Pipeline quality gas is normally dried in Triethylene Glycol to reduce its water dew point to below the lowest operating temperature in a pipeline, and the presence of glycol as a vapor into the gas has been regarded as insignificant. This paper explores how TEG vapor can exist in a pipeline in a similar manner to water, and possibly lead to corrosion. TEG vapor can condense at long distances down a gas pipeline as the line cools, with most condensing above 60°F. However, even the small quantities involved accumulate with volume and time, and can become significant. The corrosion rate of steel in glycol is lower than for water and the problem is a long term one. In-Line Inspection for gas pipelines should pick up internal corrosion as well as external corrosion. Lines that are “not piggable” should be rinsed with a water/methanol slug driven by a foam disc pig to reduce risk when high risk areas such as low spots under rivers are present.

Subject
Vapor pressure, Water, Corrosion rate, Gas pipelines, Pipelines, Gas pressure, Vapors, Natural gas, Liquids, Dehydration, Glycol, Ethylene, Dew point
Keywords:
Glycol, Triethylene Glycol, glycol corrosion, dew point, gas pipeline internal corrosion
© 2006 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).
2006
Association for Materials Protection and Performance (AMPP)
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