Material selection for hydrofluoric acid (HF) service in the petroleum industry is critical due to the severe corrosive environment. Recommendations for material selection are derived from industry experience and some laboratory data. Despite the use of recommended alloys, numerous failures have resulted from conditions that are localized or existing from construction or repair and not related to the process. This paper presents a failure analysis of a alloy 400 nozzle in main HF acid service on an acid settler column. The nozzle operated at a temperature and pressure of 285°F (140°C) and 120psi (827kPa). Optical microscopy and scanning electron microscopy were conducted to identify the failure mechanism. In addition, finite elemental analysis (FEA) was performed to evaluate the stress distribution around the nozzle. Further considerations including condensation, turbulence, and design changes are discussed. The final modified design is also presented.

Subject
Corrosion failures, Materials, Nickel based alloys, Nozzles, Welding, Leaks, Inspection, Repair, Carbon steel, Monel alloys, Refining, Alloys, Heat affected zone
Keywords:
Hydrofluoric acid, corrosion, welding
© 2004 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).
2004
Association for Materials Protection and Performance (AMPP)
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