus, under the reverse pressure differential conditions, the only stationary portion relative to the pipeline is the brake ring 26 and the collar 27.
The sliding movement of the body 10, of the cup 23 and of the portions fixedly secured to the two, relative to the collar 27 from the initial position of Fig. 3 through the intermediate state of Fig. 4 and to the terminal position of Fig. 5 draws process water coming from the free end of the hose 15, into the annular interspace 28 through a passage 29 which is at first obstructed by the collar 27 (Fig. 1 or 3) but is free (Figs. 4 and 5) when the body 10 slides through the collar 27 in the direction from the state of Fig. 3 to Fig. 4.
The removal of the contaminated water from the interspace 28 takes place via drains 30 into the interior of the hollow cylindrical body 10 and through the open back end out into the pipeline as indicated by arrows in Fig.
4. Eventually, the collar 27 reaches the front position (Fig. 5) and obstructs the drains 30.
At the same time, the conical bi-directional disc 18, scrapes wax and oil from the inside surface of the pipe. As a result, a mixture of the wax, oil and water is forced out from what eventually becomes the outermost extreme of the interspace 28 between the neoprene or the like discs 17, 18 thus further reducing the contamination of process water therein.
When the interspace 28 is filled with clean water, the movement of the body 10 through the collar 27 is stopped and freezing process may be started.
The freezing process is - preferably, but not exclusively - carried out by a method of the present invention described hereafter.
When the icepig travels in the water filled pipeline, the brake ring 26 assumes the position at the rear of the pig as shown in Fig. 1. This is caused by friction at the between the ring 26 and the inside wall of the pipe. In this position, the collar 27 overlaps the clean water inlet 29. The sealing of the closure of the inlet 29 is secured by two 0-rings 31, 32.
At the same time, the drains 30 are open and permit the flow of contaminated water into the centre of the body 10 as shown in Fig. 4. When the body 10 reaches its rearmost position relative to the brake ring 27 (Fig.
5), the collar 27 now overlaps the drains 30. Thus closing the discharge from the interspace 28 which is now filled with relatively clean process water.
Reference should now be had to a second embodiment of the icepig of the present invention. This icepig is designated for use in operations where water in the pipe is too contaminated to provide a reasonably clean process water by the method described above. In Fig. 6 clean water is supplied to the interspace from within the pig. The needed clean process water is stored in the body of the pig and is transferred into an inflatable seal through inlets by a piston which is actuated by a reverse pressure in the pipeline.
_7_ The second embodiment of the icepig comprises a body 40 enclosed at front end by a welded plate 41, with an opening for a flexible piston rod 42.
The rear end is sealed by plate 43 which co-operates with an O-ring 44, fastened to a rear flange 45 of the body 40 by bolts 46. The front end of the body 40 is provided with a carrying bi-directional rubber disk 47 and the rear end with a carrying bi-directional rubber disk 48. Front and rear collars 49, and spacer discs 51 & 52 made from soft rubber provide side support to an inflatable flexible seal 53. The seal 53 is thus held in place by the collars and 50. The front carrying rubber disc 47 is clamped by ring 54 fastened by bolts 55. The front end of the interior of the body 40 is sealed by a piston with piston seals 57. When the icepig is stopped and suitable pressure differential is created, the piston 56 is pushed back by the flexible piston rod 42. This action causes the clean process water stored within the body 40 to flow by inlet 58 into the inflatable seal 53. Vent holes 59 in plate 41 prevent vacuum creation. Eventually, the seal 53 is filled with the process water and the freezing process may be started.
The freezing process is preferably carried out by a pneumatic excavating device. The advantage of this device over the regular excavating with subsequent application of a freezing mantle to the exterior of the pipe is in that the likelihood of mechanical damage to the pipe is virtually eliminated. The use of the method and apparatus of the present invention simplifies the freezing operation to mere excavation followed up by filling the cavity thus created by liquid nitrogen , eliminating the use of a freezing mantle which is expensive to produce and to apply.
The pneumatic excavation may partly be carried out by known devices, for instance by a tool described in US Patent 4,991,321 ( issued February 12, 1991 to T.G. Artzberger, which is incorporated herein by reference.
Figure 9 shows the Artzberger device. It is described in the above patent as including a body 60 connected through a supply line 61 to a source of pressure such as an air compressor. An elongated tube 62 is connected to the _$_ body 60 and actuated by a control valve operatively associated with a trigger 63 to control the flow of air through the tube 62. The normally lower end of tube 62 is secured to a housing 64 which includes a conduit 65 to which the lower end of the tube 62 is connected. The lower end of the conduit 65 is bent inwardly to reach into a larger diameter tube portion 66 which is outwardly flared at a distal end 67, where it carries a nozzle assembly of which only an outwardly projecting part 68, concentric with an open lower end of the tube portion is visible in Fig.9. The nozzle assembly is designed to provide an increased velocity of airflow coming out of the projecting end shown in Fig. 9 and directed toward the soil to dislodge same. At the same time, the opposite end of the nozzle assembly provides aspirating action drawing the dislodged soil away through a flexible conduit 69.
The tool of this type is useful in excavating soil around cables, pipelines etc. as it does not pose the danger of damage to the underground utility lines.
Compared with regular, mechanical excavators, it removes soil from a smaller area around the pipeline or the like.
The icepig freezing method of the present invention makes use of these features and further presents a simple but technologically important supplement to the existing pneumatic excavation tools.
Referring to Figures 7 and 8, the lower end of the Artzberger tool is modified in accordance with the present invention for use in freezing icepigs in pipelines. The parts corresponding to the representation of Fig. 9 are designated with the same reference numbers and letter "A."
The tube 62A delivering the airflow as described in Artzberger, communicates with a conduit 65A which forms a part of a housing 64A. The housing 64A includes a tube portion 66A. Near the distal end 67A of the tube portion 66A, the end portion of the conduit 65A passes through the wall of the tube portion 66A and supports a nozzle assembly 71 having a distribution chamber 73 thereof. The distribution chamber 73 communicates with an _g_ upstream end of a dislodging nozzle 72 of the type increasing the velocity of the incoming airflow. The dislodging nozzle 72 is provided in that part of the nozzle assembly 71 which projects outwardly from the distal end 67A of the tube portion 66A. An aspiration nozzle 74 aimed into the tube portion 66A is disposed at a point opposite to that where the upstream end of the nozzle 72 is located. The purpose of the aspiration nozzle is to generate aspiration resulting in the removal through the tube portion 66A of particles of soil dislodged by the airflow discharged from the dislodging nozzle 72.
It is the feature of the present invention, that at least the dislodging nozzle is so disposed that its axis is generally horizontal while the tube 62A, the main part of the tube portion 66A and the flexible conduit (not shown in Figs. 7, 8) are generally upright.
It is preferred that the overall arrangement of the distal end of the tool be as shown in Figs. 7 and 8. That is to say, the distal section 75 of the tube portion 66A is bent relative to the main portion thereof generally at 90° and the nozzles 72, 74 are coaxial with each other.
In use, the tool of the present invention permits the excavation of soil immediately below an underground pipeline. Combined with the normally vertical excavation by a tool such as described in Artzberger, the present invention permits the formation of a relatively narrow cavity surrounding both sides and the underside of an underground pipeline with minimum soil having been removed. The cavity is ready to be filled with liquid nitrogen covering also the top portion of the pipeline section. The liquid nitrogen, fully surrounding the pipeline section, freezes the pipe and thus the water in the interspace 28 of the icepig. This provides substantial savings compared with known method of freezing icepigs which require a substantial excavation along both sides and under the underground pipe section to permit installation of a mantle for receiving the liquid nitrogen.
It will be appreciated that the above description pertains to the presently preferred embodiments of the present invention. Such embodiments may be modified to a greater or lesser degree without departing from the scope of the present invention.
Claims (8)
1. An ice plug for defining a barrier in a pipeline section filled with water, for inspection, maintenance or the like purposes, said ice plug comprising:
(a) a hollow cylindric body enclosed at a front end thereof and provided with guide means for sliding movement of the plug along and within the pipeline, said body having a diameter smaller than that of the pipeline to define with the latter an annular interspace enclosed at opposed axial ends of the plug and having thickness required for forming a continuous, annular ice layer firmly engaging the inside wall of the pipeline and the outer surface of said body to thus form, together with the body, a temporary water impermeable plug within the pipeline; and (b) water supply means for filling said interspace with process water, said water supply means comprising a fitting having an inlet portion open to exterior of the plug at a rear end thereof, and a discharge end communicating with said interspace at a point near the rear end of the plug.
(a) a hollow cylindric body enclosed at a front end thereof and provided with guide means for sliding movement of the plug along and within the pipeline, said body having a diameter smaller than that of the pipeline to define with the latter an annular interspace enclosed at opposed axial ends of the plug and having thickness required for forming a continuous, annular ice layer firmly engaging the inside wall of the pipeline and the outer surface of said body to thus form, together with the body, a temporary water impermeable plug within the pipeline; and (b) water supply means for filling said interspace with process water, said water supply means comprising a fitting having an inlet portion open to exterior of the plug at a rear end thereof, and a discharge end communicating with said interspace at a point near the rear end of the plug.
2. The ice plug of claim 1, wherein said fitting is connected in liquid tight fashion to a downstream end of a flexible hose, the upstream end of said flexible hose being provided with a ballast adapted to maintain the upstream end of the hose at vertically lowermost portion of the interior of the pipeline, whereby water drawn through the hose and the fitting into the interspace is taken from the pipeline outside of the plug at a lowermost location and therefore has a relatively small content of contaminants such as oil droplets or wax particles.
3. An ice plug for defining a barrier in a pipeline section filled with water, for inspection, maintenance or the like purposes, said ice plug comprising:
(a) a hollow cylindric body enclosed at a front end thereof and provided with guide means for sliding movement of the plug along and within the pipeline, said body having a diameter smaller than that of the pipeline to define with the latter an annular interspace enclosed at opposed axial ends of the plug and having thickness required for forming a continuous, annular ice layer firmly engaging the inside wall of the pipeline and the outer surface of said body to thus form, together with the body, a water impermeable plug within the pipeline; and (b) water supply means for filling said interspace with clean process water through a filling port disposed near a rear end of the plug;
(c) the water supply means including a cylindric reservoir section for clean process water disposed within said body and isolated in liquid tight manner from the exterior of the plug, (d) piston means adapted to force water from said reservoir into the interspace; and (e) piston actuation means operatively associated with said piston and adapted to force the process water into said interspace when the pressure at a front end of the plug is greater or equal to that at a rear end thereof.
(a) a hollow cylindric body enclosed at a front end thereof and provided with guide means for sliding movement of the plug along and within the pipeline, said body having a diameter smaller than that of the pipeline to define with the latter an annular interspace enclosed at opposed axial ends of the plug and having thickness required for forming a continuous, annular ice layer firmly engaging the inside wall of the pipeline and the outer surface of said body to thus form, together with the body, a water impermeable plug within the pipeline; and (b) water supply means for filling said interspace with clean process water through a filling port disposed near a rear end of the plug;
(c) the water supply means including a cylindric reservoir section for clean process water disposed within said body and isolated in liquid tight manner from the exterior of the plug, (d) piston means adapted to force water from said reservoir into the interspace; and (e) piston actuation means operatively associated with said piston and adapted to force the process water into said interspace when the pressure at a front end of the plug is greater or equal to that at a rear end thereof.
4. The plug of claim 3, further comprising a resilient, flexible, inflatable seal located within said interspace and sealed at both axial ends of the interspace, said seal forming an annular sealing layer between the outer surface of the body and the inner wall of the pipeline, said filling port discharging into a space limited by the body and by the seal.
5. A method of freezing an ice plug at a predetermined location of an underground pipeline of the type comprising the steps of conveying the ice plug within the pipeline to said predetermined location and providing process water layer at an inner wall of said location; said method comprising the steps of:
(a) furnishing at said location, by means of pneumatic excavation, a narrow cavity having a generally U-shaped cross-section and disposed along both sides of and below said predetermined location; and (b) filling said cavity by a freezing liquid such as to entirely surround the exterior of said pipeline at said location to freeze process water in the ice plug inside the pipeline.
(a) furnishing at said location, by means of pneumatic excavation, a narrow cavity having a generally U-shaped cross-section and disposed along both sides of and below said predetermined location; and (b) filling said cavity by a freezing liquid such as to entirely surround the exterior of said pipeline at said location to freeze process water in the ice plug inside the pipeline.
6. A pneumatic tool for excavating and removing soil of the type comprising a normally generally upright pressure tube having an inlet end connected to a source of pressurized air and an outlet end, said air being discharged from said outlet end into contact with soil to dislodge same, a removal tube having an entry end disposed near the outlet end of the pressure tube and having an exit end disposed to deliver dislodged soil, and aspirating means for directing air under pressure to the removal tube to cause a flow of air from the entry end of the removal tube to the exit end to draw dislodged soil through said removal tube, characterized in that said outlet end is disposed to discharge said air in a normally generally horizontal direction while the pressure tube is general upright.
7. The tool of claim 6, wherein said aspirating means is adapted to direct air under pressure in a normally generally horizontal direction, opposite to the direction of discharge from said outlet end.
8. The tool of claim 7 or claim 8, wherein said entry end of said removal tube is a part of an end section of the removal tube and is bent at about a right angle to a normally generally upright pressure tube.
Priority Applications (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2231609 CA2231609A1 (en) | 1998-03-10 | 1998-03-10 | Inflatable icepig and method of installing same |
| CA 2246213 CA2246213A1 (en) | 1997-09-04 | 1998-08-31 | Plug for forming an ice barrier in a pipeline |
| US09/144,958 US6041811A (en) | 1997-09-04 | 1998-09-01 | Plug for forming an ice barrier in a pipeline |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2231609 CA2231609A1 (en) | 1998-03-10 | 1998-03-10 | Inflatable icepig and method of installing same |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2231609A1 true CA2231609A1 (en) | 1999-09-10 |
Family
ID=29409407
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2231609 Abandoned CA2231609A1 (en) | 1997-09-04 | 1998-03-10 | Inflatable icepig and method of installing same |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2231609A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114635353A (en) * | 2022-04-11 | 2022-06-17 | 王兴磊 | Drainage anti-blocking device for bridge |
| CN114923059A (en) * | 2022-04-27 | 2022-08-19 | 华能桐乡燃机热电有限责任公司 | A sealing for pipeline of power plant's pipeline is experimental |
-
1998
- 1998-03-10 CA CA 2231609 patent/CA2231609A1/en not_active Abandoned
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114635353A (en) * | 2022-04-11 | 2022-06-17 | 王兴磊 | Drainage anti-blocking device for bridge |
| CN114635353B (en) * | 2022-04-11 | 2022-10-14 | 王兴磊 | Drainage anti-blocking device for bridge |
| CN114923059A (en) * | 2022-04-27 | 2022-08-19 | 华能桐乡燃机热电有限责任公司 | A sealing for pipeline of power plant's pipeline is experimental |
| CN114923059B (en) * | 2022-04-27 | 2023-09-05 | 华能桐乡燃机热电有限责任公司 | Pipeline sealing device for power plant pipeline test |
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