Optimization of UOE Pipe Manufacturing Process for Improved Collapse Performance Under External Pressure

Author(s):  
Stelios Kyriakides ◽  
Mark D. Herynk ◽  
Heedo Yun

Large-diameter pipes used in offshore applications are commonly manufactured by cold-forming plates through the UOE process. Collapse experiments have demonstrated that these steps, especially the final expansion, degrade the mechanical properties of the pipe and result in a reduction in its collapse pressure, upwards of 30%. In this study, the UOE forming process has been modeled numerically so that the effects of press parameters of each forming step on the final geometry and mechanical properties of the pipe can be established. The final step involves simulation of pipe collapse under external pressure. An extensive parametric study of the problem has been conducted, through which ways of optimizing the process for improved collapse performance have been established. For example, it was found that optimum collapse pressure requires a tradeoff between pipe shape (ovality) and material degradation. Generally, increase in the O-strain and decrease in the expansion strain improve the collapse pressure. Substituting the expansion by compression can not only alleviate the UOE collapse pressure degradation but can result in a significant increase in collapse performance.


Author(s):  
Giannoula Chatzopoulou ◽  
Konstantinos Antoniou ◽  
Spyros A. Karamanos

Large-diameter thick-walled steel pipes during their installation in deep-water are subjected to external pressure, which may trigger structural instability due to excessive pipe ovalization with catastrophic effects. The resistance of offshore pipes against this instability mode strongly depends on imperfections and residual stresses introduced by the line pipe manufacturing process. In the present paper, the JCO pipe manufacturing process, a commonly adopted process for producing large-diameter pipes of significant thickness, is examined. The study examines the effect of JCO line pipe manufacturing process on the structural response and resistance of offshore pipes during the installation process using nonlinear finite element simulation tools. At first, the cold bending induced by the JCO process is simulated rigorously, and subsequently, the application of external pressure is modeled until structural instability is detected. For the simulation of the JCO manufacturing process and the structured response of the pipe a two dimensional generalized plane strain model is used. Furthermore, a numerical analysis is also conducted on the effects of line pipe expansion on the structural capacity of the JCO pipe.



Author(s):  
Konstantinos Antoniou ◽  
Giannoula Chatzopoulou ◽  
Spyros A. Karamanos ◽  
Athanasios Tazedakis ◽  
Christos Palagas ◽  
...  

Large-diameter thick-walled steel pipes during their installation in deep-water are subjected to external pressure, which may trigger structural instability due to pipe ovalization, with detrimental effects. The resistance of offshore pipes against this instability is affected by local geometric deviations and residual stresses, introduced by the line pipe manufacturing process. In the present paper, the JCO-E pipe manufacturing process, a commonly adopted process for producing large-diameter pipes of significant thickness, is examined. The study examines the effect of JCO-E line pipe manufacturing process on the external pressure resistance of offshore pipes, candidates for deepwater applications using nonlinear finite element simulation tools. The cold bending induced by the JCO forming process as well as the subsequent welding and expansion (E) operations are simulated rigorously. Subsequently, the application of external pressure is modeled until structural instability (collapse) is detected. Both the JCO-E manufacturing process and the external pressure response of the pipe, are modeled using a two-dimensional (2D) generalized plane strain model, together with a coupled thermo-mechanical model for simulating the welding process.



Author(s):  
Giannoula Chatzopoulou ◽  
Spyros A. Karamanos ◽  
George E. Varelis

Large-diameter thick-walled steel pipes during their installation in deep-water are subjected to a combination of loading in terms of external pressure, bending and axial tension, which may trigger structural instability due to excessive pipe ovalization with catastrophic effects. In the present study, the UOE pipe manufacturing process, commonly adopted for producing large-diameter pipes of significant thickness, is considered. The study examines the effect of UOE line pipe manufacturing process on the structural response and resistance of offshore pipes during the installation process using nonlinear finite element simulation tools.



Author(s):  
Andreas Liessem ◽  
Ulrich Marewski ◽  
Johannes Groß-Weege ◽  
Gerhard Knauf

Line pipe intended for deep water applications has to be designed predominantly with regard to external pressure in order to avoid plastic collapse. As a consequence of cold forming during UOE pipe manufacture and the subsequent application of anticorrosion coating, the characteristic stress strain behavior has to be taken into account for a reliable prediction of the collapse pressure. Verification of collapse resistance of large diameter pipes against external pressure requires adequate and reliable component testing using a sufficient number of pipe samples. These samples have to be subjected to test conditions, which closely simulate the situation in service. As the test results may depend significantly on its boundary conditions, the results needs to be thoroughly analysed and compared with existing prediction methods. It is for these reasons that such full-scale testing is time-consuming and costly. The work presented in this paper aims at clarifying and quantifying the effect of existing test boundary conditions on the results of collapse tests (collapse pressures). Correlations will be established between material properties found in laboratory tests and associated component behavior. In this context it had been necessary to develop an accurate and reproducible compression test method. The actual collapse pressures and those predicted using current available equations are compared and verified by Finite Element calculations. The paper concludes with a discussion of the major findings and with a brief outlook to future research issues.



1994 ◽  
Vol 116 (1) ◽  
pp. 93-100 ◽  
Author(s):  
S. Kyriakides ◽  
E. Corona ◽  
F. J. Fischer

A commonly used process for manufacturing large-diameter tubes for offshore pipeline, riser and tension-leg platform tether applications involves the cold forming of long plates. The plates are bent into a circular shape and then welded. The circumference of the pipe is then plastically expanded to develop a high tolerance circular shape. Collectively, these steps comprise the U-O-E manufacturing process. These mechanical steps cause changes in the material properties and introduce residual stresses in the finished pipe. This paper presents the results of a combined experimental and analytical study of the effect on the U-O-E process on the capacity of the tube to resist collapse under external pressure loading. The U-O-E manufacturing process for a 26 in. (660 mm) diameter, 1.333 in. (33.86 mm) wall thickness pipe was simulated numerically. The numerical process was validated by comparing the predicted stress-strain behavior of the material at two stages in the process with properties measured from actual pipe specimens obtained from the mill. Following the simulation of the U-O-E process the collapse pressure was calculated numerically. The manufacturing process was found to significantly reduce the collapse pressure. A similar pipe for which the final sizing was conducted (simulated) with circumferential contraction (instead of expansion) was found not to have this degradation in collapse pressure.



Author(s):  
Giannoula Chatzopoulou ◽  
Gregory C. Sarvanis ◽  
Chrysanthi I. Papadaki ◽  
Spyros A. Karamanos

Large-diameter spiral-welded pipes are employed in demanding hydrocarbon pipeline applications, which require an efficient strain-based design framework. In the course of a large European project, numerical simulations on spiral-welded pipes are conducted to examine their bending deformation capacity in the presence of internal pressure referring to geohazard actions, as well as their capacity under external pressure for offshore applications in moderate deep water. Numerical models that simulate the manufacturing process (decoiling and spiral cold bending) are employed. Subsequently, the residual stresses due to cold bending are used to examine the capacity of pipe under external pressure and internally-pressurized bending. A parametric analysis is conducted to examine the effect of spiral cold forming process on the structural behavior of spiral welded pipes and the effect of internal pressure on bending capacity. The results from the present study support the argument that spiral-welded pipes can be used in demanding onshore and offshore pipeline applications.



Author(s):  
Franz Martin Knoop ◽  
Volker Flaxa ◽  
Steffen Zimmermann ◽  
Johannes Groß-Weege

The paper discusses the development and processing of hot rolled X80 coil material and its conversion into thick-walled helical seam welded pipes. Microstructure, texture and mechanical properties of strips and pipes produced are characterized and compared. High strength characteristics and good deformability as a result of the fine homogenous mainly bainitic microstructure have been determined. Stress strain characteristics and the response to cold deformation during pipe forming have been investigated. Correlations between strip and pipe properties are described and have been used as a data basis for FEM simulations of the pipe forming process. The real pipe behavior has been investigated by means of burst tests performed on 48″ and 42″ pipe sections with 18.9mm wall thickness. The results achieved have been compared with results for other pipe grades, dimensions and types of pipe. An outlook will be given on future material and process development steps and use of X80 HSAW-pipes produced.



2008 ◽  
Vol 584-586 ◽  
pp. 661-666 ◽  
Author(s):  
Enrico Bruder ◽  
Tilman Bohn ◽  
Clemens Müller

Linear flow splitting is a new cold forming process for the production of branched sheet metal structures. It induces severe plastic strain in the processing zone which results in the formation of an UFG microstructure and an increase in hardness and strength in the flanges. Inbuilt deformation gradients in the processing zone lead to steep gradients in the microstructure and mechanical properties. In the present paper the gradients in the UFG microstructure and the mechanical properties of a HSLA steel (ZStE 500) processed by linear flow splitting are presented, as well as a calculation of local strength from hardness measurements on the basis of the Ludwikequation. In order to investigate the thermal stability of the UFG microstructure heat treatments below the recrystallization temperature were chosen. The coarsening process and the development of the low angle to high angle grain boundary ratio in the gradient UFG microstructure were monitored by EBSD measurements. It is shown that heat treatment can lead to a grain refinement due to a strong fragmentation of elongated grains while only little coarsening in the transverse direction occurs. A smoothing of the gradients in the UFG microstructure as well as in the mechanical properties is observed.



Author(s):  
Rodrigo De Lucca ◽  
Rafael F. Solano ◽  
Doug Swanek ◽  
Fabio B. de Azevedo ◽  
Fábio Arroyo ◽  
...  

Energy consumption outlook shows that the demand for Oil and Gas is increasing worldwide and since most of the undemanding reserves are already being explored, new reserves means longer distances from the shore and increasing water depths, of up to 3,000 meters. Collapse resistance has become a key factor in the design of pipelines for ultra-deepwater applications. UOE process is commonly used for manufacturing pipelines of large diameter and the cold work involved in this forming process modifies the mechanical properties of the pipes. This paper presents the effect of thermal treatment on final material properties, proving the validity of enhancing collapse for different D/t, as allowed by DNV-OS-F101 αFab, and extending what has been shown as valid on previous studies. In this work, the inputs for the processing strategies are presented, along with coupon compression testing and full scale testing, in order to qualify the selected route as compliant with producing pipes with αFab equal to 1, for usual D/t combinations. An analysis of the predicted collapse pressure compared to the real collapse pressure of the pipes is also presented. The extension of the qualification process achieved successful results and allows the use of a fabrication factor equal to 1 in ultra-deepwater offshore pipeline projects. This enables the reduction of wall thickness, generating reductions in material and offshore installation costs and also potentially enhancing the feasibility of many challenging offshore projects.



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