GB2342971A

GB2342971A - A pipeline pig

Info

Publication number: GB2342971A
Application number: GB9924547A
Authority: GB
Inventors: Ding Zhao Luo
Original assignee: PIPELINE ENGINEERING Ltd; Hyperlast Ltd
Current assignee: PIPELINE ENGINEERING Ltd; Hyperlast Ltd
Priority date: 1998-10-22
Filing date: 1999-10-19
Publication date: 2000-04-26
Anticipated expiration: 2019-10-19
Also published as: GB9924547D0; GB9823118D0; GB2342971B

Abstract

A pipeline pig 10 is formed from a deformable material and has circumferential grooves 16 over at least part of its longitudinal length. Preferably, the pipeline pig 10 comprises a body of microcellular polyurethane material such as an MDI and polyether or polyester polyol based polyurethane. The body preferably has a nose portion 12, a central portion 13 and a tail portion 14. The central portion is formed with the circumferential grooves 16 defining ribs therebetween, and peripheral sealing faces 17, 19, 20 and 18 are provided on the nose portion, ribs and tail portion respectively.

Description

A PIPELINE PIG This invention relates to a pipeline pig.

Pipeline pigs are used in pipelines for cleaning or other purposes.

Conventionally pigs are sized so as to be a close sliding fit in the pipeline.

However, internal diameters can vary along the run of pipeline, in some cases by as much as 40-45% over very small distances. It is therefore necessary for a pig to be able to move along such pipelines without losing their sealing to the pipe wall in order that they can perform their function properly.

Conventional pigs for this purpose are usually formed by front and rear cups of a resilient rubber material joined by a central body of reduced diameter to the cups. The circumference of the cups bear against the internal surface of the pipeline wall and being resilient are capable of deformation to accommodate different internal pipeline diameters without loss of sealing. In some modified pigs, resiliently biassed brushes are provided in the central body which in, in use, bear against the pipe wall to provide the sealing function and also carry out the cleaning. Once again, due to resilient mounting of the brushes, such an arrangement can also accommodate different internal pipeline diameters.

However, a problem arises with these known pigs insofar as they are unable to pass through pipeline diameters which vary by more than approximately 25%. This arises as a consequence both of the material they are made from and the shape and configuration of the pigs. Such pigs are therefore relatively useless where larger variations in pipe diameter are present since they result in a loss of sealing between the pig and the pipe wall where the transition is too great.

It is an object of the present invention to provide an improved pig which has a greater capability for accommodation of variation in internal

pipeline without

sealing between the pig and the pipe wall.

In accordance with the present invention therefore there is provided a pipeline pig formed from a deformable polymeric material, said pig including shaped circumferential grooves therein along at least a part of its longitudinal length.

With this arrangement it is possible to provide a pipeline pig which can pass through pipe internal diameter variations of up to 45% without significant effect on the sealing of the pig to the pipe wall.

Preferably the pig is formed from a polyurethane material. Preferably the polymeric material has a density of between 0.3 and 0.75 g/cm3. Most preferably the polyurethane material is in microcellular form. The material is preferably a microcellular polyurethane material based on MDI and polyether or polyester polyol, for example Dynathane 1000. The preferred material characteristics are derived from a combination of chemical structure, density, and precise cell structure control.

Preferably the shaped circumferential grooves are provided over a central portion of the pig.

Preferably the pig has a nose which is tapered inwardly such that the nose has a front Snd face of reduced diameter relative to the remainder of the pig.

Preferably the grooves are shaped so as to be generally saw toothed in configuration.

The invention will now be described further by way of example only and with reference to the accompanying drawing, wherein: Figure 1 shows a diagrammatic axial sectional view, not to scale, of one embodiment of pig in accordance with the present invention; and Figure 2 illustrates the use of the pig in a pipe with sections of different diameters.

Referring now to the figure, there is shown a deformable pipeline pig 10 in accordance with the invention formed from a microcellular polyurethane material. The pig is a solid of rotation about axis X of Figure 1.

The pig 10 comprises a shaped nose 11, tapered front portion 12, a central part 13 and rear portion or tail 14. The central portion 13 has circumferential grooves 16 therein which define ribs therebetween and in cross section, are generally sinusoidal. Whilst generally sinusoidal grooves 16 are described it is to be understood that the invention contemplates any suitable shape or grooves which can provide the required deformability.

The grooves are in fact assymmetric in cross section with steeper faces towards the nose, and less steep faces towards the tail. The shape of the grooves 16, whilst rendering the necessary deformability in combination with the choice of material, are dictated by the particular requirements of the pipeline through which the pig 10 is to pass. In the preferred embodiment, the pig is made from a microcellular polyurethane material based on MDI and a polyether or polyester polyol, and is preferably DYNATHANE 1000.

In use (see Figure 2) the pig 10 is inserted into the bore of a pipeline 30 to be cleaned. The pig 10 is pushed through the pipeline by pressurised liquid or gas such as water (indicated by arrows A), from one end of the pipeline to the other. With the pig of the invention, the outer diameter of the pig can vary by deformation to a much greater extent than any of the prior art pigs. This is as a consequence of the presence of the grooves 16.

It has been shown in tests that when the pig 10 of the invention passes down the pipeline it can pass from a pipe of internal diameter of 98mm to o a pipe section Xof 58mm and back into a pipe section 32 of diameter of 98mm as shown diagrammatically in Figure 2 without significant reduction in the sealing of the outer surface of the pig 10 to the internal pipe wall.

This means that the pig can pass through a pipe internal diameter variation of 45% compare to the prior art pigs which at best can pass through a 25% variation in internal diameter. The flexibility of the pig arises from the chemical structure, density, and precise cell structure control as well as from its geometry.

The geometry of the pig provides major sealing lands such as 17 at the nose of the pig 11 and 18 at the tail 14, and minor lands 19,20 on the crests of the ribs separating the grooves 16. This provides for multiple sealing between the pig and the pipe walls, so that failure of one or two seals will not lead to complete failure of sealing by the pig.

It can therefore be seen that the pig 10 of the present invention offers significant advantages over existing pigs insofar as it is considerably more versatile in its uses.

It is of course to be understood that the invention is not intended to be restricted to the details of the above embodiment which are described by way of example only.

Claims

CLAIMS 1. A pipeline pig formed from a deformable polymeric material, the pig having shaped circumferential grooves over at least part of its longitudinal length.
2. A pipeline pig according to claim 1, comprising a nose portion, a central portion and a tail portion, the shaped circumferential grooves being provided over at least part of said central portion.
3. A pipeline pig according to claim 2, wherein said nose portion tapers to a reduced diameter extreme front end.
4. A pipeline pig according to claim 1,2 or 3 wherein the grooves present a saw-toothed profile when viewed in cross-section.
5. A pipeline pig according to any preceding claim wherein said deformable polymeric material comprises a microcellular polyurethane material based on MD ! and a polyether or polyester polyol.
6. A pipeline pig according to any preceding claim wherein the circumferential grooves define ribs therebetween which provide sealing lands for engagement with the interior surface of a pipe.
7. A pipeline pig according to claim 6 wherein further major sealing lands are provided by the tail and nose portions of the pig.
8. A pipeline pig according to claim 4 wherein the grooves are asymmetric in cross-section, with a steeper face to the nose side of each respective groove, and a less steep face to the tail side of each respective groove.
9. A pipeline pig according to any preceding claim which is propelled through a pipeline by fluid pressure acting on the tail portion of the pig.
10. A pipeline pig substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.