AU742107B2 - Pipeline P.I.G.S. - Google Patents

Description

P/00/0oII Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT The following statement is a full description of this invention, including Invention Title: PIPELINE P.I.G.S.

the best method of performing it known to me: 1 C:%WlNWORDY)ELILAI-NANDREVWLETTFMS.DOC -2- PIPELINE P.I.G.S The present invention relates to an apparatus and a method for forming an apparatus for use in pipeline or conduit maintenance, in particular, the internal cleaning of industrial pipelines and conduits. The expression P.I.G.S.

is used as an abbreviation for Pipeline Internal Gauging Systems, which is the type of system to which the present invention relates. The word "pig" is used to describe a certain component of a P.I.G.S. and for convenience, that word will be used throughout the specification.

In the maintenance of industrial pipelines, it is often necessary to clean the internal surface of the pipe, in order to remove sediment which has built up on that surface over time. The sediment may, for example, be in the form of sewerage or heavy metal deposits and by adhering to the internal surface of oo the pipe, that sediment can adversely restrict the passage of material. Cleaning of the internal surface of a pipe can present major difficulties, although one method presently employed involves dragging or pushing body of material known as a pig through the pipe, in a manner in which the pig frictionally engages the internal surface of the pipe, thereby dislodging sediment which has adhered to that surface during passage through the pipe. The dislodged o sediment is pushed ahead of the pig to an opening or an open end of the pipe for removal.

A pig of the above kind is generally only applicable for use with S• cylindrical pipes and has a cylindrical form in which the outside diameter of the pig is substantially equal to the inside diameter of the pipe. It is important that the diameter of the pig be correctly matched to the pipe to be cleaned, so as to ensure the correct frictional engagement with the inside surface of the pipe, which in part depends on the type of sediment to be removed. The pig can also be manufactured from various materials, also depending on the type of sediment to be removed.

One known type of pig comprises a foam core covered by a polyurethane coating. In use, the polyurethane coating engages the inside surface of the pipe and the foam core is provided to prevent that coating from DO C:VVNWORD\DELILAH\COMPLETE\PIPELINE.DOC 3 collapsing during its passage through the pipe. The polyurethane coating is applied to the foam core, either by manually painting the coating on to the core, or by coating the core with a ribbon flow painting machine. The latter method applies the polyurethane coating in a ribbon form to the outer surface of the core, normally while the core is being rotated. The ribbon coating is applied to the foam core over its outer cylindrical surface by rotating the core about its longitudinal axis in a single direction and by applying the ribbon as a spiral from the front of the core to the rear and then in the return direction, so that the spiral intersects itself in the return direction forming a diagonal grid-like coating.

The coating is applied to leave intermittent portions of the foam core exposed and these portions are left exposed for moisture absorbency and for trapping :any sediment which has become wedged between the outer cylindrical surface of the pig and the internal surface of the pipe during passage of the pig through the pipe.

15 Manual application of the polyurethane coating is labour intensive and therefore is unattractive especially for larger production runs. Application of the coating by way of a ribbon flow machine is less labour intensive and therefore more attractive, but the cost of such machinery is prohibitive, 0particularly when several of such machines are required for high production 20 output.

Additionally, the above methods are limited to the application of plastics which have suitable properties allowing them to be painted on to the foam core either manually or by appropriate machinery. Generally however, the plastic must be mixed with additives to extend its life, so that the plastic remains in a condition suitable for painting throughout the painting process. That is, it must include additives which extend the pot life of the plastic and which enables it to be curable at room temperature.

It is an object of the invention to overcome or at least alleviate some of the above disadvantages.

According to one aspect of the present invention, there is provided a pig for removing sediment deposits from the internal surface of a pipe, the pig including an outer jacket moulded from plastic material, the jacket having a 4 body of cylindrical form and defining an internal core cavity in the jacket body, and the jacket body having an outer surface for slidable engagement with the internal surface of the pipe in order to dislodge sediment deposits therefrom; and, stiffening means in the core cavity for supporting the jacket against inward collapse during engagement with the internal surface of the pipe.

According to another aspect of the present invention, there is provided a method of forming a pig for removing sediment deposits from the internal surface of a pipe, the method including the steps of: moulding an outer jacket from plastic material, the jacket having a body of cylindrical form and defining an internal core cavity in the jacket body, and the jacket body having an outer surface for slidable engagement with the internal surface of the pipe; and, providing stiffening means for supporting the jacket against inward collapse during engagement with the internal surface of the pipe, the stiffening means being located in the core cavity of the formed jacket.

15 For the purposes of this invention, the expression "moulded" and its variations are intended to embrace all techniques which work a plastic material in a moulding die. These techniques can include injection and blow moulding, as well as known casting techniques.

The plastic material can be any material which is moldable and which 20 has appropriate characteristics suitable for the cleaning function of the pig. For example, the material chosen may be a relatively soft material, if the sediment to be removed is relatively non-abrasive and is easily dislodged from the internal pipe surface. Alternatively, the material might include abrasive elements such as silicon carbide bits, or wire brush threads, if the internal surface requires medium to heavy burnishing.

In one form of the invention, the pig includes a polyurethane jacket and a foam core as stiffening means. In forming the pig, a female die is provided to accept a charge of polyurethane material. The die is heated to a suitable temperature for moulding of the plastic charge and a male plunger is inserted into the female die, to mould the plastic and form the jacket. The jacket can be left to cure within the die, after which it is removed therefrom. Removal can be simultaneous with removal of the plunger. The core cavity of the jacket thus formed can then be filled with a suitable core as may be required.

In this arrangement, a foam core can be poured in liquid form into the formed jacket so that the foam fills the jacket fully. Advantageously a moulded jacket that has been provided with openings for moisture absorption and trapping of sediment, is suited to receive liquid foam, because the foam also fills the openings allowing the foam core to be exposed in use, in the region of those openings to the internal surface of the pipe. In forming the pig in this manner, foam may tend to flow out of the openings, but if this does occur, it will normally only be a small portion of foam and that can be easily removed. If however, it is desirable to prevent the foam from exiting through the openings, the jacket can be placed in a snug fitting sleeve when the foam is being poured. A particular advantage is realised in an arrangement in which the foam fills the openings, whereby the exposed foam portion of the openings is 15 flush with the outer surface of the jacket, so that those portions of the core 0 slidingly engage the internal surface of the pipe during passage of the pig therethrough, in the same manner as the outer surface of the jacket. Thus, sediment or moisture trapped between the outer surface of the jacket and the inner surface of the pipe can be absorbed within the foam in an opening.

20 Additionally, location of foam core portions within the openings provides a 6 locking effect against removal of the core from the jacket, which alleviates the need for adhesives or other such means to be used.

In an alternative form of the invention the foam core can be used to form the male plunger, so that insertion of the foam core into the die moulds the jacket as required, but in this form, the jacket is removed from the female die already attached to the foam core. The foam core can be created with raised portions, about which the jacket is formed, so that openings are provided in the jacket which are filled with foam.

Where the jacket is injection moulded or blow moulded then, in one form, injection moulding takes place about suitable stiffening means such as a foam core described earlier, or about an ordinary male die element.

The jacket can be moulded to have any suitable form which assists the S. operation of the pig. For example, openings provided in the jacket can have a shape conducive to the trapping of sediment, or alternatively or additionally, 15 conducive to the absorption of moisture. Furthermore, it is advantageous that the pig rotate about the longitudinal axis of the pipe during movement i therethrough and a diagonally disposed grid-like pattern of openings promotes such rotation.

The jacket has opposite end regions that can have any suitable form or shape. For example, the end regions could be flat, disposed in a plane perpendicular to the axis of the cylindrical body. Alternatively, the end regions could be conical or frustoconical shaped, coaxial with the cylindrical body. A conical or like end region shape facilitates passage of the pig through curves or bends in the pipe and through constrictions which may form part of the pipe.

Also, this type of end region shape facilitates attachment of a rope or cable to the pig, for the purpose of pulling the pig through the pipe. An end region of that shape also facilitates cleaning treatment of the pipe by enabling dislodgment of sediment along the inclined surface of the cone or frustocone.

Alternatively, one end region of the pig could be flat, while the other end region could be conical or frustoconical. Other forms may equally be applicable, such as concave, convex or other contour. The pig can thus be constructed as unidirectional, in which the end regions are constructed as a front or rear end, so 6A that the pig only passes through a pipe with the front end leading, or as bidirectional, in which either end can lead. The end regions may be constructed differently, so that different end characteristics can be achieved, for use under different circumstances.

The end regions of the pig jacket can be formed integral with the cylindrical body during the jacket moulding process, or one or both can be fixed to the cylindrical body later. The fixing can be integral or otherwise.

The ends of the pig jacket are preferably sealed, if necessary by a cap and that cap may be formed of the same material as the jacket and may be integral with the jacket. The cap can be formed during the jacket moulding •process or alternatively can be later applied to the jacket such as by painting, or otherwise.

The foam core can have any suitable characteristics relative to ~absorption, density etc and may be preformed or liquid cast, as appropriate for l 7 the method adopted to construct the jacket. The foam core might be solid, or might be tubular, depending on the degree of stiffness required.

As an alternative to a foam core, the jacket may be cast or molded with stiffening ribs in the core cavity, which stiffen the jacket sufficiently that an additional core is unnecessary. In this respect, the type of core or other stiffening means adopted is generally required to have a small amount of resilient flexibility suitable to allow the jacket to flex to accommodate small variations in the inside diameter of a pipe or, to accommodate large or difficult to dislodge sediments. An alternative kind of stiffening means might take the form of an internal sleeve, preferably of plastic, although other materials could be used. Like the foam core, such a sleeve could be inserted into the core cavity of a moulded jacket, or could form part of the mould during moulding of the jacket.

"The jacket can be formed of any suitable plastic or rubber. For the 15 purposes of this specification, all forms of rubbers and any other materials *suitable to form a jacket are embraced under the term "plastic". These may include additives suitable to assist with the sediment removal treatment, such as abrasive additives to remove heavy or well adhered sediment. Softer or o. less abrasive materials can be used to treat less aggressive sediment.

20 By moulding or casting the jacket, the pot life of a plastic need not be extended, because the formation process of the jacket occurs rapidly, i.e. in a matter of seconds. Further, the plastic can be cured at a temperature elevated above room temperature as preferred in such molding/casting techniques.

Additionally, the expense and time consideration associated with a ribbon flow painting machine is avoided.

In order to assist in arriving at an understanding of the present invention, a preferred embodiment is illustrated in the attached drawings.

However, it should be understood that the following description is illustrative only and should not be taken in any way as a restriction on the generality of the invention as described above.

Figure 1 shows an example form of a pig jacket according to the R A invention. The jacket 10 is a polyurethane jacket having body 11, a front end -8- 12 and a rear end 13. The body 11 is cylindrical while the front end 12 has a frustoconical form. The rear end 13 is open-ended. The front end 12 has a flat face 14 and this face may be fully or partially sealed in the moulding process by the same polyurethane material used for the rest of the jacket 10, although it may equally be left open during the moulding process in the manner of the rear end 13.

The form of the jacket 10, as moulded or cast by any suitable process includes a plurality of openings 15 provided in the body 11. The openings shown extend completely through the thickness T of the body and have either a generally triangular or diamond shape.

The jacket 10 is tubular in order to receive stiffening means internally thereof. While the stiffening means may take the form of ribs extending circumferentially about the longitudinal axis of the jacket, on the internal surface of the body 11 or an internal frame or sleeve, a more preferred form is provided by a foam filling 16 which is shown in Figure 2. As shown in Figure 2, the foam filler completely fills the internal cavity of the jacket 10, being the cavities of both the body 11 and the frustoconical front end 12.

The foam filling 16 can be any suitable foam or sponge, preferably •t which resiliently supports the jacket 10 against collapse. In the embodiment of Figure 2, the foam fills the internal cavity of the jacket 10 so that each of the openings 15 is filled with foam and the foam is flush with the outside surface 17 of the jacket 10. The foam need not be absolutely flush with the outside surface 17 of the jacket 10, but preferably the openings are substantially filled to the thickness T (Figure 1) of the jacket Foam filling of the jacket can be conducted in one of a number of ways.

The preferred method adopted in the arrangement of Figure 2 involves pouring of liquid foam into the internal cavity of the jacket 10, after the jacket has been moulded. This may take place in the moulding die, or alternatively, the moulded jacket can be removed from the die and then filled. To prevent overflow of foam through the openings 15, it may be necessary to place the jacket 10 inside a snug fitting container made for that purpose to block that flow DG C:\WINORDDELILAHCOMPLETE\PIPELINE.DOC -9of foam, although that will depend on the density and viscosity of the foam. It might be that while the foam may tend to flow out of the openings, any overflow may only be minor, such that it is easily removed in the final stages of manufacture of the pig.

A final form of the jacket 10 which is not shown in Figure 2, includes a cap extending across the rear end 13. The cap may be applied during the moulding process of the jacket 10 or may be applied manually following the moulding process. The cap may also be of polyurethane plastic, which integrally joins to the body 11 and seals the rear end 13. Equally, if the flat end 14 of the front end 12 is not fully sealed during the moulding process, the uncovered portion may be sealed with a cap manually following the moulding process. Such caps may be provided by manually painting polyurethane over the portions to be covered.

The foam filled jacket with end caps completes the pig of the invention.

The method used to manufacture the pig is such as to avoid many of the Smanual operations used previously and avoids the need for ribbon painting machines.

In use, the pig is matched to a pipeline or conduit so that the inside diameter of the pipe is substantially the same as the outside diameter of the body 11. To clean the pipe, the pig is pulled or pushed through a pipeline or conduit in the manner shown in Figure 3, in the direction D. The pig may be lO pulled through the pipe by a rope or cable. Alternatively the medium normally carried by the pipe can be used to push the pig therethrough. The medium might be a gas or liquid for example.

As shown, the pipeline 18 has an undesirable sediment 19 which is adhered to the internal surface 20 of the pipeline 18. The sediment may be grime or sludge or the like which has built up to an unacceptable level over time.

As the pig is pushed or pulled through the pipeline, the front end 12 thereof engages and dislodges the sediment 19 and that sediment 19 is pushed forward in the same direction D as the pig, as indicated by the arrows DG C:W1NWORD\DELILAH\COMPLETE\PIPELINE.DOC A. The openings 15 (not illustrated in Figure 3) promote rotation of the pig in the direction R, which assists with dislodgement of the sediment 19. Some small pieces of sediment may not be pushed forward in the direction A, and may move or be trapped between the internal surface 20 of the pipeline 18 and the outside surface 17 of the jacket 10. That sediment may be trapped in the foam 16 exposed in the openings 15 and be carried forward with the pig The flush nature of the foam 16 with the outside surface 17 of the jacket promotes trapping of that type of sediment. Ultimately, all sediment that is dislodged is removed with the pig through an opening in the pipeline.

Those skilled in the art will appreciate that there may be many variations and modifications of the configuration and method described herein which are within the scope of the present invention.

0* o i* DG C:\WINWORD\DELILAH\COMPLETE\PIPELINE.DOC

Claims (38)

1. A pig for removing sediment deposits from the internal surface of a pipe, the pig including an outer jacket moulded from plastic material, the jacket having a body of cylindrical form and defining an internal core cavity in the jacket body, and the jacket body having an outer surface for slidable engagement with the internal surface of the pipe in order to dislodge sediment deposits therefrom; and, stiffening means in the core cavity for supporting the jacket against inward collapse during engagement with the internal surface of the pipe.

2. A pig according to claim 1, wherein the jacket body has a plurality of openings in the outer surface thereof, the openings, in use, of the pig, facilitating removal of deposits trapped between the outer surface and the ""internal surface of the pipe.

3. A pig according to claim 2, wherein the openings are arranged in a spiral 15 pattern about a longitudinal axis of the jacket body to promote rotation of the jacket about the longitudinal axis during passage of the pig through a pipe.

4. A pig according to claim 2 or 3, wherein the openings, at least in part, have a generally triangular shape. 2

5. A pig according to any preceding claim, wherein the stiffening means includes ribs extending circumferentially about an internal surface of the core cavity of the jacket.

6. A pig according to any one of claims 1 to 4, wherein the stiffening means includes a frame or sleeve within the internal core cavity

7. A pig according to any one of claims 1 to 4, wherein the stiffening means includes a foam core within the internal core cavity.

8. A pig according to claim 7, wherein the foam core is cylindrical shaped.

9. A pig according to claim 7 or 8 when dependent on any one of claims 2 to 4, wherein the foam core extends into the openings.

A pig according to claim 9, wherein the foam core extends into the openings and flush with the outer surface of the jacket body.

11. A pig according to any preceding claim, wherein the jacket includes a Rnose extending from an end of the jacket body. 12

12. A pig according to claim 11, wherein a respective nose extends from each end of the jacket body.

13. A pig according to claim 11 or 12, wherein the internal core cavity extends into the or each nose.

14. A pig according to claim 13, wherein the stiffening means is in the or each nose.

A pig according to any one of claims 11 to 14, wherein the or each nose is moulded integrally with the jacket body.

16. A pig according to any one of claims 11 to 15, wherein the or each nose has a frustoconical form, coaxial with the jacket body.

17. A pig according to any one of claims 11 to 15, wherein the or each nose has a convex or concave form.

18. A pig according to any preceding claim, wherein the jacket has opposite ;ends, and at least one of the ends is sealed. 15

19. A pig according to claim 18, wherein at least one of the ends is sealed by a cap composed of the same plastic material as the jacket.

A pig according to claim 19, wherein the or each cap is moulded integrally with the jacket.

21. A pig according to any preceding claim, wherein the plastic material from 20 which the jacket is moulded includes additives which promote removal of sediment deposits.

22. A pig according to claim 21, wherein the additives include silicon carbide bits which are exposed on the outer surface of the jacket body.

23. A pig according to claim 21, wherein the additives include wire brush threads which are exposed on the outer surface of the jacket body.

24. A method of forming a pig for removing sediment deposits from the internal surface of a pipe, the method including the steps of: moulding an outer jacket from plastic material, the jacket having a body of cylindrical form and defining an internal core cavity in the jacket body, and the jacket body having an outer surface for slidable engagement with the internal surface of the pipe; and, providing stiffening means for supporting the jacket against inward 13 collapse during engagement with the internal surface of the pipe, the stiffening means being located in the core cavity of the formed jacket.

A method according to claim 24, wherein the moulding step includes placing a charge of plastic material within a die, inserting a plunger into the die to cause the plastic material charge to flow about the plunger to form the outer jacket with the plunger providing the core cavity, allowing the jacket to cure within the die, and removing the formed jacket from the die.

26. A method according to claim 25, wherein the moulding step includes removing the plunger from the formed jacket so as to vacate the core cavity.

27. A method according to claim 26, wherein the step of providing the stiffening means includes placing liquid foam into the vacated core cavity of the formed jacket, and allowing the foam to set to form a stiffening core.

28. A method according to claim 27, wherein the step of providing the stiffening means occurs after the formed jacket is removed from the die, and includes inserting the jacket into a sleeve prior to placing the liquid foam into the internal core cavity.

29. A method according to claim 27, wherein the step of providing the stiffening means occurs after the jacket has cured in the die but before removal of the formed jacket from the die. 20

30. A method according to claim 25, wherein the plunger includes a foam *insert, and the step of providing the stiffening means includes placing the insert into the die during insertion of the plunger into the die in the moulding step, whereby the jacket is formed about the insert and the insert forms a stiffening core in the core cavity of the formed jacket.

31. A method according to claim 30, wherein the foam insert includes raised portions about which the plastic material is moulded which form openings in the jacket body.

32. A method according to claim 24, wherein the step of providing the stiffening means includes placing a stiffening core in a die for moulding the outer jacket, and the moulding step includes supplying a charge of plastic material to the die and causing the plastic material to charge to flow about the 14 stiffening core to form the outer jacket, allowing the jacket to cure within the die, and removing the formed jacket and stiffening core from the die.

33. A method according to any one of claims 24 to 32, wherein the plastic material is polyurethane.

34. A method according to any one of claims 24 or 33, wherein the outer jacket is moulded with a plurality of openings in the outer surface of the jacket body for facilitating removal of deposits trapped between the outer surface and an internal surface of the pipe.

A method according to claim 25 or 32, or any claim appended thereto, wherein the moulding step includes heating the die to heat the charge of plastic material for facilitating flow in the die.

36. A pig when formed by a method according to any one of claims 24 to

37. A pig substantially as herein described with reference to what is shown S.in the accompanying drawings. 15

38. A method of forming a pig substantially as herein described with reference to what is shown in the accompanying drawings. o: DATED: 9 October 2001 PHILLIPS ORMONDE FITZPATRICK 20 Attorneys for: LETTELA PTY. LTD.