# 1982 York
Fracture propagation is a phenomenon in which a long brittle crack runs along the pipeline at high speeds of approximately 350 m/s. More stringent operating and test pressures of larger diameter polyethylene gas pipes have had to be introduced nationally. Full scale tests on 250 mm SDR 17.6 medium and high density polyethylene pipes have been conducted to define safe pressure levels for crack arrest. The arrest pressures were found to be highly temperature sensitive.