# 1992 Eindhoven
Eight excavated HDPE pipes of the 1st generation along with 3 modern PE types have been investigated. Comonomer content as a function of molecular weight of the old HDPE pipes appeared to be nonoptimal with respect to the modern PE types. Further unwanted effects in the old pipes were : particles, oxydation, inhomogeneity. Premature failures were due to previously unexpected effects of external point loadings.
Author(s) : Ernst van der Stok, Frans Scholten 2016 Berlin
Samples machined directly from pipe show that orientation has a large influence on the strain hardening modulus. No effects arising as a result of residual stresses were found. Samples machined in the axial direction from a hydrostatic pressurised pipe showed no effect as a result of this mechanical degradation. For...
Author(s) : Frans Scholten, Ernst van der Stok 2016 Berlin
The residual quality of first generation PE50 gas pipes, installed in Netherland between 1961 and 1979, is still remarkably good. The only premature failures of a few PE50 pipes were exclusively caused by point loads. When under point loading, they started failing in practice after 8 to 26 years, in a brittle manner....
Author(s) : Frans Scholten, Ernst van der Stok, Britta Gerets, Mirko Wenzel, Mike Boege 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...
Author(s) : Ernst van der Stok, Jeroen Weller, Frans Scholten 2016 Berlin
This paper describes falling-weight tests as a first step towards determining the effect of residual stresses on the fracture behaviour of old PVC-U gas pipes at impact. Results showed that the level of surrounding pipe support, the quality of the material and the diameter of the striker had a major effect on the...
Author(s) : Frans Scholten, Ernst van der Stok, Jan Breen 2014 Chicago
Very occasionally PVC-U water pipes suddenly fail due to a long brittle crack with a length of many meters which propagates with the speed of sound along the pipe and causes extensive water loss. This phenomenon has been recognized as Rapid Crack Propagation (RCP). The conditions under which RCP can occur are an...
Author(s) : Frans Scholten 2014 Chicago
When electro fused joints in newly installed PE100 pipelines are tested using the Peel test (ISO 13954 [1]) they too often fail in a brittle manner. Contamination in the interface between the surfaces to be fused is usually the cause. About 77 % of the contaminants in 39 cases of brittle test bars could be identified...
Author(s) : Ernst van der Stok, Frans Scholten 2014 Chicago
The Strain Hardening (SH) test and the Point Load Test (PLT) are two complementary tests designed to determine the quality of PE 100-RC. The SH test is a resin test, whereas the PLT is a pipe test. The SH test is a tensile test performed at 80 °C. Extensive research on the SH test has been conducted and published in...
Author(s) : Hella J.M.Rijpkema, Hendrik J.Roebers, Marco C.A.Mekes 2012 Barcelona
The application of plastic pipework for gas inside buildings is still restricted by national laws or local regulations in many countries, while other countries allow this application. The exclusion of plastics is in the main based on the supposed fear of the impact of a fire on the pipework and the escape of unburned...
Author(s) : Van der Stok, Scholten 2012 Barcelona
The Strain Hardening (SH) test developed by Kurelec et al. has been applied to a variety of PE pipe and resin materials. The clear trend in the strain hardening modulus, of first, second and third generation PE pipe resins and PE100 RC pipe resins, illustrates the large progress in resin quality during the past four...
Author(s) : E.J.W. van der Stok, F.L. Scholten, L.G.P. Dalmolen 2010 Vancouver
A mathematical model was set up to assess the equilibrium gas pressure in the annulus of the reinforcement layer of an RTP pipe. This is done by using the theory of gas permeation, ruled by Fick's Law and the theory for a temperature gradient over the pipe wall, ruled by Fourier's law. The model allows calculating the...
