|Content Type||Conference Paper|
|Title||INSIGHTS INTO ATLAS CELL TESTING FOR SELECTION OF LININGS FOR OIL AND GAS PRODUCTION VESSELS AND TANKS|
|Authors||Linda G. S. Gray and Nicole DeVarennes, KTA-Tator (Canada) Inc; Blake Bloor, Encana Resources; Michael O'Donoghue, Ron Graham, Ron Garrett, and Vijay Datta, Devoe Coatings; Bob Franke, International Polymer Canada Inc|
|Source||CORROSION 2008, March 16 - 20, 2008 , New Orleans LA|
|Copyright||2008. NACE International|
|Keywords||Atlas cell test, Autoclave test, tank linings, coating selection, laboratory testing, Electrochemical Impedance Spectroscopy, cold wall effect|
The Atlas cell test (NACE TM0174) and the autoclave test (NACE TM0185) are laboratory tests that are regularly used to select internal linings for vessels and tanks used in processing oil and gas production fluids. The results from the two tests are often quite different and in some notable instances the correlation between Atlas cell test results and field performance is poor. This paper documents our investigation of the various operational details of the Atlas cell test and their influence on the nature of the cold wall effect created in the Atlas cell. A number of commonly used tank linings were evaluated under Atlas cell conditions. The results are used to offer an explanation regarding some of the contradictory behaviour of coatings in Atlas testing, autoclave testing, and field performance.
In the oil and gas production industry, two laboratory tests are commonly used for selection of tank Linings1 for use in surface production equipment1-5. In the autoclave test (NACE TM01856) coated test panels are exposed to simulated oil and gas production fluids at elevated temperature and pressure under isothermal conditions. In the Atlas cell test (NACE TM01747 / ASTM C8688) coated test panels are exposed to hot fluids in the presence of a temperature gradient across the test panel. The Atlas cell test is intended to approximate the conditions in an un-insulated steel tank or vessel which has an internal lining and handles hot process fluids. The temperature gradient that occurs across the coating produces a so-called "cold wall effect" which tends to draw water into the coating, thereby promoting disbondment and blistering. At first glance, the Atlas cell test would seem more suitable than the autoclave test for tank lining testing and selection. Most oil and gas production piping, tanks, and vessels contain hot production fluids and are un-insulated, with large temperature gradients across the coating particularly during winter. Further, due to the temperature gradient the Atlas cell test should be a more aggressive test, resulting in a better ranking of coatings in terms of their performance. A complication however, is that some tank lining products which have an excellent track record in field performance consistently fail in Atlas cell testing. In service these coatings are subjected to large temperature gradients in aggressive conditions, particularly in the winter time. Outside winter temperatures can range from 0°C to -40°C. Inside process fluid temperatures of 40 to 75°C are very common, resulting in temperature gradients of 40°C to 115°C. Process fluids typically consist of one or some combination of the following: saline water, produced oil, and methane gas which may contain hydrogen sulphide or carbon dioxide. Further, these coatings are observed to perform well in autoclave testing, under considerably higher temperatures and pressures, and more aggressive chemistries. The objective of this project was to gain a better understanding of the Atlas cell test and to determine the reasons for the discrepancies between field performance, autoclave test results, and Atlas cell test results. This understanding can subsequently be used to intelligently select the most appropriate laboratory test for coating selection in specific oil and gas production systems.
|File Size||1505 KB||25|