Keywords:
Pipeline Casing Vapor Phase Corrosion Inhibitor ER Probe Remote Monitor System 

Abstract:
Pipeline casings are widely used at locations where a pipeline crosses beneath railroad tracks highways and other areas where external pressure and stress can impact pipeline integrity or areas where rehabilitation or replacement of the pipeline could significantly disrupt other systems.  The casing protects the pipeline but also creates an environment that can trap water in the area surrounding the pipeline.  The water and water vapor inside the casing can lead to galvanic external corrosion.  Additionally the presence of water can short the pipeline to the casing affecting the level of cathodic current on the pipe and sacrificing the casing.

A variety of water displacing substances are used to prevent water and water vapor related problems inside pipeline casings.  Many are wax-based or petrolatum-based agents that provide an effective barrier between the pipe and potentially corrosive elements.  These substances fill the casing and typically become semisolid.  The material is subject to degrade over time.  It is difficult to measure or monitor on an on-going basis the effectiveness of these barrier agents due to the difficulty of detecting voids that can develop inside areas of the casing.  Additionally as the fill material settles areas of the casing can be exposed to galvanic corrosion agents.  Typically there is no cathodic protection on the casing.  In recent years an increasing number of “vapor phase corrosion inhibitor” substances have been developed for use as displacement agents for casing applications.  A unique characteristic of this type of inhibitor is the ability to displace water without entirely filling the casing.  This allows the technician to monitor the corrosion rate inside the casing environment with ER probes.

This paper is a case study on the use of corrosion rate monitoring probes to determine the rate of material loss inside the pipeline casing where a vapor phase corrosion inhibitor substance is used.  The probe can be suspended in the protective vapor and provide continual measurements of probe material loss.  The data can be transmitted using remote monitor technology and accessed by the technician from any web-enabled device.  The availability of this data allows the technician to track and trend the rate of corrosion develop predictive analysis using near real-time data and proactively address any acceleration of the corrosion rate inside the casing that could be due to inadequate moisture displacement.

This study focuses on combining elements of several evolving technologies to enhance pipeline integrity in casing installations.  The vapor phase corrosion inhibitor provides very effective displacement and the combination of the ER probe and a web-based remote monitor system provides accurate near real-time performance data.