# 1985 York
Hot water pipes made of cross linked polyethylene have been studied at Studsvik Energiteknik A6 since 1973. The work has mainly been concentrated to studying different evaluation and extrapolation methods. The results show that today the best method of lifetime extrapolation for hot water pipes is based upon long-term pressure testing at elevated temperature, in which the external testing environment is taken into consideration. The suitability of rapid evaluation methods like thermal analyses is limited. For the best of the cross linked polyethylene grades studied, a service life of 50 years can be expected at a continuous temperature of up to 85 to 90'~.