In 1995, there were two failures in the 20.000 BPD HF Alky unit at the Amuay Refinery causing a shutdown of the unit. The failures occurred in one flange and one weld in the depropanizer charge carbon steel pipe, containing propane, isobutane and anhydrous hydrofluoric acid at 190 F (88 C) and 321 psig (22.5 Kg/cm2). Examination showed severe uniform corrosion at the inside surface of the flange while the adjacent elbow showed minimal corrosion loss. The other failure showed preferential attack in the weld without corrosion loss in the pipe components.

A complete evaluation of the Alky plant was necessary to identify other lines in similar conditions that could cause future emergency shutdown of the unit. An extensive on stream inspection program was performed on critical lines of the unit. This paper summarizes the results and conclusions of this evaluation.

Subject
Corrosion failures, Piping, Microstructure, Chromium, Ultrasonic testing, Inspection, Flanges, Analytical techniques, Carbon steel pipes, Metal loss, Carbon steel, Copper, Nickel
Keywords:
alkylation, hydrofluoric acid, ultrasonic testing, chemical analysis, on stream inspection, carbon steel fittings, carbon steel pipe, copper, nickel, chromium
© 1999 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).
1999
Association for Materials Protection and Performance (AMPP)
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