Analysis of Failure Mechanisms in High-Density Polyethylene Gas Distribution Pipes in Abuja Metropolitan Distribution Network

The expansion of Nigeria's domestic gas distribution network into urban residential areas has brought increasing attention to the long-term structural reliability of high-density polyethylene distribution pipes, which are susceptible to slow crack growth, oxidative degradation, and mechanical damage during and after installation if quality control and installation standards are not rigorously enforced. This study analyses the failure mechanisms and contributing factors in high-density polyethylene gas distribution pipes extracted from failure locations in the Abuja metropolitan distribution network. A forensic failure analysis programme was applied to 18 pipe failure samples collected from the network over a two-year period, encompassing failures in straight runs, fittings, electrofusion joints, and butt-fusion joints. Failure mode categorisation, wall thickness measurement, cross-section optical microscopy, differential scanning calorimetry, oxidation induction time testing, melt flow index measurement, and scanning electron microscopy of fracture surfaces were conducted on all specimens. Slow crack growth was identified as the primary failure mechanism in 61 percent of specimens, with characteristic stress whitening and craze crack morphology confirmed by microscopy. Electrofusion joint failures represented 28 percent of the sample, with joint interface debonding attributed to surface contamination before fusion and inadequate clamp stabilisation during cooling. Oxidation induction time measurements indicated premature antioxidant depletion in pipes exposed to hydrocarbon soil contamination, consistent with reduced service life. Keywords: HDPE pipe failure, slow crack growth, electrofusion joint, failure analysis, gas distribution.