This International Standard specifies a method for the derivation of pressure reduction factors to obtain the allowable operating pressure for operation of polyethylene (PE) pipeline systems at temperatures between 20 °C and 50° C. NOTE 1 – The end user should take into account the maximum temperature for continuous operation and duration of operation at that temperature. NOTE 2 – Basing the design on the maximum temperature only may result in over design of the system. NOTE 3 – When the temperature profile of operation is known, ISO 13760 Miner's rule can be used for design purposes. Reference lines for PE are provided in ISO 15494, [1], [2].