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51316-7801-Analysis and Evaluation of Cathodic Protection within a Vapor Corrosion Inhibitor Gel Filled Casing

Product Number: 51316-7801-SG
ISBN: 7801 2016 CP
Author: Len Krissa
Publication Date: 2016
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$20.00
$20.00
Cased pipeline crossings are segments typically situated at road and railway crossings where the pipeline (carrier pipe) is surrounded by a larger diameter pipe (casing) for protection from mechanical damage. Although these locations face a similar threat of external corrosion as those which are conventionally buried; the management approach is considerably different. With time spacers and end seals deteriorate and an environment conducive to external corrosion is created inside the casing and leaves the pipeline vulnerable to damage if the coating system has also become compromised at any point. Execution of repair activities under these circumstances is very expensive and time constrained. Recently a major North American pipeline operator has implemented gel based vapor corrosion inhibitors (VCIs) in conjunction with cathodic protection to contend with such situations and control external corrosion at cased crossings. A VCI fluid mixture is initially injected into the casing’s annular space at a water equivalent viscosity and within a designed period of time it then sets to a gel-like consistency. Since the gel is electrically conductive it theoretically should enable the carrier pipe to receive cathodic current.Although the technique is proving to be very effective based from pipe-to-soil potential and ER probe measurement perspectives; some debate exists within industry regarding the parallel application of the two mitigation practices. The compatibility testing of VCI gel and CP that is being conducted will determine any influences effects or interactions between the two corrosion control methodologies. The study will also determine whether CP current can be partially diverted to the casing from the carrier pipe within the gel filled environment. Results from this effort are being compiled to further validate and optimize the use of VCI gel for this application. The overall objective of the project is to comprehensively identify and understand any reciprocating effects between the concurrent use of VCI gel and cathodic protection inside a casing. The experimental studies and modeling work associated with the simultaneous application of VCI gel and CP under various scenarios are discussed within this article.Key words: cathodic protection CP volatile corrosion inhibitor VCI cased pipeline casing
Cased pipeline crossings are segments typically situated at road and railway crossings where the pipeline (carrier pipe) is surrounded by a larger diameter pipe (casing) for protection from mechanical damage. Although these locations face a similar threat of external corrosion as those which are conventionally buried; the management approach is considerably different. With time spacers and end seals deteriorate and an environment conducive to external corrosion is created inside the casing and leaves the pipeline vulnerable to damage if the coating system has also become compromised at any point. Execution of repair activities under these circumstances is very expensive and time constrained. Recently a major North American pipeline operator has implemented gel based vapor corrosion inhibitors (VCIs) in conjunction with cathodic protection to contend with such situations and control external corrosion at cased crossings. A VCI fluid mixture is initially injected into the casing’s annular space at a water equivalent viscosity and within a designed period of time it then sets to a gel-like consistency. Since the gel is electrically conductive it theoretically should enable the carrier pipe to receive cathodic current.Although the technique is proving to be very effective based from pipe-to-soil potential and ER probe measurement perspectives; some debate exists within industry regarding the parallel application of the two mitigation practices. The compatibility testing of VCI gel and CP that is being conducted will determine any influences effects or interactions between the two corrosion control methodologies. The study will also determine whether CP current can be partially diverted to the casing from the carrier pipe within the gel filled environment. Results from this effort are being compiled to further validate and optimize the use of VCI gel for this application. The overall objective of the project is to comprehensively identify and understand any reciprocating effects between the concurrent use of VCI gel and cathodic protection inside a casing. The experimental studies and modeling work associated with the simultaneous application of VCI gel and CP under various scenarios are discussed within this article.Key words: cathodic protection CP volatile corrosion inhibitor VCI cased pipeline casing
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