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51313-02239-A New Approach to Pipeline Integrity—Combining In-Line Inspection and CP Simulation Technology

Product Number: 51313-02239-SG
ISBN: 02239 2013 CP
Author: Dennis Janda
Publication Date: 2013
$0.00
$20.00
$20.00

The integrity of pipelines can be assessed by using in-line inspection (ILI) tools and direct assessment (DA) methods. Conventional ILI techniques like magnetic flux and ultrasonics quantify the severity of corrosion that has already occurred but they do not give any information on the performance of the cathodic protection (CP) system. Traditional DA data often require a great deal of interpretation leaving unanswered questions as what is really happening on the pipeline and more importantly what to do about it. These traditional DA surveys are labor intensive operator dependent and costly to execute.

This paper presents an advanced inspection method that combines a CP current measurement ILI tool with a CP simulation technology. The ILI CP tool measures the true electrical current patterns on the pipe that originate from a CP system or interference source. The current density data from the CP ILI tool data are then used by the simulation model to predict pipe-to-soil potentials.

A case study is discussed where a simulation model is constructed for an 8-in. (219mm) pipeline 16.15 miles (26 km) in length. The axial current measured by the CP tool is used to fit the model with respect to potential survey data and rectifier characteristics. As an outcome the model predicts the local coating resistance local ON/OFF potentials and enables prediction of the corrosion risk.

This combined approach offers the benefit that a simulation model can be developed that fits well to the actual conditions of the pipeline with a minimum of assumptions. Through modeling the CP system can be further improved by running different what-if-scenarios such as changing the rectifier outputs connecting/disconnecting bonds changing coating condition (e.g. long-term degradation) varying soil resistivity etc. with a minimum amount of survey cost and greatly reduced field time.

Keywords: Cathodic Protection Current In-line Inspection Current Measurement Potential Modeling Simulation
 

The integrity of pipelines can be assessed by using in-line inspection (ILI) tools and direct assessment (DA) methods. Conventional ILI techniques like magnetic flux and ultrasonics quantify the severity of corrosion that has already occurred but they do not give any information on the performance of the cathodic protection (CP) system. Traditional DA data often require a great deal of interpretation leaving unanswered questions as what is really happening on the pipeline and more importantly what to do about it. These traditional DA surveys are labor intensive operator dependent and costly to execute.

This paper presents an advanced inspection method that combines a CP current measurement ILI tool with a CP simulation technology. The ILI CP tool measures the true electrical current patterns on the pipe that originate from a CP system or interference source. The current density data from the CP ILI tool data are then used by the simulation model to predict pipe-to-soil potentials.

A case study is discussed where a simulation model is constructed for an 8-in. (219mm) pipeline 16.15 miles (26 km) in length. The axial current measured by the CP tool is used to fit the model with respect to potential survey data and rectifier characteristics. As an outcome the model predicts the local coating resistance local ON/OFF potentials and enables prediction of the corrosion risk.

This combined approach offers the benefit that a simulation model can be developed that fits well to the actual conditions of the pipeline with a minimum of assumptions. Through modeling the CP system can be further improved by running different what-if-scenarios such as changing the rectifier outputs connecting/disconnecting bonds changing coating condition (e.g. long-term degradation) varying soil resistivity etc. with a minimum amount of survey cost and greatly reduced field time.

Keywords: Cathodic Protection Current In-line Inspection Current Measurement Potential Modeling Simulation
 

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