A gripping mechanism for an isolation plug within a pipeline

Abstract

The invention relates to an isolation plug within a polymer lined pipeline, a thermoplastic composite pipeline or a reinforced thermoplastic pipeline, gripping mechanism comprising: a plurality of grips integrated into an umbilical controlled or autonomous isolation plug. Each of said grips is configured to include multiple dome-shaped protuberances which extend from the surface of the grip, and which are operable to engage with and slide along an inner surface of a pipeline, to facilitate engagement with a pipeline wall. The grips are adapted to provide a secure locking mechanism for the isolation plug. In this invention, the grips are ideally characterized by a 17.5-degree ramp angle selected from a range of 25 to 10 degrees, to enable an effective wedge to be facilitated with the pipeline wall.

Description

[0001] A GRIPPING MECHANISM FOR AN ISOLATION PLUG WITHIN A PIPELINE

[0002] The present invention relates to improvements in and relating to an isolation plug. More particularly, it relates to a gripping mechanism for an isolation plug within a polymer lined pipeline, as herein defined.

[0003] Background to the Invention

[0004] An isolation plug in a pipeline is a mechanical device used to temporarily block or isolate a specific section of a pressurised pipeline. Such tools are crucial for maintenance, repairs, modifications or testing within pressurised pipeline systems. Isolation plugs are designed to create a barrier that prevents the flow of pressurised fluids or gases, allowing work to be performed on the isolated segment without depressurising the entire pipeline.

[0005] It is known in the industry, that an isolation plug typically consists of a plug mechanism, often equipped with sealing elements like packers or seals, that can be inserted into the pipeline. The use of autonomous isolation plugs is common in industries such as oil and gas, water treatment, and petrochemicals, where maintaining or modifying specific sections of the pipeline without shutting down the entire system is essential for operational efficiency. These autonomous isolation plugs may have features such as grips or wedges to securely lock them in place and ensure an effective seal.

[0006] It is to be appreciated that an autonomous isolation plug grip or gripping mechanism refers to a component of an isolation plug used in pipelines. The grip is a specialized element designed to contact and engage the pipeline wall, providing a locking mechanism for the isolation plug. Its primary function is to secure the plug in a position, within the pipeline, and prevent movement or dislodgement during various operations.

[0007] It is known in the art, that isolation plug grips often have specific features such as a ramp angle, teeth, and coatings for enhanced functionality. The ramp angle allows the grip to wedge between the pipeline wall and the plug, providing a secure lock. Conventionally, teeth on the grip, usually coated with materials like Ti-nitride for hardness retention, contribute to the grip's ability to engage with the pipeline surface effectively.

[0008] These grips are pivotal for maintaining the integrity of the isolation plug, especially during activities like maintenance, repairs, modifications, or testing within a pipeline. The design and materials of the grip are generally optimized to withstand the conditions and pressures present in the pipeline environment and to provide a reliable and secure isolation when needed.

[0009] In one known invention, a gripping mechanism is provided which is designed to engage the pipeline wall, to provide a secure locking grip for the plug. With a specific 17.5-degree ramp angle, these grips wedge between the bowl and the pipeline wall, effectively locking the plug in its place. Within this invention, each isolation plug is typically equipped with eight grips featuring consecutive ribs or teeth coated with Ti-nitride for hardness retention. Each grip includes a number of ribbed teeth which are machined from a solid billet of Grade 5 Titanium 6AI-4V.

[0010] It will be appreciated by those in the industry that the use of internal protective linings in host pipelines is becoming a common occurrence. These protective linings are often used to mitigate the effects of corrosion. The reason is that pipelines, particularly within the oil and gas industry, often contain corrosive elements that can degrade the material of the pipeline over time. Internal linings provide a protective barrier, preventing direct contact between the corrosive fluids and the pipe material. These linings become especially important for maintaining the integrity and longevity of the pipeline infrastructure. For example, in hydrocarbon transport water injection, gas lift, chemical injection, methanol injection and renewable applications such as hydrogen and CO2 transfer polymer liners are installed inside host pipelines making them more resistant to the corrosive properties of the product being transported. A typical example of such a liner would be a PE100 or similar polymer material swaged into the carbon steel carrier pipe.

[0011] It is to be appreciated that although the use of internal linings is becoming a mainstream addition to a conventional pipeline, the gripping mechanisms which are currently available on the market are not designed to cater for this addition. In particular, the grips used in isolation plugs, such as the grip described with reference to the invention mentioned earlier, often bite into and damage the structural integrity of these protective internal linings, when setting. This, in turn, damages the pipeline’s polymer liner.

[0012] There is a need in the industry for a gripping mechanism that doesn’t compromise the internal lining of the pipeline and yet provides as secure a locking of the isolation plug as can be achieved with existing teethed grip technologies in non-polymer or swage lined pipelines. It is a therefore an object of the present invention to provide a gripping mechanism which overcomes the drawbacks of existing solutions, addresses some of the issues and deficiencies described above, and provides a suitable alternative.

[0013] Summary of the Invention

[0014] The present invention addresses the problem of damage being caused to the internal polymer lining of a pipeline when a conventional grip is used to secure an isolation plug into position. More particularly, the sharp grip teeth currently used to facilitate effective engagement of the grip-within the surface of the pipeline which it sets in or bites into, and causes damage to, the internal polymer lining of the pipeline. The present invention also addresses the problem of ensuring that an effective engagement of the grip within the pipeline is maintained, whilst addressing the deficiency described above.

[0015] This problem is solved by replacing the teeth used in existing grips with semi-circular or domeshaped protuberances, which could be known as dimples.

[0016] Within the context of materials science, Hooke's Law asserts that the deformation of a material is directly proportional to the applied force, within the material's elastic limit. In the case of the present invention, the semi-circular or dome-shaped protuberances act as compliant elements that undergo deformation under the applied load, as dictated by Hooke's Law. These protuberances provide a means to secure the grip onto the pipeline without resorting to sharp teeth that could potentially damage the internal polymer lining. The design allows for controlled deformation, ensuring effective engagement without exceeding the elastic limit of the material.

[0017] Additionally, the application of Saint-Venant's Principle is noteworthy in the analysis of the stress distribution along the surface of the pipeline. Saint-Venant's Principle suggests that the details of the load application become less significant at a sufficient distance from the applied load. In the context of the present invention, the distribution of stresses on the pipeline's surface, induced by the semi-circular or dome-shaped protuberances, is more uniform and mitigates the risk of localized damage compared to conventional toothed grips. This ensures that the gripping force is applied in a manner that minimizes stress concentration and potential harm to the protective lining.

[0018] In the context of the present invention, the application of Hoop and von Mises stress is integral to understanding the mechanical behaviour and stress distribution in the polymer lined pipeline.

[0019] Hoop stress refers to the circumferential stress in a cylindrical structure, such as a pipeline, caused by internal or external pressure. In the case of the isolation plug with dome-shaped protuberances, the Hoop stress becomes crucial in evaluating how the gripping mechanism handles pressure within the pipeline. The semi-circular or dome-shaped protuberances, acting as compliant elements, distribute the Hoop stress more uniformly along the inner surface of the polymer lining. This ensures that the pressure exerted by the gripping mechanism is distributed evenly, reducing the risk of localized stress concentrations that could potentially damage the polymer lining. Therefore, the application of Hoop stress aligns with the design goal of the invention, which is to prevent damage to the internal polymer lining during engagement.

[0020] Von Mises stress, on the other hand, is a measure of the combined effect of normal and shear stresses in a material. It is particularly useful in predicting yielding of materials under various loads. In the context of the present invention, the von Mises stress analysis becomes relevant in assessing the overall stress state induced by the gripping mechanism with dome-shaped protuberances. The compliant nature of the protuberances allows controlled deformation, and the von Mises stress helps ensure that the material remains within its elastic limit during this deformation. This is crucial for maintaining the structural integrity of the gripping mechanism and preventing permanent deformation or failure. The design choice of dome-shaped protuberances, guided by Hooke's Law and von Mises stress considerations, contributes to a gripping mechanism that engages effectively without causing harm to the polymer lining.

[0021] Advantageously, the invention not only leverages Hooke's Law to facilitate controlled deformation for effective grip engagement but also aligns with Saint-Venant's Principle by promoting a more even distribution of stresses on the pipeline surface, thus addressing the issues associated with damage to the internal polymer lining caused by conventional teethed grips. The application of Hoop stress, von Mises stress, Hooke's Law, and Saint-Venant's Principle collectively contributes to a gripping mechanism that ensures controlled deformation, even stress distribution, and effective engagement without causing harm to the polymer lining of the pipeline.

[0022] The present invention provides an isolation plug for use within a polymer lined pipeline, a thermoplastic composite pipeline or a reinforced thermoplastic pipeline, the isolation plug including a gripping mechanism which is operable to provide a rigid grip between the isolation plug and an inner surface or wall of the pipeline, said gripping mechanism comprising: a plurality of grips integrally located about the isolation plug; wherein each of said grips is configured to include multiple dome-shaped protuberances which extend from the surface of the grip, and which are operable to engage with and slide along the inner surface of the pipeline, to facilitate engagement with the pipeline wall, said grips being further adapted to provide a secure lock for the isolation plug within the pipeline without damage to the inner surface or wall of the pipeline.

[0023] In an embodiment of the invention, each of the plurality of grips are characterized by a ramp angle within the range 25 degrees to 10 degrees, preferably within the range 22.5 degrees to 12.5 degrees and most preferably of 17.5 degrees or less. In a preferred embodiment, the grips are characterized by a 17.5-degree ramp angle, to enable an effective wedge to be facilitated with the pipeline wall.

[0024] Additionally, or alternatively, each of the grips contain rows of dome-shaped protuberances. In this embodiment, each of the rows contain multiple symmetrically spaced dome-shaped protuberances. In a preferred embodiment, each dome-shaped protuberance is scalable and of a calculated diameter, which is sized to match and mirror the internal diameter of the polymer lined pipeline, which is being isolated, and the length of the grip is calculated to minimise the Von Mises and Hoop stress on the pipeline at that location.

[0025] In a particularly preferred embodiment, each grip can be manufactured from 3D printed material with dome-shaped protuberances.

[0026] The gripping mechanism as described above, wherein the one or more grip segments are operable to be connected to an actuator flange of the isolation plug. In a preferred embodiment, the gripping mechanism is connected to the actuator flange by one more socket headed shoulder bolts. In this embodiment, one or more double washers are located on the shoulder bolts, and are operable to engage a back end of the actuator flange, to provide a torospherical-sliding washer effect.

[0027] In this embodiment, in the gripping mechanism the grips' back face is ramped at 10 degrees, to allow the grip segments to ascend a matching 10-degree face of the actuator flange. In an embodiment, each grip contains an edge trim operable to facilitate folding of the grip segments against one or more anti-rotation rods within the isolation plug.

[0028] In a preferred embodiment, the grips, when nested, are dimensioned to enable the isolation plug to traverse through the 3-dimensional or 5-dimensional pipeline geometry. In this preferred embodiment, the grips are optimally sized to prevent displacement from their locking position, in use.

[0029] Advantageously, the gripping mechanism described herein is designed to resist displacement. In this regard, the grips are configured to withstand forces preventing them from being pushed from a locking position.

[0030] Advantageously, the dimpled grips are 3D printed from Ti 6AI 4V using a DMLS (Direct Metal Laser Sintering) process or similar or. In an embodiment, depending on pipeline size, the dimpled grips may be precision-machined from a solid billet of Grade 5 Titanium 6AI-4V alloy or similar suitable material. The invention is set out in the claims.

[0031] The skilled person will understand that where the same feature has been referenced in different aspects of the invention, this feature comprises the same parts and operates in the same way unless otherwise stated.

[0032] Brief Description of the drawings

[0033] Certain preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

[0034] Figure 1a is a sectional side view of a grip in accordance with embodiments of the invention;

[0035] Figure 1b is a sectional frontal view of a grip in accordance with embodiments of the invention;

[0036] Figure 1c is a perspective view of a grip in accordance with embodiments of the invention;

[0037] Figure 1d is a top view of a grip in accordance with embodiments of the invention; and Figure 2 is a side sectional view of the pipeline plug in an unset configuration within a pipeline, showing a grip similar to Figure 1 , in accordance with embodiments of the invention; and

[0038] Figure 3 a side sectional view of the pipeline plug in a set configuration within a pipeline showing a grip similar to Figure 1 , in accordance with embodiments of the invention

[0039] Detailed

[0040] In overview, a gripping mechanism for an isolation plug within a pipeline is provided, the gripping means comprising multiple dome-shaped protuberances.

[0041] Various embodiments of the present invention will be described in detail with reference to the drawings, where like reference numerals represent like parts and assemblies throughout the several views.

[0042] It will be appreciated that the invention should not be construed to be limited to the examples, which are now described; rather, the invention is construed to include all applications provided herein and all equivalent variations within the skill of the ordinary artisan.

[0043] Referring to the drawings, in Figure 1 , there is shown various angles of a grip for use in an isolation plug.

[0044] Referring to the drawings, in Figure 1a, there is shown a sectional side view of a grip, in accordance with embodiments of the invention, generally referred to herein by reference numeral 100.

[0045] The grip 100 includes multiple dome-shaped protuberances 102 extending from an upper, outer surface of the grip 100. In a preferred embodiment, each of the protuberances 102 is 6.36 millimetres in diameter. The size of the grip is scalable. The length of this particular grip is 76.21 millimetres in total, to keep the Von Mises stresses for its associated 6-inch pipeline below the required level of SMYS (Specified Minimum Yield Strength).

[0046] Referring to the drawings, in Figure 1 b, there is shown sectional frontal view of a grip in accordance with embodiments of the invention, generally referred to herein by reference numeral 100.

[0047] The grip 100 is dimensioned to enable the isolation plug to traverse through the particular pipeline geometry.

[0048] The grip 100, when nested, is sized appropriately to facilitate the passage of the isolation plug through a pipeline geometry. Importantly, the grip 100 is dimensioned to resist displacement from its locked position.

[0049] Referring to the drawings, in Figure 1c, there is shown perspective view of a grip in accordance with embodiments of the invention, generally referred to herein by reference numeral 100.

[0050] The back face 106 of the grip 100 is ramped at a 10-degree angle, enabling the grip segments to smoothly ascend the corresponding 10-degree face of an actuator flange, in use.

[0051] To enhance functionality and facilitate controlled movement, the grip 100 is trimmed at its edge 108 to allow folding against anti-rotation rods.

[0052] Referring to the drawings, in Figure 1 d, there is shown top view of a grip in accordance with embodiments of the invention, generally referred to herein by reference numeral 100.

[0053] On the grip 100, the dimples 112 are 3D printed in Ti 6AI 4V using the DMLS (Direct Metal Laser Sintering) process or similar or precision-machined from a solid billet of Grade 5 Titanium 6AI-4V or other suitable similar material.

[0054] In terms of complexity, the shape of the dimples 112 are challenging to machine using the subtractive process (standard machining) and is more efficiently produced through the 3D printing process, especially for small-sized pipelines. However, for larger pipelines, typically exceeding 12 inches, the 3D printing process becomes less cost-effective. In such cases, it is more practical to procure a large forging or casting and subsequently machine the dimples 112 onto the outer surface of the grip 100.

[0055] Referring to the drawings, in Figure 2, there is shown a side sectional view of the pipeline plug in an unset configuration within a pipeline, showing the grip of Figure 1, generally referred to herein by reference numeral 200. The preferred embodiment of the plug of the present invention is shown in Figure 2, in the operational sequence of the isolator plug within a pipeline, specifically during the setting cycle.

[0056] Within Figure 2, a single module of a two module (double block and monitor) autonomous isolation plug is shown. As can be seen in Figure 2, the carbon steel carrier pipe 202 contains the polymer liner 204. The autonomous isolation plug 200 travels through the pipeline interior using octagonally located, sprung loaded wheel sets 206. Grip and packer activation is enabled by a hydraulic system driving a piston connected to an actuator flange 208. The actuator flange 208 combines with the grips 210, bowl 212, packer 214, and pressure head 218 to set the isolation plug utilising hydraulic pressure within the hydraulic cylinder system 220. In use, the sealing means of the plug 200 includes the gripping means 210 and a packing means 214 which encircle the body of the pressure head 218. The gripping means 210 and packing means 214 are designed depending on the internal diameter and wall thickness of the pipeline to be isolated and on the material strength of the pipeline which is being isolated. Thus, different sized isolation tools are required for different sized pipelines. The outside shell of the grips 210 must match exactly the internal diameter of the polymer lined pipeline.

[0057] Ramp means (also known as a bowl) 212 encircle the pressure head 218 in between the gripping means 210 and packing means 214. The bowl 212 is shaped such that an angle is formed between the circumferential edge of the bowl 212 and the internal circumferential edge of the grips 210. It is noted that in this embodiment of the invention, the bowl 212 is not fixed to the body of the pressure head 218. The bowl 212 of the invention is of a predetermined size. In this embodiment of the invention, the bowl 212 can move freely along the body of the pressure head 218.

[0058] Once the isolation plug 200, is at the desired location, the gripping means 210 and packing means 214 are brought into engagement with the internal polymer lined pipeline wall 204 to isolate a section of the polymer lined pipeline 204.

[0059] There are typically eight grips 210 on each isolation plug 200.

[0060] During the piston hydraulic setting cycle, the grips 210 experience loads from the actuation flange 208 which forces them up the bowl 212 and outwards. The grips 210 engage with the pipeline wall 204, ascending along the cone of the bowl 212 as they are subjected to forces from the actuator flange 208. This upward and outward movement of the grips 210 allows the dome-shaped protuberances on the grips to engage with, and securely grip to, the pipeline wall 204. The grips 210 then engage and hold against the pipeline wall 204 while the piston within the hydraulic cylinder 220 continues to exert hydraulic force to pull the pressure head 218 and actuator flange 208 together to exert a squeeze on the packer 214, to bed into the pipeline wall 204 and generate a seal.

[0061] The back face of the grips 210 are ramped at a 10-degree angle, enabling the grips 210 to smoothly ascend the corresponding 10-degree face of the actuator flange 208. Importantly, the grips 210 are dimensioned to resist displacement from their locked position, even under the influence of the packer 214 which contains garter springs 216 sized larger than the extrusion gap between the bowl 212 and the pipeline 204, and the pressure head 218 and the pipeline 204, to prevent unwanted extrusion.

[0062] Tests have indicated that the dimpled grips 210 can withstand high loads of hydraulic pressure within the current configuration.

[0063] Once the autonomous isolation plug 200 is set, the downstream delta pressure within the pipeline is allowed to come onto the pressure head 218, which enables an intensified delta set of the autonomous isolation plug 200. Tests have indicated that the dimpled grips 210 can also withstand high loads of downstream delta pressure within the current configuration.

[0064] Neither hydraulic set or delta set cause cutting or shredding damage to the polymer lined pipeline wall 204. Once the downstream delta comes onto the plug 200, the load is so great that any hydraulic action becomes redundant. Hydraulic action (e.g., facilitated by the internal hydraulic cylinder 220) can only be enabled again when the isolation plugs 200, with grips 210, are balanced. In other words, when the upstream pressure is equal to the downstream pressure (i.e. , when the downstream delta is removed).

[0065] Referring to the drawings, in Figure 3, there is shown a side sectional view of the pipeline plug in a set configuration within a pipeline showing a grip similar to Figure 1 , generally referred to herein by reference numeral 300.

[0066] Within Figure 3, an autonomous multi-set pipeline isolation plug with a single module is showcased, which features a hydraulic system as set out with reference to US Patent No. 9400001. The isolation plug 300 including the hydraulic system, is tailored for the setting and unsetting of isolation plugs within a pipeline and includes, amongst other components, a carbon steel carrier pipe 302, a polymer inner liner pipe 304, a sprung loaded wheel set 306, an actuator flange 308, a dimpled grip 310, a bowl 312, a packer 314, a garter spring 316, a pressure head 318 and a hydraulic cylinder with a piston 320.

[0067] During use of the autonomous isolation plug 300, the sealing packer 314 and holding grips 310 ensure a secure and effective setting and unsetting of the isolation plug 300 within the pipeline 302, 304, enhancing the system's reliability and operational versatility by providing an improved grip mechanism for seamless engagement with the polymer lined inner pipe 304 within the carbon steel carrier pipe 302.

[0068] Non-metallic pipe solutions such as TCP (Thermoplastic Composite Pipe) consisting of an inner liner, thermoplastic composite reinforcement layers and a protective outer coating may also be isolated at high pressure, without causing damage or cuts to the internal wall of the TCP when this design of grip is used within an autonomous isolation plug. This includes shallow water RTP (Reinforced Thermoplastic Pipes) up to 70 bar and deepwater TCP (Thermoplastic Composite Pipes) which are capable of high pressures of up to 600 bar. It will be appreciated that any reference herein to polymer lined pipeline also includes TCP or RTP pipelines.

[0069] It is to be understood that the invention is not limited to the specific details described herein which are given by way of example only and that various modifications and additions are possible without departing from the scope of the invention as defined in the appended claims.

Claims

CLAIMS:

1. An autonomous or umbilical controlled isolation plug for use within a polymer lined pipeline a thermoplastic composite pipeline or a reinforced thermoplastic pipeline, the isolation plug including a gripping mechanism which is operable to provide a rigid grip between the isolation plug and an inner surface or wall of the pipeline, said gripping mechanism comprising: a plurality of grips integrally located about the isolation plug; wherein each of said grips is configured to include multiple dome-shaped protuberances which extend from the surface of the grip, and which are operable to engage with and slide along the inner surface of the pipeline, to facilitate engagement with the pipeline wall, said grips being further adapted to provide a secure lock for the isolation plug within the pipeline without damaging the inner surface or wall of the pipeline.

2. An isolation plug, as claimed in claim 1 , wherein each of the plurality of grips are characterized by a ramp angle within the range 25 degrees to 10 degrees, preferably within the range 22.5 degrees to 12.5 degrees and most preferably of between 17.5 degrees or less.

3. An isolation plug, as claimed in claim 2, wherein the grips are characterized by a 17.5-degree ramp angle, to enable an effective wedge to be facilitated with the pipeline wall.

4. An isolation plug, as claimed in any of the preceding claims, wherein each of the grips contain scalable rows of dome-shaped protuberances.

5. An isolation plug, as claimed in claim 4, wherein each of the rows contain a calculated number of dome-shaped protuberances, sized to maintain Von Mises stresses on the pipeline wall below the allowable level of SMYS (Specified Minimum Yield Stress) for that location.

6. An isolation plug, as claimed in any of the preceding claims, wherein each domeshaped protuberance is diameter is scalable to suit that polymer lined pipeline size(internal diameter).

7. An isolation plug, as claimed in any of the preceding claims, wherein the one or more grip segments are operable to be connected to an actuator flange of the isolation plug.

8. An isolation plug, as claimed in claim 8, wherein the gripping mechanism is connected to the actuator flange by one more socket headed shoulder bolts.

9. An isolation plug, as claimed in claim 8, wherein one or more double washers are located on the shoulder bolts and are operable to engage a back end of the actuator flange, to provide a torospherical-sliding washer effect.

10. An isolation plug, as claimed in any of the preceding claims, wherein in the gripping mechanism the rear face of each grip is ramped at 10 degrees, to allow the grip segments to ascend a matching 10-degree face of the actuator flange.

11. An isolation plug, as claimed in any of the preceding claims, wherein each grip contains an edge trim operable to facilitate folding of the grip segments against one or more anti-rotation rods within the isolation plug.

12. An isolation plug, as claimed in any of the preceding claims, wherein the grips, when nested, are dimensioned to enable the isolation plug to traverse through the pipeline geometry.

13. An isolation plug, as claimed in any of the preceding claims, wherein the grips are 3D printed from Ti 6AI 4V using the DMLS (Direct Metal Laser Sintering) process or similar or precision-machined from a solid billet of Grade 5 Titanium 6AI-4V alloy or similar suitable material

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