The polymer barrier is the key component in a flexible pipe structure that is specifically designed to contain hydrocarbon media within the pipe. Maintaining the integrity of the barrier for the total service life of the pipe is therefore an essential requirement to prevent any leaking or spilling of the hydrocarbon into the external environment. For high temperature (> 100°C) service PVDF is commonly used as a barrier material, and the barrier designs are based on either single layer or multilayer (two or three layers) structures depending on design strategy, manufacturing constraints and service application.
This paper presents a critical review of the barrier design strategies, considering both single and multilayer structures. The main parameters in deciding a reliable barrier structure are discussed and the advantages/disadvantages of multilayers over single layers are highlighted. The different pipe failure modes/mechanisms that may be related to different barrier structures, the analyses and test requirements to evaluate and overcome these failures are discussed.