Metallic strips flexible pipe has been favored in the offshore pipelines engineering for its good corrosion resistance, high strength, easy installation etc. This new composite pipe can be regarded as promising alternative for submarine pipelines. In this paper, the cross-sectional design process for this specific kind of pipe is illustrated. Three formulas for calculating the individual strength capacities of the pipe when subjected to internal pressure, external pressure and pure bending are presented for initial screening assessment. And then a case study for an 8 inch metallic strip flexible pipe based on a shallow water application is carried out. Several FE models are established by using commercial software ABAQUS to verify the designed cross section. The two methods presented could be used to assess the structural performance of the pipe in the early design phase, which might be interesting to the manufacture engineers.
Composite pipes are extensively used in the offshore oil/gas industries for decades. Typical composite pipe, take reinforced thermoplastic pipe (RTP) as example, is favored in engineering for its good corrosion resistance, high strength, high flow rates and etc. Recently, metallic strips flexible pipe is emerging in the offshore application. It has the same advantages as RTP. Furthermore, it exhibits better on-bottom stability due to its relatively greater weight and the production costs are quite low. Fig.1 shows the typical configuration of metallic strips flexible pipe. Generally, it can be divided into three components:
an inner extruded thermoplastic tube that seals the transported products.
metallic strips reinforced layers with winding structure that provide the strength against internal pressure and tension.
an outer PE sheath that isolates the underlying layers of the pipe from external environments.
The winding angle and the geometry of the metallic strips can be selected based on the design pressure and the corresponding functional requirements. During the metallic strips flexible pipe's installation and service periods, it will inevitably carry operational and environmental loads such as external pressure, internal pressure, bending, tension, torsion and etc. The requirements of these capacities of metallic strips flexible pipe have a significant impact on the cross-sectional design. The derivations of the individual capacities for the metallic strips flexible pipe are illustrated step by step in this paper, which may be of interest to manufacturer engineers.
