Stress-corrosion cracking ruptures of natural gas pipelines are caused by growth and linkage of multiple longitudinal stress-corrosion cracks that initiate on the outside pipe surface. Because of the difficulty of analyzing multiple-crack systems, most previous research has focused on the growth of single cracks. Unfortunately, performance estimates based on single cracks predict leaks rather than ruptures and they overestimate failure times. To properly characterize flaw growth in pipelines, multiple crack initiation, growth, and linkage must be considered.

In the research described, a probabilistic Monte-Carlo simulation was used to model flaw growth. The model starts with random array of cracks, whose lengths and numbers are determined from line pipe specimens taken from the line being analyzed. Crack growth is modelled, along with additional crack nucleation, until a crack or group of linked cracks reaches the critical size for hydrotest rupture. Growth is then modelled until critical size for service rupture is reached. The process is repeated a number of times, each with a new original crack array, to develop a probability function for the minimum time to failure after hydrotesting.

Subject
Pipe surfaces, Crack growth, Piping, Modeling, Nucleation, Pipelines, Probability, Stress cracking, Mechanical failure, Defects, Hydrostatic testing, Cracks, Stress corrosion cracking
© 1988 Association for Materials Protection and Performance (AMPP). All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means (electronic, mechanical, photocopying, recording, or otherwise) without the prior written permission of AMPP. Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s).
1988
Association for Materials Protection and Performance (AMPP)
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