An Alaskan utility has experienced many premature failures of DIP as a result of external corrosion. These failures have occurred on both bare DIP, and DIP installed with polyethylene encasement installed in accordance with AWWA C1151.

The depth of bury of water mains in the Anchorage bowl is a 10 foot (3 meter) minimum cover for freeze protection. The high costs associated with deep excavation repairs and early replacement of this pipe has had a large impact on the ratepayers. Because of the high cost associated with deep excavations, the pipe materials with delivery only contribute to approximately 10% of construction and repair costs. In an effort to extend the life of new water main installations, the utility made the decision to install external tightly bonded coatings on new DIP water main installations or to use nonmetallic piping in corrosive soils.

This paper will review some of the case studies of the different types of coating systems that have been used on DIP and will present a summary of the findings that have been learned from these coating applications.

Subject
Holidays, Zinc rich coatings, Water, Materials, Piping, Cathodic protection, Tape, Solids, Epoxy coatings, Dry film thickness, Zinc, Epoxies, Annealing
Keywords:
Ductile Iron Pipe (DIP), American Water Works Association (AWWA), dry film thickness (DFT), SSPC PA 2 (PA2), polyethylene encasement (PE) bags, annealing layer, cathodic protection (CP), polyurethane (PUR), epoxy, linear feet (LF)
© 2013 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).
2013
Association for Materials Protection and Performance (AMPP)
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