SYSTEM FOR INSPECTION OF PIPELINES

Abstract: System for inspecting pipelines (1), especially in the coupling between pipe parts, comprising an x-ray source (3), a detector device (4) for x-rays or a photographic film being sensitive to x-rays, adapted to receive radiation and to be positioned on the opposite side of the pipe wall or said pipeline in relation to said source (3). The pipelines including indicators or marks (11, 12) being laid into the pipeline material and having a larger absorption of x-rays than the layers material (5).

Description: SYSTEM FOR INSPECTION OF PIPELINES The invention relates to a system for inspection of pipelines, especially the coupling between parts of the pipe, comprising an x-ray source, a detector means for detection of x-rays, possibly a photographic film being sensitive in the x-ray range, adapted to receive the radiation and to be positioned on the opposite side of the pipe wall or pipeline in relation to the source. Pipelines being used in the oil and gas field are often subject to large strain in the form of stress, pressure and temperature variations. Because of this the pipelines are frequently inspected for displacements, cracks or possible leaks. A known method for performing such inspections is x- ray photographing of the pipeline. Different performing such inspections are available on the market. Flexible pipelines are built to stand the above- mentioned strains. A usual structure of flexible pipelines is a multi layer system of steel pipes with polymer materials between them. The polymer layers includes a pressure sheet which hinders diffusion and leakage of the pipeline content out into the environment. It is also demanded that the pressure sheet is able to move relatively freely in relation to the steel pipes, thus not to be subject to unnecessary strain when the pipeline moves. Between the pressure sheet and the steel pipes an anti-creep sheet is often placed in order to keep the pressure sheet from fastening to the steel layers. In the ends of each pipe part a coupling part is comprised which among other things may comprise a sealing or a packing ring providing a seal between the pipelines and also between the pressure sheets. A problem relating to the abovementioned structure is that the pressure sheet has shown a tendency to contract and thus be drawn passed the sealing ring, making the pipeline leaky. It is an object of the present invention to provide a system to be able to detect relative displacements between parts in a pipe system. It is especially preferred to prove a system being capable of detecting and measuring displacements in polymer layers or similar between steel layers in a pipeline, especially in the vicinity of the coupling points between the different pipe elements. The abovementioned objects are obtained using a system characterized as given in claim 1. This way a simple system is obtained for inspecting pipelines being mainly based upon already available equipment, the implementation of which in new (and existing) pipe systems being easy and relatively cheap. The invention is described in detail below with refer- ence to a specific example shown in the enclosed figures. Figure 1 shows a sketch of the system for inspecting the end of a pipe, as seen from one side. Figure 2 shows a sketch of a system corresponding to the system shown in figure 1, as seen from above. Figure 1 and figure 2 illustrate an inspection of the pipe end 2 in a pipeline 1 comprising a polymer layer 5 being positioned between two steel layers 8,9. The pipe end also comprises a sealing or packing ring 7 for tight coupling to another pipe element . In the polymer layer 5 marks or indicators 11,12 are placed, being made from a material having a higher dampening than the rest of the material in the pipeline, e.g. platinum or tungsten. Preferably these reference points have a known position. In this way reference points in the polymer layer 5 are obtained which may be seen by x-ray photography of the pipe end 2, and which thus may indicate a displacement of the polymer layer in relation to the steel layers . Thus it may be discovered if the pressure sheet shrinks and moves past the seal 7. Preferably there are structures in the steel layers 8,9, possibly provided for other purposes, e.g. recesses for the sealing ring, which may serve as reference points so that movements in the polymer layer in relation to the steel layers may be measured easily. In a preferred embodiment of the invention the indicat- ors/marks 11,12 have oblong shapes and are position with a chosen orientation in the polymer layer 5 so that its position may be determined more easily. In the figures the indicators are given axial 11 and tangential 12 orientations, respectively. Intermediate orientations may of course also be chosen. In certain cases a radial orienta- tion may also be chosen, which will provide an improved possibility for detecting squeezing and deformations in the polymer layer. The most simple way to produce the indicators 11,12 may be from strings or wires by cutting them in desired lengths. The thickness of the wires may be chosen depending on the dimensions of the pipeline and the thickness of the polymer layer, and may also depend on the relationship between the x-ray absorption of the indicators and of the pipeline. In a preferred embodiment the indicators have a thickness of approximately 1/3 of the thickness of the polymer layer. Used in the oil and gas related activities the indicators are preferably made from a corrosion resistant material. The polymer layer will, as mentioned above, often comprise more than one layer, usually with a pressure sheet hindering leaks and diffusion of the pipelines contents and a anti creep sheet stopping the pressure sheet from sticking to the steel layer. The indicators may be placed in one or more of these layers . The x-ray imaging of the pipeline may be performed by using different types of well-known equipment, e.g. based upon cobalt sources, linear accelerators or corresponding high energy sources, preferably in the range of MeV, but the requirements to the source will of course depend on the materials used in the pipeline. To detect the radiation and provide a picture of the pipeline suitable types of photographic film may be used. Electronic detectors and imaging devices may, however, also be used. Neither the choice of source nor the choice of imaging unit are important to the present invention other than the obvious choices relating to the materials in the pipeline, the wanted intensity etc, that need to be made in order to obtain a sufficiently sharp picture with sufficient contrast. In the figures a method is illustrated in which a photographic film is placed inside the pipe. In an embodiment of the present invention several pictures are taken at different angles, which are combined electronically to, with available software, to provide a tomographic picture of the pipeline. In another embodiment of the invention the source and the film 4 or imaging device are positioned outside, and on either side, of the pipeline. Using tomographic techniques a complete picture of the pipeline and the possible displacements of the indicators may be obtained. This solution may also give an opportunity to inspect the pipeline in its full length, possibly without disassembling the pipeline. If method for measuring is to be used it may under some circumstances be topical to place the indicators along the whole length of the pipeline. The figures show a simplified version of a pipeline. As mentioned above the pipeline 1 will comprise several types of polymer layers, pressure sheets and anti-creep sheets, and layers of steel or corresponding materials. The indicators in the different layers may be placed with varying positions or orientations depending on in which layer they are, or possibly with other, more complex shapes in order to provide a clearer view showing which layers are out of place. In such complex pipelines tomographic method may be utilized advantageously. In another emodiment of the invention the system according to the invention may be used control the position of the sealing or packing rings by laying the indicators 11,12 into it. If the pipeline comprises more than one ssealing rings the indicators may be placed in one or more of them. In another embodiment of the invention the system according to the invention may also be utilized inspecting pipelines that do not comprise several layers, e.g. simple plastic or steel pipes. In this case the indicators may be positioned directly in relation to the pipeline material, e.g. in order to measure displacements between two coupled parts of a pipeline. The present invention may, as mentioned above, be used in relation to pipelines in oil or gas related activities, but is not limited to this. Different pipe materials, radioactive or x-ray sources, detectors or imaging methods, and indicator-materials may be chosen depending on the interesting pipe system and the available equipment .

Claims: C l a i m s 1. System for inspecting movable or deformable layers in pipelines (1) , especially in the coupling between pipe parts, comprising an x-ray source (3) , a detector device (4) for x-rays or a photographic film being sensitive to x-rays, adapted to receive radiation and to be positioned on the opposite side of the pipe wall or said pipeline in relation to said source (3) , said pipeline including at least two layers (8,9) of a relatively hard material, e.g. steel, and positioned between these layers at least one moveable or deformable layer (5) of a material, e.g. polymer or similar, being softer than said other material, c h a r a c t e r i z e d in that det soft layer (5) includes indicators or marks (11,12) placed in chosen positions in said layer, and having a larger absorption of x-rays than the layers material (5) . 2. System according to claim 1, c h a r a c t e r i z e d in that the marks/indicators (11,12) have a length being larger than their thickness or width, 3. System according to claim 2, c h a r a c t e r i z e d in that the marks/indicators (11,12) consists of parts of wires or strings of a suitable material, e.g. platinum or tungsten, with a thickness being approximately one third of the thickness of the polymer layer (5) . 4. System according to claim 2 or 3 , c h a r a c t e r i z e d in that the orientation of each of the marks/indicators (11,12) is chosen, thus providing an opportunity to find the position of the x-ray photographed structures . 5. System according to one of claims 1-4 c h a r a c t e r i z e d in that the pipeline includes more than two layers of the hard material (8,9), these layers being separated by said softer material (5) , and that at least two of the softer layers (5) includes marks/indicators (11,12) . 6. System according to claim 5 c h a r a c t e r i z e d in that the marks/indicators (11,12) have a shape related to the polymer layer in which they are positioned. 7. System according to one of the preceding claims, c h a r a c t e r i z e d in that the imaging of the pipeline (1) is performed from a plurality of different directions and that a tomographic picture of the pipeline is made on this basis. 8. System according to one of the preceding claims, c h a r a c t e r i z e d in that the pipeline (1) at each coupling point between two parts of the pipeline includes one or more sealing rings (7), and that the sealing ring(s) also includes indicators (11,12). 9. System according to one of the preceding claims, c h a r a c t e r i z e d in that each layer of softer material per se includes a number of layers of different materials, e.g. pressure sheets and anti-creep sheets. 10. System according to one of the preceding claims, c h a r a c t e r i z e d in that the pipeline includes a number of interconnected pipes, and that the marks/indicators (11,12) are mainly positioned close to the ends (2) of the pipes. 11. System according to one of the preceding claims, c h a r a c t e r i z e d in that the indicators are made from a corrosion resistant material.

Inventors: DAALAND ALF, HOLEN SVEIN AAGE, DAALAND, ALF, HOLEN, SVEIN, AAGE
Applicants: DAALAND ALF, HOLEN SVEIN AAGE, NORSKE STATS OLJESELSKAP, DAALAND, ALF, DEN NORSKE STATS OLJESELSKAP A.S, HOLEN, SVEIN, AAGE
Application year: 1997
Main classification: G01N23
IPC codes: F17D5, G01N23