PRESSURE PIPELINE MADE OF HDPE – DETERMINATION OF REMAINING LIFETIME AFTER 47 YEARS OF OPERATION IN LAKE OSSIACH (CARINTHIA, AUSTRIA)

Februari 14, 2022 by admin in Industry News, Market Reports, Uncategorized

Ulrich Schulte, Dr. -Ing. Joachim Hessel

# 2021 Amsterdam

In order to protect the Austrian lakes effectively against the discharge of effluent, a 13 km long pressure pipeline made of high density polyethylene was laid on the bottom of Lake Ossiach back in 1971. The DN355 to DN200 pipes were produced from a first generation HDPE-compound. The classification would have been close to “PE63”. [1]. This pipeline serves to collect waste water and to pump an average volume of about 1.1 Mill. m3/year with a maximum pressure of 4 bar to a nearby sewage treatment plant. The maximum temperature of the lake water is 15°C.

In the design phase in 1970 the planned lifetime for such a pipeline was set to 50 years. While this pipeline is still in operation to the satisfaction of all stakeholders, it now reaches the end of the planned operating time. As part of a general risk assessment of pressure pipelines in the Austrian lakes, studies were carried out to determine the residual life of a sample that had been installed in 1971 to allow the operator to decide whether a rehabilitation of the pipeline needs to be considered or whether a longer operation time can be justified. The studies are based on the empirical relationships for temperature dependent reactions, discovered by the Swedish physicist Arrhenius in the 19th century. The Arrhenius law allows for accelerated testing at elevated temperatures and extrapolation to expected lifetimes at ambient temperatures.

A sample of a DN 355 SDR 17 pipe had been taken from the pipeline and analysed with respect to slow crack growth resistance, as well as thermal ageing properties. With the Arrhenius approach, it could be concluded that with respect to both stress crac k resistance as well as thermal aging, the pipe made out of Ziegler HDPE could be operated for at least another 50 years, doubling the lifetime of the original plan [2]. The outcome of these investigations confirms like former investigations on other pipes

Article source : https://www.pe100plus.com/PPCA/PRESSURE-PIPELINE-MADE-OF-HDPE-DETERMINATION-OF-REMAINING-LIFETIME-AFTER-47-YEARS-OF-OPERATION-IN-LAKE-OSSIACH-CARINTHIA-AUSTRIA-p1729.html
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