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Corrosion Under Insulation And Atmospheric Corrosion In The Refinery Industry. An Accurate Approach To Estimate Corrosion Growth Rates, A Texas Refinery Case Study

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External corrosion in uninsulated pipelines is normally able to be prevented by cathodic protection (CP). Generally, external corrosion on buried pipelines cannot occur if CP current is getting onto the pipe. CP is an electrochemical means of corrosion control in which the oxidation reaction in a galvanic cell is concentrated at the anode and suppresses corrosion of the cathode (pipe) in the same cell. For instance, to make a pipeline a cathode, an anode is attached to it.

Product Number: 51322-17751-SG
Author: Bernardo Cuervo, Mark McQueen
Publication Date: 2022
Industries: Corrosion Monitoring and Control , Coatings and Linings , Coatings
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$20.00
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Corrosion under insulation (CUI) is corrosion that results from moisture buildup on pipelines covered by insulation. Atmospheric corrosion is the electrochemical decay of a carbon steel pipeline in an air environment, under the presence of an electrolyte such as rain, dew, humidity, or snow. Salt and pollutants in the air and soil aggravate atmospheric corrosion and CUI. Both CUI and atmospheric corrosion are costly problems in refineries. In a Texas refinery, CUI causes approximately 60% of all pipe leaks and was particularly difficult to prevent, track, and mitigate. In this paper, a case study will be presented that addresses one of three different methods to calculate corrosion growth rates, remaining life, and reinspection interval. The traditional approach includes an initial inspection and the estimation of aggressive corrosion growth rates that will require frequent and costly re-inspections. This paper presents an ILI data point-to-point comparison methodology to address the damage caused by CUI so that it can be easily quantified, and its growth rate accurately estimated. This method will save time and money by decreasing expensive shutdowns and unnecessary direct examination of insulated areas. Based on the results of the point-to-point comparison, the pipeline operator conducted a cost-based analysis, resulting in a repair program that maximizes the re-inspection interval.
In addition, the paper shows typical examples of CUI and points out some of the major impacts of CUI on in-line inspection (ILI) technologies like magnetic flux leakage (MFL) and ultrasonic compression wave also called ultrasonic wall thickness measurement. The results of different assessment methods for pressure-based assessment as well as for the estimation of corrosion growth rates from consecutive ILIs are compared. The discussed integrity assessment method also includes a new method specifically designed for pipelines difficult to inspect in a refinery setting. In this paper, a case study will be presented that addresses a pipeline that was subjected to both CUI and atmospheric corrosion. A 6-inch diameter pipeline was subject to CUI with corrosion rates as high as 0.047 inches per year (1.2 mm/yr.) The paper will explain a simple methodology to filter the results of the inspection data to avoid unnecessary and expensive repairs. The results are also applicable to atmospheric corrosion.

Corrosion under insulation (CUI) is corrosion that results from moisture buildup on pipelines covered by insulation. Atmospheric corrosion is the electrochemical decay of a carbon steel pipeline in an air environment, under the presence of an electrolyte such as rain, dew, humidity, or snow. Salt and pollutants in the air and soil aggravate atmospheric corrosion and CUI. Both CUI and atmospheric corrosion are costly problems in refineries. In a Texas refinery, CUI causes approximately 60% of all pipe leaks and was particularly difficult to prevent, track, and mitigate. In this paper, a case study will be presented that addresses one of three different methods to calculate corrosion growth rates, remaining life, and reinspection interval. The traditional approach includes an initial inspection and the estimation of aggressive corrosion growth rates that will require frequent and costly re-inspections. This paper presents an ILI data point-to-point comparison methodology to address the damage caused by CUI so that it can be easily quantified, and its growth rate accurately estimated. This method will save time and money by decreasing expensive shutdowns and unnecessary direct examination of insulated areas. Based on the results of the point-to-point comparison, the pipeline operator conducted a cost-based analysis, resulting in a repair program that maximizes the re-inspection interval.
In addition, the paper shows typical examples of CUI and points out some of the major impacts of CUI on in-line inspection (ILI) technologies like magnetic flux leakage (MFL) and ultrasonic compression wave also called ultrasonic wall thickness measurement. The results of different assessment methods for pressure-based assessment as well as for the estimation of corrosion growth rates from consecutive ILIs are compared. The discussed integrity assessment method also includes a new method specifically designed for pipelines difficult to inspect in a refinery setting. In this paper, a case study will be presented that addresses a pipeline that was subjected to both CUI and atmospheric corrosion. A 6-inch diameter pipeline was subject to CUI with corrosion rates as high as 0.047 inches per year (1.2 mm/yr.) The paper will explain a simple methodology to filter the results of the inspection data to avoid unnecessary and expensive repairs. The results are also applicable to atmospheric corrosion.

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Corrosion under thermal insulations namely CUI (Corrosion under insulation) is among the key damage mechanisms which poses integrity risk to the hydrocarbon facilities. CUI is reportedly known as the reason behind 40-60% of failures in the facility piping whereas small bore piping (i.e., NPS < 4”) are even more sensitive to CUI failures, where up to 81% of reported failures in small-sized piping are known to be from CUI.  Monetary spending to inspect and fix CUI-related failures cost 10% of overall maintenance budget in a typical medium-sized oil refinery.  CUI risk is influenced by numerous operational and environmental factors which impedes its management in a typical AIM (Asset integrity management) program.
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Petrochemical facilities and refineries consist of many miles of above ground piping that transports product between processing and storage units. These pipes are either supported at ground level or in multi-story pipe racks on varying types and sizes of supporting structures. A common problem these structures create is corrosion and erosion at the junction between the pipe and the support, which reduces the remaining wall thickness of the pipe and compromises the integrity of the entire system. 
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Product Number: 51219-196-SG
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