Non-Destructive Ultrasonic Inspection to Detect Flaws in Plastic Pipe Walls and Joints [PEX]

# 2006 Washington DC

Ultrasonic detection equipment was used to investigate defective pipes and fusion joints. The following examples of its application are presented. Electro-fused joints were tested in four different 110mm PE100 and PEX pipes. The PEX pipes showed a less complete fusion between pipe and fitting in comparison to PE100 pipe, although there are also differences between the three types of PEX pipes. The slightly poorer joints showed internal surfaces at the fusion plane and hence a lower homogeneity of the fused material. These differences in joint quality correlate with the results of a new long-term testing method (the Slow Peel test) on the same four electro-fused joints. The differences noted by ultrasonic and Slow Peel testing were not seen using the traditional Peel test according to ISO 13954 at 23°C, performed in a tensile testing machine. PE pipes with many voids resulting from poor extrusion procedures were also inspected. At each of three locations in the pipe wall, more than one hundred individual voids could be counted. Butt-fused joints in these pipes also contained many voids. This correlated well with very poor tensile test results obtained on these joints. A defective jacket pipe from a district heating (hot water distribution) pipeline was investigated. Constant Tensile Load tests at 80°C according to EN 253 on strips taken from the jacket pipe showed a sub-standard long-term quality. Again, several voids were detected in the wall of the jacket pipe and these had clearly served as crack initiation sites. A further example was also from a district heating system. Jointed Polyethylene plugs to fill up holes in a shrink-sleeve were investigated. A brief comparison with other imaging techniques for defective PE pipe materials was made.

Please note that the whole article content is available on PPCA website onlySource : 2006 Washington DC


Related papers

DETERMINING THE RESIDUAL QUALITY OF PE PIPES USING THE STRAIN HARDENING TEST

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...

PREDICTING THE LIFETIME OF PE50 GAS PIPES UNDER POINT LOADING

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....

RESIDUAL QUALITY OF EXCAVATED UPVC GAS AND WATER DISTRIBUTION PIPELINES

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...

THE EFFECT OF RESIDUAL STRESSES AND EXTERNAL EFFECTS ON THE FRACTURE BEHAVIOUR OF PVC PIPES

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...

Designing Against Rapid Crack Propagation in PVC Water Pipes

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...

Energy-to-Failure to Assess the Quality of Electro Fusion Joints in PE Pipes

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...

Two Complementary Tests to Determine the Quality of PE 100RC

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...

Strain Hardening Tests on PE Pipe Materials

Author(s) : Van der Stok Ernst&Scholten Frans 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...

STRAIN HARDENING TESTS ON PE PIPE MATERIALS

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...

COVER BLOW-OFF RESISTANCE OF REINFORCED THERMOPLASTIC PIPES FOR GAS SERVICE

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...

Members of the Association

BOREALISBOROUGEINEOS O&PIRPCKorea Petrochemical IND. Co., LTDLyondellBasellPetroChina Dushanzi Petrochemical CompanyPRIME POLYMERSABICSCG Chemicals & Thai PolyethyleneSinopecTASNEE
TOP