AC Mitigation
It is increasingly common for new pipelines to be constructed in existing high voltage overhead power line rights-of-way and for new power lines to be placed near existing pipelines. All pipelines are being impacted—petroleum, natural gas, water and wastewater. When underground metallic pipelines are in close proximity to high voltage power transmission lines, an electromagnetic field is created by the alternating current (AC). The potentially devastating effects of power line operations can include compromising personnel safety, equipment malfunction and negatively impacting pipeline reliability. AC voltages greater than 15 volts are a shock hazard, raising safety and liability concerns. While rare, pipe failures caused by excessive voltages under power line fault conditions have been reported.
AC interference can result in severe corrosion of the pipeline. Depending on soil characteristics and other factors, the corrosion can occur at voltages less than those considered tolerable relative to electrical safety. Extensive AC-caused corrosion is becoming more common, particularly for pipelines that have operated in collocated rights-of-way for many years without appropriate mitigation. In certain instances, AC-caused corrosion was detected in as little as four years after the pipeline was put into operation.
Corrpro is the established leader in corrosion control and has unparalleled experience in AC detection and mitigation. With experience protecting thousands of miles of pipeline and ancillary facilities, Corrpro has confidently handled AC interference issues ranging from one pipeline and one power line in a simple cross-country setting to multiple pipelines and multiple power lines in congested urban corridors. Corrpro pipeline projects involving AC interference and mitigation have ranged from a few miles to over six hundred miles.
Corrpro’s registered professional electrical engineers and NACE International certified corrosion specialists can predict AC effects on proposed pipelines to design and construct suitable mitigation measures. This includes extensive hands-on expertise and state-of-the-art modeling software. Corrpro has provided assistance to countless pipeline operators as well as power companies in an effort to minimize the AC interference directly at the source by enhancing the power line design.
Corrpro’s state-of-the-art AC mitigation designs use a combination of off-the-shelf equipment and unique components developed by Corrpro engineers. AC mitigation needs are integrated with cathodic protection and other corrosion control requirements to realize the greatest return on investment.
Corrpro has an established track record in evaluating existing AC concerns and establishing cost effective remedial measures that are maintenance friendly. This includes Corrpro-unique multi-channel AC/DC close interval potential survey capabilities that allow for simultaneously determining AC interference and cathodic protection levels at 3-foot intervals along a given pipeline. Anomalous conditions are flagged with sub-meter GPS for further investigation.
Corrpro has taken a lead position in developing industry standards and evaluation procedures in AC mitigation. As a total solutions company, Corrpro has the capability to meet all of your AC safety and corrosion control needs. Similar to Corrpro’s full offering of services in cathodic protection and protective coatings, we routinely provide the following AC-related services:
- Pre-design evaluations
- Computer modeling
- Mitigation designs
- On-site QA/QC
- Full turnkey construction
- System start-up and baseline
- Training
- Operation and maintenance
- Detection and resolution of existing AC problems
