A failure analysis was made with an austenitic stainless steel, YUS 170, pipe installed close to a flush tank of the field exposure test apparatus at Onikobe geothermal wells in Japan. The pipe eventually experienced severe leakage of geothermal fluids from the top side of the laid pipe within two weeks operation. The cracks initiated underneath thick deposits and propagated toward thickness direction transgranularly. The analysis of the deposits, corrosion products and fractographic observation have indicated that chloride stress corrosion cracking is responsible for the leakage. The field exposure tests of various stainless steels in the same geothermal fuids, however, exhibited general corrosion for materials containing less than 18 % Cr and slight pitting corrosion for the rest of the materials exposed. This study suggest that the condensation of salts on steel surfaces may cause serious corrosion problems in addition to those in flowing geothermal fluids. The replacement of YUS 170 by Low C-19Cr-2Mo ferritic stainless steel, YUS 190, has resulted in no stress corrosion cracking for more than eight months in the same environmental conditions.

Subject
Pipe surfaces, Geothermal energy, Materials, Piping, Leaks, Mechanical failure, Fluids, Crevice corrosion, Pitting, Deposit corrosion, Stainless steel, Stress corrosion cracking, Chloride stress corrosion cracking
© 1982 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).
1982
Association for Materials Protection and Performance (AMPP)
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