Tubes in the secondary superheater of an eighteen month old kraft recovery boiler failed causing a serious safety concern. The tube failures were caused by high tube metal temperatures brought about by internal scale deposits and high flue gas temperatures. The high metal temperatures melted the slag layer on the outside of the tubes generating rapid tube wall corrosion. Analyses have shown that a tube metal temperature on the order of 1100°F was present, sufficiently high to melt the slag layer and generate rapid stress rupture. The affected tubes were replaced and the unit was returned to service. Recommendations for limiting the future occurrence of these conditions were developed and implemented by the Mill. Of particular importance was the installation of a "sweet water" condenser that will assure a high quality water supply to the attemporator and prevent the buildup of internal deposits in the superheater that was a principle cause of the tube failures.

Subject
Water, Materials, Tubes, Walls, Flue gas, Scale deposition, Failure analysis, Stress, Metals, Heat, Deposit corrosion, Steam, Chlorides
© 1989 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).
1989
Association for Materials Protection and Performance (AMPP)
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