Frans Scholten, Ernst van der Stok, Britta Gerets, Mirko Wenzel, Mike Boege
Papers # 2016 Berlin
The current condition of 35-50 years old uPVC main (110 mm) and service (32 mm) pipes for gas and water distribution was assessed. From 27 excavation sites in total about 400 segments of 1.2 meters length each were tested using many techniques. The K-value (average molecular weight) of the PVC, the degree of gelation (Differential Scanning Calorimetry and the Dichloromethane Test) and the relative calcium carbonate concentration using FTIR spectroscopy were measured. Residual pipe stresses in the hoop direction were measured using the Janson method. The Longitudinal Reversion Test was used for frozen-in deformations in axial direction. All pipes still meet the requirements of Hydrostatic Pressure (HP) tests at 20 and 60 °C. Cyclic Step-Load Tests (Fatigue Tests) were also carried out. To study impact behavior Tensile Impact tests and Rapid Crack Propagation (RCP) tests were performed. The RCP (S4) behavior is rather good. The residual quality of solvent-cemented joints was assessed (Linear Shear Test and the homogeneity of the solvent cement distribution) and was found to be good as well.
Correlation analyses were also performed on the test results. The year of installation and the operation pressure were found to have no influence on the pressure resistance of the pipes. Effects of ageing of the uPVC pipes were thoroughly investigated but have not been found.
The excavated pipes still meet the relevant requirements of modern standards such as EN 1452, regarding installation and service durability. The results obtained show no limitation for further operation of the investigated uPVC pipelines during several decades to come. The integrity of the pipelines is good.
