The effect of spiral cold-bending manufacturing process on pipeline mechanical behavior

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 spiralwelded pipes can be used in demanding onshore and offshore pipeline applications. © Copyright 2016 by ASME

Buckling of internally-pressurized spiral-welded steel pipes under bending

The mechanical behavior of spiral-welded large-diameter steel pipes is simulated, with the purpose of defining their bending deformation capacity against local buckling. The steel pipes are candidates for hydrocarbon onshore pipeline applications with diameter-to-thickness ratio D/t equal to 53 and 69, and are subjected to longitudinal bending under internal pressure levels ranging from zero to 75% of the nominal yield pressure. Initial geometric imperfections are considered in the form of short-wave axial wrinkles and girth weld misalignment, whereas residual stresses are taken into account as computed from a special-purpose finite element simulation of the spiral bending process, which also accounts for both de-coiling process and hydrotesting. The sensitivity of critical bending curvature on the level of internal pressure is examined, the value of buckling wave length is discussed and the effects of hydrotesting after spiral forming on structural performance are also investigated. Finally, the value of critical bending curvature is compared with analytical and empirical equations, widely used in pipeline design applications. The results of the present study determine the main parameters affecting the buckling deformation capacity of large-diameter spiral welded pipes in a strain-based design framework, and indicate that these pipes can be used in demanding pipeline applications, such as in geohazard areas. © 2018 Elsevier Lt

Modelling of spiral-welded pipe manufacturing and its effect on pipeline structural performance

The increasing use of large-diameter spiral-welded pipes in demanding hydrocarbon pipeline applications constitutes an engineering challenge, which requires the definition of an appropriate strain-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, and their capacity under external pressure. The manufacturing process of spiral-welded tubes consists of two steps: (a) the decoiling process and subsequently, (b) cold bending process. Numerical models are developed in finite element software ABAQUS/Standard for the simulation of the above manufacturing steps. Upon completion of the manufacturing process, the residual stresses due to cold bending are calculated, and are used to examine the capacity of pipe under external pressure and bending capacity. The results from numerical models are compared with available experimental results. Furthermore, a parametric analysis is conducted in order to examine the effect of spiral cold forming process on the structural behavior of spiral welded pipes. © Copyright 2016 by the International Society of Offshore and Polar Engineers (ISOPE)