WO2010027271A2

WO2010027271A2 - Clamp for preventing deformation in a pipe wall

Info

Publication number: WO2010027271A2
Application number: PCT/NO2009/000311
Authority: WO
Inventors: Kenneth Langerud; Vigmund BJØRSVIK
Original assignee: Tdw Offshore Services As
Priority date: 2008-09-08
Filing date: 2009-09-07
Publication date: 2010-03-11
Also published as: NO20083826L; WO2010027271A3

Abstract

A clamp (10) for assembly on the outside of a pipe (4), having a first end section (11a) and a second end section (11b) interconnected by a plurality of arcuated clamp sections (12) connected in an end-to-end relationship so that the clamp (10) is flexible in its own plane but substantially inflexible transversely of this plane, said end sections (11a,b) comprising clamp fastening means (15, 17) and clamp tensioning means (16), for fastening the clamp (10) on the pipe. Each clamp section (12) may comprise a plurality of clamp elements (7) arranged in a side-by-side relationship, substantially transversely of said plane.

Description

Clamp for preventing deformation in a pipe wall Field of the invention

This invention relates to a clamp for assembly on the outside of a pipe. More specifically, it relates to a clamp for selective and controllable reinforcement of a pipe wall, particularly where the pipe wall is subjected to loads generated by a plug set inside the pipe.

Background of the invention

It is known in the art to use internal plugs for isolating sections of pipe in order to e.g. perform maintenance or repair. One example of such internal plug is disclosed by EP 1 552 211, and typically comprises a number of slips arranged around the plug periphery and a radial gasket arranged peripherally between two compression elements (such as a ring and an end plate). When the plug is to be set at a desired location within the pipe, the slips are moved into engagement with the pipe inner wall and the gasket is displaced radially, into a sealing relationship with the pipe inner wall, by moving the two compression elements towards each other, for example by means of a hydraulic cylinder.

When the plug is set in this manner, it may exert a considerable radial pressure on the pipe wall in order to seal off the pipe as intended. There are instances where this sealing pressure may overstress the pipe wall and cause damage to the pipe, thus creating a potentially hazardous situation, for example if the pipe is inadequately dimensioned, if the pipe wall has weak regions (due to e.g. internal or external damages or corrosion), or if the operator is generally uncertain of the condition of the pipe. This is particularly a problem with thin-walled pipes.

It is therefore a need to ensure that, on the one hand, setting a plug within a pipeline will not damage the pipe wall and, on the other hand, remaining confident that the plug may be set with a sealing pressure sufficient for sealing or blocking off the pipeline.

Welded reinforcement rings and temporarily installed bolt-on clamps are known in the art to be used for preventing overstressing of pipe walls subjected to internal plugs. The use of welded reinforcement rings require an elaborate installation procedure, including welding on "live" pipelines, and an equally complicated removal procedure. Should the operator decide to let the reinforcement ring remain on the pipe after the internal plug has been removed, a thorough corrosion protection of the clamp will be necessary. The known bolt-on clamps are heavy and bulky and often need additional support during when installed. Moreover, the known pipe clamps are normally designed specifically for one dimension of a pipe; also these clamps normally are designed for different tasks than the problem of enhancing the strength of a pipe wall. Examples of these other kind of clamps are for instance described in GB 2355293, US 466138 and CA 1240277. However, internal plugs for sealing off pipelines may be designed to be used for a range of internal diameters of pipelines, and by this set in one pipe, removed and thereafter used in another pipeline which may have a different internal diameter. The outer diameter of pipes may also vary for pipes with a similar internal diameter. For pipes with weaknesses in the wall or pipes which possibly may rupture during the setting of a plug, there is therefore a need for a device for strengthening a pipe wall, which device may also be used for several external diameters of a pipe.

Summary of the invention

The invention is set forth and characterized in the independent claim 1 , while the dependent claims 2 - 15 describe other characteristics of the invention

One purpose of the invention is to provide a method and a device which may be used to prevent the pipeline wall of pipelines to deform in an outwards radial direction, when setting an internal plug in the pipeline, by counteracting forces in the pipeline wall caused by a plug set inside the pipeline. Another purpose of the invention is to provide a method and a device specially designed to support the pipe in the event of setting a plug within the pipeline, which device may be used for different external diameters of a pipeline. It is also an aim to provide a device which is simple in design, which is easy to use and operate. There is also an aim to provide a device which may prevent the pipe to deform outwards for a length of the pipe.

The invention comprises a clamp for selective assembly and disassembly on the outside of a pipe, for preventing the pipe wall from deforming in an outwards radial direction, characterized by a first end section and a second end section, interconnected by a plurality of arcuated clamp sections connected in an end-to-end relationship so that the clamp is flexible in its own plane but substantially inflexible transversely of this plane; and said end sections comprising clamp fastening means and clamp tensioning means, for fastening the clamp with a predetermined tension onto the pipe whereby retraining loads are distributed along the perimeter in an even and controlled manner, thereby reinforcing the pipe wall in the region of the clamp and increasing the pipe's capacity for withstanding internal forces.

In one embodiment, each clamp section comprises a body which is substantially inflexible in said plane.

In one embodiment, each clamp section comprises a plurality of clamp elements, substantially inflexible in said plane and arranged in a side-by-side relationship, substantially transversely of said plane.

In one embodiment, end portions of the clamp elements of each clamp section overlap respective end portions of clamp elements of the adjoining clamp section. In one embodiment, end portions of the clamp elements of the clamp sections are connected to end portions of the clamp elements of the adjoining clamp section in a staggered or overlapping relationship, substantially transversely of said plane.

In one embodiment, the clamp sections are connected in an end-to-end relationship by means of pins extending through corresponding holes in the clamp sections or elements thereof, whereby the clamp is substantially flexible in said plane.

Each clamp element may comprise a plate shaped element, and each clamp element may comprise an arcuated element having an inner radius r_e, substantially corresponding to an outer radius r_p of the pipe and an arc length between the pin attachment holes determined by a first angle and an overall arc length determined by a second angle. Also, each clamp element may comprise a first end and a second end, each end region may comprise a respective hole for accommodating said pin.

In one embodiment, the clamp's width, transverse of said plane, corresponds substantially to the sum of the widths of each clamp element of two successive clamp sections. In one embodiment, each clamp section comprises an arcuated section having an inner radius substantially corresponding to an outer radius of the pipe and an arc length between the pin attachment holes determined by a first angle and an overall arc length determined by a second angle.

Each end section may comprise an elongated element having a first end rotatably connected to its respective clamp section, and fastening means preferably in the region of a second end of the end section.

Each end section comprises at least one means for tensioning, preferably intermediate of an end section first end and said fastening means. The means for tensioning may comprises a hydraulic tensioner. The clamp reinforces the pipe wall in the region of a plug set in the pipe.

The invented pipe clamp allows the operator to apply the load to the pipe outside wall in a controlled manner. It is light weight, reusable, and provides for easy handling and safe operations (particularly during subsea operations). The invented clamp is easily installed and removed, compared to existing clamps. By tensioning the invented pipe clamp around the outside wall of the pipe, the pipe's capacity for withstanding internal load forces will increase. The clamp design ensures that the restraining loads are distributed along the pipe perimeter in an even and controlled manner, thereby counteracting the loads on the pipe wall generated by the internal plug. The inherent stiffness of the clamp sections and each sections' clamp elements allows to the operator to apply a predetermined tension to the clamp and thus apply a predetermined load to the pipe wall prior to setting the internal plug. Brief description of the drawings

Fig. 1 is a longitudinal section of the device according to the invention, installed on a pipe comprising plugs;

Fig. 2 is a perspective, an partly cut-away, view of a pipe comprising plugs and having the device according to the invention installed;

Fig. 3 A is a side view of the device according to the invention;

Fig. 3B is another side view, perpendicular to the view in Fig. 3a, of the device according to the invention;

Fig. 3 C is a perspective view of the device according to the invention; Fig. 4 A to Fig. 4E are perspective views, schematically illustrating an installation sequence of the device according to the invention onto a pipe;

Figs. 5 and 6 are side views of an element of the device according to the invention. Detailed description of an embodiment

Fig. 1 shows a longitudinal section of a plug train inside a pipe 4 having an inner wall 6 and an outer wall 8. The pipe 4 may be a part of a pipeline, either subsea or onshore, as the skilled person will understand. The plug train comprises in this illustration two interconnected plugs 2, a backup module 3 and a control module 5, which is commonly known in the art as a tool for isolating selected sections of pipe. Each plug 2 comprises basically a plurality of slips 1 a arranged around the plug periphery and a radial gasket Ib arranged peripherally between two compression elements. The plugs in Fig. 1 are shown in an unset state, i.e. the wedges and gaskets not engaging the pipe inner wall. When a plug is to be set, the plug slips are moved into engagement with the pipe inner wall and the gasket is displaced radially into a sealing relationship with the pipe inner wall, e.g. by moving the two compression elements towards each other, for example by means of a hydraulic cylinder (not shown). When the plug is set in this manner, it may exert a considerable pressure on the pipe wall in order to seal off the pipe as intended.

Fig. 1 also shows how a number of clamps 10 are attached to the pipe outside wall, one clamp 10 at a location along the pipe corresponding to the location of the respective plug slips and gasket. Fig. 2 shows a similar configuration, also illustrating how each clamp 10 is positioned on the pipe outside wall 8 in the vicinity of plugs 2 inside the pipe.

Figs. 3 A - 3C show an embodiment of the clamp 10 in an assembled state, i.e. as it would appear when mounted on a pipe (the pipe not shown in Figs. 3 A - 3C). Fig. 4A shows the clamp 10 in an unassembled state, prior to assembly on a pipe 4. The clamp 10 comprises in the illustrated embodiment a plurality of arcuated sections 12 interconnected in a circumferential direction by pins 14 (having a bolt head at one end and a nut at the other end), thus forming a chain or belt of clamp sections 12 along the circumference of the pipe 4. Each clamp section 12 comprising a plurality of clamp elements 7, in the illustrated embodiment plate shaped elements, arranged in a side-by-side relationship, substantially transversely of the clamp plane. Each clamp element 7 - and consequently each clamp section 12 - comprises in the illustrated embodiment a sector of a circular arc, having an effective arc length a between the pin attachment holes 18, as shown in Figs. 5 and 6, illustrating an embodiment of one such clamp element 7. Fig. 5 shows how the clamp element comprises an arcuated shape with an inner radius r_e, which substantially corresponds to an outer radius r_p of the pipe onto which it is mounted. Fig. 5 also shows the holes 18 through which the pins 14 are inserted in order to build individual clamp sections 12 and to connect adjoining clamp sections.

Fig. 6 is a further illustration of the arcuated shape of the clamp element 7 - and consequently each clamp section 12. The first arc length a between the pin attachment holes 18 is defined by the first angle β, while the effective overall arc length is made up of the first arc length a, plus the overhanging arc length sections b at either end, defined by the second angle α. This arcuated shape of the clamp element, having the overall effective arc length of a+2b ensures a homogenous load distribution around the pipe.

Fig. 3B illustrates how the end portions of the clamp elements 7 of each clamp section 12 overlap respective end portions of clamp elements 7 of the adjoining clamp section 12. The end portions of the clamp elements 7 of the clamp sections 12 are connected to end portions of the clamp elements 7 of the adjoining clamp section 12 in a staggered or overlapping relationship. The width w of the clamp corresponds substantially to the sum of the widths of each clamp element 7 of two successive clamp sections 12, as is illustrated by fig. 3B. Here, as an example, the lowermost clamp section A is made up of ten clamp elements 7, the adjoining clamp section B is made up of nine clamp elements 7, while the next clamp section C is made up of ten clamp elements; and so on along the entire length of the clamp belt (cf. e.g. Fig. 3C, 4A). Thus, the variance in clamp elements between each successive clamp section is +1 and -1.

The width w of the clamp belt may be set depending on the required section of pipe that needs reinforcement. For example, knowing the axial dimension of the pipe plug 2, the length of the pins 14 and the number of clamp elements 7 per clamp section 12 may be determined such that optimum pipe reinforcement is obtained. Thus, by adding or removing clamp elements from each clamp section, the strength of the clamp may be tailor made to suit the particular requirements.

Also, while the invention is described with reference to an embodiment having ten clamp sections 12, the skilled person will understand that other numbers of clamp sections 12 are possible, comprising clamp elements 7 having other arc lengths a and/or other radii r_e. At each end of the chain or belt of clamp sections 12 are respective end sections 1 la,b for assembly and tensioning of the clamp 10 onto the pipe 4. Each end section 1 la,b comprises an elongated element having a first end rotatably connected to its respective clamp section 12 and a second end comprising a hole 17 through which a suitable bolt 15 is extended to connect the two end sections 1 la,b. For tensioning of the clamp 10, tensioning bolts or tensioners 16 are provided on the end sections 1 la,b, preferable a distance from the second end where the bolt 15 has been inserted into the hole 17. The tensioners 16 may be e.g. mechanically operated or hydraulically operated, in a manner known in the art. Figs. 4A - 4E show an installation sequence of the clamp 10 around a pipe 4. In

Figs. 4A and 4B, the clamp is conveyed to and around the pipe 4; Fig. 4C shows the clamp in position around the pipe and ready for assembly. In Fig. 4D, the bolt 15 is extended into the corresponding holes 17 on the end sections 1 la,b, while on Fig. 4E the clamp 10 is tensioned in place on the pipe 4 by means of the tensioners 16. Thus, the clamp sections 12, clamp elements 7 and the pins 14 are subjected to tension, such that the clamp 10 is tightened a desired amount around the pipe outside wall 8. When this tension is dimensioned to correspond to the loads applied by the plug 2 on the pipe internal wall 6, the pipe 2 is reinforced in this region. When the internal plug has been removed, and the need for the clamp has ceased, the clamp may be removed in a manner reverse of the steps illustrated in Figs. 4A - 4E.

Thus, the wall of the pipe 4 may be reinforced locally by activating the tensioners 16 in a controlled manner, in conformity with the setting of the plug.

When the invented clamp is mounted onto the pipe as described above, a predetermined tension is applied in the clamp, due to a careful design for each clamp element 7 and/or clamp section 12 of parameters such as arc length a, radius of curvature, number of sections 12 per clamp, and number of elements 7 per section 12. The clamp sections and clamp elements are substantially inflexible elements, at least in the plane of the clamp, and the arc length a is a determining factor for the stiffness of the clamp when it is assembled on a pipe. In general, as the number of sections 12 increase (and the individual arc lengths a decrease) the number of rotatable connections between the sections 12 (by virtue of the pin connections 14) increase correspondingly, making the assembled clamp more flexible. Prior to the installation of a clamp according to the invention, the above mentioned parameters are set so as to provide the most suitable reinforcement for a given pipe and plug configuration.

Claims

1. A clamp (10) for selective assembly and disassembly on the outside of a pipe (4), for preventing the pipe wall from deforming in an outwards radial direction, characterized by a first end section (l la) and a second end section (1 Ib), interconnected by a plurality of arcuated clamp sections (12) connected in an end-to-end relationship so that the clamp (10) is flexible in its own plane but substantially inflexible transversely of this plane, said end sections (1 la,b) comprising clamp fastening means (15, 17) and clamp tensioning means (16), for fastening the clamp (10) with a predetermined tension onto the pipe whereby restraining loads are distributed along the pipe perimeter in an even and controlled manner, thereby reinforcing the pipe wall in the region of the clamp and increasing the pipe's capacity for withstanding internal load forces.

2. The clamp of claim 1, wherein each clamp section (12) comprises a body which is substantially inflexible in said plane.

3. The clamp of claims 1 or 2, wherein each clamp section (12) comprises a plurality of clamp elements (7), substantially inflexible in said plane and arranged in a side-by-side relationship, substantially transversely of said plane.

4. The clamp of claim 3, wherein end portions of the clamp elements (7) of each clamp section (12) overlap respective end portions of clamp elements (7) of the adjoining clamp section (12).

5. The clamp of claims 3 or 4, wherein end portions of the clamp elements (7) of the clamp sections (12) are connected to end portions of the clamp elements (7) of the adjoining clamp section (12) in a staggered or overlapping relationship, substantially transversely of said plane.

6. The clamp of any one of claims 1 - 5, wherein the clamp sections (12) are rotatably connected in an end-to-end relationship by means of pins (14) extending through corresponding holes (18) in the clamp sections (12) or elements (7) thereof, whereby the clamp(lθ) is flexible in its own plane.

7. The clamp of any one of claims 3 - 6, wherein each clamp element (7) comprises a plate shaped element.

8. The clamp of any one of claims 3 - 7, wherein the clamp's width (w), transverse of said plane, corresponds substantially to the sum of the widths of each clamp element (7) of two successive clamp sections (12).

9. The clamp of any one of claims 3 - 8, wherein each clamp element (7) comprises a first end and a second end, each end region comprising a respective hole (18) for accommodating said pin (14).

10. The clamp of any one of claims 3 - 9, wherein each clamp element (7) comprises an arcuated element having an inner radius r_e, substantially corresponding to an outer radius r_p of the pipe and an arc length (a) between the pin attachment holes (18) determined by a first angle (β) and an overall arc length (a,b,b) determined by a second angle (α).

11. The clamp of any one of claims 1 - 9, wherein each clamp section (12) comprises an arcuated section having an inner radius r_e, substantially corresponding to an outer radius r_p of the pipe and an arc length (a) between the pin attachment holes (18) determined by a first angle (β) and an overall effective arc length (a,b,b) determined by a second angle (α).

12. The clamp of any one of claims 1 - 11, wherein each end section (1 la,b) comprises an elongated element having a first end rotatably connected to its respective clamp section (12), and fastening means (15, 17) preferably in the region of a second end of the end section.

13. The clamp of any one of claims 1 - 12, wherein each end section (1 la,b) comprises at least one means for tensioning (16), preferably intermediate of an end section first end and said fastening means (15, 17).

14. The clamp of any one of claims 1 - 13, wherein the means for tensioning (16) comprises a hydraulic tensioner.

15. The clamp of any one of claims 1 - 14, wherein the clamp (10) reinforces the pipe wall in the region of a plug (2) set in the pipe (4).