Inspection method for pipe joints used in underwater pipelines

Abstract

To provide a method for inspecting a pipe joint used for a marine pipeline.SOLUTION: A method for inspecting a pipe joint used for a marine pipeline comprises the steps of: receiving a pipe joint; measuring the ellipticity of the pipe joint to acquire ellipticity data; determining that the ellipticity data do not exceed a predetermined maximum pipe joint ellipticity value; and performing an external pressure collapse test to a ring cut from one end of the received pipe joint to acquire data showing the hydrostatic pressure collapse pressure of the pipe joint used for checking that the pipe joint is suitable for its intended use. A method for manufacturing a pipe joint used for a marine pipeline using the inspection method is further disclosed.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a method for inspecting a pipe joint used in a submarine pipeline, and a method for manufacturing a pipe joint used in a submarine pipeline employing the inspection method. One aspect of the present invention relates to a method for inspecting the ovality of a pipe joint and using the findings of the inspection to minimize the wall thickness of the pipe joint and / or improve the maximum hydrostatic pressure rating of the pipe joint.

Background Art

[0002] In the oil and gas industry, over the past 25 years, the design of submarine pipelines suitable for installation and operation in ultra-deep waters, typically deeper than 2,000 m, for accessing or transporting oil and / or gas to deep reservoirs has been steadily progressing. Currently, small-diameter pipes with a diameter of about 16 inches (about 41 cm) are installed up to a water depth of about 3,000 m. For water depths up to 2,500 m, large-diameter pipes with a diameter of up to 32 inches (about 81 cm) are installed. In future projects, it is highly likely that the installation and operation of pipes at depths from 3,500 m to 4,000 m will be required, and this range covers a large section of the world's oceans.

[0003] Such pipelines are typically installed filled with atmospheric air, and then, once installation is complete, filled with pressurized oil or gas. The primary risk during the installation of this type of pipeline is the hydrostatic pressure exerted by the water, which can deform the pipeline substantially from its initial round shape to a nearly flat shape. This is called external pressure collapse and, if left uncontrolled, can lead to the total loss of the pipeline. When determining the likelihood of external pressure collapse, the primary dimensions of the pipeline are the inner diameter and wall thickness. These dimensions are also key factors in determining whether the pipeline is economically viable; the inner diameter controls the speed at which oil or gas can be transported through the pipeline and therefore affects operating costs over the pipeline's lifespan, while the wall thickness is strongly related to the cost of manufacturing and installing the pipeline. In other words, the cost of manufacturing and installing the pipeline increases as the wall thickness increases.

[0004] The sensitivity of external collapse pressures in underwater pipelines (such as thick-walled pipelines) to a wide range of material and geometric imperfections, as well as to manufacturing standards, is well documented.

[0005] Typically, before the design for a pipeline is finalized, sample pipe joints are formed in small batches, transported to a laboratory, and pressurized in a large tank until they implode. Such tests are known as destructive tests. Destructive tests provide some insight into the actual strength of similar pipes that are manufactured much later in the project and welded and placed on the seabed. Destructive tests, when combined with a large safety factor, are becoming useful in estimating actual collapse performance and helping to validate empirical formulas in industrial submarine pipeline design guidance, linking several factors to the predicted collapse depth of other pipes with different properties, dimensions, and design pressures.

[0006] Pipeline design involves numerous factors suitable for medium-depth, deep-sea, and ultra-deep-sea applications, all of which are specified in design guidance. One example of such design guidance is the DNV GL-OS-F101 design code (hereinafter referred to as the "DNV GL design code" or "DNV GL method"). Factors to consider include the ellipticity of the pipeline, material compressive strength, wall thickness variation, average diameter, material anisotropy ("variation") both around the pipeline and in the wall thickness, and strain in longitudinal seam welds present in all deep-sea pipes. This includes changes in material properties, the shape of the stress-strain curve (usually defined by the "tangent coefficient"), and the heat treatment and expansion applied after pipe fabrication. Design guidance provides empirical formulas that account for most (if not all) coefficients by a mixture of empirical coefficients and common safety factors. There are many factors to consider, some of which are interrelated. Knowing how a change in one variable affects other properties of the pipe joint is difficult, and one is reluctant to deviate from trial-and-error design guidance.

[0007] Destructively testing enough sample pipes to establish true statistical significance—enough to make accurate statistical predictions for design guidance on minimum collapse pressure or depth for pipe joint inventories intended for underwater installation—is costly and cumbersome. The scarcity of adequate destructive pipeline testing facilities worldwide further exacerbates the impracticality of destructive testing of pipe joints.

[0008] Since no non-destructive tests are available for the strength of the actual pipes to be installed in the pipeline, and operational experience for deep-sea pipeline installations (e.g., thick-walled underwater pipeline installations) remains limited, verification obtained from destructive tests of only small, statistically insignificant samples of pipe joints requires the use of a high safety factor / class to maintain confidence in the integrity of the entire pipeline. This is a standard and good engineering practice in any type of prototype or early-stage project.

[0009] Other industries, such as drilling and processing, provide an acceptable guarantee of safety by using older rules of thumb, which simply rely on very conservative wall thicknesses and / or years of experience.

[0010] The primary factors in determining the range of safety classes are typically the consequences of pipeline failure for humans, the environment, and cost. Using safety factors corresponding to medium or high safety classes is common in pipeline collapse pressure design practices; however, this often leads to overly conservative pipe thickness, resulting in heavy and expensive pipes.

[0011] One advance in pipeline design has been made in understanding the effects of heat treatment applied after pipe manufacturing, particularly the effect of light heat treatment (LHT) on the collapse strength of pipes manufactured according to the UOE / JCOE method. The practical development of LHT has shown that it can increase collapse pressure and therefore reduce pipe wall thickness relative to the specified maximum hydrostatic pressure, thereby reducing pipe costs while maintaining the same level of safety according to current design guidance. However, the reduction in wall thickness provided by LHT is limited, and the industry is still seeking other methods to reduce wall thickness.

[0012] Therefore, it is necessary to address the problems surrounding conservative wall thickness in underwater pipeline design, and / or the problems surrounding the selection of safety factors in underwater pipeline design. The object of the present invention is to mitigate one or both of the aforementioned problems.

[0013] As used herein, the term “pipe” refers to a portion through which fluid flows, having a substantially circular cross-section. As used herein, the term “cross-section” refers to a plane substantially perpendicular to the longitudinal axis of the pipe, i.e., substantially the cross-section of the pipe. As used herein, the term “pipe joint” refers to a single pipe element having two substantially circular ends that can be joined with other similar types to form a pipeline. With respect to pipe joints (also called deep-sea pipes for the same effect), the term “thickness” as described herein is used. The term "wall" refers to a pipe whose collapse is the failure of its cross-section under uniform external pressure, rather than the more common pipe failure mode of tensile fracture under internal pressure. This collapse failure can be plastic, elastoplastic, or elastic buckling of the cross-section, depending primarily on the ratio of the pipe diameter to its wall thickness. In other words, a thick-walled pipe as defined herein is one in which the ultimate failure mode of a critical design condition is internal fracture under external hydrostatic pressure, rather than internal fracture under internal pressure, without any limiting inferences regarding water depth, pipe wall thickness, material properties, or the ratio of pipe diameter to its wall thickness. As used herein, "ellipticity" can be expressed as a percentage obtained by dividing the difference between the maximum measured pipe diameter and the measured pipe diameter perpendicular to it by the nominal diameter. That is, a pipe joint with a certain degree of ellipticity may have an elliptical cross-section. "Ellipticity" is a parameter that has historically been used in implementation standards and design guidance to characterize the roundness of a pipe. As used herein, "roundness" is the difference between the measured radius at any given point on the circumference and the nominal radius of the pipe joint. In other words, "roundness" is the deviation of the pipe from the circle around it, and can be expressed as a mathematical or graphical function. "Topographic mapping" as used herein refers to the investigation of the inner or outer surface of a pipe, expressed as the radius of each investigation point from the pipe axis. The topographic mapping disclosed herein provides roundness data that, if necessary, allows for the calculation of ellipticity at any point along the axis. [Overview of the project]

[0014] In a first aspect of the present invention, a method for inspecting pipe joints for use in underwater pipelines is provided, the method comprising the following steps: - The process of receiving pipe joints; - The process of measuring ellipticity and obtaining ellipticity data; - A step of determining that the ellipticity data does not exceed a predetermined maximum pipe joint ellipticity value, and - A step of performing an external pressure collapse test on a ring cut from one end of a received pipe joint and obtaining data representing the hydrostatic collapse pressure of the pipe joint for use in confirming that the pipe joint is suitable for its intended use.

[0015] The inspection method of the first embodiment non-destructively verifies that the hydrostatic collapse pressure of the pipe joint is sufficient for its intended use and that the ellipticity of the pipe joint for installation in a pipeline is below a specific predetermined value. Verification of suitability for intended use means, for example, suitability for intended use at a specific water depth, temperature, and / or hydrostatic pressure.

[0016] By ensuring that the ellipticity of pipe joints for use in underwater pipelines is below a predetermined maximum, it becomes possible to favorably use less conservative safety factors and maximum pipe joint ellipticity in the design of pipe joints, while reducing the risk of unknown vulnerabilities caused by high ellipticity away from the cut-off pipe joint end of the ring. For example, if a predetermined maximum ellipticity is 0.4%, the pipe joint may be designed based on a maximum ellipticity of 0.4%. Using such less conservative safety factors and maximum pipe joint ellipticity results in thinner pipe joint walls but leads to improved safety. The method according to the first embodiment has been found to safely enable the use of design guidance with a low safety factor selected from the "high," "medium," or "low" safety class options.

[0017] This inspection method can be advantageously performed on pipe joints that are installed and functioning in underwater pipelines, in contrast to testing samples from manufacturing pipes that will not be used in pipelines, thereby providing a reliable, rapid, and cost-effective method for inspecting pipe joints, such as light-wall and heavy-wall pipe joints underwater. Suitable for use in any type of pipe joint for use in pipelines.

[0018] The steps of the inspection method for performing an external pressure collapse test may include performing the external pressure collapse test on a ring cut from one end, or on two rings cut one from each end of a received pipe joint, or on two or more rings cut progressively from the cross section along the length of a received pipe joint.

[0019] This method represents a significant departure from conventional methods established decades ago and still in use today, offering considerable commercial advantages in the design, manufacture, and installation of pipe joints for use in pipelines.

[0020] Next, preferred features of the optional selection of the method according to the first embodiment will be described.

[0021] Preferably, if an external pressure collapse test confirms that the pipe joint is suitable for its intended use and the ellipticity does not exceed a predetermined maximum pipe joint ellipticity, the method may further include the following steps: - The process of receiving additional pipe joints for inspection; - A process to measure the ellipticity of further pipe joints and obtain ellipticity data; - A step of determining that the ellipticity data does not exceed a predetermined maximum pipe joint ellipticity that is reduced from a predetermined maximum pipe joint ellipticity; and, - Performing an external pressure collapse test on rings cut from one or both ends of the received additional pipe joints, and obtaining data representing the hydrostatic collapse pressure of the additional pipe joints for use in verifying that the pipe joints are suitable for their intended use.

[0022] By inspecting additional pipe joints as described above, a predetermined maximum pipe joint ovality can be minimized with respect to a predetermined manufacturing tolerance.

[0023] Preferably, the received pipe joints have an inner diameter and wall thickness based on the necessary fluid flow through the pipeline, the hydrostatic pressure corresponding to the depth at which the pipe joints should be used safely (i.e., the depth at which external pressure collapse does not occur), and a predetermined maximum pipe joint ovality.

[0024] Preferably, the method further includes the step of applying or adding a safety factor to the depth at which the pipe joints are used in order to increase the minimum allowable hydrostatic pressure and thus the wall thickness of the pipe joints. Preferably, the safety factor is a coefficient (the coefficient is applied to the depth at which the pipe joints are used, essentially adding the safety factor to the determined inner diameter and wall thickness). Preferably, the safety factor is 1.0 to 1.2, more preferably 1.1 to 1.2.

[0025] The external pressure collapse test can be configured to apply external pressure to at least one ring cut out from the received pipe joint to at least simulate the pressure at which the pipe joint is used in a subsea pipeline. Preferably, the external pressure collapse test applies external pressure to at least one ring cut from the received pipe joint to determine at what pressure the ring fails. Preferably, the external pressure collapse test is performed on a statistically significant number of received pipe joints, such as 200 pipe joints in a pipeline, i.e., every joint in a 2.5 km pipeline, or every 100th joint in a 250 km pipeline (assuming a pipe joint length of 12.2 m).

[0026] Preferably, the external pressure test includes the following steps: - The step of cutting a ring from one end of the received pipe joint; - The step of forming a flat and substantially parallel surface on the end of the ring; - The step of providing means for measuring the strain and deformation of the ring; - The step of installing the ring in the pressure chamber so that the ends of the ring form a seal with the opposing walls of the chamber and isolating the inside of the ring from the outside; - The step of increasing the pressure outside the ring and measuring the strain and deformation of the ring as the pressure increases; and, - The step of determining the comparison between the pressure applied outside the ring and the maximum strain measured to detect the onset of acceleration of the non-linear decrease in the ring diameter with increasing pressure.

[0027] The data from the hydrostatic collapse pressure test can be compared with the data representing the failure collapse test of the sample pipe joint that has undergone the destructive hydrostatic collapse test. By comparing the hydrostatic collapse pressure test data with the destructive hydrostatic collapse test data, it may be possible to verify the accuracy of the obtained hydrostatic collapse pressure test data.

[0028] Preferably, the step of cutting the ring from one or both ends and performing the external pressure collapse test is carried out before, after, or simultaneously with measuring the ovality.

[0029] Preferably, an ovality exceeding 10% along the length of the pipe joint, preferably an ovality exceeding 50% of the pipe joint, and most preferably an ovality exceeding 90% of the pipe joint is inspected. Alternatively, the ovality may be inspected along the entire length of the pipe joint (i.e., inspecting 100% of the ovality of the pipe joint).

[0030] Preferably, the predetermined maximum ellipticity is 3% or less, preferably 1.2% or less, more preferably 0.5% or less, and most preferably less than 0.5%. For example, the maximum ellipticity may be 0.5%, 0.45%, 0.4%, 0.35%, 0.30%, 0.25%, 0.2%, 0.15%, 0.1%, or 0.05%. The predetermined maximum ellipticity value may vary depending on the manufacturing technique and tolerances used.

[0031] Preferably, measuring the ellipticity includes measuring the roundness of the pipe joint to obtain roundness data, and measuring the ellipticity of the pipe joint using the roundness data.

[0032] Preferably, the roundness is determined by measuring the radius around the cross section at intervals of 0.1° to 4°, preferably 0.2° to 3°, more preferably 0.3° to 2°, and most preferably 0.3°.

[0033] Preferably, the pipe joint is measured by one or more lasers. The one or more lasers can be configured in a laser array and mounted on a rig.

[0034] Preferably, the step of measuring the ellipticity of the pipe joint includes the step of topographically mapping at least a portion of the pipe joint. Preferably, the topographic map of the pipe joint is obtained at points from the axis to the radius of the pipe joint.

[0035] Preferably, the ellipticity data is obtained from measurements taken inside or outside the pipe joint.

[0036] Preferably, the pipe joints are received from a pipe joint manufacturing facility such as a pipe mill. Preferably, the ellipticity inspection is performed while the pipe joints are being manufactured. Preferably, the process of measuring the ellipticity of the pipe joint is carried out at the same rate as the pipe joint is being manufactured. That is, preferably, the process of measuring the ellipticity is kept at the pace of pipe joint manufacturing. Alternatively, pipe joints can be received from a storage facility where pipe joints have been manufactured and are awaiting inspection before being installed in an underwater pipeline.

[0037] Any delay in the process of inspecting pipe joints for use in underwater pipelines increases the backlog of manufactured pipe joints awaiting inspection in quarantine. The problem with the backlog of quarantined pipe joints is that if any one of the quarantined backlogs is found to be non-compliant in any way, the entire backlog must be scrapped or the manufacturing production line must be stopped until all of them are scanned, resulting in considerable cost and delay. Receiving pipe joints directly from the manufacturing facility and / or conducting an ellipticity inspection process while the pipe joints are being manufactured advantageously means that any problems will be identified while the pipe joints are being manufactured or immediately thereafter.

[0038] Preferably, the method further includes a step of determining a new depth to which the pipe joint can be safely used when the ellipticity of the pipe joint exceeds the maximum value of the ellipticity of the pipe joint.

[0039] Preferably, the pipe joints being inspected are coated or uncoated. Pipe joints intended for use in underwater pipelines may include coatings such as concrete (applied to their outer surface) that add weight to them, or corrosion-resistant coatings such as epoxy or polyethylene that can minimize corrosion of the pipe joints. An uncoated pipe joint is one that does not have such a coating. If the pipe joint is coated, elliptic data can be obtained based on internal measurements of the pipe joint based on the uncoated surface.

[0040] Preferably, one or more steps are performed during the manufacture of the pipe joint, for example, an inspection method is performed on the manufactured portion of the pipe joint at the end of the pipe mill.

[0041] A second aspect of the present invention provides a method for manufacturing a pipe joint for use in an underwater pipeline, the method comprising the steps of manufacturing a pipe joint and then performing an inspection method according to the first aspect.

[0042] The preferred and optional features described above in relation to the first aspect of the present invention may also be preferred and optional features related to the second aspect having similar effects. [Brief explanation of the drawing]

[0043] The above and other aspects of the present invention are described herein merely as examples with reference to the accompanying drawings. [Figure 1] An example of a laser-based device rig for measuring the roundness and ellipticity of pipes is shown. [Figure 2] This shows the type of pipe joint for inspection. [Figure 3] Figure 2 shows a cross-section of a test ring cut from the pipe joint shown. [Figure 4]This shows a cross-section of the test apparatus. [Figure 5] Figure 4 shows a cross-section along line AA. [Figure 6] A cross-section of a second embodiment of the test apparatus is shown. [Figure 7] A cross-section of a third embodiment of the test device is shown. [Modes for carrying out the invention]

[0044] Detailed explanation When selecting an underwater pipeline system, all aspects of its design should naturally be considered, including the inner diameter and wall thickness of the pipe joints used in the manufacture of the pipeline. The inner diameter of the pipe joints is calculated to ensure that the fluid flow through the pipeline is sufficient to guarantee the economic success of the pipeline during its operational life. Once the inner diameter is calculated, the target wall thickness of the pipe joints is then calculated, depending on the inner diameter and hydrostatic pressure at the depth to which the pipeline will be used, in order to avoid external pressure collapse as much as possible during pipeline installation.

[0045] Wall thickness can be calculated using standard industrial design guidance. An example of such guidance commonly used for such calculations is the DNGVL design code. In this code, safety from pressure buckling failure during pipeline installation is determined by the use of an approximate theoretical model of the pressure collapse process, along with several theoretically derived factors related to pipe material properties and a general theoretically derived safety factor.

[0046] One theoretically derived factor considered when determining wall thickness is ellipticity, or the geometric property of the pipe joint. The ellipticity of a manufactured pipe joint can vary depending on the equipment used to form it or defects introduced into the pipe during the manufacturing process. Ideally, a pipe joint is perfectly circular with no range of ellipticity (ellipticity = 0.0%), but achieving this in practice is difficult.

[0047] Once pipes are designed using design guidance, non-destructive techniques can be used to test that the pipe joints meet the desired standards. An example of a non-destructive technique is a ring test, where one or more rings are cut from a manufactured pipe joint, and a collapse pressure test is performed on one or more rings to verify that the actual collapse pressure corresponds to the designed collapse pressure. Thus, such non-destructive tests directly guarantee the collapse strength of the actual pipe joint (e.g., a thick-walled pipe joint) intended for installation in a pipeline during its manufacturing process. The methods disclosed herein relate to the development of such non-destructive tests.

[0048] Next, an example of the method according to the present invention will be described.

[0049] The pipe joint to be inspected is supplied to a laser measuring device (hereinafter sometimes referred to as "the device") that uses one or more lasers to evaluate the geometric shape of the pipe. The laser can be configured to acquire pipe radius or diameter data at multiple cross-sections along the length of the pipe joint, thereby topographically mapping the pipe joint.

[0050] The laser may be configured to determine the radius at intervals around the cross-section of the pipe (for example, at intervals of 0.3 degrees) and to repeat this process at frequent intervals along the entire length of the pipe (i.e., 100% of the pipe joint) thereby mapping the pipe joint in a three-dimensional manner.

[0051] The radius measurement interval is not limited to 0.3 degrees, but can be any interval within the range of 0.1 to 10 degrees, or 1, 5, 15, 20, 25, 30, 45, 90 degrees, etc. For example, by performing radius measurements every 0.3 degrees around the cross-section of the pipe, 1200 radius measurements (360 / 0.3) are performed by the device for each cross-section along the length of the pipe joint. It can be done.

[0052] The laser can perform radius measurements at intervals of 5 along the length of the pipe joint, or similarly, it can perform radius measurements at cross-sectional intervals of 10, 100, 1000, 10000, 100000, 1000000, and 10000000 along the entire length of the pipe joint. For example, radius measurements can be performed at intervals of 1000 along the entire length of a 24.4 m (80 foot) pipe joint (i.e., 100% of the pipe), resulting in a total of 1000 radius measurements.

[0053] Once inspected, the pipe joint passes through the device and is withdrawn from it so that another pipe joint can be inspected. The inspection method is performed at the same rate as the received pipe joints are manufactured, thus avoiding the inspection method becoming a bottleneck in the pipe joint manufacturing and inspection process.

[0054] An example of a laser measuring device for use with the method disclosed herein (a laser rig), which includes several lasers and shows a pipe joint section, is shown in Figure 1 as item 100. The pipe joint is shown as item 102. A typical example of the pipe joint is approximately 12.2 m in length, 508 mm in outer diameter, and 35 mm in wall thickness. The device 100 comprises two end ring pieces 108, which are held opposite each other and connected to one another by a plurality of connecting rods 110 between them. The end ring pieces 108 and the connecting rods 110 (some of which are not labeled in Figure 1) define the space of the pipe joint 102 through which the pipe joint 102 passes so as to position the pipe joint 102 perpendicular to the incident laser beam from the laser 104. The connecting rods 110 support the laser 104.

[0055] Device 100 can be provided with any number of lasers. If one laser 104 is provided, device 100 may be configured to rotate around the pipe joint 102 (around the axis indicated by the dashed line in item A) to allow the laser to inspect the pipe joint as needed (i.e., to obtain radius measurements). By providing several lasers 104 facing a single cross-section of the pipe joint 102 (such as the cross-section in item B with the dotted line), the range over which device 100 may need to rotate can be avoided or reduced. Device 100 may also be provided with rollers (not shown) to support and assist the pipe joint as it passes through. The rollers may also be configured within device 100 to position the pipe joint 102 in a fixed location relative to the laser 104.

[0056] The laser rig can be equipped with any number of processors, sensors, motors, etc., to acquire and determine measurement data regarding the roundness and ellipticity of pipe joints passing through it. The laser rig can be equipped with transmitters for sending measurement data to external devices such as remote monitors and / or computer systems.

[0057] During pipe joint inspection, the device measures the maximum and minimum radii (or diameter). The maximum and minimum radii (or diameter) determined by the device are used to determine the roundness and pipe joint ellipticity using known design formulas, which can be found, for example, in the DNVGL design code. The pipe joint ellipticity data obtained from the inspection is used to verify that the ellipticity for all measured sections is less than the maximum ellipticity specified when designing the pipe joint, in which case the pipe joint is considered suitable for use at its planned operating depth. In other words, the obtained ellipticity data is checked to verify that the ellipticity does not exceed a maximum predetermined ellipticity at any point along the length of the pipe joint. For example... For example, if a pipe joint is designed based on a maximum ellipticity of 0.5%, the inspection method must verify that the ellipticity of the joint does not exceed 0.5%. Similarly, if a pipe joint is designed based on a maximum ellipticity of 0.4%, the inspection method must verify that the ellipticity of the joint does not exceed 0.4%, and so on.

[0058] The effect of a pipe joint exceeding a specified maximum ellipticity value does not automatically mean that the pipe should be rejected for use in an underwater pipeline, as it may be used at shallower water levels along the pipeline route. An appropriate shallower operating depth can be determined using a design formula based on the maximum ellipticity data discovered through inspection.

[0059] After measuring the ellipticity and confirming that it does not exceed the specified maximum ellipticity, the hydrostatic collapse pressure of the pipe joint is determined to confirm that the manufactured pipe joint is suitable for its intended use. One method for determining the hydrostatic collapse pressure is to test a ring test piece (hereinafter referred to as "test ring") cut from the received pipe joint.

[0060] The ring test uses a testing method based on cutting rings from pipe joints and processing them to a uniform length. This is explained in more detail below. The pipe joints from which each test ring has been cut can still be used as production pipe joints and are therefore not wasted.

[0061] The ring test provides accurate data on the characteristics of the test ring, specifically the hydrostatic collapse pressure of the test ring, which can be extrapolated to correspond to the characteristics of the pipe joint from which the test ring was cut. Since uniform characteristics such as ellipticity cannot be guaranteed along the entire pipe joint, the analysis of the hydrostatic collapse pressure data from the ring test is combined with the ellipticity data obtained from ellipticity measurements to confirm that the hydrostatic collapse pressure data can be considered to correspond to that of the pipe joint from which the test ring was cut.

[0062] Here, a ring test method disclosed herein will be described.

[0063] A ring is cut from a pipe joint and machined. The test ring is placed on a rigid frame that seals the machined surface of the test ring, allowing pressure to be applied only to the outer circular surface of the test ring. The inner circular surface of the test ring is maintained by ambient pressure and is therefore suitable for mounting a device to measure the strain and deformation caused by pressure on the outer circular surface of the test ring.

[0064] The seals on both machined flat surfaces of the test ring are designed to prevent deformation of the rounded surface of the test ring during the pressure collapse test. During the test, the pressure on the seals on the flat surfaces of the ring is confined to only the outer rounded surface of the test ring and only to a small area of ​​the flatly machined surface. The seals are designed so that the test ring is not subjected to substantial forces parallel to the machined flat surface, thus preventing deformation of the rounded surface of the test ring.

[0065] Pressure is applied from an external pump, and the pressure is increased or decreased by adding or removing a specific volume of fluid into or from the space surrounding the outer circular surface of the test ring. This configuration allows for controlled increases or decreases in the radial deformation of the test ring caused by pressure on the outer cylindrical surface.

[0066] The sealing action on the machined flat surface of the test ring is achieved by housing the test ring within a rigid block shaped to ensure no deformation of the seal. This is possible. An alternative arrangement is to make the space in which the seal operates adjustable and controllable by the action of a piston that receives the same (or different) pressure as the pressure applied to the outer cylindrical surface of the test ring.

[0067] A typical test includes the following steps: i) cutting a test ring from a pipe and machining the end flat and parallel to a specified tolerance; ii) attaching an attachment and measuring the strain and deformation of the test ring; iii) fitting the test ring into a frame having a seal in place; vi) applying pressure to ensure the seal is activated and effective; v) increasing the pressure and recording the strain and deformation measurements; and vi) continuing to increase the pressure until the maximum value is reached, i.e., until external pressure collapse occurs.

[0068] Furthermore, independently of any leakage of hydraulic fluid through the seal, it is useful to plot the pressure curve against the maximum strain measured to detect the onset of the acceleration of the nonlinear decrease in the ring diameter with increasing pressure.

[0069] Figure 2 shows a pipe joint 10 used in an underwater pipeline. A test ring 12 (also shown in Figure 3) is cut from one end of the pipe and has a length of 70 mm, which is approximately twice the wall thickness. Even after this length of test ring 12 has been cut off, the pipe joint 10 can still be used in the construction of the pipeline. The end face 14 of the test ring 12 is machined to be substantially parallel and flat. Being substantially parallel and flat means that there is a tolerance of ±0.01 mm along the entire length of the test ring 12.

[0070] Figures 4 and 5 show an embodiment of a test apparatus for use in the above test method, with a test ring 12 installed for testing. The test ring 12 is mounted between the upper section 16 and the lower section 18, which together define the pressure test chamber. Positioning spigots 19 are provided in the two sections of the pressure test chamber 16, 18, which are positioned in corresponding positioning holes with the associated seal 21, enabling two-half positioning. O-ring or pressure-energized pressure seal The containing seals 20 are provided at the top and bottom. These are engaged by the test ring 12 and form an annular section accessible by supplying pressurized hydraulic test fluid through a suitable inlet port 24. The central void 26 inside the test ring 12 is vented to the atmosphere through a bleed hole 28 with a diameter large enough to also provide access by any instrumentation cable to strain gauges (not shown) on the inner cylindrical surface of the test ring 12.

[0071] The two halves 16 and 18 are held together by a mechanical seal screw 30. The screw 30 extends through a hole 32 in the upper part 16, passes through the void 26, and engages with a screw hole 34 in the lower part 18. Although two screws 30 are shown, using the appropriate number can ensure proper clamping.

[0072] The force holding the two sections 16 and 18 together is sufficient to pressurize the annular portion 22 internally and externally against the pressure-retaining seals 20 and 21. The tolerance to which the test ring 12 is cut from the pipe is such that leakage from the annular portion 22 to the void 26 occurs, while avoiding excessive restraining friction against the inward radial movement of the outer diameter of the test ring 12 under hydraulic pressure.

[0073] Figure 6 shows a second embodiment of the test apparatus, and the cluster shown in Figures 4 and 5 The clamping screw has been replaced with a hydraulic piston arrangement. A cylinder 36 is formed in the lower section 18 in which a piston 38 is slidably positioned. The outer end of the cylinder is closed by a plate 40. A bore 42 with a sliding seal extends from the inner end of the cylinder 36 to a void 26. A connecting rod 44 extends from the piston 38 through the bore 42 to a positioning bore 46 in the upper section 16, where it is fixed to a piston ring clamp 48. An inlet port 50 is provided at the lower end of the cylinder 36, into which pressurized fluid can be introduced, driving the piston 38 along the cylinder 36 to clamp the upper section 16 to the lower section 18.

[0074] Figure 7 shows a further embodiment of the test apparatus for use in the above test method, with a test ring 12 positioned in a predetermined location for testing. The test ring is mounted between an upper cylindrical section 16 and a lower cylindrical section 18, with a spacer ring section 52 positioned between them, and together these sections define a pressure test chamber. The apparatus is provided with an inlet port 24 for supplying pressurized fluid to the pressure chamber.

[0075] The upper and lower sections are ring-shaped and have a central opening 26. This central opening provides access to the center of the test apparatus and the inner surface of the test ring for mounting sensors and other devices for performing pressure collapse tests. The opposing surfaces of the upper and lower sections have steps that form shoulders 54 extending circumferentially around the lower and upper edges of the upper 16 and lower 18 sections, respectively. This provides a projecting annular step 56 between the shoulders and the openings of each section. The shoulders 54 of each section provide a support surface for positioning a spacer ring 52 between them. Each annular step 56 of the upper and lower sections provides a support surface for mounting the test ring 12. The outer diameter of the annular step is approximately equal to the inner diameter of the spacer ring 52. The spacer ring 52 helps to adjust the distance between the two surfaces of the upper and lower sections. The inner diameter of the spacer ring 52 is smaller than the outer diameter of the upper 16 and lower 18 sections, but larger than the diameter of their respective openings. The outer diameter of the spacer ring 52 is larger than the outer diameters of the upper 16 and lower 18 sections.

[0076] A circumferential groove for holding the sealing means 20 is provided on the opposing surfaces of the upper 16 and lower 18. Further sealing means 58 is provided in the circumferential groove on the side surface of the annular step 56 between the spacer ring 52 and the side surface of the annular step 56 of the upper 16 and lower 18 sections.

[0077] The upper and lower sections are held together by mechanical sealing means, such as screws (not shown), which extend through holes 32 around the outer edge of the upper section 16 and through the spacer ring 20 and engage with holes 32 in the lower section 18. Additional fastening means may extend through holes in the upper annular step 56 and engage with holes in the lower annular step 56. Any number of fastening means may be used to ensure proper fastening of the sections.

[0078] In another preferred configuration with a larger pipe diameter without a corresponding increase in wall thickness, the buckling deformation of the test ring within the rig becomes large enough for the ring to move out from under the O-ring seal, allowing for a sudden and undesirable pressure loss from the ring. In such cases, a modified rig configuration would be employed in which the sealing O-ring is positioned in a groove of the sample ring and slides between two rings on a highly polished plate surface.

[0079] Using the method of the present invention to inspect pipelines and applying current design guidance (such as the DNGVL design code), safety assurance is improved, and the pipelines can be used in waters 30% deeper than a given wall thickness, or with a wall thickness 12% thinner than a given operating depth. It was found that it would be possible to design the input.

[0080] The method according to the present invention represents a remarkable departure from conventional methods for designing and inspecting pipe joints, which were established decades ago and continue to be used today. The method offers considerable commercial advantages in the availability of submarine pipelines, as well as in the manufacture and installation of pipe joints for use in pipelines. Those skilled in the art will understand that the method disclosed herein is taught as an example and not an limitation. Accordingly, matters included in the above description or shown in the accompanying drawings should be construed as illustrative and not as limiting. The following claims are intended to encompass all general and specific features described herein, as well as all statements regarding the scope of the method and device, which, as a matter of language, may be said to fall between them.

Claims

1. A method for inspecting pipe joints for use in underwater pipelines, The process of receiving the pipe joint, A step of measuring the ellipticity of the pipe joint and obtaining ellipticity data, A step of determining that the ellipticity data does not exceed a predetermined maximum pipe joint ellipticity of 0.5% or less, A step of performing an external pressure collapse test on a ring cut from one end of the received pipe joint and obtaining data representing the hydrostatic collapse pressure of the pipe joint for use in confirming that the pipe joint is suitable for its intended use, The received pipe joint has an inner diameter and wall thickness based on the required fluid flow through the pipeline and the hydrostatic pressure corresponding to the depth to which the pipe joint is safely used. A method comprising the step of determining a new depth to which the pipe joint can be safely used if the ellipticity of the pipe joint exceeds the maximum pipe joint ellipticity.

2. The method according to claim 1, further comprising the step of applying or adding a safety factor to the depth to which the pipe joint is used.

3. The method according to claim 2, wherein the safety factor is a coefficient.

4. The method according to claim 2, wherein the safety factor is 1.0 to 1.

2.

5. The aforementioned external pressure collapse test is, The process of cutting a ring from one end of the received pipe joint, A step of forming a flat, substantially parallel surface on the end of the ring, The step of providing means for measuring the strain and deformation of the ring, The steps include: installing the ring inside the pressure chamber such that the end of the ring forms a seal with the opposing wall of the chamber, and isolating the inside of the ring from the outside; A step of increasing the pressure on the outside of the ring and measuring the strain and deformation of the ring while increasing the pressure, The method according to any one of claims 1 to 4, comprising the step of determining a comparison between the pressure applied to the outside of the ring and the maximum strain, and detecting the start of acceleration of nonlinear decrease in the ring diameter with increasing pressure.

6. The method according to claim 5, wherein the steps of cutting off a ring from one end and performing an external pressure collapse test are performed before measuring the ellipticity, after measuring the ellipticity, or simultaneously with measuring the ellipticity.

7. The method according to any one of claims 1 to 6, wherein the ellipticity of the pipe joint is inspected to be greater than 10%, 50%, or 90%.

8. The method according to any one of claims 1 to 6, wherein the ellipticity along the entire length of the pipe joint is inspected.

9. The method according to any one of claims 1 to 8, wherein measuring the ellipticity includes measuring the roundness of the pipe joint and obtaining roundness data, and determining the ellipticity of the pipe joint using the roundness data.

10. The method according to claim 9, wherein the roundness is determined by measuring the radius around the cross-section at intervals of 0.1° to 4°.

11. The method according to claim 9, wherein the roundness is determined by measuring the radius around the cross section at intervals of 0.3°.

12. The method according to any one of claims 1 to 11, wherein the ellipticity of the pipe joint is measured by one or more lasers.

13. The method according to any one of claims 1 to 12, wherein the step of measuring the ellipticity of the pipe joint includes the step of topographically mapping at least a portion of the pipe joint.

14. The method according to any one of claims 1 to 13, wherein the ellipticity data is obtained from measurements taken from inside or outside the pipe joint.

15. The pipe joint is received from a pipe joint manufacturing facility such as a pipe mill, according to the method according to any one of claims 1 to 14.

16. The method according to any one of claims 1 to 15, wherein the pipe joint to be inspected is a coated or uncoated pipe joint.

17. The method according to any one of claims 1 to 16, wherein any of the steps described above are performed while the pipe joint is being manufactured, or are performed at the end in the pipe mill.

18. The method according to any one of claims 1 to 17, wherein the pipe joint to be received is a thick-walled pipe joint.

19. A method for manufacturing pipe joints for use in underwater pipelines, (a) A process for manufacturing a pipe joint, and (b) A method comprising the step of inspecting the pipe joint using the method according to any one of claims 1 to 18.

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