The External Corrosion Control System of a 16 inch diameter (406 mm), 70 miles long (113 km.) pipeline, was evaluated using the Direct Current Voltage Gradient DCVG, Close Interval Potential Survey CIPS and Continuous Soil Resistivity Evaluation CSRE techniques.

Sixteen thousand five hundred meters (16.500 meters. 10,23 miles) of the pipeline were evaluated using the three techniques simultaneously and the rest was inspected separately in previous years.

The results from the survey were taken as parameters to classify all defects found on the protective coating. A Defect Severity Classification (DSC) was established and used as an input for a maintenance program for the rehabilitation of the pipeline integrity. The parameters taken to establish the DSC were: a) Instant Off Potential, b) %IR, c) Soil Resistivity, d) defect shape, e) Geographic location, f) Distance from drain point.

A Maintenance Program for the Pipeline External Corrosion Control System was designed by implementing the Integral Evaluation of the Corrosion Control System for Buried Pipelines (IEECCSBP). The priority was to achieve pipeline integrity and then, gradually improve the protection level of the system.

The implementation of IEECCSBP will help to reduce the frequency of Electromagnetic Metal Loss Inspections, which in the future will serve only as an audit of the External Corrosion Control System performance.

Subject
Coating inspection, Cathodic protection, Pipeline sections, Pipelines, Soil resistivity, Metal loss, Defects, Repair, Below ground pipelines, External corrosion, Coating defects, Instant off potential, Soil
Keywords:
External Corrosion Control System for Buried Pipelines, instant off potential, cathodic protection, cathodic protection criteria, voltage gradient, soil resistivity, %IR
© 1998 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).
1998
Association for Materials Protection and Performance (AMPP)
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