# 2012 Barcelona
Keywords : PE, Pressure Surge, Force Main Force mains, by the nature of their operation, commonly generate cyclic loading conditions which, in some cases, can be quite severe. Consideration of these cyclic loads is, therefore, a critical component of force main piping design. This paper examines the demands of force main applications and the projected performance of PE4710 piping materials to the repetitive surge events in these applications. The potential magnitude and frequency of surge loads in force mains is examined along with the current design approaches for PE materials for addressing these loads. The results of cyclic loading testing of PE4710 piping, both with and without butt-fusion joints, are then examined to assess the validity of the design approaches. Currently, the Dura-Line PE4710 piping has surpassed 4.2 million cycles between 0 and 1.5x’s the Pressure Class without failure (testing is on-going). The fatigue resistance of PE4710 materials is seen to be excellent, and shows these materials are capable of providing for essentially unlimited fatigue resistance under the operating conditions of force main systems. The current design approaches for both occasional (short-term) surge resistance and repetitive (long-term) fatigue resistance for PE4710 materials are conservative and justified based on the data.