Menu
Search
Filters
Close
Menu

Investigation into Possible AC Corrosion from a Cathodic Protection Groundbed

Picture for Investigation into Possible AC Corrosion from a Cathodic Protection Groundbed
Available for download

This case study involves an investigation into corrosion anomalies on an NPS 6 approximately 4 km long Yellow Jacket coated pipeline that interconnects two terminals. An in-line inspection (ILI) in 2017 identified 70 external corrosion anomalies with two of them exceeding 55% wall loss. An additional five corrosion anomalies had been previously repaired.Recent annual cathodic protection (CP) surveys and a close-interval potential survey conducted in 2015 all indicate good cathodic protection levels along the line.AC voltages as high as 6 V were measured along the pipeline which was unexpected as there are no high voltage powerlines in this area. A distribution powerline that parallels the pipeline for approximately 0.6 km was identified near the location with the elevated AC voltages.More surprisingly AC current densities of up to 1400 A/m2 and DC current densities of 2100 A/m2 were recorded on AC coupons in this area indicating a severe AC corrosion risk.Waveforms indicated that very little of the AC voltage was related to the fundamental 60 Hz powerline frequency. The majority of the AC voltage was 120 Hz frequency indicating that the AC is likely from an unfiltered single-phase rectifier. There are several CP rectifiers that influence this pipeline and one of these is associated with a ground bed installed in the area of concern.This paper discusses the testing performed to confirm the source of the elevated AC current densities and quantify the associated corrosion risk. The mitigation strategy employed to address this risk is provided.Keywords:AC Corrosion AC Interference AC Mitigation Cathodic Protection CP Ground Bed Rectifier Interference Unfiltered Rectifier Corrosion Investigation Pipeline.

Product Number: 51319-13188-SG
Author: Wolfgang Fieltsch
Publication Date: 2019
$0.00
$20.00
$20.00
Also Purchased
Picture for 51318-11271- AC Corrosion Control: When Too Much Cathodic Protection Might Just be a Bad Thing!
Available for download

51318-11271- AC Corrosion Control: When Too Much Cathodic Protection Might Just be a Bad Thing!

Product Number: 51318-11271-SG
Author: Dale Lindemuth / Dan Crabtree
Publication Date: 2018
$20.00

Case histories where throttling down the cathodic protection was evaluated to determine the impact on reducing the AC corrosion threat. Includes the use of fast-response electrical resistance corrosion rate probe monitoring technology.
Picture for The AC Close Interval Survey and Other Common AC Measurement Errors
Available for download

The AC Close Interval Survey and Other Common AC Measurement Errors

Product Number: 51317--9455-SG
ISBN: 9455 2017 CP
Author: Wolfgang Fieltsch
Publication Date: 2017
$20.00

The measurement of induced AC voltages along a pipeline is a primary indicator of electrical safety hazards and AC corrosion risks under operating powerlines. This paper addresses several fallacies, misconceptions and common errors related to the measurement of these AC induced voltages.

 
Picture for AC Interference and Mitigation: Heartland Case Study
Available for download

AC Interference and Mitigation: Heartland Case Study

Product Number: 51317--9461-SG
ISBN: 9461 2017 CP
Author: Matthew Lechelt
Publication Date: 2017
$20.00

Challenges associated with coordinating the modelling, design, and installation of an alternating current interference and mitigation systems. The project consisted of a 65 kilometer long double circuit 500 kilovolt (kV) overhead transmission in a heavily congested right-of-way corridor with more than 80 pipelines.
Categories
Industry
Recently viewed
Popular tags
View all

Association for Materials Protection and Performance

© AMPP All Rights Reserved.
Membership Terms of Content Use
Contact Customer Support