AU714700B2

AU714700B2 - Protection of pipelines

Info

Publication number: AU714700B2
Application number: AU76452/96A
Authority: AU
Inventors: Samuel P Costin
Original assignee: Vinidex Tubemakers Pty Ltd
Current assignee: Vinidex Pty Ltd
Priority date: 1996-01-05
Filing date: 1996-12-24
Publication date: 2000-01-06
Anticipated expiration: 2016-12-24
Also published as: AU7645296A

Description

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P/00/0 11 28/5/9 1 Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLEESPECIFICATION

STANDARD

PATENT

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Name of Applicant: Actual Inventor(s): VINIDEX TUBEMAKERS PTY LTD Samuel P Costin Address for service is: WRAY ASSOCIATES 239 Adelaide Terrace Perth, WA 6000 Attorney code: WR Invention Title: "Protection of Pipelines" Details of Associated Provisional Application No(s): PN7434 The following statement is a fultidescripion-of-this invention, including the best method of Peirfor ming it known to-me:- I 1 -2- TITLE: PROTECTION OFPIPENES This invention relates to pipelines and fluid conduits and in particular those which may be subjected to radiant heat in use.

Pipelines which can be formed of metal or a suitable plastics material are used for the transportation of water in agriculture, in mining, and industrial applications. Such pipelines are often laid above the ground and as a result are the subject of heating through solar radiation and conductive radiation as a result of ambient conditions. In addition, such installations are often exposed to conditions where in the summer the air temperature can exceed 50 0 C in the shade and below OOC during the night in winter. The average temperature of e water which is delivered into the pipes is approximately 20°C however as a result of the heat absorbed by the pipe the temperature can increase significantly which in some cases can be undesirable.

The strength of most plastics material is reduced when subjected to increased 15 temperature and therefore in the case of plastic pipes it is necessary, when designing a pipeline system, to accommodate for the effect of temperature variations upon the structure of the pipes which may occur in the pipeline. In addition the elasticity of the plastics material which is subjected to repetitive expansion, contraction, heating and cooling, can in some instances reduce with 20 age.

Furthermore the variation in temperature of the pipeline whether plastics or metal can result in considerable longitudinal expansion and contraction of the pipeline. For example pipes formed of polyethylene have a thermal expansion coefficient of 18 x 10 5 mm/mmP/C. The resultant longitudinal expansion and contraction of the pipe as a result of fluctuations in temperature can result in mechanical damage to the pipeline.

Australian patent application 636672 is directed to an apparatus and method for protection of a pipeline from excessive temperature variations and the contents of that specification are included herein by reference.

It is an object of this invention to provide a means for reducing the temperature variation in pipelines which are exposed to radiant heat sources such as solar radiation.

Accordingly the invention resides in an above ground fluid conduit comprising a pipe and a flexible sleeve wherein the pipe is formed of a plastics material and wherein the flexible sleeve is formed from a strip formed by a membrane composed of a plastics material, said strip being of a width dimensioned to be able to be laid over a length of above ground pipe and loosely received around the pipe, said sleeve being loosely received over the pipe and held in position around the pipe by a fixing means at spaced intervals to fix the sleeve to the pipe at said spaced intervals, said sleeve being coloured to be a substantial 15 reflector of radiant heat, wherein the plastics materials of which the pipe and sleeve are composed have the property of being electrical insulators whereby an electrostatic charge is capable of being established between the sleeve and the 0**0 pipe to generate repulsive forces therebetween.

According to an alternative preferred feature of the invention the pipe is formed 20 of a metallic material and the strip is loosely applied over the pipe.Accordingly the invention resides in a sleeve for an above ground pipe wherein the pipe is formed of a plastics material said sleeve being formed from a strip of flexible membrane, said membrane being composed of a plastics material, said strip being of a width dimensioned to be able to be laid over a length of above ground 25 pipe and loosely received around the pipe, said sleeve being coloured to be a substantial reflector of radiant heat and wherein the plastics materials of which the pipe and sleeve are composed have the property of being an electrical insulator whereby an electrostatic charge is capable of being established R between the sleeve and the pipe to generate repulsive forces therebetween.

Accordingly the invention also resides in a method of protecting an above ground pipe wherein the pipe is formed of a plastics material said method comprising applying over the pipe a flexible sleeve which is formed from a strip of a flexible membrane and which is loosely received over the pipe, said flexible sleeve being formed of a membrane composed of a plastics material, said sleeve being coloured to be a substantial reflector of heat wherein the plastics materials of which the pipe and sleeve are formed are electrical insulators whereby an electrostatic charge is capable of being established between the sleeve and the pipe to generate repulsive forces therebetween said method further comprising laying the strip over a length of pipe, loosely wrapping the strip around the pipe and fixing the strip to the pipe at spaced intervals along its length.

According to a further preferred feature of the invention the sleeve only encompasses a part of the circumference of the pipe to provide openings between the lower edges of the strip and the lower portion of the pipe.

According to an alternative preferred feature to the previous feature of the invention the sleeve fully encompasses the pipe.

oo0% According to a further preferred feature of the invention the sleeve is provided with a plurality of axially spaced apertures along the upper surface of the sleeve.

ooo• o° S" I r According to a further preferred feature of the invention the sleeve is fixed to the pipe by a plurality of straps which are wrapped around the sleeve when applied over the pipe, at spaced intervals along the length of the pipe.

According to an alternative further preferred feature to the previous feature of the invention the sleeve is fixed to the pipe by a plurality of resilient clips which are applied over the sleeve when applied over the pipe, at spaced intervals along the length of the pipe. According one embodiment the clips only partially surround the pipe.

According to an alternative further preferred feature to the previous two features the sleeve is bonded to the pipe at spaced intervals along the length of the pipe.

The invention will be more fully understood in the light of the following descriptions of several specific embodiments.

The description is made with reference to the accompanying drawings of which:- Figure 1 is a schematic isometric view of the first embodiment; and 15 Figure 2 is a schematic cross-section along line 2-2 of Figure 1.

The first embodiment is directed to the protection of polyethylene pipe which may be formed of Medium Density Polyethylene (MDPE) or High Density Polyethylene (HDPE).

As stated above, the design characteristics of pipelines incorporating polyethylene pipes must take into consideration the temperature variations that can occur in the pipeline as a result of incident solar radiation and ambient temperature conditions. Such pipelines are often laid over the surface of the ground and are subjected to the ambient solar and temperature conditions. In addition such pipelines tend to increase in temperature at a faster rate than that .Ib -6of the surrounding ground principally because the pipe is generally black in colour.

As a result of the increase in temperature the strength of the pipeline can be significantly reduced. Generally the temperature limit for such pipe is below approximately 60 0

C.

Furthermore the repetitive expansion and contraction of the pipe during its life which results from the cyclic heating and cooling of the pipe places design constraints upon the pipe due to the mechanical movement of the pipe which is generated by such expansion and contraction. In addition as a result of the repetitive expansion and contraction of the pipe the modulus of elasticity of the :pipe can degenerate with age. Therefore in the case of a pipeline which is S.formed of polyethylene, the pipes must be designed to have a wall thickness far in excess of that which is normally required in the case of pipes when operating at normal temperatures to accommodate for the anticipated reduction in its strength, resilience and elasticity when in use in an open environment.

The embodiments each comprises sleeving the plastic pipe 11 with a sleeve 12 formed of a white plastics film. The film is also formed of polyethylene and is formulated to offer high resistance to the transmission of solar energy, to be Sreflective of solar radiation to reduce the effect of ultra violet radiation. The 20 thickness of the film is such as to offer the best compromise between the resistance to tearing, product life, opacity, cost and the ease of installation. The width of the strip is a little less than the circumference of the pipe. The sleeve 12 is supplied in the form of a flat continuous strip which is folded along its central longitudinal axis and which isformed with a plurality of holes 14 formed through the folded strip at spaced intervals along its length, adjacent the fold.

The drawings provide a schematic illustration of the first embodiment which comprises a pipe 11 having a sleeve 12 over the pipe. In application of the sleeve to the pipe the strip is unfolded and laid over the pipe with the fold I I I, -7uppermost. If desired the steeve can be applied to a pipeline on site from the strip of material which is laid along the pipe and wrapped around the pipe to create a sleeve which partially encloses the pipe. Because of the width of the strip the sleeve does not fully encompass the pipe and as a result openings are created along the junction of the lower edges of the strip with the lower portion of the side wall of the pipe. The sleeve is then held in position on the pipe by straps 13 which are applied over-the sleeve at spaced intervals along the length of the pipe. The straps are applied around the pipe and the ends are interengaged and whereby the straps can be tightened to retain the straps in position in order that they can be readily removed when necessary.

The holes 14 which are formed in the sleeve at spaced intervals along its upper surface and the openings provided-between-the lower edges of the strip and the pipe jointly permit the circulation of air into and out of the space between the sleeve and the pipe.

According to a second embodiment (not shown) the strip is dimensioned to fully surround the pipe and is held in position by the straps referred to above at spaced intervals along the pipe to create a protective sleeve which completely surrounds the pipe.

S• In the case of each of the above embodiments, the similar nature of the plastics material of which the pipe and sleeve areformed results in the establishment of to. an electrostatic charge between the opposed faces of the sleeve and the pipe which causes a repulsion force between such faces and as a result the sleeve is forced out of engagement with the surface of the pipe between the fixings provided by the straps. Such repulsion serves to effect separation between the pipe and the sleeve except in the region where the pipe is in engagement with the ground and where the weight of the pipe overcomes such repulsive forces.

It has been found in practice that sufficient electrostatic charge can been established between the sleeve and the pipe during the application of the sleeve onto the pipe to create sufficient repulsive forces to maintain the sleeve out of I or I -8engagement with the pipe. Such electrostatic forces are maintained due to the electrical insulating properties of the plastics material of which the sleeve and pipe are composed. Furthermore additional electrostatic charges are created as a result of relative movements between-the pipe and the sleeve which can be as a result of differential expansion between the pipe and the sleeve and also of environmental conditions such as wind.

As a result of the repulsion of the sleeve away from the surface of the pipe a blanket of air is created between the pipe and the sleeve, This blanket of air serves to prevent the conduction of heat between the sleeve and the pipe. In addition the white colouring of the sleeve serves to reflect a significant proportion of the radiant heat and light which is incident on the sleeve thus reducing heat that is available-for conduction between the sleeve and the pipe.

Furthermore during conditions of incident solar radiation, the solar radiation which is absorbed by the sleeve causes-heating of the air in the blanket between the sleeve and pipe whereby the hotter less dense air is located at the upper portion of the space between the sleeve and the pipe. This heated air can escape from the apertures 14 in the sleeve to induce the evolution of SC*convectional currents in the space and the introduction of cooler air into the space between the sleeve and the-pipe as a result of such convection currents.

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As a result of the reduction in heat transfer from the sleeve to the pipe and reduction in the amount of radiation absorbed by pipe by the presence of the sleeve the increase in temperature of the pipe and its contents is significantly reduced.

According to a third embodiment the straps of the previous embodiments are provided at their end with interengagable members which can be interengaged on application of a strap around the pipe and whereby the strap can then be then tightened.

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-9- According to a fourth embodiment the straps of the previous embodiments are replaced by resilient clips whichpartially encompass the pipe on application and which retain the strip in position as a result of their resilience.

According to a fifth embodiment the strip is bonded to the pipe at spaced intervals along the length of the pipe by a suitable adhesive or by welding instead of the use of straps or clips.

According to a sixth embodiment the straps of the previous embodiments are applied around the pipe and can be formed of a material whereby the ends can be twisted together to retain the straps in position and in order that they can be readily removed when necessary.

The advantages provided by the each of the above embodiments over conventionally exposed polyethylene pipes include the capacity to use a lower pipe classification for any particular tasks; extended pipe life, since the lower the operatingtemperature of the pipe 15 the longer will be the life of the pipe; increased reliability since the pipe will have an improved capacity to cope with pressure fluctuations; reduction in thermal expansion and contraction and thus mechanical movement of the pipe withrespectto its supporting surface; improved resistance to buckling since the Youngs Modulus of the material is significantly increased if-the pipe temperature is reduced; the increase in the Youngs modulus will result in a reduction in the number of pipe supports required in overhead process applications; reduced heating of water passing through the pipeline which is critical for potable water pipelines; a reduction in the amount of plastics material required for the manufacture of pipes due to the possibility of being able to use a thinner pipe; an increase in the inner diameter of the pipe with respect to the outer diameter which can result in a reduced pump energy loss due to friction; a reduction in butt welding due to the use of a thinner pipe wall which can accelerate the installation time of a pipeline; reduction in the delivery time and delivery costs of the pipeline due to the reduced weight of the pipeline; -reduced mechanical movement of the pipeline as a result of an expansion and contraction.

According to a sixth embodiment the pipe is formed of a metallic material and the strip is fixed to the pipe by a set of straps or clips in the same manner as has been described above. In the case of the sixth embodiment the creation of convectional air flow through the space between the sleeve and the pipe serves to maintain the separation therebetween.

It should be appreciated that the scope of the present invention 20 need not be limited to the particular scope of the embodiment described above.

Claims

1. An above ground fluid conduit comprising a pipe and a flexible sleeve wherein the pipe is formed of a plastics material and wherein the flexible sleeve is formed from a strip formed by a membrane composed of a plastics material, said strip being of a width dimensioned to be able to be laid over a length of above ground pipe and loosely received around the pipe, said sleeve being loosely received over the pipe and held in position around the pipe by a fixing means at spaced intervals to fix the sleeve to the pipe at said spaced intervals, said sleeve being coloured to be a substantial reflector of radiant heat, wherein the plastics materials of which the pipe and sleeve are composed have the property of being electrical insulators whereby an electrostatic charge is capable of being established between the sleeve and the pipe to generate repulsive forces therebetween.

2. An above ground fluid conduit as claimed at any one of the preceding claims the pipe is formed of a metallic material and the strip is loosely applied over the pipe.

3. An above ground fluid conduit as claimed at any one of the preceding claims the sleeve only encompasses a part of the circumference of the pipe to provide openings between the lower edges of the strip and the lower portion of the pipe.

4. An above ground fluid conduit as claimed at any one of claims 1 to 3 ~wherein the sleeve fully encompasses the pipe.

5. An above ground fluid conduit as claimed at any one of the preceding claims wherein the sleeve is provided with a plurality of axially spaced apertures along the upper surface of the sleeve.

6. An above ground fluid conduit as claimed at any one of the preceding RAclaims wherein the sleeve is fixed to the pipe by a plurality of straps which -12- are wrapped around the sleeve when applied over the pipe, at spaced intervals along the length of the pipe.

7. An above ground fluid conduit as claimed at any one of claims 1 to wherein the sleeve is fixed to the pipe by a plurality of resilient clips which are applied over the sleeve when applied over the pipe, at spaced intervals along the length of the pipe.

8. An above ground fluid conduit as claimed at of claim 7 wherein the clips only partially surround the pipe.

9. An above ground fluid conduit as claimed at any one of claims 1 to wherein the sleeve is bonded to the pipe at spaced intervals along the length of the pipe.

A sleeve for an above ground pipe wherein the pipe is formed of a plastics material said sleeve being formed from a strip of flexible membrane, said :membrane being composed of a plastics material, said strip being of a 15 width dimensioned to be able to be laid over a length of above ground pipe o °°and loosely received around the pipe, said sleeve being coloured to be a substantial reflector of radiant heat and wherein the plastics materials of which the pipe and sleeve are composed have the property of being an electrical insulator whereby an electrostatic charge is capable of being @14h 20 established between the sleeve and the pipe to generate repulsive forces therebetween.

11. A sleeve for an above ground fluid conduit as claimed at claim 10 wherein the pipe is formed of a metallic material and the strip is intended to be ft. ft loosely applied over the pipe.

12. A sleeve for an above ground fluid conduit as claimed at any one of claims 10 and 11 wherein the sleeve is dimensioned to only encompasses a part -13- of the circumference of the pipe to provide openings between the lower edges of the strip and the lower portion of the pipe.

13. A sleeve for an above ground fluid conduit as claimed at any one of claims and 11 wherein the sleeve is dimensioned to fully encompass the pipe.

14. A sleeve for an above ground fluid conduit as claimed at any one of claims to 13 wherein the sleeve is provided with a plurality of axially spaced apertures along its central axis.

A sleeve for an above ground fluid conduit as claimed at any one of claims to 14 wherein the sleeve is intended to be fixed to the pipe by a plurality of straps which are wrapped around the sleeve when applied over the pipe, at spaced intervals along the length of the pipe.

16. A sleeve for an above ground fluid conduit as claimed at any one of claims to 14 wherein the sleeve is intended to be fixed to the pipe by a plurality of resilient clips which are applied over the sleeve when applied over the pipe, at spaced intervals along the length of the pipe. *o

*17. A sleeve for an above ground fluid conduit as claimed at of claim 16 wherein the clips only partially surround the pipe.

18. A sleeve for an above ground fluid conduit as claimed at any one of claims 2010 to 14 wherein the sleeve is intended to be bonded to the pipe at spaced intervals along the length of the pipe.

19. A method of protecting an above ground pipe wherein the pipe is formed of a plastics material said method comprising applying over the pipe a flexible i ;sleeve which is formed from a strip of a flexible membrane and which is loosely received over the pipe, said flexible sleeve being formed of a membrane composed of a plastics material, said sleeve being coloured to be a substantial reflector of heat wherein the plastics materials of which the -14- pipe and sleeve are formed are electrical insulators whereby an electrostatic charge is capable of being established between the sleeve and the pipe to generate repulsive forces therebetween said method further comprising laying the strip over a length of pipe, loosely wrapping the strip around the pipe and fixing the strip to the pipe at spaced intervals along its length.

A method of protecting an above ground pipe as claimed at claim 19 wherein the pipe is formed of a metallic material and the strip is intended to be loosely applied over the pipe.

21. A method of protecting an above ground fluid conduit as claim 19 or wherein the sleeve only encompasses a part of the circumference of the pipe to provide openings between the lower edges of the strip and the lower portion of the pipe.

22. A method of protecting an above ground fluid conduit as claimed at any one of claims 19 or 20 wherein the sleeve fully encompasses the pipe.

23. A method of protecting an above ground fluid conduit as claimed at any one of claims 19 to 22 wherein the sleeve is provided with a plurality of axially spaced apertures along the upper surface of the sleeve.

24. A method of protecting an above ground fluid conduit as claimed at any one of claims 19 to 23 wherein the sleeve is fixed to the pipe by a plurality straps which are wrapped around the sleeve when applied over the pipe, at spaced intervals along the length of the pipe.

A method of protecting an above ground fluid conduit as claimed at any one of claims 19 to 23 wherein the sleeve is fixed to the pipe by a plurality of resilient clips which are applied over the sleeve when applied over the pipe, at spaced intervals along the length of the pipe.

26. A method of protecting an above ground fluid conduit as claimed at of claim 25 wherein the clips only partially surround the pipe.

27. A method of protecting an above ground fluid conduit as claimed at any one of claims 19 to 23 wherein the sleeve is bonded to the pipe at spaced intervals along the length of the pipe.

28. An above ground fluid conduit having a sleeve applied thereto substantially as herein described.

29. A sleeve for an above ground pipe substantially as herein described. A method of protecting an above ground fluid conduit substantially as herein described. Dated this second day of November 1999. Vinidex Tubemakers Pty Ltd Applicant Wray Associates Perth, Western Australia 1 Patent Attorneys for the Applicant a a a a. a. *e