Study on the Barrier Layer Structure and Failure Analysis of HBPE Liner Insertion Pipe

This study investigates the failure mechanisms of high‐barrier polyolefin (HBPE) liner insertion pipes used in oil and gas systems. Structural and mechanical analyses reveal that the pipe utilizes an ethylene‐vinyl alcohol copolymer (EVOH) barrier layer with excellent gas resistance. Crucially, field failures are driven not by chemical aging, but by the physical swelling and plasticization of the inner high‐density polyethylene (HDPE) liner due to long‐term medium exposure. This swelling drastically reduces the adhesive layer's cohesive strength, causing interfacial peel strength to drop from 5.49 to 0.59 N/mm, which triggers complete interlayer debonding and ultimate liner collapse. The long‐term reliability of these composite pipes fundamentally depends on the adhesive layer's resistance to medium‐induced swelling under actual service conditions.