Tube testing apparatus and method

Abstract

An apparatus for testing rings cut from tubes, comprising: a body; a ring-shaped pressure member that is inflatable and connected to a source of pressurized fluid; and one or more sensors for measuring strain and deformation of the ring and fluid pressure. Wherein the body defines a generally circular opening for receiving the ring-shaped pressure member and the ring, and in use the ring-shaped pressure member is disposed between an inner surface of the generally circular opening and an outer circular surface of the ring for applying pressure to the outer circular surface of the ring.

Description

Technical Field

[0001] This disclosure relates to an apparatus for testing pipes, such as those used to form underwater pipelines, and to a method for testing pipes using the apparatus. Background Technology

[0002] Ultra-deepwater reservoirs for natural gas and / or oil have been gradually developed worldwide. Until recently, ultra-deepwater was defined as any depth greater than approximately 1,000 meters. However, so many pipelines have been installed at depths greater than this that the definition of ultra-deepwater has now exceeded 2,000 meters.

[0003] Pipelines are typically installed empty, meaning they are filled with air under ambient pressure, and only filled with oil or natural gas under pressure after installation. The primary risk experienced during the installation of these deepwater pipelines comes from the pressure exerted by the water, which causes the pipe to deform away from its initial circular shape and into a nearly flat structure. This is known as external pressure collapse and, if left uncontrolled, can lead to the total loss of the pipeline. Therefore, the dimensions of ultra-deepwater pipelines (i.e., diameter and wall thickness), as well as the material properties, are all potentially constrained by external pressure collapse.

[0004] This is completely different from the design of traditional shallow water or land pipelines, where the wall thickness is designed to withstand internal pressure from the fluid being transported, rather than external pressure.

[0005] Numerous theoretical studies have been conducted on external pressure collapse, and numerical simulations have been used to calculate the maximum water depth at which pipelines of specific dimensions can be safely installed. However, the consequences of external pressure collapse are so severe that these theoretical studies are insufficient to confidently manage the risk. Furthermore, the potentially most important method for mitigating such localized collapse by increasing pipe wall thickness is so expensive and likely technically impractical that the proposed pipelines are probably not commercially viable. This, in turn, increases the likelihood of abandoning the extraction of natural gas or oil reservoirs.

[0006] Besides basing all designs on theoretical results, another option is to conduct additional testing. Historically, several tests have been performed for a range of pipe wall thicknesses. These tests involve placing the entire length of a particular manufactured pipe in a specific pressure chamber and increasing external pressure until collapse occurs. Currently, the number of laboratories with appropriate facilities is very limited, and the testing costs are extremely high.

[0007] Several standards have been established to provide a basis for calculating the dimensions of pipes that need to operate at specific great depths. These standards include safety factors designed to ensure that, when manufacturing 1000-kilometer-long pipelines, natural variations in pipe dimensions and material properties do not compromise the pipeline's ability to withstand external pressure without collapsing. However, these factors are based on a limited number of previous collapse tests of the entire pipe length. Performing such tests on the entire pipe length (also known in industry as "pipe fittings") during pipe manufacturing is impractical because the tests would require a lengthy setup and completion time, and would, of course, damage the pipe being tested.

[0008] If even one pipe joint collapses in a pipeline, the entire pipeline will be flooded. Pipeline failure due to external pressure collapse bears a direct resemblance to the "weakest link in a chain." Given that practice specifications are based on collapse test results from a limited number of pipe joints, design specifications introduce a factor to allow for all possible variations in the many factors influencing collapse pressure, thereby increasing the wall thickness throughout the deepwater route.

[0009] Recently, improved testing methods have been developed to replicate the effect of external pressure causing pipe joint collapse, and these methods are easy to set up and perform (and more cost-effective than historical testing methods).

[0010] These improved testing methods are based on the understanding that the deformation that causes external pressure collapse is uniform along the pipe. Therefore, for a ring cut from the pipe, the external pressure collapse occurs in the same way as for the entire pipe joint length that has been fully subjected to external pressure.

[0011] A prior art tube test apparatus for implementing an improved test method is known from WO2008 / 114049.

[0012] This type of pipe testing equipment has proven highly effective for testing pipes used to form underwater pipelines. However, a certain level of expertise and precision is required to implement these testing methods. These tests are typically conducted by highly skilled technicians in a pipe testing laboratory. Summary of the Invention

[0013] The present invention aims to provide an improved tube testing apparatus that allows for efficient non-destructive testing of tubes outside of a dedicated testing laboratory, allows for precise and repeatable operations by less skilled individuals, and allows for higher throughput of test samples.

[0014] Representative features are set forth in the following clauses. These features may exist alone or in combination with one or more features disclosed in the text of the specification and / or the accompanying drawings in any combination.

[0015] According to a first aspect of the invention, an apparatus for testing a ring cut from a pipe is provided, comprising: a body; an annular pressure member that is expandable and connected to a pressurized fluid source; and one or more sensors for measuring strain and deformation of the ring and fluid pressure, wherein the body defines a generally circular opening for receiving the annular pressure member and the ring, and the annular pressure member is disposed in use between an inner surface of the generally circular opening and an outer circular surface of the ring to apply pressure to the outer circular surface of the ring.

[0016] An annular pressure member is a different type of fluid-filled member. It can expand radially. It preferably comprises a closed hollow ring.

[0017] The main body is preferably axially open. Preferably, the ring is substantially free of axial load. The device is preferably configured to apply pressure only to the outer circular surface of the ring.

[0018] According to another aspect of the present invention, a method for testing a ring cut from a pipe using the above-described apparatus is provided, the method comprising: a. Cut the ring from the tube; b. Assemble the ring into the equipment, and c. Use the equipment to apply pressure and record strain and deformation measurements.

[0019] Furthermore, preferred features are given in the dependent claims.

[0020] It should be noted that the principles of this invention can be applied to the testing of tubes with a wide range of diameters and wall thicknesses, and this invention is not limited in this respect. Attached Figure Description

[0021] Non-limiting embodiments of the invention will now be discussed with reference to the following figures: Figure 1 A schematic plan view of a test apparatus having a ring to be tested in situ, according to a first embodiment, is shown. Figure 2 It shows along Figure 1 A schematic cross-sectional view of section AA in the diagram; Figure 3 A schematic enlarged cross-sectional view of a pressure collar and associated gasket according to one possible embodiment is shown, as well as a schematic cross-sectional view of the gasket taken along the BB line; and Figure 4 A schematic diagram illustrates an alternative arrangement of introducing a reservoir into a pressurized system to alter the system's hydraulic stiffness, according to one possible embodiment. Detailed Implementation

[0022] Tests on the long portion of a single pipe fitting have shown that the deformation leading to external collapse is uniform along the pipe. This observation is supported by theoretical studies and numerical simulations. This means that the occurrence of external pressure collapse for a ring cut from the pipe will be the same for the entire fitting length of a pipe fully subjected to external pressure. Therefore, the test method of the present invention is based on a short portion cut from the pipe. The ring is placed in a novel testing apparatus such that pressure can be applied only to the outer circular surface of the ring. A device is provided for measuring the strain and deformation caused by pressure on the outer circular surface of the ring.

[0023] Pressure is applied from an external pump, increasing the pressure by adding a specified volume of fluid to a pressure member surrounding the outer circular surface of the ring. This arrangement allows for radial deformation of the ring caused by controlled expansion of the pressure member.

[0024] A typical test will include the following steps: a. Cut the ring from the tube; b. Assemble the ring into the equipment, and c. Use the equipment to apply pressure and record strain and deformation measurements.

[0025] It may also be useful to plot the applied pressure against the measured maximum strain to detect the onset of an accelerated nonlinear decrease in the ring diameter as pressure increases.

[0026] Reference Figure 1 and Figure 2 The diagram illustrates a test apparatus comprising a body 1, an annular pressure member 2, and one or more sensors 3. The annular pressure member 2 is expandable and connected to a pressurized fluid source (not shown). The sensors 3 are used to measure the strain and deformation of a ring 4, as well as the fluid pressure. The body defines a generally circular opening 5 for receiving the annular pressure member 2 and the ring 4. As clearly shown, the annular pressure member 2 is positioned in use between the inner surface of the generally circular opening 5 and the outer circular surface of the ring 4. The annular pressure member 2 applies pressure to the outer circular surface of the ring 4 through its radial expansion.

[0027] The shape of the body 1 is not particularly limited. It must allow for a generally circular opening 5 and be configured to allow for the insertion of the annular pressure member 2 and the ring 4. The body may include a clamp. This is preferred because it provides a simple structure that can be opened to prepare for the insertion of the annular pressure member 2 and the ring 4, while providing the desired circular opening and appropriate resistance to deformation during testing. It may include two or more bent hinged sections. In the arrangement of this application, as... Figure 1As clearly seen, there are three curved hinged sections, which engage via hinge 7 and are closed by clamping / locking sections 8. In alternative arrangements, there may be more or fewer hinged sections. The hinged sections are not particularly limited in form and are not required to be limited to the form shown. The body may include multiple curved anchor blocks 9, which are received by the clamp and define the inner surface of a generally circular opening 5. By using the anchor blocks 8, the body 1, and especially the generally circular opening 5 defined therein, the dimensions can be varied by replacing the anchor blocks 9 with anchor blocks of different sizes, thus allowing the device to easily accommodate rings of different diameters. As will be understood, the anchor blocks 9 may be omitted in an alternative arrangement.

[0028] There are no particular limitations on the number, location, and form of the sensors 3. Preferably, there are separate pressure sensors and strain / deformation sensors, although they may be combined in some arrangements. One or more sensors are preferably fixed to the body such that the force caused by the radial expansion of the annular pressure member 2 is transmitted to the body via the anchor block 9 (in this arrangement) or otherwise. In this arrangement, the pressure sensing element 3 is disposed between the anchor block 9 and the body 1. Providing such a pressure sensing element allows for cross-checking of pressure readings by any pressure sensor, thereby ensuring, for example, that the anchor blocks 9 do not contact each other. Preferably, each of the anchor blocks 9 includes one or more pressure sensing elements 3 associated with it.

[0029] The annular pressure member 2 is a different member and preferably comprises a closed hollow ring, as shown in the figure. It can be formed of stainless steel or any other suitable alternative material, as will be apparent to those skilled in the art. Figure 1 and Figure 2 The pressure member 2 is enclosed except for the provided fluid inlet / outlet 6. In this arrangement, there are inlets separately located from the outlet; these inlets can be combined in other arrangements, i.e., a single opening can exist for introducing and discharging fluid from the pressure member 2. The form of any opening / inlet / outlet is not particularly limited and can take any conventional form, as will be readily understood by those skilled in the art. One or more suitable pumps / valves can be provided for controlling the inflow / outflow of pressurized fluid into / out of the pressure member 2, as well as for controlling the fluid pressure within the annular pressure member 2 and the expansion of the annular pressure member 2, as will also be readily understood by those skilled in the art.

[0030] Annular pressure member 2 in Figure 2The solid line indicates the expanded state, while the dashed line indicates the form of the annular pressure member 2 before expansion. In this arrangement, as shown, the wall of the annular pressure member is thicker in the region defining the inner surface for engaging the generally circular opening than in the region defining the outer circular surface 17 for engaging the ring 4. This is not necessarily the case, but preferred. It is worth noting that the reduced wall thickness increases flexibility. The first surface 10 and the second surface 11 are preferably parallel to each other. The first surface 10 and the second surface 11, regardless of whether their thicknesses differ, preferably have a width / axial length equal to or greater than the contact portion of the ring 4 and the body 1. The annular pressure member 2 may have an elongated elliptical profile, such as... Figure 2 As shown, it may be formed in other ways, as will be discussed below.

[0031] The first surface 10 and the second surface 11 can be spaced apart by a predetermined distance, which is set based on the expected collapse pressure of the sample ring 4, such that the circumferential Poisson contraction of the second surface 11 results in the circumference of the second surface 11 being substantially equal to the circumference of the outer circumferential surface 17 of the ring at the start of failure. Under a load that controls the circumferential contraction of the second surface 11 of the annular pressure member 2, the outer diameter of the ring decreases. The distance between the first and second surfaces determines the lateral tension in the second surface 11, which in turn controls the Poisson contraction in the circumference of the second surface 11. Therefore, the spacing between the first surface 10 and the second surface 11, as well as the thickness of the wall of the annular pressure member 2 in the region of the second surface 11, can be selected such that the second surface 11 of the annular pressure member 2 contracts by the same amount as the sample circumference under the Poisson effect, to eliminate or minimize the second surface 11 entering compression.

[0032] Following the above discussion, as will be readily understood by those skilled in the art, the thickness T can be selected to control the desired circumferential Poisson contraction in the inner surface 11. As the annular pressure member 2 expands and more fluid is pumped in, the pressure is maintained or intentionally increased towards a destructive pressure. However, as T increases in this manner, although the pressure may remain well constant or only increase slowly, the lateral tension increases directly proportional to the increase of T. For a unit circumference of the pressure element, this total lateral tension is equal to [T * pressure], shared between surfaces 10 and 11.

[0033] The lateral strain in surface 11 is linearly controlled by the tension in surface 11, and the circumferential Poisson contraction (and therefore radial contraction) in surface 11 is then linearly controlled by the lateral strain.

[0034] Therefore, those skilled in the art will again understand that, prior to testing, the initial distance between surfaces 11 and 12 is set by prior calculations based on previous testing experience to increase to the spacing T during testing, wherein the lateral tension that subsequently occurs in surface 11 causes circumferential shrinkage strain in surface 11, which is approximately equal to the shrinkage in the circumference of the surface (the sample of the gasket) at the point where the ring "fails" and the test is completed.

[0035] Reference Figure 3 An alternative form of the annular pressure member 2 is shown, which includes a central portion 12 and an enlarged end portion 13 in cross-section, the enlarged end portion 13 having a greater thickness than the central portion. The enlarged end portion is preferably spherical. The central portion 12 preferably has a width substantially equal to or greater than the width / axial length of the ring 4 being tested. The first surface 10 and the second surface 11 may differ in thickness, as described above. The first surface 10 and the second surface 11 are again preferably substantially parallel to each other.

[0036] The enlarged / spherical end increases the flexibility of the pressure member 2, allowing the same pressure member 2 to be used with varying ring diameters (and anchor block widths) to change the radial dimension of the pressure member 2. Furthermore, as the size of the enlarged end portion 13 increases, flexibility increases, and the force required to change the distance between the first surface 10 and the second surface 11 decreases. This helps to maximize the percentage of applied pressure that is actually applied to the sample rather than acted upon by components of the device.

[0037] Figure 3 A ring-shaped washer 14 is further shown, which is arranged in use between the annular pressure member 2 and the ring 4. The ring-shaped washer 14 is preferably formed of an elastic material. It can be rubber or other materials. It preferably includes one or more reinforcing material layers 15, which are spaced apart from each other in the thickness direction of the washer 14. The reinforcing layers are preferably in sheet form. Figure 3 In the arrangement, as seen in section BB (not to scale), two layers 15 are shown; however, more layers 15 or a single layer may be present. The reinforcing material layers 15 may undulate in the circumferential direction, as shown. Layers 15 impart significant stiffness to the gasket 14 under compression and lateral expansion throughout its thickness. However, through their wavy / wave-like shape, they possess very low circumferential stiffness, thereby allowing for a reduction in the diameter of the ring 4 and the inner / second surface 11 under hydrostatic radial pressure, while minimizing the dissipation of applied pressure due to the circumferential compressive force introduced into the rubber gasket.

[0038] The outer surface 16 of the washer can also be wavy, as shown by the dashed line in the cross-sectional BB image. The size of the wave can be selected such that during compression, the inner / second surface 11 of the initially non-wavy pressure member 2 is pushed downward into the undulating groove, such that the minimum / nominal compressive strain is introduced into the second surface 11.

[0039] It should be noted that although washer 14 is discussed in the context of annular pressure member 2 with enlarged ends, it is not necessarily so limited and can be used in combination with different forms of annular pressure member 2, including those related to... Figure 2 The subject of this discussion. As those skilled in the art will understand, its form may be adjusted accordingly.

[0040] exist Figure 3 In this arrangement, the washer to be inserted between the enlarged ends 13 can be rolled into a folded shape and inserted into the space between them. The ring 4 can then slide within the washer 14. The washer preferably fills the gap between the enlarged ends to present a flat / flush inner surface.

[0041] refer to Figure 4 This illustrates another alternative arrangement that can be applied with respect to any of the arrangements described above. This represents an optional introduction of the reservoir 32 into the pressurization system (which includes a pressurized fluid source) to allow for variations in the "hydraulic stiffness" of the pressurization system. In an alternative arrangement, the reservoir can be omitted from the pressurization system.

[0042] Figure 4 As will be understood, the arrangement is shown for illustrative purposes only. The pressurization system preferably includes a pump 20. The pump 20 receives fluid through an inlet line 21 for injection into the system through a pressurization line 22.

[0043] The introduction of reservoir 32 provides a means of altering the stiffness of the pressurized system to enhance the visibility of the "permanent deformation limit," i.e., when the irreversible plastic strain caused by a standard increment of pressure exceeds a predefined acceptable level. This is valuable when such permanent deformation of the tube cross-section is a selected practically acceptable threshold, beyond which the level of permanent deformation of the tube cross-section is considered unacceptable for practical reasons, even if the tube integrity has not been compromised.

[0044] As will be clear from the following discussion, the form of the reservoir 32 is not particularly limited. For example, any conventional gas-supported reservoir can be implemented, as will be readily understood by those skilled in the art.

[0045] refer to Figure 4The arrangement ensures that the system has a constant maximum stiffness when valve 30 is closed, and pressure increments are mitigated by very small strain. Opening valve 30 and filling reservoir 32 with compressed gas (e.g., but not limited to dry air, nitrogen, or carbon dioxide) by opening valve 31 to, for example, a first level (indicated by dashed line 33) provides greater system flexibility, where standard pressure increments would require more strain to release. Further increasing the gas pressure will drive the fluid downwards to, for example, a second level (indicated by dashed line 34), where the larger gas volume provides even greater flexibility, whereby a standard system pressure rise matching the gas pressure rise to maintain the second level would require even more strain on the sample ring to release. This means that the operator's sensitivity in detecting the "permanent deformation limit" described below can be effectively enhanced, allowing for faster and more manageable non-destructive testing procedures.

[0046] As those skilled in the art will understand, the memory can take any suitable known form.

[0047] The methods and apparatus according to the invention exhibit numerous advantages over the prior art. They allow for the testing of representative samples of test rings taken from all pipe fittings required for a long pipeline, providing direct, physical, quantitative evidence of the ability of each of these samples to resist collapse under external hydrostatic pressure. The collapse tolerance of each sample test ring can be reliably maintained as a representation of the collapse tolerance of the fitting from which it was cut. Using the invention in the described manner can allow for the reduction of factors currently used in the design process to increase the wall thickness of the entire pipeline. The fitting from which each test ring is cut can still be used as a production fitting and is not wasted. The end result can be a significant reduction in the height of the pipeline wall thickness, which will provide improved commercial usability of the pipeline and significant cost savings. Compared to the cited prior art, they provide accurate and repeatable operation by less skilled individuals and allow for a higher throughput of test samples. This allows for the testing of many samples to be carried out at the source, in a tube mill as part of the production process, or otherwise. The disclosed apparatus also allows for the performance of multiple tests without any changes to any components.

[0048] Within the scope of the appended claims, those skilled in the art will readily understand many alternative arrangements and modifications of the apparatus as described herein.

[0049] When used in this specification and claims, the terms "comprises" and "comprising," and variations thereof, mean to include the stated features, steps, or whole. These terms should not be construed as excluding the presence of other features, steps, or components.

[0050] Features disclosed in the foregoing description, the claims, or the drawings, expressed in their particular form or as means for performing the disclosed functions or as methods or processes for obtaining the disclosed results, may, as the case may, be used alone or in any combination of such features to implement the invention in its various forms.

[0051] Although certain exemplary embodiments of the invention have been described, the scope of the appended claims is not intended to be limited to these embodiments. The claims are to be interpreted literally and intentionally, and / or include equivalents.

Claims

1. An apparatus for testing rings cut from a tube, comprising: main body; An annular pressure member that can expand and connect to a pressurized fluid source; as well as One or more sensors are used to measure the strain and deformation of the ring, as well as the fluid pressure; The main body is defined as having a generally circular opening for receiving the annular pressure member and the ring, and in use, the annular pressure member is disposed between the inner surface of the generally circular opening and the outer circular surface of the ring for applying pressure to the outer circular surface of the ring; The cross-section of the annular pressure member includes a central portion and an enlarged end portion, wherein the thickness of the enlarged end portion is greater than the thickness of the central portion.

2. The device as claimed in claim 1, wherein, The annular pressure member comprises a closed hollow ring.

3. The device as claimed in claim 1, wherein, The annular pressure member is made of stainless steel.

4. The device as claimed in claim 1, wherein, The width of the central portion is substantially equal to or greater than the length of the ring being tested.

5. The device as claimed in claim 1, wherein, The wall of the annular pressure member defines a first surface and a second surface, the first surface being for engaging the inner surface of the generally circular opening, and the second surface being for engaging the outer circular surface of the ring.

6. The device as claimed in claim 5, wherein, The first surface and the second surface are substantially parallel to each other.

7. The device as claimed in claim 5, wherein, The first surface and the second surface are separated by a predetermined distance, which is set according to the expected collapse pressure, such that the circumferential Poisson contraction of the second surface causes the circumference of the second surface to be substantially equal to the circumference of the outer circular surface of the ring at the start of failure.

8. The device as claimed in claim 5, wherein, The second surface is thinner than the first surface.

9. The device of claim 1, further comprising an annular washer located between the annular pressure member and the ring during use.

10. The device as claimed in claim 9, wherein, The annular washer is made of an elastic material and includes one or more reinforcing materials in the thickness direction.

11. The device as claimed in claim 10, wherein, The one or more layers of reinforcing material are wavy in the circumferential direction.

12. The device as claimed in claim 9, wherein, The outer circular surface of the washer is wavy along the circumference.

13. The device as claimed in claim 9, wherein, The washer is configured to fill the void defined by the thinner central portion.

14. The device as claimed in claim 1, wherein, The main body includes a clamp.

15. The device as claimed in claim 14, wherein, The clamp includes two or more curved hinged sections.

16. The device as claimed in claim 1, wherein, The body includes a plurality of curved anchor blocks that define the inner surface of the generally circular opening.

17. The device as claimed in claim 16, wherein, Each anchor block includes at least one pressure sensing element arranged between the anchor block and the body for measuring the load on the annular pressure member.

18. The device of claim 1, further comprising a pressurization system, the pressurization system including a pressurization fluid source, wherein the pressurization system includes a reservoir.

19. The device as claimed in claim 18, wherein, The reservoir includes a gas-supported reservoir.

20. The device as claimed in claim 18, wherein, The storage device is configured to change the stiffness of the pressurization system.

21. A method for testing a ring cut from a tube using the apparatus as described in any one of claims 1 to 20, the method comprising: a. Cut the ring from the tube; b. Assemble the ring into the device; as well as c. Apply pressure using the device and record the strain and deformation measurements.

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