Characterization of Crack Initiation and Slow Crack Growth Resistance of PE100 and PE100-RC pipe Grades with Cyclic Cracked Round Bar Tests


Papers # 2014 Chicago

During the past years the Cyclic Cracked Round Bar (CRB) Test has been developed and meanwhile standardized as a new and modern test method for a quick material ranking of polyethylene pipe grades by their resistance against slow crack growth (SCG). As an additional benefit this test method allows a very precise determination of crack initiation which provides further lifetime relevant information of the material. The objective of the current paper is a demonstration of the practical application of the Cyclic CRB Test for a quick material ranking. On the one hand, the study of the crack initiation and SCG behavior of ten PE 100 and PE 100-RC pipe grades from five different raw material supplier demonstrate that there are significant differences in the material performance, even within one material class. On the other hand, based on the failure curves of 35 different PE pipe grades the results show that, at least at room temperature, the performance of PE 100 and PE 100-RC has an overlap.

Pressurized pipes of polyethylene (PE) used for gas and water applications are designed to fulfill operating times of at least 50 years [1-6]. As a result of developments and improvements of the raw materials, particularly in the bimodal molecular mass distribution and in the controlled implementation of short chain branches, an increase in minimum service expected [5]. The classification of PE pipe grades is based on the long-term failure behavior of internal pipe pressure tests at different temperatures and extrapolation methods as described in EN ISO 9080 [7] or ASTM D2837 [8]. The long-term failure mechanisms of pressurized PE pipes have been studied comprehensively and are well known as crack initiation and quasi-brittle slow crack growth (SCG) [2, 3, 9-11]. Internal pipe pressure tests on PE pipe grades typically last several months or even years. In practice testing of pipes that do not fail after duration of 104 hours (approx. 13.5 months) are usually stopped. Based on such tests the minimum required strength (MRS) to ensure pipe lifetimes of at least 50 years is determined and leads to a classification of the materials as PE 63 (MRS=6,3 MPa), PE 80 (MRS=8 MPa) or PE 100 (MRS=10 MPa). For PE 100 which also pass the requirements according PAS 1075 [12] an additional classification PE 100-RC (RC=Resistant to Crack) has been defined.

The appreciated material improvements of the raw material suppliers have increased the failure times of internal pipe pressure tests significantly resulting in time consuming and expensive test procedures. Especially for modern grades of the classification PE 100 and PE 100-RC no quantitative information about the relevant quasi-brittle failure region can be determined with internal pipe pressure tests anymore. To meet the demand for an accelerated material characterization and to rank different materials by their SCG resistance, several laboratory tests like the Notched Pipe Test (NPT) [13-15], the Pennsylvania Edge-Notch Test (PENT) [16-18], the Notched Ring Test (NRT) [19] or the Full Notch Creep Test (FNCT) [20-22] have been developed. All this test methods are usually conducted at elevated temperatures of T=80 °C or even under the influence of stress cracking liquids (FNCT). Although the mentioned tests provide a significant acceleration of testing times, characterization of modern PE pipe grades is still related to long testing times of several months up to years. According to further time reduction in the characterization of SCG properties, recent studies have shown promising results 2 Copyright © 2014 by PPCA for two new test methods, the Strain Hardening Modulus [23-26] and the Cyclic Cracked Round Bar (CRB) Test [27-47] which has been recently standardized by the Austrian Standards Institute in ONR 25194 [48].

The current paper investigates ten PE 100 and PE 100-RC pipe grades from five different raw material supplier which are currently available in the market with the Cyclic CRB Test. On the one hand, the results demonstrate the practical application of the Cyclic CRB Test for a quick material ranking by the crack resistance of the materials. On the other hand, the additional information about crack initiation also allows a more detailed investigation of the materials. Moreover, based on Cyclic CRB Tests of 35 different PE pipe grades in the laboratory of the authors the generated data demonstrate that different failure ranges are determined depending on the PE classification and that, at least at room temperature, the failure performance of PE 100 and PE 100-RC has an overlap.

Related keywords : crack, pe100, material, based, slow, resistance, mpa, different.
Please note that the whole article content is available on PPCA website only

Related papers

2018 Las-Vegas : Accelerated pipe test methods to evaluate PE 100-RC materials - Possibilities for iso standardisation

Author(s) : Thomas R. Kratochvilla, Raimund Eremiasch, Christoph Bruckner

In the last years effort has been made to develop and standardise new accelerated test methods to evaluate PE 100-RC materials in short times in form of test bars. The two most important developments, the cracked round bar test (CRB test) and the strain hardening test (SH test) were published as final ISO standards in...

2018 Las-Vegas : 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

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...

2018 Las-Vegas : Chlorine dioxide resistant HDPE mechanism, analytical tools and solutions

Author(s) : M. Boerakker, S. van Mierloo, D. v. Beek, R. Schipper, P. Voets, M. Soliman, K. Jacobson, D. Lukes, B. Rabaud, F. Zraick

HDPE pipes are used for standard pressurized water pipes, offering an excellent solution for safe transport of (drinking) water. The HDPE pipe market is growing globally. Especially in countries that suffer from water scarcity, surface water and water from rivers have to be used for drinking water supply. To guarantee...

2018 Las-Vegas : Determination of the slow crack growth resistance of PA12 pipe grades

Author(s) : Mario Messiha, Andreas Frank, Isabelle J. Berger, Jan Heimink, Hermann van Laak, Florian Arbeiter, Gerald Pinter

Since the last decade polyamide 12 (PA12) has been successfully introduced as material for SDR 11 gas piping systems up to 18 bar, representing itself as an attractive alternative to steel pipes for high-pressure applications. Practical experience has confirmed that beside the higher strength, PA12 pipe grades also...

2018 Las-Vegas : Effect of beta-nucleation on aging and crack growth resistance of polypropylene exposed to chlorinated water

Author(s) : Joerg Fischer, Paul J. Freudenthaler, Patrick R. Bradler, Reinhold W. Lang, Susan C. Mantell

This research addresses the effect of nucleation on the global aging behavior and the fatigue crack growth (FCG) resistance of commercial alpha- and beta-nucleated polypropylene random copolymer pipe grades (PP-R) when exposed to chlorinated water (5 mg/l free chlorine) at an elevated temperature of 60°C. Comparing...

2018 Las-Vegas : Evaluation and comparison of standard and accelerated slow crack growth determination methodologies: effect of the comonomer type influence

Author(s) : Carlos Domínguez, Álvaro Pérez, Nuria Robledo, Cristina González, Beatriz Paredes, Rafael A. García-Muñoz

Last methodologies for fast evaluation of the SCG resistance on polyethylene pipe materials are analyzed in this work and compared with traditional PENT and FNCT tests. Strain Hardening (SH), Crack Round Bar (CRB) and Accelerated Creep Test (ACT) will be good alternatives for evaluating PE100RC resins. Moreover, SH...

2018 Las-Vegas : Fatigue crack growth testing in chlorinated water at elevated temperatures - Test equipment and test procedure

Author(s) : Joerg Fischer, Patrick R. Bradler, Reinhold W. Lang

In the present paper, a novel test system for conducting fatigue crack growth (FCG) experiments under superimposed mechanical-environmental conditions is presented. FCG experiments were performed on a polypropylene (PP) grade and a short-glass fiber reinforced polyamide 66 (PA-GF) grade as model materials. The...

2018 Las-Vegas : High density polyethylene (HDPE): an overview of the first ever asme bPVC section iii, class 3 nuclear piping installation

Author(s) : Ali Al Hammadi, Shane R. Schuessler, Mohamed Ali Awadh Jaber

This paper presents the advancements of HDPE piping materials, design and installation for use in ASME Class 3 piping systems at nuclear power plants. The paper will specifically introduce details of the first ever ASME Class III nuclear new build use of Class 3 HDPE pipe and fittings at the Emirates Nuclear Energy...

2018 Las-Vegas : Investigation of the failure behavior of polyethylene electrofusion sockets

Author(s) : Isabelle J. Berger, Andreas Frank, Gerald Pinter, David Nitsche, Dirk Petry

Electrofusion (EF) sockets constitute a well-established and practically proven technology for the joining of polyethylene (PE) pressure pipes. As for the pipes, the potential lifetime of such welding connections is beside other properties also depending on the resistance against slow crack growth (SCG). The current...

2018 Las-Vegas : Large pressure pipe system – Fully PE100

Author(s) : Sverre Tragethon, Martin Andersson

Global mega trends push for investments in sewage treatment capacity & efficiency. A trend is to go for central regional treatment sites, typically remotely located from dense populated cities. This calls for high capacity pressure sewage transmission pipelines. Reliable operation is of course of paramount...

2018 Las-Vegas : Modern PE pipe enables the transport of hydrogen

Author(s) : R.J.M. Hermkens, H. Colmer, H.A. Ophoff

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...

2018 Las-Vegas : Multilayer polymer pipes - Possible utilization of recycled material

Author(s) : Pavel Hutar, Jan Poduska, Pavol Dlhy, Andreas Frank, Jaroslav Kucera, Jiri Sadilek, Gerald Pinter, Lubos Nahlik

This paper investigates possible use of recycled material as a part of a multilayer polyethylene pressure pipe system. Crack propagation in different configurations is simulated. Lifetimes of pipes containing recycled material are calculated. Results are compared with lifetimes of pipes made of virgin...

2018 Las-Vegas : 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

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...

2018 Las-Vegas : Pe100 large diameter water transmission pipelines take off in Asia

Author(s) : Andrew Wedgner, Muhammad Qasim, Arsenio Sembrano

Developments in material and pipe extrusion technology now enable converters to produce PE100 solid wall pipes of up to 2,800mm OD, but the use of such large diameters has been limited to industrial applications. This is now starting to change with water transmission pipelines of up to 1400mm OD being laid in the UAE...

2018 Las-Vegas : Preparation and studying of two-layer oxygen barrier plastic pipe

Author(s) : Mingyuan Hu, Dongming Yu, Zhangcheng Chen, Cheng Zhi, Kaige Duan

Studying in barrier property of TLCP/PO alloy and EVOH/PO alloy. Filtrating formulas with extruding alloy into pipes. Trying to coat alloy on pipes and co-extrude into two-layer oxygen barrier plastic pipe. The traditional Ethylene vinyl alcohol copolymer (EVOH) barrier plastic pipe used in internal closed-loop...

2018 Las-Vegas : 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

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...

2018 Las-Vegas : Rehabilitation of abandoned dn1000mm steel pipe with PE100 in malaysia

Author(s) : KianLin Ng, WengKeong Tan, KumHoong Lou

Heavy and constant trucked container traffic combined with an accelerated ground settlement in a coastal reclaimed land caused a DN1000mm cement-lined mild steel water pipeline that crossed under it to sink by more than 6m from its original buried depth. This then caused the internal & external cement lining to...

2018 Las-Vegas : Sensitivity of strain hardening modulus to molecular structure of polyethylene

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

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...

2018 Las-Vegas : 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

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...

2018 Las-Vegas : The influence of molecular design variables of bimodal HDPE on the slow crack growth resistance measured by accelerated methods

Author(s) : Cliff Mure, Siddharth Athreya, Dane Chang, Rujul Mehta

New generations of PE100 and PE4710 pressure pipe materials exhibit a superior balance of mechanical properties. The slow crack growth performance of these materials measured by traditional tests such as PENT and FNCT can exceed one year. Accelerated test methods, including strain hardening modulus, accelerated FNCT,...

Members of the Association

BOREALISBOROUGEFormosa Plastics CorporationINEOS O&PIRPCKazanorgsintez PJSCKorea Petrochemical IND. Co., LTD (KPIC)LyondellBasellPetroChina Dushanzi Petrochemical CompanyPRIME POLYMERSABICSCG Chemicals & Thai PolyethyleneSinopecTASNEE