51316-7833-Effect of CO2 Partial Pressure on Cold Wall Failures

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Product Number: 51316-7833-SG

ISBN: 7833 2016 CP

Author: James McDonald

Publication Date: 2016

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Objectives/Scope: Pressurized Atlas Cell Testing is commonly understood to be the most aggressive accelerated test for tank lining systems due to The Cold Wall Effect. This is especially true when CO2 is added to the gas phase as CO2 is miscible with oil and soluble in water. A familiar gas mix of 5% CO2 5% H2S and 90% CH4 are added to test protocols to simulate head space conditions of tanks and pressure vessels in oil and gas production conditions. The temperature and pressure conditions in these protocols are adjusted to match field conditions as closely as possible. Results are often inconsistent between tests when the same gas mixtures are used but changes are made to temperature and pressure only. This author believes that there is a connection between the test pressure and the percentage of CO2 also described as partial pressure and the failure of coatings by blistering. Often understood as Cold Wall Effect blistering it is the aim of this paper to describe additional failure considerations when testing with CO2. This research will describe testing methodology and key findings for using the partial pressure of CO2 rather than current 5% calculations to determine the effect of Carbon Dioxide in Cold Wall Effect type failures. Methods Procedures Process: Testing was centered around NACE TM 0174 Laboratory Methods for the Evaluation of Protective Coatings and Lining Materials on Metallic Substrates in Immersion Service - Modified otherwise known as Pressurized Atlas Cell Testing. Multiple frequently used tank linings were tested in conditions with the primary consideration given to partial pressure of CO2 and Cold Wall Effect blister type failures. In addition thermocouples were applied to test specimens to determine if temperature variances in the test protocol had any impact on test results.Novel/Additive Information: Understanding specific conditions and failure mechanisms in which linings will be exposed is paramount.