Liner stability analysis for HDPE-lined pipe under bending

For the transport of hydrocarbons that may contain corrosive elements such as H2S, CO2 or other corrosive products, the steel pipelines are required to be lined with corrosion resistant alloys (CRAs) liner for better corrosion resistance and service life of the pipeline. However, the CRA-lined pipes are special made-to-order products that can be quite expensive due to high cost of the liner and the manufacturing techniques involved. A promising alternative technology to CRA-lined steel pipelines is the use of HDPE-lined steel pipe. This will improve the corrosion resistance and prolong service life of the pipelines. The plastic-lined pipe consists of a thermoplastic inner liner and a carbon steel outer pipe. One of the possible failure modes which could be considered in offshore pipeline installation is the stability of the liner under bending. Nonlinear Finite Element (FE) models have been developed to study the liner behaviour under bending during the offshore installation phase. The outer pipe has been modelled using shell elements while the liner has been modelled using three-dimensional brick elements in Abaqus/Standard. The effects of different types of liner fit (e.g., snug-fit, tight-fit), contact pressure and friction between the outer pipe and the liner on the stability of the liner have been explored. For large diameter lined pipe (24 in.), the minimum bend radius for the pipeline which could safely be applied during installation without the buckling and separation of the liner has been determined.