Full-scale gas transmission pipeline fracture tests

Full-scale gas transmission pipeline fracture tests

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Commission of the European Communities
technical steel research
Properties and service performance
Full-scale gas transmission pipeline
fracture tests 5
Commission of the European Communities
technical steel research
Properties and service performance
Full-scale gas transmission pipeline
fracture tests
Mannesmann/
(for the European Pipeline Research Group)
Ehringer Strasse, 200
D-4100 Duisburg 25
Contract No 7210-KE/114
(1.5.1983-30.4.1986)
Final report
Directorate-General
PA;:L EURO? CAÁ. Science, Research and Development
N.C. EUR 12104 EN 1990 Published by the
COMMISSION OF THE EUROPEAN COMMUNITIES
Directorate-General
Telecommunications, Information Industries and Innovation
L-2920 Luxembourg
LEGAL NOTICE
Neither the Commission of the European Communities nor any person acting
on behalf of then is responsible for the use which might be made of
the following information
This document was reproduced with the best original available
Cataloguing data can be found at the end of this publication
Luxembourg: Office for Official Publications of the European Communities, 1990
ISBN 92-826-1187-6 Catalogue number: CD-NA-12104-EN-C
© ECSC-EEC-EAEC, Brussels · Luxembourg, 1990
Printed in Belgium TABLE OF CONTENTS
Page
Abstract V
1.Introduction1
2."PublishedModels" Analysis2
3. EPRG­Programme6
3.1. Line pipe materials 6
3.2. Tests6
4. Standard characterisationtests6
5. Test site andfacilities,7
5.1. Test line7
5.2. Instrumentation« 8
6. Full scale test results8
6.1. Fracture appearanceofbrokenpipes10
6.2. Pressure transducer fandiagram11
7. Additional laboratory measurements#12
7.1. British Gas Laboratory testevaluation12
7.2. h Level Corporation examinations 13
7.3. Mannesmann crack speed measurements14
7.4. Italian Group DWTT evaluation15
8. Deformation measurements 16
8.1. Strain­gaugesmeasurements" 16
8.1.1. Throughthicknessdifferential measurements16
8.1.2. hsaveraged s17
8.2. After burstmeasurements17
9. Discussion18
10. Concluding remarks19
References 21
Tables23
Figures37
Appendices63
AppendixA65xΒ68
AppendixC69Abstract
This research programme was designed to study the phenomenon of unstable
shear fracture propagation in gas transmission pipelines for thick wall
pipes and pipes of grade X80.
It was intended to study the validity of the extrapolation of earlier
studies on materials up to grade X70 to these pipes.
Three full scale tests, proposed by EPRG, were conducted on 36" and 48"
pipes. The test procedure followed the previous practice. The tests were
accompanied by detailed laboratory investigations and additional
instrumentation of the full scale tests.
A comparison of the tests results with the existing analyses was made.
It appears that existing predictions based on Charpy-V values which have
been established for grades up to X70 do not give toughness levels
sufficient for crack arrest in pipes of grade X80 under these test
conditions.
The anomalous behaviour of the thick wall pipes may be due to the fact
that they were tested within the transition region of the DWT tests.
An initial attempt was made to improve toughness measurements to
describe fracture propagation behaviour of pipes by using fracture
propagation energies from new developed parameter studies. It is
expected that future laboratory work on this topic will provide an
improved prediction of the full scale fracture behaviour of pipes
especially of those with high toughness. 1. Introduction
During the last fifteen years intensive research work related to
gas transmission pipelines has been carried out in order to opti­
mize their reliability and safety. An important objective has
been to define the conditions under which running shear fracture
in a pipeline can be arrested. In Europe, the European Pipeline
Research Group (EPRG), Table I, a group of gas transmission and
pipe manufacturing companies, has carried out several series of
full scale tests to investigate the effect of diameter and wall
thickness on the toughness required to give fracture arrest in
X65 and X70 pipes. All of the 14 full scale tests (Table II) were
sponsored by the European Community for Steel and Coal (ECSC) and
by the member companies of EPRG.
As a result of these tests the existing formulae to derive tough­
ness values for fracture arrest could be evaluated and this led
to recommendations for toughness requirements for line pipes (1).
Since modern pipeline design requires higher pressures and conse­
quently higher wall thickness and alsor strength steel, it
was necessary to check the validity of the extrapolation to very
high (65 + 72 % SMYS of X80) stress levels, to newly developed
steels and to thick walled pipes. This new programme, which will
be reported here, included two similar tests on 48 in diameter,
17 mm wall thickness, grade X80, and one test on 36 in,
25.4 mm wall, grade X70 (Table III).
The programme was the first cooperative investigation of newly
developed X80 steels and required considerable efforts by the
steel producers in the development of these new steels and in
providing suitable test pipes.
The most important part of the programme is the full scale tests.
The aim of such a full scale test is to ensure that fracture be­
haviour in a test length represents the behaviour of a complete
gas transmission line. In this respect consideration must be gi­
ven to the interaction of the gas dynamics, the propagating crack
1 -and the test length dimensions. It is essential, therefore, that
the actual dimensions of the test length are such that the re­
flected wave of gas decompression doe*- not interact with the
fracture.
Suitable test lines were made available by British Gas, Enginee­
ring Research Station, Newcastle, at the test site at Spadeadam
(test n° 1 and n° 3), and by CSM, Rome, at the test site at
Perdasdefogu/Sardinia (test n° 2).
In another part of the programme a standard characterisation of
the test materials was performed, followed by some high sophisti­
cated laboratory tests to supply special toughness parameters to
aid interpretation of the results of the full scale tests.
2. "Published Models" Analysis
The first attempts to interpret ductile fracture behaviour were
made by using the Charpy-V energy as the material toughness cha­
racterising parameter. The simplicity of Charpy testing aids the
application of semi-empirical theories.
The published well known CV-based analyses are from:
- Battelle Memorial Institute (BMI) (2)
- American Iron and Steel Institute (AISI) (3)
- British Gas Corporation (BGC) (M)
- Nuova Italsider/Centro Sperimentale Metallurgico (N.ITS/CSM)
(5).
They are reported in Table IV. Since a statistical analysis of
available full-scale tests results showed that these formulae
satisfactorily predict fracture behaviour of traditional steel
line pipes, EPRG made recommendations for toughness requirements
(1).