Compliant component for support of bend enhancer

Abstract

A compliant component for supporting curvature stiffeners. The present invention comprises a structure with the same external geometry as a generic hook, but with a topology (internal structure) that allows for a greater distribution of deformation energy to all elements of the part, with load transfer to other less stressed regions. When the present invention is subjected to a load, said flexible parts deform in a pre-specified manner, transferring part of a load that would be excessive in a given region to another less loaded region, without any external power or interference. In this way, the deformation pattern that occurs in the present invention relieves stresses where they are highest and at the same time provides flexibility (compliance), more adequately distributing the coupling loads between the various fastening components.

Description

1 / 16 Compliant component for supporting curvature stiffeners. Technical field:

[001] The present invention falls within the field of technologies related to oil exploration. More specifically, it relates to a device for attaching the head of Bend Stiffeners to Bellmouths to withstand the bending and shear loads of risers and umbilicals. Fundamentals of the technique:

[002] DOGs are crucial components that integrate the support system of Bend Stiffeners and Bellmouths to support bending and shear loads, acting as hooks to support the stiffener helmet, as can be seen in Figure 1.

[003] This type of support is widely used in ultra-deepwater oil extraction. During the support of the Bend Stiffener, the DOGs ensure the support of the Helmet & Stiffener assembly; more specifically, for the ring and the DOG-holder plates, allowing the transmission of the Bending Moment and Shear Force from the Helmet to the Bell Mouth structure. Thus, the structural efficiency of the DOGs is fundamental to ensuring the correct coupling and support of flexible risers under bending loads.

[004] Figure 1 illustrates the characteristic shape, the usual solution in these cases, of a DOG as used in the Bell Mouth concepts.

[005] The curvature on the DOG support face acts as a bed for supporting the coupling structure, called the Stiffener Helmet, as illustrated in Figure 1.

[006] On several occasions, these components have experienced complete fracture well before the projected end-of-life period. Petition 870260085651, dated 08 / 21 / 2026, page 43 / 89 2 / 16

[007] Investigations of events that occurred on some Petrobras and chartered platforms indicated, for the most part, that the failure of the DOGs occurred due to fatigue, with the complete fracture occurring in the curvature region between the body of the DOG and the face that supports the stiffener helmet, as can be seen in Figure 2. Therefore, it can be inferred that, since the component may present non-conformities in relation to the characteristics defined in the design, these foster the emergence of imperfections that will be the prelude to serious structural failures that manifest as the fracture of the DOGs.

[008] In general, the process initially occurs with the nucleation of cracks, which, under a state of high structural stress in the DOG curvature region, as well as its lack of flexibility, favor the emergence of cracks that evolve to the brittle failure stage, leading to the collapse of the components. This situation is undesirable, generating a series of losses, whether operational or economic, such as inoperative bell mouths, maintenance shutdowns, lost profits due to reduced production volume, use of divers to replace components, among others.

[009] For the dimensioning of the DOGs, these are considered as subcomponents of the bell mouth, and must be dimensioned together using the forces from the riser. Figure 3 shows a representation of these forces, through a simplified free-body diagram of the flexible riser near the SPU (Stationary Production Unit). As the Bend Stiffener is braced in the bell mouth by the DOGs, the lateral loads from the riser tension (T) are transferred in the form of shear force (C) and bending moment (M) to the support at a position below the waterline. These forces are evaluated at the Stiffener Workpoint, denoted in Figure 3 by p0. Due to the lack of longitudinal bracing of the riser with the Stiffener, the riser is deflected and realigned, Petition 870260085651, dated 08 / 21 / 2026, page 44 / 89 3 / 16 establishing a vertical extension between the Bell Mouth and the Hang-Off. In this way, the riser traction (H), without curvatures, is anchored to the Hang-Off.

[010] Typically, DOGs are designed with high stiffness to withstand a critical load scenario which, as mentioned earlier, has not been shown to be the failure factor for these components.

[011] A preliminary solution used for the problem of DOG failure was to reinforce the geometry of this component; however, this method did not prove very effective.

[012] Thus, an assessment was made of the nature of the stresses acting on these components, aiming to find the reason why they exhibit a high rate of fatigue failure, but not collapse (extreme load).

[013] Figure 3 shows the forces that the riser transfers to the Bend Stiffener, namely the shear force “C” and the bending moment “M” (already presented above), detailing how they are transmitted to the DOGS and the Bell Mouth. It can be observed that the loads acting on the Bend Stiffener, and consequently on the Bell Mouth, are mostly oriented in the transverse direction. Thus, the principal reaction forces (primary stresses), Ra and Rb, commonly referred to as the Bell Mouth reaction couple, are the main loads acting on the structure, and can cause both its collapse due to overload and the failure of the structure due to fatigue.

[014] Thus, disregarding the self-weight of the Bend Stiffener, which is of negligible magnitude in relation to the reaction torque, no other significant force is applied in the longitudinal direction of the Bell Mouth.

[015] However, due to the existing clearance between the Bend Stiffener Helmet and the Bell Mouth and the elastic deformations of the structures, a relative rotation occurs between these two components, causing an imposed displacement of the helmet. Petition 870260085651, dated 08 / 21 / 2026, page 45 / 89 4 / 16 Bend Stiffener on the DOG positioned in the opposite direction to the direction of the riser's top forces. As a reaction to the imposed displacement, a reaction force "u" arises on the DOG, which, due to its nature as a stress (imposed displacement), can be considered a secondary reaction. That is, the probability of failure of the DOG under critical load is quite low; however, fatigue stresses can be significant.

[016] Secondary reaction behavior was first identified during a structural analysis aimed at verifying the influence of DOG failure on the overall behavior of the Bell Mouth, in which the absence of the three most stressed DOGs was considered.

[017] Evidently, due to the inefficient support of the Stiffener, an increase in the stress level at the Bell Mouth was observed. However, even with the absence of the most stressed DOGs, the position of the Bend Stiffener's Helmet inside the Bell Mouth was not significantly altered, and the Helmet remained sufficiently contained in its intended operating position. This result confirmed that the reaction at the DOG is not essential to counteract the operational loads of the riser, thus characterizing a secondary reaction.

[018] Based on the results obtained in this preliminary structural analysis, the concept of compliant DOGs emerged, in which it was shown that if the DOG presented a certain flexibility that allowed the attenuation of the secondary reaction “u”, or the conformation to this displacement, then the stress acting on the DOGs would be reduced, thus increasing their fatigue life. This evidence is clearer through the graph in Figure 4, which presents an overview of the behavior of the compliant DOG as a function of its theoretical stiffness, in which the DOG is evaluated as a spring element with stiffness “k” positioned between the Bell Mouth Dog Plate (Position “X” in Figure 1) and the region Petition 870260085651, dated 08 / 21 / 2026, page 46 / 89 5 / 16 of the helmet in which the displacement “u” of Figure 4 is applied. Two results are presented in the graph of Figure 4: the characteristic fatigue stress in the critical region (center of curvature shown in Figure 2, identified by region XV) of the DOG (scale on the left) - reference stress for the fatigue calculation, and the maximum resulting displacement of the DOG (scale on the right). The reference values, represented by the lines with constant value in the graph, indicate the results obtained considering the current design of the bell mouth (DOGs without the compliant system).

[019] The behavior shown in Figure 4 indicates that the compliant DOG system acts as assumed during its conceptual development; that is, the stress acting on the DOG has an inverse proportionality relationship to its stiffness. As for the displacement results, the behavior obtained is more trivial, it being evident that larger displacements will be observed for lower stiffness values.

[020] These two results indicate a duality that must be respected in the detailed design of the compliant DOG; that is, this component must be flexible enough to reduce the secondary stresses to which it is subjected; however, it must also have a satisfactorily high rigidity so that its displacement is compatible with the design space of the Bell Mouth.

[021] Conceptually, the project demonstrates that there is a DOG configuration that supports the working loads through an appropriate deformation mechanism, but this configuration is not obtained through a solid DOG, such as is typically adopted in Bell Mouths.

[022] The combination of flexibility and mechanical strength of the DOG was achieved by removing material both inside the body and in its lower region, thus modifying the geometric concept and the way the component responds. Petition 870260085651, dated 08 / 21 / 2026, page 47 / 89 6 / 16 external excitations compared to a typical solid DOG as illustrated in Figure 2. This results in displacement amplification and a consequent drop in voltage peaks, as well as minimally modifying the external design of the DOGs, in order to make the best possible use of the other components already built.

[023] Furthermore, a geometry concept that mimics the behavior of a Compliant Mechanism (CM) was also used, based on compliance strategies for displacement reversing mechanisms, force amplifiers, and Origami-type structures. This type of geometric alteration causes the DOG to act similarly to a mechanism and no longer to a conventional structure. This can be visualized in the way that the bending of internal members of the component forms coupling pairs, and thus the displacement is amplified while the lower half of the DOG moves as a whole. The behavior of compliant DOGs ensures greater flexibility without compromising its strength and purpose; that is, the support exerted by the component in forming a support bed for the Bend Stiffener Helmet.

[024] Applying these strategies to the original geometry of the DOGs, a concept was reached in which the upper end of the DOG's curvature is physically separated from the front face, as illustrated in Figure 5. Furthermore, the support face has a curved element (bending member) that extends through the lower region of the DOG and acts to the initial part of its body. This curved element acts by generating locking points with rods connected to the front and rear faces of the DOG. This results in a component that will always have iteration of all external walls to support the load, regardless of the loading direction. This is crucial to ensure that the DOG operates correctly not only in normal operating conditions, but also in coupling (pull-in) and decoupling situations. Petition 870260085651, dated 08 / 21 / 2026, page 48 / 89 7 / 16 (pull-out) with the Bell Mouth frame (Bend Stiffener helmet).

[025] The results found in the simulations for validating this concept highlighted the potential that the use of compliant DOG geometries can bring in terms of mechanical efficiency to the support system. The proposed concept was able to significantly reduce the peak maximum stress acting in the critical regions of the DOGs; that is, support faces and curvature. This implies a direct and significant gain in fatigue life, something crucial for the adverse environment in which these components operate.

[026] Furthermore, in a direct comparison with the original concepts, the stress distribution in the proposed concepts extended over a larger region along the body of the DOGs, resulting in components with greater efficiency in the distribution of internal stresses.

[027] Furthermore, the gain in terms of reducing the acting stress on the DOGs, conferred by the compliance concept, was reflected in the fatigue life estimate, where the performance was far superior to the original DOGs currently employed.

[028] Alternatively to the solution described above, the compliant system can be obtained by altering the stiffness of another component of the Bell Mouth, such as the DOG shaft (indicated IX in Figure 1).

[029] Furthermore, the present invention provides the following advantages: reduced downtime for maintenance and repairs due to failures in the DOGs and, consequently, in the support system as a whole; weight reduction, resulting in cascading cost reductions (less material, lighter for transport and installation, easier handling); due to their high fatigue life, the use of compliant components implies a drastic reduction in the need for intervention for repairs / replacements by divers; life of Petition 870260085651, dated 08 / 21 / 2026, page 49 / 89 8 / 16 fatigue high enough to meet the design criteria practiced by companies in the oil and gas sector; compliance couplings provide greater safety throughout their service life, as these components are naturally more reliable than couplings with moving parts. State of the art:

[030] Document US6799124B2 discloses a coupling system between a Curvature Stiffener and a Bell Mouth, comprising a plurality of locking mechanisms, wherein each locking mechanism is fixed externally to the Bell Mouth and comprises a movable tongue, positioned at an angle downwards, wherein the tongue accesses the interior of the Bell Mouth and is actuated by an elastic element adapted to exert pressure on the tongue towards the interior of the Bell Mouth.

[031] The aforementioned document US6799124B2 does not disclose or describe any modification to the dog's body to confer compliance to it in order to mitigate fatigue damage to the component.

[032] The document Numerical Analysis of a Flexural Stiffener for I-tube, Gustavo Alves Pinto Mosqueira Gomes. - Rio de Janeiro: UFRJ / COPPE, 2018, deals with an evaluation of the behavior of the riser when it is subjected to a given axial load with a set angle of rotation. In the work, finite element models were developed to verify the differences between the traditional coupled configuration, which considers the riser and the Bend Stiffener embedded in the same position, and the I-tube configuration, which considers a significant length of flexible duct above the Bend Stiffener and different embedding positions. In addition, the clearance between the duct and the Bend Stiffener, which is normally disregarded in the analyses, was also evaluated. Petition 870260085651, dated 08 / 21 / 2026, pp. 50 / 89 9 / 16

[033] The document SCHIMIDT, FELIPPE & Fortes, Marcio & Silva, Agnaldo (2016). Installation of flexible lines and umbilicals: conditioning tests and operational failures, reveals the characteristics and components of flexible lines and umbilicals, highlighting the stages and types of installation scope. In addition, it describes the tests carried out on the launching vessel for validation and conditioning of the flexible line and umbilical for operation in the offshore field.

[034] Document BR102013019602A2 deals with an accessory provided to the top termination of the riser, capable of allowing a certain rotation around the axial axis of the riser and, consequently, alteration of the horizontal projection angle of said riser, reducing the stresses on the fixing structures and their supports on the platform. Consequently, it allows for cost reductions across the board, from design to supply, of all components involved in fixing the riser end to the platform. Alternatively, the accessory is capable of providing flexibility in the angle of entry of the risers in relation to the platform, obtaining arrangements with shorter pipeline lengths on the seabed, avoiding interference or geographical impediments on the seabed.

[035] The documents Numerical Analysis of Bend Stiffener for I-tube, Installation of flexible lines and umbilicals: conditioning tests and operational failures and the application BR102013019602A2 describe only Bend Stiffener support systems with single-component DOGs and without indicating any modification to the dog body in order to increase its fatigue resistance.

[036] Note that the present invention maintains the original external geometry of commonly used DOGs, removing internal material without altering the composition of the steel, maintaining its functional specification in accordance with the cited documents. Petition 870260085651, dated 08 / 21 / 2026, page 51 / 89 10 / 16

[037] Thus, it is evident that although changes in geometry improve the fatigue life of a part, the change proposed in the present invention would not be obtained by a person skilled in the art in a trivial manner from the State of the Art. Brief description of the invention:

[038] Due to the nature of the loads involved in the support process, DOGs must exhibit high strength / stiffness characteristics to ensure coupling and sufficient flexibility to allow absorption of the stresses arising from the kinematic movements of the coupling. These characteristics are rarely obtained simultaneously, so that, in recent decades, critical failures of DOGs have been occurring prematurely.

[039] The present invention comprises a component similar to a conventional DOG, equipped with a structural mechanism formed by a more flexible optimized geometry, which guarantees flexibility to the component as a whole. When the present invention is subjected to a load, said flexible parts deform in a pre-specified manner, transferring part of a load that would be excessive in a given region to another less loaded region, without any external power or interference. In this way, the deformation pattern that occurs in the present invention relieves stresses where they are highest and at the same time provides flexibility (compliance), distributing the coupling loads more adequately between the various DOGs. Brief description of the figures

[040] To obtain a better understanding of the characteristics of the present invention and in accordance with a preferred practical embodiment thereof, a set of drawings is attached to the description, in which its operation is represented by way of example, though not limitation: Figure 1 shows a typical current approach to the components. Petition 870260085651, dated 08 / 21 / 2026, page 52 / 89 11 / 16 involved in the flexible riser support system (BSN900E), where the following are indicated: (A) components coupled for operation; (B) detailing for the bell mouth components. In Figure 1, we have: (I) Top connector of the flexible riser, (II) Flexible riser, (III) Lower riser rail, (IV) Itube, (V) Bell mouth, (VI) Bend Stiffener, (VII) Bend Stiffener cap, (VIII) Dog, (IX) Shaft, (X) Ring and Dog Holder Plates; Figure 2 shows a representation of the different regions that make up a DOG, currently used in the BSN-900. In Figure 2, we have: (I) Hole for coupling the locking system, (II) Hole for coupling the support shaft, (III) Rear face, (IV) Front face, (V) Heel, (VI) Bottom face, (VII) Center of curvature, (VIII) Support face, (IX) Coupling region, (X) Locking region, (XI) Body, (XII) Heel, (XIII) Bottom region, (XIV) Curvature region, (XV) Support face region; - Figure 3 shows a simplified representation of the acting forces normally used for the dimensioning of DOGs, where the following are indicated: (A) global load (T) and reaction (H); (B) distribution of forces in the support system as a bending moment M and a shear C; Figure 4 shows the graph of the preliminary study results on increasing the flexibility in the assembly of the DOGs, demonstrating the reduction in the characteristic fatigue stress level; Figure 5 shows the present invention in one of its preferred configurations based on a Compliant Mechanism (CM) for bell mouths, considering the BSN900E model, where: (A) front view and (B) isometric view; Figure 6 shows a side view of the present invention in its preferred configuration, highlighting the Compliant Mechanism (CM). Petition 870260085651, dated 08 / 21 / 2026, page 53 / 89 12 / 16 Figure 7 shows a side view of the present invention, representing the operation of the Compliant Mechanism (CM) under reverse (left) and normal (right) vertical forces; Figure 8 shows a side view of the present invention, representing the operation of the Compliant Mechanism (CM) under reverse (left) and normal (right) horizontal forces. Detailed description of the invention:

[041] With reference to Figures 5, 6, 7, and 8, the present invention comprises, in its preferred configuration, a non-solid component with at least one upper portion (1), a lower portion (2), a compliant member (3), an opening end (3b), a front contact rod (4), a rear contact rod (5), and wherein the upper portion (1) and the lower portion (2) are connected by at least one front element (10) and at least one rear element (11).

[042] The upper portion (1) preferably comprises a preferably solid region with at least one through hole and / or blind hole, or elements for fixing. The central region, where the compliant mechanism is located, and the lower portion (2) comprise hollow spaces in order to allow movement of the compliant members (3).

[043] Furthermore, the upper (1) and lower (2) portions may have geometric variations such as different shapes and / or curvatures to accommodate different fixings, provided that the central portion of the compliant component remains substantially similar to the preferred shape shown.

[044] The compliant member (3) comprises a curved extension projecting from the upper part of the lower portion (2) to the central region, located between the anterior (4) and posterior (5) rods. Said member (3) comprises a displacement restriction region (3a), which is positioned between the anterior (4) and posterior (5) rods, an opening end (3b), located immediately Petition 870260085651, dated 08 / 21 / 2026, page 54 / 89 13 / 16 below the discontinuity of the anterior face (10), and a locking end (3c), located above the anterior rod (4).

[045] The front rod (4) and the rear rod (5) comprise extensions that start from the front element (10) and the rear element (11), respectively. The front element (10) has a discontinuity in the upper part of the opening end (3b), which allows a large amplification of the movement imposed by the Helmet on the support face of the DOG, as can be seen in Figures 7 and 8.

[046] However, when this movement occurs, the curved element acting internally to the DOG, called the compliant member (3), causes the couplings with the faces of the front (10) and rear (11) elements to redistribute the mechanical stress. This redistribution occurs through communication between the contact rods, front (4) or rear (5), with the displacement restriction region (3a). Thus, a highly efficient component is obtained, where the amount of material supporting deformation energy is maximized; that is, the compliant member redistributes the displacement effect to the regions that were previously not stressed.

[047] It is important to emphasize that all internal elements were defined with the same thickness. This maintained homogeneity between external walls and internal elements. This thickness must be defined based on the maximum static stress acting as a critical load, as well as fatigue stresses. In the case of DOGs, the possibility of corrosion due to environmental exposure must also be taken into account, and the selection of corrosion-resistant materials or the definition of a corrosion allowance should be considered.

[048] Considering that the upper portion of the DOG (1) operates under displacement restrictions, while the lower portion of the DOG (2) is subject to the forces from the Stiffener Helmet, there is a combination with four directions of Petition 870260085651, dated 08 / 21 / 2026, pp. 55 / 89 14 / 16 possible displacements for the lower portion of the DOG. Obviously, the combination of two or more directions of action of these efforts is possible. For illustrative purposes, only the four alternatives illustrated in Figures 7 and 8 will be discussed here.

[049] Thus, considering a force acting in the vertical direction and starting from the lower portion (2) to the upper portion (1), the compliant system locks in the curvature region (6a) and at the end of the posterior inner rod (6b). As this movement is the opposite of that expected for the DOG under operating conditions, these lockings are defined as reverse movements. When considering the same force, but now in the opposite direction; that is, from the upper portion (1) to the lower portion (2), an upper internal locking (7a) occurs at the free end of the compliant member (4), while at the same time there is a posterior internal locking (7b). As this direction of force is that normally supported by DOGs, these lockings are defined as originating from normal forces. Considering a longitudinal force starting from the posterior face (11) towards the anterior face (10), a translational / rotational movement occurs towards the body of the Bell Mouth.This results in the locking of the compliant system by the inner wall (8a) at the free end of the compliant member (3c), while at the same time anterior internal locking (8b) occurs in the restriction region (3a).

[050] Now assuming the longitudinal effort in the opposite direction, moving the lower portion of the DOG in the opposite direction of the Bell Mouth, the locking of the compliant system occurs by closing the discontinuity line at the end of the DOG curvature (9a) and with a repetition of the subsequent internal locking movement (9b).

[051] Depending on the magnitude and direction of the forces acting, one or more locking regions may occur. Petition 870260085651, dated 08 / 21 / 2026, pp. 56 / 89 15 / 16 During an operational load, therefore, the locking regions can migrate from one region to another along the structure of the compliant member (3).

[052] Thus, the deformation mechanism of this invention allows it to withstand all types of stresses required in couplings of this type and similar ones, avoiding high stress concentrations that occur in conventional solutions. This versatility is precisely what makes the compliant DOG so efficient in redistributing stresses to non-stressed regions and providing greater structural flexibility.

[053] Structurally, the present invention proposes a structural mechanism formed by parts that are individually more flexible than a solid DOG. However, when under load, these parts deform in a pre-specified manner, transferring part of a load that would be excessive in a given region to another less loaded region. This occurs through the action of the external load itself, using the deformation of the component, without any external power or interference. It is this deformation pattern that relieves stresses where they are highest and, at the same time, provides the flexibility (compliance) that better distributes the coupling loads among the various DOGs.

[054] Thus, essentially, the present invention relies on a structure with the same external geometry as a generic hook, but with a topology (internal structure) that allows for greater deformation of the part with load transfer to other less stressed regions.

[055] The motion-conforming strategy to maximize displacement on the support face and minimize stresses acting on critical regions (curvature) of the DOG makes this type of component applicable to any operations / structures that make use of components acting in a gripping position (hook type) coupling components Petition 870260085651, dated 08 / 21 / 2026, pp. 57 / 89 16 / 16 distinct in specific positions / configurations. Among the possible fields of application, we can mention: - End caps for lifting loads in mining; - Lifting systems used in airports and the construction industry; - Anchoring tips for structures subject to wind loads; Any and all systems that require high mechanical strength in supporting weight / load, while also exhibiting high flexibility to conform to considerable displacement and / or force stresses.

[056] Due to the ability to conform to displacements of considerable magnitude with material distribution absorbing a greater amount of deformation energy, the concept of compliant DOG can be extended to applications that combine the needs of high mechanical strength with high flexibility to accommodate prescribed cyclic displacement requirements.

[057] Thus, those skilled in the art will appreciate the knowledge presented here and will be able to reproduce the invention in the modalities presented in other variants, covered within the scope of the appended claims. Petition 870260085651, dated 08 / 21 / 2026, pp. 58 / 89

Claims

1 / 2 CLAIMS 1. A compliant component for supporting curvature stiffeners, comprising: a non-solid component with at least one upper portion (1) and one lower portion (2); a compliant member (3); an anterior contact rod (4); and a posterior contact rod (5);wherein the upper portion (1) and the lower portion (2) are connected by at least one anterior element (10) and at least one posterior element (11), characterized in that the compliant member (3) comprises a curved extension projecting from the upper part of the lower portion (2) to a central region, located between the anterior (4) and posterior (5) contact rods, the compliant member (3) comprises a displacement restriction region (3a), positioned between the anterior (4) and posterior (5) contact rods, an opening end (3b) located immediately below a discontinuity of the face of the anterior element (10), and a locking end (3c) located above the anterior contact rod (4).

2. Compliant component for supporting curvature stiffeners, according to claim 1, characterized in that the upper portion (1) comprises a solid region with at least one through and / or blind hole or elements for fixing in a riser support system, such as a bell mouth.

3. Compliant component for supporting curvature stiffeners, according to claim 1, characterized in that the central region and the lower portion (2) comprise hollow spaces to allow movement of the compliant member (3). Petition 870260085651, dated 08 / 21 / 2026, page 59 / 89 2 / 2 4. Compliant component for supporting curvature stiffeners, according to claim 1, characterized in that the upper portion (1) and the lower portion (2) have different shapes and / or curvatures to adapt to different fixings. Petition 870260085651, dated 08 / 21 / 2026, pp. 60 / 89

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