Optimizing Subsea Tie-in Spools Design Using Different Mathematical Approaches - Literature review Example

Literature Review Name: University: Date: Optimizing the Design of Subsea Tie-in Spools by Using Different Mathematical Approaches – Literature Review In Fyrileiv and Collberg (2005) study, they observed that the effective axial force was the virtual force achieved through the stresses’ integral over the steel cross-section. The effective axial force, according to the authors, can be described as a concept utilized for avoiding the pressure effects integration over the surfaces of double-curves such as a pipe that have been deformed through bending. Still, the key challenge associated with the external and internal pressures is attributed to the fact that their effect is normally contrary to what one instantly believes is accurate. For that reason, such effects have become basis of wrong designs and misunderstandings. Fyrileiv and Collberg (2005) observed that the structural pipeline response is governed by the effective axial force; thus, having an effect on the anchor forces, upheaval buckling, lateral buckling, end expansion as well as free spans’ natural frequencies. Therefore, the authors insist that it is imperative to understand the effects associated with effective axial force in order to achieve a reliable and safe design. On the other hand, the local effects such as yielding, steel stresses and local buckling are governed by the true axial force. Furthermore, it was observed that the effective axial force can be utilized in simplifying the design criterion. Although the utilization of effective axial force in pipeline codes has happened for many years, Fyrileiv and Collberg (2005) mention that it is still misinterpreted as well as misunderstood, especially with the view to pressures’ effect. The authors suggest that although the effective axial force expression within the DNV code appears accurate, numerous simplifications is needed. In his study, Madeley (2013) established that although spools are normally utilized to facilitate the installation as well as tie-in of various structures, they also have a functional role at the time of operation, facilitating product cooling where needed and absorbing flowline end expansion. At the time of its design life, the spools have to resist numerous potential load combinations. Such loads, accoridng to Madeley (2013), comprise of structure settlement, flowline end expansion, temperature, pressure, wave, and connector misalignment. A spool design that is considered acceptable must be able to resist all these combination of forces. Madeley (2013) applied the evolutionary algorithm to problems associated with spool design. The evolutionary algorithm managed to successfully iterate to combining different optimal solutions set anchored on the defined performance parameters. Utilization of the algorithm design helps to significantly reduce time because of the speed of generating and analyzing the designs. The author further observed that algorithm results visualization allowed for the quantification of the relationship between conflicting design goals. The additional information leads to improved decisions making, especially when there is need for tradeoff between the two performance goals. According to the author, the algorithm design’s modularity as well as flexibility, together with its robustness, allows for more comprehensive application in this area. Therefore, spools optimization against numerous performance goals allows the designer to create lots of potential solutions. More importantly, the extra information achieved through designs that have been generated and analyzed automatically facilitates the making of better decisions. According to Chan, Mylonas, and McKinnon (2008), utilization of Abaqus or other complex Finite element programs allows for achievement of more comprehensive solution; therefore, reducing the redundant conservatism. The Abaqus has two major features which can be exploited; the first feature is the analysis mode, which the authors have described as a spoolpiece designed purposely for accommodating large end displacements attributed to the expansion of the pipeline. Therefore, the geometric nonlinear effects have to be taken into account during the element analysis of finite. Using the nonlinear analysis techniques is beneficial since it offers a solution that is highly accurate to the problem. The second feature is the boundary condition, whereby the authors assert that the tolerances of spool fabrication and metrology could result in misalignment, especially at the connector hub face. For this reason, the residual loads could stem from the deformation of the spool because of the induction of the installation forces to be consistent with the connector faces. The residual loads magnitude depends on the system stiffness at the area nearby the connectors. The loading can be reduced by the finite element technique; that is to say, the load path stiffness coupled with its mounting structure as well as the inboard structures’ steel framework should be integrated to ensure flexibility and connector loads reductions. At the connector supporting system, the localised bending moments can be reduced when the misalignments tolerances are modeled with the kinematics constraints. Through their field life, subsea structures as observed by the authors could face consolidation and immediate and settlement. These settlements qualification and prediction is crucially important since it ensures that the structure is not only serviceable but also stable. In their study, Aleksandersen, Langen, Meling, and Lien (2001) observed that most tie in systems, especially for the deep water pipelines (large diameter) are normally complicated and large in size; therefore, they need operations that are time consuming. In their study, the authors discuss about a new development tie in system that is not only simple, but very reliable for deep waters’ large diameter pipelines going down almost 2500 meters. This new system, according to the authors, utilizes simple tie in heads that are modularized, each attached to the end of the pipeline spool, combined with communication packages as well as hydraulic control. The authors observed that their tie in system could reduce the operations time by between 50 and 70 per cent in contrast to the marketed systems. In addition, the system simplicity made the tie in operations to be conducted effectively because of the fewer associated operations such as lifting. The authors emphasize that the number of tie in systems that can connect large diameter pipelines on 1000 meters water levels and beyond are very few. More importantly, a 28" rigid spool tie in operation needs utilization of high forces. The alignment capacity and pull-in capacity of 800 kNm and 300 kNm, respectively results in higher demand for structural strength and performance of the tie in tool. This tool is relatively simple and has only three mechanisms, the tie in porch lock-on, spool lock-on and pull-in mechanism. When the tool’s mechanisms are few, the authors observed it is beneficial since the likelihood of failure is decreased. Eliminating the subsea operations as established by the authors is crucial to the costs associated with connection process of the pipeline, given that between 80 and 90 per cent of these costs are associated with offshore installation. Hydrodynamic stability of the pipeline according to Tørnes, Zeitoun, Cumming, and Willcocks (2009) has become an important design topic amongst the pipeline engineers. It is imperative to consider a simple force balance approach to make sure that the pipeline does not laterally displace when instantaneously facing maximum hydrodynamic loads related to the extreme conditions of the metocean. According to the authors, ensuring the stability cost-effectively through utilization of less amount of concrete weight coating is a straightforward and robust approach. Still, pipeline stabilization in many instances has become a major driver of cost, resulting in costly as well as complex stabilization solutions. As a result, many designers have started espousing the refined techniques whereby there is allowance for pipeline displacement under the extreme conditions. The authors found out that although calibrated and simplified techniques could be adequate for pipelines, a full dynamic analysis of FE was not valuable for pipelines, especially when stability is considered to be a key design problem. They further observed that a simple Coulomb friction dynamic based analysis can lead to conservative results that are significantly less as compared to using the simple force balance techniques that intrinsically creates no room for lateral displacement. Generally, the pipeline response achieved by means of highly developed transient FE analyses could be utilized to realize robust designs devoid of resorting to strict lateral displacement limits. A deepwater project known as TotalFinElf SA’s Girassol was initiated late in 2001 in West Africa. According to Alliot and Frazer (2002), utilization of modular advanced tie-in system (MATIS) by means of cheap flanges demonstrated the type of technological advancement associated ultra-deepwater and deepwater developments. Generally, the subsea tie-back projects’ capital expenditure was split evenly between the flowlines as well as the wells. The authors note that reducing the flowlines cost could influence the project economics. In this case, the cost of flowline comprised of tie-in, installation, as well as line pipe and coating. The installation costs as well as line pipe costs could be subjected into the market forces while the flowline tie-in costs could be influenced through tie-in method selection. The remote flowline tie-in techniques according to the authors are essential for the deep as well as ultra-deepwater field developments. A number of the available systems created the need for the utilization of complex mechanical connectors that are costly and reduce the flexibility of the operator. The authors also observed that the flanges turned out to be considerably cost-efficient as compared to mechanical connectors when the number of spools was increased to the standard of subsea development projects. References Aleksandersen, J., Langen, I., Meling, M., & Lien, A. (2001). Autonomous Subsea Tie In System (AUSTIN) for Large Diameter Pipelines in Deep Waters. Proceedings of the Eleventh (2001) bTternational Offshore and Polar Engineering Conference, (pp. 19-26). Stavanger, Norway,. Alliot, V., & Frazer, I. (2002). Tie-in system uses low-cost flanges on deepwater Girassol development. Oil and Gas Journal, 100(18), 96–104. Chan, H. H., Mylonas, L., & McKinnon, C. (2008). Advanced Deepwater Spool Piece Design. IBC’s 31st annual Offshore Pipeline Technology Conference & Exhibition, (pp. 1-28). London. Fyrileiv, O., & Collberg, L. (2005). Influence Of Pressure In Pipeline Design – Effective Axial Force. 24th International Conference on Offshore Mechanics and Arctic Engineering, (pp. 1-8). Halkidiki, Greece. Madeley, C. (2013). Optimisation Of Subsea Tie-In Spools Using Evolutionary Algorithms. Proceedings of the ASME 2013 32nd International Conference on Ocean, Offshore and Arctic Engineering, (pp. 1-9). Nantes, France. Tørnes, K., Zeitoun, H., Cumming, G., & Willcocks, J. (2009). A Stability Design Rationale - A Review Of Present Design Approaches. Proceedings of the ASME 2009 28th International Conference on Ocean, Offshore and Arctic Engineering, (pp. 1-13). Perth, WA, Australia. Read More

Utilization of the algorithm design helps to significantly reduce time because of the speed of generating and analyzing the designs. The author further observed that algorithm results visualization allowed for the quantification of the relationship between conflicting design goals. The additional information leads to improved decisions making, especially when there is need for tradeoff between the two performance goals. According to the author, the algorithm design’s modularity as well as flexibility, together with its robustness, allows for more comprehensive application in this area.

Therefore, spools optimization against numerous performance goals allows the designer to create lots of potential solutions. More importantly, the extra information achieved through designs that have been generated and analyzed automatically facilitates the making of better decisions. According to Chan, Mylonas, and McKinnon (2008), utilization of Abaqus or other complex Finite element programs allows for achievement of more comprehensive solution; therefore, reducing the redundant conservatism.

The Abaqus has two major features which can be exploited; the first feature is the analysis mode, which the authors have described as a spoolpiece designed purposely for accommodating large end displacements attributed to the expansion of the pipeline. Therefore, the geometric nonlinear effects have to be taken into account during the element analysis of finite. Using the nonlinear analysis techniques is beneficial since it offers a solution that is highly accurate to the problem. The second feature is the boundary condition, whereby the authors assert that the tolerances of spool fabrication and metrology could result in misalignment, especially at the connector hub face.

For this reason, the residual loads could stem from the deformation of the spool because of the induction of the installation forces to be consistent with the connector faces. The residual loads magnitude depends on the system stiffness at the area nearby the connectors. The loading can be reduced by the finite element technique; that is to say, the load path stiffness coupled with its mounting structure as well as the inboard structures’ steel framework should be integrated to ensure flexibility and connector loads reductions.

At the connector supporting system, the localised bending moments can be reduced when the misalignments tolerances are modeled with the kinematics constraints. Through their field life, subsea structures as observed by the authors could face consolidation and immediate and settlement. These settlements qualification and prediction is crucially important since it ensures that the structure is not only serviceable but also stable. In their study, Aleksandersen, Langen, Meling, and Lien (2001) observed that most tie in systems, especially for the deep water pipelines (large diameter) are normally complicated and large in size; therefore, they need operations that are time consuming.

In their study, the authors discuss about a new development tie in system that is not only simple, but very reliable for deep waters’ large diameter pipelines going down almost 2500 meters. This new system, according to the authors, utilizes simple tie in heads that are modularized, each attached to the end of the pipeline spool, combined with communication packages as well as hydraulic control. The authors observed that their tie in system could reduce the operations time by between 50 and 70 per cent in contrast to the marketed systems.

In addition, the system simplicity made the tie in operations to be conducted effectively because of the fewer associated operations such as lifting. The authors emphasize that the number of tie in systems that can connect large diameter pipelines on 1000 meters water levels and beyond are very few. More importantly, a 28" rigid spool tie in operation needs utilization of high forces. The alignment capacity and pull-in capacity of 800 kNm and 300 kNm, respectively results in higher demand for structural strength and performance of the tie in tool.

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