# 1985 York
As polyethylene pipes increase in size above 250 mm, the avoidance of high-speed brittle fracture propagation becomes of overriding importance. More stringent operating and test pressures have had to be introduced. A full scale test programme on a variety of pipe sizes is being conducted by British Gas. In this paper, the results on several 250 mm SDR17.6 pipes are presented and in order to study the phenomenon more closely, the fracture speeds and initial decompression speed of the internal air pressure have been measured. It was concluded that fracture propagation will not occur in these British Gas pipes during pressure testing at 3 bar and that, as expected, the strain energy theory is highly conservative.