Analytical Investigation of the Failure Mechanisms of Polymer-Lined Pipes Used in Corrosive Chemical Process Industries in Port Harcourt

Polymer-lined pipes are critical infrastructure components in chemical process plants, providing corrosion protection against aggressive process fluids including acids, alkalis, and halogens encountered in oil refining and chemical manufacturing in Port Harcourt, Rivers State, South South Nigeria. This study analytically investigates failure mechanisms of polymer-lined pipes retrieved from service at three chemical facilities in Port Harcourt, employing comprehensive failure analysis methodologies. Twenty-two failed pipe segments of polyethylene-lined, polypropylene-lined, and PVDF-lined constructions were examined. Failure analysis procedures included visual examination, cross-section microscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy, FTIR spectroscopy, thermogravimetric analysis, and hardness profiling across lining cross-sections. Process history, operating temperature, fluid chemistry, and service duration were documented for each failed component. Results identified three primary failure modes: blistering from permeant accumulation at liner-substrate interface in 45 percent of cases, longitudinal cracking from thermal cycling stress in 32 percent of cases, and chemical degradation of polymer liner from process chemical incompatibility in 23 percent of cases. Blistering was most prevalent in lower-temperature applications where permeant vapour pressure drove delamination. Chemical degradation was associated with unexpected process upsets introducing chemistries outside the liner material service rating. Thermal cycling cracks initiated at liner end connections and propagated along extrusion flow lines. The study provides a structured failure classification framework and recommends liner material selection protocols, connection detail standards, and process chemistry monitoring procedures for chemical plant operators in South South Nigeria to reduce polymer-lined pipe failure rates. Keywords: polymer-lined pipe, failure analysis, corrosion protection, chemical process industry, Port Harcourt