CA2171525A1 - Pipe pig with abrasive exterior - Google Patents
Pipe pig with abrasive exteriorInfo
- Publication number
- CA2171525A1 CA2171525A1 CA 2171525 CA2171525A CA2171525A1 CA 2171525 A1 CA2171525 A1 CA 2171525A1 CA 2171525 CA2171525 CA 2171525 CA 2171525 A CA2171525 A CA 2171525A CA 2171525 A1 CA2171525 A1 CA 2171525A1
- Authority
- CA
- Canada
- Prior art keywords
- pig
- abrasive
- pipe pig
- pipe
- mold
- 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
- 239000003082 abrasive agent Substances 0.000 claims abstract description 13
- 238000004519 manufacturing process Methods 0.000 claims abstract description 4
- 239000000463 material Substances 0.000 claims description 19
- 239000012858 resilient material Substances 0.000 claims description 7
- 238000000034 method Methods 0.000 claims description 4
- 239000000203 mixture Substances 0.000 claims description 2
- 238000004140 cleaning Methods 0.000 abstract description 8
- 241000282887 Suidae Species 0.000 description 11
- 238000000576 coating method Methods 0.000 description 7
- 238000007790 scraping Methods 0.000 description 6
- 239000006260 foam Substances 0.000 description 5
- 239000002245 particle Substances 0.000 description 5
- 239000011248 coating agent Substances 0.000 description 4
- 229920000642 polymer Polymers 0.000 description 3
- 239000004576 sand Substances 0.000 description 3
- 238000000227 grinding Methods 0.000 description 2
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 2
- 230000002093 peripheral effect Effects 0.000 description 2
- -1 polyethylene Polymers 0.000 description 2
- 229920002635 polyurethane Polymers 0.000 description 2
- 239000004814 polyurethane Substances 0.000 description 2
- 229910010271 silicon carbide Inorganic materials 0.000 description 2
- JOYRKODLDBILNP-UHFFFAOYSA-N Ethyl urethane Chemical compound CCOC(N)=O JOYRKODLDBILNP-UHFFFAOYSA-N 0.000 description 1
- MBMLMWLHJBBADN-UHFFFAOYSA-N Ferrous sulfide Chemical compound [Fe]=S MBMLMWLHJBBADN-UHFFFAOYSA-N 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- 230000003466 anti-cipated effect Effects 0.000 description 1
- 239000000571 coke Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 229910003460 diamond Inorganic materials 0.000 description 1
- 239000010432 diamond Substances 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 229920001971 elastomer Polymers 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 239000012948 isocyanate Substances 0.000 description 1
- 150000002513 isocyanates Chemical class 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000011236 particulate material Substances 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000005060 rubber Substances 0.000 description 1
- 238000009991 scouring Methods 0.000 description 1
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 238000011179 visual inspection Methods 0.000 description 1
Landscapes
- Cleaning In General (AREA)
Abstract
A method of making a rotationally symmetric pipe pig in which abrasive material is distributed to the periphery of the pipe pig by centrifuging the pipe pig.
The pipe pig is cylindrical with a central axis and the pipe pig is centrifuged about its central axis. Such a pipe pig may also include a plurality of appendages disposed about and extending radially outward from the body of the pig. The combined cleaning function of the appendages and abrasive provides an efficient cleaning function.
The pipe pig is cylindrical with a central axis and the pipe pig is centrifuged about its central axis. Such a pipe pig may also include a plurality of appendages disposed about and extending radially outward from the body of the pig. The combined cleaning function of the appendages and abrasive provides an efficient cleaning function.
Description
~_ 2l7l525 TITLE OF THE INVENTION
Pipe Pig with Abrasive Exterior INVENTOR
Orlande Sivacoe FIELD OF THE INVENTION
This invention relates to pipe pigs, and a method of making pipe pigs.
R~GROUND AND SU~ARY OF THE INVENTION
Pipe pigs are used to remove coatings or scale from the inside of pipes. This coating can vary in thickness and hardness. For example, deposits of coke can form soft coatings several millimeters thick, while hard scale such as iron sulphide may form coatings less than 1 mm thick. Pipe pigs are forced through the pipes under hydraulic pressure and the coating is removed by the scraping action of the pig6.
To improve the scraping action, such pigs may include 2S hard appendages that scrape the coating. These appendages are subject to wear, and can be expensive and inconvenient to replace.
The inventor has previously provided a pipe pig with detachable appendages for use with a generally cylindrical or spherical foam pipe pig, as described in United States patent no. 5,265,302 of Orlande Sivacoe to overcome problems associated with the appendages wearing out. Such pigs are particularly useful in removing hard scale.
Pigs are also known that have abrasive material, such as sand, glass, diamond dust, silicon carbides, etc, on the sur~ace of the pig, as for example described in United States patent no.
4,016,620 of Marvin D. Powers. In addition, the inventor has for several years used pigs with abrasive distributed within them that enhances the scraping action of the pigs.
One difficulty with making foam pigs having abrasive distributed within the foam pig is that much of the abrasive remains deep within the foam pig and does not provide a useful scraping action. The present invention overcomes this limitation and provides an improved pipe pig.
In one aspect of the invention, there is provided a method of making a rotationally symmetric pipe pig in which abrasive material is distributed to the periphery of the pipe pig by centrifuging the pipe pig. Preferably, the pipe pig is cylindrical with a central axis and the pipe pig is centrifuged about its central axis. Preferably the abrasive is a particulate material. Such a pipe pig may also include a plurality of appendages disposed about and extending radially outward from the body of the pig. The combined cleaning function of the appendages and abrasive provides an efficient cleaning function. In another aspect of the invention, there is provided a pipe pig made in accordance with the method of the invention.
BRIEF DESCRIPTION OF THE DRAWING
There will now be described a preferred embodiment of the invention, with reference to the figure, which shows a longitudinal section of a pipe pig according to the invention.
DETATT-~n DESCRIPTION OF ~n~r-~nRED EMBODIMENTS
Referring to the figure, there is shown a generally cylindrical pig 12 constructed from resilient material. The body of the pig is preferably generally cylindrical, but may also be oval with varying degrees of elongation. As can be seen from the ribbed shape of the pig, it is believed nece6sary only that the pig have an axis of rotational symmetry (for example the axis A shown in the figure), not that it be exactly cylindrical. Such an axis is provided by the axis of a cylinder in the case of a cylindrical pig.
The pig 12 includes a plurality of ribs 26, and central annular recessed sections 28 and outer annular recessed sections 30 on either side of the central recessed sections. The recessed sections may be interrupted and the annular ribs reinforced by longitudinal ribs. The ribs 26 are preferably all the same diameter, although for some applications, such as when the pig is made with flared ends (as for example shown in Fig. 1 of United States patent no.
5,265,302), the central section of the pig will have reduced diameter, such that the more central ribs have reduced diameter.
A plurality of appendages 38 are disposed about and extend radially outward from the pig 12.
Each appendage 38 comprises a head portion 44, with tip 48, and a threaded shank portion 42, preferably integral with each other. The head portion 44 includes a nut shaped portion 46 for engagement by a wrench.
The appendages have a hardness and size chosen for the intended application.
Each appendage 38 is secured in the pig 12 by being threaded into a first end of a threaded 21 71~25 sleeve 34 that is itself secured to the pig 12. The nut portion 46 allows the appendage to be readily grasped, rotated and removed from the threaded sleeve 34. The sleeves 34 have laterally extending flanges 36 at their bases. The flanges 36 secure the sleeves 34 in the body and help prevent the sleeves from being removed from the body, and from being forced deeper into the body. Each appendage 38 with sleeve 34 is secured in one of the annular recesses 28 or 30 thus forming a plurality of rows of appendages, each row being disposed in a recess. The sleeve is sunk into the pig 12 to create a depression 31 about each appendage. The depressions 31 allow the addition of washers (not shown) to enable extension of the appendages radially outward as they wear.
The pig 12 is symmetrical, and preferably elongate along the axis A, with conical ends 21 forming the leading edge of the pig (in whichever direction the pig is moving). The conical ends 21 assist in preventing the pig 12 becoming stuck on defects and sharp corners in a pipe. The shape of the ends 21 may also be curved.
The pig 12 is made by using a mold. The mold itself will have an internal cavity having the same shape as the pig, and an internal periphery corresponding to the periphery of the pig, and, like the pig, the internal cavity of the mold will have an axis of rotational symmetry defined by the axis A. The pig is made by placing the sleeves 34 in the internal cavity of a mold in the desired position, and by filling the mold with known techniques with a suitable curable material for building pigs. A suitable curable material includes polyurethane 8uch as isocyanate available from BASF and a suitable resin, plastic, polyethylene, polypropylene, rubber, urethane and foam. The curable material should form a re~ilient material upon curing. Abrasive material 18 such as sand (for example sand used in fracturing wells), S silicon carbide, aluminum oxide (9 Moh), etc, is added to the curable material before the curable material is placed in the mold such that the abrasive 18 is fairly evenly distributed in the curable material. Grit size 12-20 particles per inch is believed to be suitable.
Particulate abrasive material is preferred, although the particles could be elongate or needlelike, the constraint being that the abrasive material must be mobile in the mold when it is centrifuged. Even distribution can be obtained by stirring the abrasive 18 into the curable material or otherwise agitating a mixture of the abrasive 18 and curable material. The amount of abrasive 18 is such that the abrasive is densest around the periphery of the pig, preferably forming a layer of about 0.5 to 1 cm thick (for a 10 cm diameter pig) around the periphery of the pig upon curing of the curable material. This layer of abrasive should not be homogenous, there must be enough curable material between the particles of abrasive to bind the abrasive to the pig. As seen the figure, a few abrasive particles will tend to remain in the body of the pig, but this does not affect the manner of operation of the pig.
The mold is then rotated about an axis preferably passing through the center of the mold. If the mold forms a generally cylindrical cavity, as might be used to produce the pig shown in the figure, then the mold is rotated about the axis A. The centrifugal force on the abrasive 18 within the mold (providing the abrasive 18 has higher density than the ~_ 2171525 curable material) migrates outward away from the axis of rotational symmetry to become dispersed around the periphery 14 of the pig.
The curable material is allowed to cure to form a resilient pipe pig, with the abrasive 18 dispersed and concentrated around the periphery 14 of the pig 12. Once the curable material cures to form a resilient material, the abrasive 18 and sleeves 34 will be secured within the resilient material around the periphery 14 of the pig. The abrasive 18 forms a layer, dispersed within the peripheral material of the pig, that preferably extends the length of the pig, from end 24 to end 24, and is relatively uniform in thickness about the circumference of the pig. If the abra6ive is not relatively uniformly distributed within the curable material used to form the pig before being centrifuged, the abrasive filled peripheral layer will have uneven thickness, and may even be absent in some locations. While some unevenness is acceptable, even with abrasive being absent in some locations, it is preferred that the abrasive at least be present all around the periphery of the pig, and preferably be present in a relatively uniform layer as shown. Due to the nature of the process, the density of abrasive within the pig forming resilient material tends to be greater towards the outer boundary of the pig, and this is desirable since the abrasive action of the abrasive material is enhanced by having more of the abrasive present at the actual boundary of the pig. Centrifuging the pig tends to cause the abrasive to migrate first into the ribs, where it is most dense. Greater density of the abrasive in the ribs 26 tends to enhance the cleaning action of the pig.
However, if the density of the abrasive 18 becomes too great, the abrasive 18 may be inadequately secured by the polymer forming the body of the pig. In this case, the abrasive 18 will be worn away too quickly and the pig soon rendered ineffective for cleaning. Some care must be taken with the amount of abrasive to be used. A ratio of 10-20 parts by volume abrasive to 100 parts by volume polymer is believed to be adequate for a pig made of 20 lbs density polyurethane and 12 particle/inch aluminum oxide grit.
However, the amount of abrasive 18 that is most suitable for a given application is dependent upon the grit size of the abrasive and the hardness and density of the polymer forming the body of the pig.
The abrasive material should be present along the length of the pig (between the ends 24) for most efficient cleaning, but it is also possible for the abrasive to occupy a portion of the length of the pig.
The manner of operation of the pig is as follows. The first run of the pig is used to establish the location of the scale. A pig without appendages may be used for this purpose. The pig is first driven through the pipe a first time while recording the hydraulic pressure used to drive the pig. High peaks on the recorded pressure chart indicate tight bends in the pipe or large scale build up. Lower peaks tend to indicate scale build up. The higher the peak, the greater the build up of scale.
Visual inspection of the pressure recording can be used to identify sections of the pipe that are contaminated with scale. The type of scale can be determined since the hydraulic fluid will typically bring some of the scale with it, if not during a first ~ 2171525 run then through a subsequent run. Appendages are then selected and inserted into the pig that are selected for the type, hence hardness, and thickness of the scale that is anticipated. The pig is then driven through the pipe, backwards and forwards, primarily through the sections that are contaminated with scale.
Each time the pig is run through a part of the pipe is called a pass. It may require several hundred passes to clear the coating in a bad section of the pipe. The pig may be run through 1000 meters of pipe, while the coated section may only be 200 meters long. Appendages may be replaced or extended radially outward using washers as they wear. The abrasive provides a relatively light cleaning or grinding function all around the inner circumference of the pipe, while the appendages tend to provide a deeper scraping or scouring action, and together the abrasive and appendages clean the pipe. The pig may also be run without appendages on the pig, before or after a run with appendages. Placing the appendages on the same pig with the abrasive centrifugally dispersed to the outer periphery of the pig enables simultaneous scraping and grinding.
A person skilled in the art could make immaterial modifications to the invention described and claimed in this patent without departing from the essence of the invention.
Pipe Pig with Abrasive Exterior INVENTOR
Orlande Sivacoe FIELD OF THE INVENTION
This invention relates to pipe pigs, and a method of making pipe pigs.
R~GROUND AND SU~ARY OF THE INVENTION
Pipe pigs are used to remove coatings or scale from the inside of pipes. This coating can vary in thickness and hardness. For example, deposits of coke can form soft coatings several millimeters thick, while hard scale such as iron sulphide may form coatings less than 1 mm thick. Pipe pigs are forced through the pipes under hydraulic pressure and the coating is removed by the scraping action of the pig6.
To improve the scraping action, such pigs may include 2S hard appendages that scrape the coating. These appendages are subject to wear, and can be expensive and inconvenient to replace.
The inventor has previously provided a pipe pig with detachable appendages for use with a generally cylindrical or spherical foam pipe pig, as described in United States patent no. 5,265,302 of Orlande Sivacoe to overcome problems associated with the appendages wearing out. Such pigs are particularly useful in removing hard scale.
Pigs are also known that have abrasive material, such as sand, glass, diamond dust, silicon carbides, etc, on the sur~ace of the pig, as for example described in United States patent no.
4,016,620 of Marvin D. Powers. In addition, the inventor has for several years used pigs with abrasive distributed within them that enhances the scraping action of the pigs.
One difficulty with making foam pigs having abrasive distributed within the foam pig is that much of the abrasive remains deep within the foam pig and does not provide a useful scraping action. The present invention overcomes this limitation and provides an improved pipe pig.
In one aspect of the invention, there is provided a method of making a rotationally symmetric pipe pig in which abrasive material is distributed to the periphery of the pipe pig by centrifuging the pipe pig. Preferably, the pipe pig is cylindrical with a central axis and the pipe pig is centrifuged about its central axis. Preferably the abrasive is a particulate material. Such a pipe pig may also include a plurality of appendages disposed about and extending radially outward from the body of the pig. The combined cleaning function of the appendages and abrasive provides an efficient cleaning function. In another aspect of the invention, there is provided a pipe pig made in accordance with the method of the invention.
BRIEF DESCRIPTION OF THE DRAWING
There will now be described a preferred embodiment of the invention, with reference to the figure, which shows a longitudinal section of a pipe pig according to the invention.
DETATT-~n DESCRIPTION OF ~n~r-~nRED EMBODIMENTS
Referring to the figure, there is shown a generally cylindrical pig 12 constructed from resilient material. The body of the pig is preferably generally cylindrical, but may also be oval with varying degrees of elongation. As can be seen from the ribbed shape of the pig, it is believed nece6sary only that the pig have an axis of rotational symmetry (for example the axis A shown in the figure), not that it be exactly cylindrical. Such an axis is provided by the axis of a cylinder in the case of a cylindrical pig.
The pig 12 includes a plurality of ribs 26, and central annular recessed sections 28 and outer annular recessed sections 30 on either side of the central recessed sections. The recessed sections may be interrupted and the annular ribs reinforced by longitudinal ribs. The ribs 26 are preferably all the same diameter, although for some applications, such as when the pig is made with flared ends (as for example shown in Fig. 1 of United States patent no.
5,265,302), the central section of the pig will have reduced diameter, such that the more central ribs have reduced diameter.
A plurality of appendages 38 are disposed about and extend radially outward from the pig 12.
Each appendage 38 comprises a head portion 44, with tip 48, and a threaded shank portion 42, preferably integral with each other. The head portion 44 includes a nut shaped portion 46 for engagement by a wrench.
The appendages have a hardness and size chosen for the intended application.
Each appendage 38 is secured in the pig 12 by being threaded into a first end of a threaded 21 71~25 sleeve 34 that is itself secured to the pig 12. The nut portion 46 allows the appendage to be readily grasped, rotated and removed from the threaded sleeve 34. The sleeves 34 have laterally extending flanges 36 at their bases. The flanges 36 secure the sleeves 34 in the body and help prevent the sleeves from being removed from the body, and from being forced deeper into the body. Each appendage 38 with sleeve 34 is secured in one of the annular recesses 28 or 30 thus forming a plurality of rows of appendages, each row being disposed in a recess. The sleeve is sunk into the pig 12 to create a depression 31 about each appendage. The depressions 31 allow the addition of washers (not shown) to enable extension of the appendages radially outward as they wear.
The pig 12 is symmetrical, and preferably elongate along the axis A, with conical ends 21 forming the leading edge of the pig (in whichever direction the pig is moving). The conical ends 21 assist in preventing the pig 12 becoming stuck on defects and sharp corners in a pipe. The shape of the ends 21 may also be curved.
The pig 12 is made by using a mold. The mold itself will have an internal cavity having the same shape as the pig, and an internal periphery corresponding to the periphery of the pig, and, like the pig, the internal cavity of the mold will have an axis of rotational symmetry defined by the axis A. The pig is made by placing the sleeves 34 in the internal cavity of a mold in the desired position, and by filling the mold with known techniques with a suitable curable material for building pigs. A suitable curable material includes polyurethane 8uch as isocyanate available from BASF and a suitable resin, plastic, polyethylene, polypropylene, rubber, urethane and foam. The curable material should form a re~ilient material upon curing. Abrasive material 18 such as sand (for example sand used in fracturing wells), S silicon carbide, aluminum oxide (9 Moh), etc, is added to the curable material before the curable material is placed in the mold such that the abrasive 18 is fairly evenly distributed in the curable material. Grit size 12-20 particles per inch is believed to be suitable.
Particulate abrasive material is preferred, although the particles could be elongate or needlelike, the constraint being that the abrasive material must be mobile in the mold when it is centrifuged. Even distribution can be obtained by stirring the abrasive 18 into the curable material or otherwise agitating a mixture of the abrasive 18 and curable material. The amount of abrasive 18 is such that the abrasive is densest around the periphery of the pig, preferably forming a layer of about 0.5 to 1 cm thick (for a 10 cm diameter pig) around the periphery of the pig upon curing of the curable material. This layer of abrasive should not be homogenous, there must be enough curable material between the particles of abrasive to bind the abrasive to the pig. As seen the figure, a few abrasive particles will tend to remain in the body of the pig, but this does not affect the manner of operation of the pig.
The mold is then rotated about an axis preferably passing through the center of the mold. If the mold forms a generally cylindrical cavity, as might be used to produce the pig shown in the figure, then the mold is rotated about the axis A. The centrifugal force on the abrasive 18 within the mold (providing the abrasive 18 has higher density than the ~_ 2171525 curable material) migrates outward away from the axis of rotational symmetry to become dispersed around the periphery 14 of the pig.
The curable material is allowed to cure to form a resilient pipe pig, with the abrasive 18 dispersed and concentrated around the periphery 14 of the pig 12. Once the curable material cures to form a resilient material, the abrasive 18 and sleeves 34 will be secured within the resilient material around the periphery 14 of the pig. The abrasive 18 forms a layer, dispersed within the peripheral material of the pig, that preferably extends the length of the pig, from end 24 to end 24, and is relatively uniform in thickness about the circumference of the pig. If the abra6ive is not relatively uniformly distributed within the curable material used to form the pig before being centrifuged, the abrasive filled peripheral layer will have uneven thickness, and may even be absent in some locations. While some unevenness is acceptable, even with abrasive being absent in some locations, it is preferred that the abrasive at least be present all around the periphery of the pig, and preferably be present in a relatively uniform layer as shown. Due to the nature of the process, the density of abrasive within the pig forming resilient material tends to be greater towards the outer boundary of the pig, and this is desirable since the abrasive action of the abrasive material is enhanced by having more of the abrasive present at the actual boundary of the pig. Centrifuging the pig tends to cause the abrasive to migrate first into the ribs, where it is most dense. Greater density of the abrasive in the ribs 26 tends to enhance the cleaning action of the pig.
However, if the density of the abrasive 18 becomes too great, the abrasive 18 may be inadequately secured by the polymer forming the body of the pig. In this case, the abrasive 18 will be worn away too quickly and the pig soon rendered ineffective for cleaning. Some care must be taken with the amount of abrasive to be used. A ratio of 10-20 parts by volume abrasive to 100 parts by volume polymer is believed to be adequate for a pig made of 20 lbs density polyurethane and 12 particle/inch aluminum oxide grit.
However, the amount of abrasive 18 that is most suitable for a given application is dependent upon the grit size of the abrasive and the hardness and density of the polymer forming the body of the pig.
The abrasive material should be present along the length of the pig (between the ends 24) for most efficient cleaning, but it is also possible for the abrasive to occupy a portion of the length of the pig.
The manner of operation of the pig is as follows. The first run of the pig is used to establish the location of the scale. A pig without appendages may be used for this purpose. The pig is first driven through the pipe a first time while recording the hydraulic pressure used to drive the pig. High peaks on the recorded pressure chart indicate tight bends in the pipe or large scale build up. Lower peaks tend to indicate scale build up. The higher the peak, the greater the build up of scale.
Visual inspection of the pressure recording can be used to identify sections of the pipe that are contaminated with scale. The type of scale can be determined since the hydraulic fluid will typically bring some of the scale with it, if not during a first ~ 2171525 run then through a subsequent run. Appendages are then selected and inserted into the pig that are selected for the type, hence hardness, and thickness of the scale that is anticipated. The pig is then driven through the pipe, backwards and forwards, primarily through the sections that are contaminated with scale.
Each time the pig is run through a part of the pipe is called a pass. It may require several hundred passes to clear the coating in a bad section of the pipe. The pig may be run through 1000 meters of pipe, while the coated section may only be 200 meters long. Appendages may be replaced or extended radially outward using washers as they wear. The abrasive provides a relatively light cleaning or grinding function all around the inner circumference of the pipe, while the appendages tend to provide a deeper scraping or scouring action, and together the abrasive and appendages clean the pipe. The pig may also be run without appendages on the pig, before or after a run with appendages. Placing the appendages on the same pig with the abrasive centrifugally dispersed to the outer periphery of the pig enables simultaneous scraping and grinding.
A person skilled in the art could make immaterial modifications to the invention described and claimed in this patent without departing from the essence of the invention.
Claims (7)
PROPERTY OR PRIVILEGE IS CLAIMED ARE AS FOLLOWS:
1. A pipe pig comprising:
a pig body having an axis of rotational symmetry and a periphery, and being made of resilient material; and abrasive material centrifugally dispersed within the resilient material around the outer periphery of the pig.
a pig body having an axis of rotational symmetry and a periphery, and being made of resilient material; and abrasive material centrifugally dispersed within the resilient material around the outer periphery of the pig.
2. The pipe pig of claim 1 in which pipe pig has first and second ends and the abrasive material is dispersed along the length of the pipe pig between the first and second ends.
3. The pipe pig of claim 1 further including a plurality of appendages disposed about and extending radially outward from pipe pig.
4. The pipe pig of claim 1 further including a plurality of annular ribs extending around the pipe pig, and in which abrasive is most dense in the annular ribs.
5. The pipe pig of claim 1 in which the pipe pig is cylindrical.
6. A method of making a pipe pig comprising:
mixing a curable material and an abrasive material;
placing the mixture of curable material and abrasive material in a mold having a cavity with an internal periphery and an axis of rotational symmetry;
centrifuging the mold about the axis of rotational symmetry to force the abrasive material outward, away from the axis of rotational symmetry, to become dispersed around the internal periphery of the mold; and allowing the curable material to cure to form a resilient pipe pig with abrasive concentrated about the periphery of the resilient material.
mixing a curable material and an abrasive material;
placing the mixture of curable material and abrasive material in a mold having a cavity with an internal periphery and an axis of rotational symmetry;
centrifuging the mold about the axis of rotational symmetry to force the abrasive material outward, away from the axis of rotational symmetry, to become dispersed around the internal periphery of the mold; and allowing the curable material to cure to form a resilient pipe pig with abrasive concentrated about the periphery of the resilient material.
7. The method of claim 6 further including inserting sleeves into the mold around the internal periphery of the mold with the sleeves disposed radially outward for receiving appendages.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US40324795A | 1995-03-10 | 1995-03-10 | |
| US08/403,247 | 1995-03-10 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2171525A1 true CA2171525A1 (en) | 1996-09-11 |
Family
ID=23595075
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2171525 Abandoned CA2171525A1 (en) | 1995-03-10 | 1996-03-11 | Pipe pig with abrasive exterior |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2171525A1 (en) |
-
1996
- 1996-03-11 CA CA 2171525 patent/CA2171525A1/en not_active Abandoned
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |