ACCEPTANCE CRITERIA FOR VOLUME DEFECTS IN WELDED ASSEMBLIES, DETECTED AND SIZED USING THE PHASED ARRAY ULTRASONIC TECHNIQUE

Papers # 2018 Las-Vegas

Given the virtual absence of available up-to-date results regarding the acceptance criteria for defects at electro-welding interfaces, a study has been launched by GRTgaz RICE with the two-fold aim of confirming the accuracy of the PAUT technique for the detection and sizing of calibrated pit-shaped defects implanted in an electrofusion(EF) tapping saddle on the one hand, and of evaluating the harmfulness of these volume defects on the mechanical strength of a pipe-saddle EF assembly through hydrostatic pressure testing, on the other hand. This study reveals the good reliability level of PAUT in detecting and sizing the volume defects - even the smallest ones - implanted in the saddles on the one hand, and the fair correlation existing between PAUT and X-Ray Tomography as a complementary technique on the other hand. The hydrostatic pressure tests do not reveal any detrimental influence of the defects – in terms of both location and size - on the mechanical resistance of the welded assemblies in these laboratory conditions. At this stage, pending complementary investigations, no correlation can be established between the observed failure times and the position and size of the volume defects implanted in the tapping saddles.

Phased Array Ultrasonic Technique (PAUT) is currently recognised as the reference technique for non-destructive evaluation of electrowelded assemblies. Therefore, over the past five years, CRIGEN has managed a research pogram comprising various test campaigns both on assemblies recovered from the field and on lab specimens. The primary aim of these campaigns was to evaluate the accuracy of the technique, on the one hand in terms of the detectability of defects mainly located at the pipe-fitting interface and, on the other hand, in terms of the sizing of detected defects. Moreover, an attempt was made to correlate the proportion and distribution of surface defects with the results of peel decohesion tests; but the low sensitivity of these mechanical tests made it difficult to establish a reliable link between the energy required for decohesion and the distribution and proportion of the surface defects. Now the implementation of acceptance criteria for defects – either surfacic or volumic - in welded assemblies requires the establishment of strong correlations between PAUT data and mechanical tests capable of representing long-term performances. But to date, an extremely limited number of relevant studies have been published in this field and the subject is still a matter of debate, as seen during the NDT workshop of the Plastic Pipes XVIII. Consequently GRTgaz Research and Innovation Center for Energy has launched a new campaign in 2016 focused on the volume defects, with the two-fold aim of confirming the accuracy of PAUT for the detection and sizing of volume-type defects implanted in a pipe- saddle electrowelded assembly on the one hand, and evaluating the harmfulness of volume defects on the mechanical resistance of assemblies through hydrostatic pressure testing on the other hand. For this purpose, four pit-shaped defects were hot-machined in the heating area of a 63 mm saddle at three different locations (outer, middle and inner crown). For a given configuration, the defects had four different heights in the saddle body. PAUT examination during the welding cycle allowed evaluating the changes in height of the defects. X-ray tomography analysis was used to complete the PAUT evaluation and to evaluate the final shape of the implanted defects. Hydrostatic pressure testing was then applied to the welded assemblies up to failure, with regard to the NF EN 1555 standard requirements. Finally peel tests were carried out in order to confirm the crack paths. This study reveals the good reliability level of PAUT in detecting and sizing the volume defects in the saddles on the one hand, and the fair correlation existing between PAUT and XRay Tomography as a complementary technique on the other hand. The hydrostatic pressure data do not reveal any detrimental influence of the defects – in terms of both location and size - on the mechanical resistance of the welded assemblies in these laboratory conditions. Duplicate tests should be made in order to confirm this point.

Related keywords : Polyethylene (PE); Phased Array Ultrasonic Testing (PAUT); Calibrated volume defects; Electro-welded assemblies; Acceptance criteria; X-Ray Tomography.
Please note that the whole article content is available on PPCA website onlySource : 2018 Las-Vegas


Related papers

AGING MECHANISM OF POLYETHYLENE PIPE MATERIAL IN CHLORINE DIOXIDE AND HYPOCHLORITE SOLUTION

Author(s) : Márton Bredács, Andreas Frank, Amaia Bastero, Alex Stolarz, Gerald Pinter 2018 Las-Vegas

Accelerated aging experiments by the immersion of a commercial polyethylene (PE) pipe grade in 10 ppm of chlorine dioxide (ClO2) and in 100 ppm of hypochlorite (HOCl) solution at 60 °C were performed. An additional immersion test was conducted in 1 ppm of ClO2 at 40 °C. The exposure parameters were continuously...

ASSESSING THE REMAINING SERVICE LIFETIME OF PE PIPES: AN AUSTRALIAN CASE STUDY

Author(s) : Nolene Byrne, Rasike De Silva, Keith Lenghaus, Tim Hilditch 2018 Las-Vegas

Plastic pipes have been utilized in the Australian gas distribution network since the early 1970s. The most common plastic type found in Australia is polyethylene (PE), although nylon is extensively used in New South Wales. Early installation of PE pipe was completed using the first generation high density type PE50...

CHARACTERIZATION OF POST-USE POLYETHYLENE AND POLYPROPYLENE RECYCLATE BLENDS FOR PIPE APPLICATIONS

Author(s) : Markus Gall, Reinhold W. Lang, Joerg Fischer, Ansgar Niehoff, Steven Schmidt 2018 Las-Vegas

Despite recent efforts in promoting the utilization of recycled polymeric materials for more diverse and more advanced applications, there are still significant knowledge gaps with regards to the applicability of certain recyclate types for specific “re-use” purposes. When it comes to pipe applications, for...

DEVELOPMENT OF CYCLIC PRESSURE FATIGUE (CPF) TEST METHOD

Author(s) : Ernest Lever 2018 Las-Vegas

Six different polyethylene materials were tested using Cyclic Pressure Fatigue (CPF) as the accelerating process to correlate the results to conventional long-term hydrostatic test results that were previously developed as part of the material qualification process. The designation of the materials was unknown to the...

DEVELOPMENT OF POLYETHYLENE BALL VALVE TO PURSUE ROBUSTNESS

Author(s) : Ryosuke Nagahisa, Shinichi Katoh 2018 Las-Vegas

We investigated the possibility of using a greaseless polyethylene (PE) ball valve by applying a coating on it to improve the valve’s robustness. In order to verify the valve’s operability, we performed initial-operating-torque, abrasion, and dust tests on both grease-applied and coatingapplied ball valves. These...

EFFECT OF CARBON BLACK DISTRIBUTION ON POLYETHYLENE PIPES

Author(s) : Suleyman Deveci, Nisha Preschilla, Birkan Eryigit 2018 Las-Vegas

Pipes with inhomogeneous CB distribution showed 80% less elongation than pipes with homogenously distributed CB. Polymer domains with less or no CB (windows) showed delamination from the polymer matrix as the material elongated, finally leading to fracture much earlier than expected. In this study, we investigated the...

EXTRUSION OF THICK WALL PIPES USING A NEW BIMODAL PE 4710/PE 100 RESIN

Author(s) : Vivek Rohatg, Gregor Hiesgen, Mark J. Lamborn, Ashish M. Sukhadia, Douglas E. Simpson, David W. Borrego, Pamela L. Maeger 2018 Las-Vegas

Maintaining dimensions within specifications is problematic for the extrusion of large diameter thick-wall polyethylene (PE) pipe (> 75 mm wall) due to sag caused by insufficient resin melt strength. However, sag can be controlled through careful resin selection and optimization of the pipe cooling process. This...

INCREASING HDPE BUTT FUSION PRODUCTIVITY BY OPTIMIZING THE COOL TIME BASED ON THERMAL MASS CHARACTERISTICS WITHOUT COMPROMISING JOINT STRENGTH

Author(s) : Amanda Hawkins, Jason Lawrence, Xiangli Meng 2018 Las-Vegas

High Density Polyethylene pipes are used in various applications due to the material’s superior chemical resistance, pressure capability, and ductility. For the material to perform at the optimal design criteria, the connections and fabrications must be fused using repeatable procedures that specify proper fusion...

LABORATORY DEVICE FOR CHECKING THE THERMAL ENERGY DELIVERED BY THE ELECTROFUSION FITTINGS

Author(s) : Dominique GUEUGNAUT, Adil BOUJLAL, Aymeric LOPITAUX, Bertrand SEVRE 2018 Las-Vegas

A special concept has been developed by GRTgaz Research and Innovation Center for Energy (RICE) for temperature mapping at the interface of an electrowelded assembly.The technical solution consists of a tubular piece in place of the real PE pipe, made of a non-weldable polymer with thermal parameters close to those of...

MODERN PE PIPE ENABLES THE TRANSPORT OF HYDROGEN

Author(s) : R.J.M. Hermkens, H. Colmer, H.A. Ophoff 2018 Las-Vegas

To investigate the suitability of PE pipes for the transport of hydrogen on a specific industrial site, three topics were investigated. These topics are: the chemical resistance of PE to hydrogen, the permeation rate of hydrogen through PE and the electrofusion of PE pipes exposed to hydrogen. It can be concluded that...

NEW DISCOVERIES IN STABILIZING DRINKING WATER PIPES IN CONTACT WITH CHLORINE DIOXIDE

Author(s) : J.D. Kim, S. Kim , T. Schmutz, C. Malchaire, D. Scholz, K. Keck 2018 Las-Vegas

Since a few years, pipe producers are facing the challenge to protect their plastic pipe from degradation due to chlorine dioxide. Unfortunately, most existing stabilization solutions are not effective enough to insure the desired lifetime of the material. This study shows how the latest development allow to top-up...

PERFORMANCE EVALUATION OF COUNTER-ROTATING CONTINUOUS MIXER AND CO-ROTATING TWIN SCREW EXTRUDER FOR HIGH DENSITY POLYETHYLENE

Author(s) : Sayaka Yamada, Kazuhide Sekiyama, Shiori Watanabe, Kazuo Yamaguchi, Hideo Funahashi 2018 Las-Vegas

Performance evaluation method of plastic mixers for high density polyethylene by using flow simulation is presented in this study. First, Mixing experiments were performed to find the mixing performance of mixers. Then, flow simulations using our original software in the mixers were carried out to know the important...

POLYETHYLENE PIPELINE PERFORMANCE AGAINST EARTHQUAKE

Author(s) : Hideki Omuro, Tomokazu Himono 2018 Las-Vegas

In Japan, polyethylene (PE) pipe have been used for a long time, but its usage is limited for water service (low density PE / PE 50) and gas service (medium density PE / PE 80). However, after Hyogoken Nanbu Earthquake in 1995, it started to sell PE pipes for water distribution applications, because no damage on PE...

PREPARATION AND STUDYING OF THERMOPLASTIC CROSS-LINKED POLYETHYLENE

Author(s) : Cheng Zhi, Mingyuan Hu, Kaige Duan, Chaoxi Zhou, Dongming Yu 2018 Las-Vegas

The PE properties are obviously improved by crosslinking modified to TPEX, which can approach to that of PEX, while still remaining thermoplastic. It can be processed by the common forming method of thermoplastic; the products can be hot-melted and the scrap can be processed to be reused. The two-layer structure...

PRESERVING MARINE ENVIRONMENT FROM HYDROCARBONS CONTAMINATION WITH LEAK-FREE PE100 PIPES USED IN OFF-SHORE OIL WELLS

Author(s) : Farraj Tashman, Mohamed Ali Jaber, Sultan Al Kendi 2018 Las-Vegas

Analysis of subsea PE100 pipeline conveying oil produced water effluent with traces of hydrocarbons was done after 5 years of leak-tight continuous operation at boundary conditions showed that properties of PE100 pipes are intact when benchmarked with test results conducted on reference pipe sample kept for this...

QUALITY ASSURANCE ON WELDED JOINTS WITH THE MECHANISED LINEAR SHEAR TEST (LST)

Author(s) : Juergen Wuest, Benjamin Baudrit, Frank Dorbath, Christopher Pommer 2018 Las-Vegas

A testing apparatus for determining the mechanical properties of electrofusion and heated tool sleeve welded joints with the mechanized linear shear test (LST) was developed. The LST-apparatus allows the recording of the force as a function of the extension / shear length. It has been proved that the linear shear test...

SENSITIVITY OF STRAIN HARDENING MODULUS TO MOLECULAR STRUCTURE OF POLYETHYLENE

Author(s) : Suleyman Deveci, Senthil K. Kaliappan, Joel Fawaz, Umesh Gadgoli 2018 Las-Vegas

A series of non-commercial bimodal high density ethylene-α-olefin copolymers with systematically controlled molecular parameters over a wide range that would result in extremely low and high strain hardening modulus were prepared and tested Strain hardening modulus has been published as a standard test method (ISO...

SLOW CRACK GROWTH RESISTANCE OF NON-VIRGIN POLYMERS

Author(s) : Andreas Frank, Isabelle J. Berger, Mario Messiha, Carl-Gustaf Ek, Norbert Schuler, Jens-Martin Storheil, Erwin Mayrbäurl, Steve Heeley, Frank Krause, Lodewijk Niemöller, Philippe Gabriëls, Yogesh S. Deshmukh, Florian Arbeiter, Thomas Koch, Gerald Pinter 2018 Las-Vegas

In order to improve the circular economy of polymers in terms of sustainability and reduced carbon footprint, the increased use of recyclates has become a topic of major importance. Due to their long design lifetimes, pipe applications represent an excellent opportunity to create added value to non-virgin polymers. In...

SQUEEZE-OFF AND REROUNDING OF PLASTIC PRESSURE PIPES

Author(s) : Juergen Wuest, Mirko Wenzel, Andreas Bilsing, Peter Postma, Werner Wessing 2018 Las-Vegas

Within the scope of a DVGW (German Technical and Scientific Association for Gas and Water) research project the technology of squeezing-off for PE pipes at operating pressures higher than 1 bar and the extension to new materials with higher operating pressures were investigated. For this purpose the tightness of the...

STUDY ON PARAMETERS AFFECTING DURABILITY OF POLYETHYLENE PIPES FOR HOT WATER APPLICATION

Author(s) : Hirofumi Kyutoku, Kazuhisa Igawa, Hidekazu Honma, Sakiko Fukunishi, Hiroyuki Nishimura 2018 Las-Vegas

There are mainly two grades of polyethylene pipes for hot water supply and heating. The excellent molecular structure polyethylene resins having resistance to stress crack growth are used because hot water is flowed for a long time in both polyethylene pipes. Furthermore, various additives are mixed to prevent the...

Members of the Association

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