This paper describes three case histories concerning the similar failures of waterwall tubes in two 1800 psig (12 MPa) boilers from hydrogen attack. The paper discusses the laboratory failure analyses conducted, the effects of previous "window" repairs and boiler water chemistry on the failures, the repair procedures developed for replacement tube sections to minimize future hydrogen-attack failures, and the inspection techniques used to detect hydrogen damage in unfailed tubes. Specific corrosion mechanisms and circumstances leading to the hydrogen attack failures are proposed, and the pros and cons of chemical cleaning are discussed, based on analysis of tube internal deposit weight density.

Subject
Energy dispersive X-ray spectroscopy, Corrosion failures, Water, Tubes, Hydrogen attack, Tube samples, Failure analysis, Corrosion scales, Mechanical failure, Repair, Boilers, Corrosion coupons, Deposit corrosion
Keywords:
Corrosion, boilers, hydrogen attack, water cycle chemistry, boiler water deposits, boiler water scale, acid corrosion, caustic attack
© 1995 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).
1995
Association for Materials Protection and Performance (AMPP)
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