Deposition in superheater tubing can originate from the carryover of water droplets into the superheater bank from the steam drum. Deposition occurs because the concentration of impurities present in the entrained water droplets can be several orders of magnitude greater than that present in steam alone. When the water flashes to steam in the superheater, salts, hardness species, and corrosion products dissolved or suspended in the water build-up on the internal surfaces of the superheater tubing. The detrimental effects of carryover deposition in superheater tubing has been shown to contribute to at least three types of failure: stress-corrosion cracking, overheating, and corrosion gouging. A case history illustrating each one of these failure mechanisms is presented.

Subject
Water, Water droplets, Tubes, Stress cracking, Tubing, Internal surfaces, Sodium, Metals, Overheating, Boilers, Deposit corrosion, Steam, Low alloy steel
Keywords:
superheater tube, carryover, deposition, magnetite, corrosion gouging, overheating, creep, stress-corrosion cracking, low-alloy steel
© 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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