Purpose: The present work attempts to examine the failure performance of high density polyethylene [HDPE] gas pipe through a fractographic study of the fracture morphology following Small Scale Steady State test (S4). Failure mechanisms are discussed based on the fracture morphologies resulting from these tests. There are many instances where the rapid propagation of cracks is the result of fluid pressure acting on piping structures. This problem is recognized as one of the most important issues of dynamic fracture mechanics. A fractographic study of the HDPE type of a gas pipe has been undertaken.Design/methodology/approach: Scanning electron microscopic (SEM) observations were used to identify elementary process involved in the crack initiation and propagation.Findings: Based on an investigation of the Small Scale Steady State (S4) test, in order to assess the fracture behaviour of polyethylene (PE) gas distribution pipe material during rapid crack propagation (RCP). Failure mechanisms are discussed based on the fracture morphologies resulting from these tests. The influence of molecular architecture on the rapid crack propagation (RCP) resistance of high-density polyethylene pipes was investigated. It was concluded that high molecular weight, high crystallinity and a relatively narrow molecular weight distribution are important architectural attributes for RCP resistance.Research limitations/implications: Applying S4 test is limited to thermoplastic materials.Practical implications: Presented method can be applied for other thermoplastic materials in the future.Originality/value: The expressed method can be applied in the future for developing the research on the process with rapid crack propagation of polymers.