Z. Jimmy Zhou
# 2012 Barcelona
(Keywords : Polyethylene pipe, ligament stress, regression, notch depth, lifetime.) Hydrostatic test was conducted on notched PE100/PE4710 black pipe specimens at various temperatures and stresses. Hoop stresses were normalized to ligament stresses by taking into consideration of the effect of wall thickness reduction of the notched pipe. It was found that the ligament stress versus failure time points fell on to the same master curves regardless of notch depths. Ligament stress regression was conducted. The extrapolated 100-year LTHS exceeded the maximum hydrostatic design stresses at 20°C for 8 MPa and 40°C for 5.92 MPa for PE100, and 23°C for 1000 psi and 60°C for 630 psi for PE4710. The 100-year life was validated by the extrapolated ligament stresses. The ligament stress regression data offered a new approach to estimate the maximum wall thickness reduction. For PE100 water pipe, the projected maximum wall reduction was 38% at 20°C and 26% at 40°C. For PE4710 water pipe, the maximum wall thickness reduction was 42% at 23°C and 12% at 60°C. For PE100 gas pipe, the maximum wall thickness reduction was 60% at 20°C. For PE4710 gas pipe, the maximum wall thickness reduction was 70% at 23°C and 54% at 60°C with a 0.32 design factor.