Interpretation of the Results of the Full Notch Creep Test and a Comparison with the Notched Pipe Test [PE]

Slow Crack Growth # 2004 Milan

Design of pipe systems for lifetimes in excess of 100 years depends on accelerated testing of pipe at different temperatures, and standard extrapolation methods for assessment of the minimum required strength. However resistance to slow crack growth is an essential parameter to take into account for the development of PE materials for pressure pipe applications. The ISO 13479 Notched Pipe Test (NPT) has become well established as the benchmark test, being referenced in ISO, European, and many national and industry product standards for PE gas and water pipe. For the development of materials accelerated small-scale tests to allow rapid screening of materials and to gain an understanding of the effect of changes to the material structure are required. In recent years the Full Notch Creep Test (FNCT) has gained popularity with European PE suppliers, particularly as a tool in the development of high performance PE 100 materials. In order to accelerate this test on a notched square bar, detergents are used. A test programme using both tests on three different pipe compounds has been carried out to gain a greater understanding and interpretation of the results. The study has allowed conclusions to be reached on the interpretation of test results and the suitability of each test for product specifications.

Please note that the whole article content is available on PPCA website onlySource : 2004 Milan


Related papers

Standardisation Driving the Success of Polyethylene Pressure Piping Systems

Author(s) : S H Beech, P Belloir, C Salles 2014 Chicago

Plastics piping systems are specified against a relevant standard, giving dimensions, essential performance requirements, the design basis for pressure rating, and testing to prove fitness for purpose, giving the end user the confidence to use these systems. The plastics pipes industry has successfully developed...

HARMONISATION OF POLYETHYLENE PIPE BUTTFUSION PROCEDURES AND TEST METHODS – FINAL CONCLUSIONS

Author(s) : Stephen Beech, Christophe Salles, Ulrich Schulte 2012 Barcelona

Polyethlyene, Pipes, Buttfusion, Joining, Testing Several well established procedures are used for butt fusion welding of PE pipes globally. The most widely used are the European Single Pressure, UK Dual Pressure, and the USA High Pressure procedures. In the future it may be possible to rationalise these procedures....

HARMONISATION OF POLYETHYLENE PIPE BUTTFUSION PROCEDURES AND TEST METHODS

Author(s) : S.Beech 2010 Vancouver

Several well established procedures are used for butt fusion welding of PE pipes globally. The most widely used procedures are the European Single Pressure, UK Dual Pressure, and the USA High Pressure procedures. In the future it may be possible to rationalise these procedures. Materials and machinery developments are...

Mechanisms of Slow Crack Growth in PE Pipe Grades

Author(s) : Beech, Ferguson, Clutton 2001 Munich

Design of pipe systems for 50 year lifetimes depends on accelerated testing of pipe at different temperatures and standard extrapolation methods for assessment of whether the minimum required strength is achieved. Further acceleration is used in the notched pipe test (NPT), which is a medium term (up to 1000 hour)...

PE Pipeline Systems - The Big Success Story

Author(s) : Beech, Ducan, Millar 2001 Munich

Polyethylene has been used for pipeline applications for nearly 50 years now. It has become the prime material choice for gas and water distribution systems and many other applications worldwide. This paper reviews the growth in the market for polyethylene pipe products for both pressure and non pressure applications...

The Evaluation of Factors Governing Long Term Performance of PE Electrofusion Fittings

Author(s) : Allcard, Beech 2001 Munich

It is widely accepted that in testing, the long term fracture mode for Electrofusion (EF) socket fittings is via Slow Crack Growth (SCG), initiating from the first wire turn from the centre cold zone of the fitting. This study examines the injection moulding process and the EF welding process and their potential to...

Key Properties of Plastics for Installation and Service

Author(s) : Beech 1998 Gothenburg

Pressure pipeline systems are a critical application for materials and demand high levels of performance and reliability. It is not by chance that plastics pipeline systems have gained a considerable market share, particularly in the gas and water utilities supply system. This paper briefly reviews the key properties...

Slow Crack Growth and Impact Mechanisms in PE

Author(s) : Clutton, Rose, Capaccio 1998 Gothenburg

The development of pipe grades requires the careful balance of several mechanical properties, of which two of the most important are the resistance to slow crack growth (SCG) and rapid crack propagation (RCP). In this paper, we present small-scale tests which enable the rapid assessment of these properties. These...

Slow Crack Growth Performance of Today's Plastics Pipeline Materials

Author(s) : Beech 1998 Gothenburg

Pressure pipeline systems are a critical application for materials and demand high levels of performance and reliability. Resistance to slow crack growth is a key consideration for both metals and polymers alike, which must be dealt with by the appropriate material selection, product design and manufacturing control....

The Resistance of PE Water Pipeline Systems to Surge Pressure

Author(s) : Beech, Headford, Hunt, Sandilands 1995 Edinburgh

The guldeUnes g h n in BS CP 312 :Pwt 2 : 1973 w e recommended to the UK toater industryfor the deslgn of polyethylene pfpeline systems to toke inin account the effects of tmnsient [surge) pressurejluctuatlons with respect to fatigue (ref.1). These guIdelInes we based on earlier experience wlth PVC-Usewer h...

The Role of Crazing in the Impact Fracture Toughness of PE Pipe Grades

Author(s) : Channell, Clutton 1995 Edinburgh

A new method based on the Dugdale zone solution for finite geometries is presented to analyse the case of craze growth at the notch tip in Charpy impact experiments. It is believed that correct values of initiation toughness are calculated via this method, leading to greater confidence in the extrapolation technique...

The Cooling Phase of Large Pipe Manufacture

Author(s) : Pittman, Whitman, Gwynn, Beech 1992 Eindhoven

Comprehensive operating data from a large-scale pipe cooling lime are reported, including in-situ measurements of temperatures within the pipe wall. A finite element simulation of cooling, coupled with gravity induced flow, or slump, in the pipe wall is described. Computed temperatures within the wall are compared...

The Development of the Notched Pipe Test for the Assessment of the Slow Crack Growth Resistance of PE Pipe

Author(s) : Beech, Allwood 1992 Eindhoven

The basis for the evaluation of polyethylene materials for pressure pipe applications is hydrostatic stress rupture testing for the prediction of long term hoop strength.However it is crucially important that the fracture properties of the materials are understood and indeed may result in limitations of their use....

The Use of recently Developed Experimental Methods and Modelling Techniques to study Crack Propagation in Viscoelastic Materials

Author(s) : Clutton, Dear, Channell 1992 Eindhoven

Two novel techniques have been applied to the problem of determining the fracture toughness of polyethylene appropriate to the situation of rapid crack propagation in pipe systems.Agreement is found between the data from the two methods used for evaluating four grades of polyethylene of widely different toughness. By...

Residual Stress in Large Diameter MDPE Water Pipe

Author(s) : Beech, Burley, Bunn 1988 Bath

Production of plastics pipes by conventional extrusion results in 'frozen i n r stress in the pipe wall, termed residual stress. Techniques have been established for assessina the levels of ~, this stress and relating to extrusion coaling conditions by mathematical modelling. However, the effects on long term...

Harmonisation of PE Pipe Buttfusion Procedures and Test Methods

Author(s) : Beech, Hutten, Ritz 2008 Budapest

Members of the Association

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