Southwest Research Institute® (SwRI®) News
Printer Friendly VersionSwRI develops new process for measuring crude oil corrosivity
San Antonio - March 31, 2004 - Engineers at Southwest Research Institute® (SwRI®) have developed a new tool for fast, precise measurement of corrosivity in crude oil using a proven technology for automotive wear testing.
The device uses a heated flow loop with an irradiated metal coupon inserted into the flowstream. Using gamma ray spectrometry, it detects and measures the buildup of radioactive corrosion products in the oil as it flows over the coupon. The oil sample can be heated to 650 degrees Fahrenheit and subjected to flow rates that simulate refinery operations.
"Buyers and sellers of crude oils whose chemical properties are unknown, sometimes referred to as opportunity crudes, can use this tool to make informed pricing decisions," says Martin B. Treuhaft, manager of the Filtration and Fine Particle Technology program within SwRI's Fuels and Lubricants Research Division. "Refiners also can use it to assess the corrosivity of a crude before it is refined," Treuhaft points out.
Oil circulating in the flow loop is radiometrically monitored at 10-minute intervals to track rising radiation levels as the crude oil sample carries minute amounts of radioactive corrosion products from the coupon. The resulting trends are more precise, faster and more reliable than those obtained using existing methods.
The recirculating flow loop allows tests to be tailored for specific conditions of shear stress and temperature, resulting in measurements that are accurate, repeatable and highly sensitive.
A lower-cost alternative method, in which the crude sample is placed in a heated autoclave and agitated in the presence of an irradiated coupon, can yield corrosion values in as little as 1.5 hours, both for corrosion products dissolved in the oil and for corrosion that is mechanically removed from the coupon and measured separately.
Older, standard coupon weight-loss methods of measuring corrosivity take 24 to 48 hours and can be influenced by corrosion products adhering to the coupon and by degradation of the crude oil during long periods at elevated temperatures. Also, existing corrosivity indexes such as the total acid number are insufficient indicators of a crude stock's real potential to corrode the storage tanks, pipelines and refining equipment that contain, transport and process it.
SwRI drew on its long experience with radioactive tracer technology (RATT) to develop the new tool. Previous RATT applications at SwRI have included measuring real-time wear in operating engines, pumps and other mechanical components, and in medical applications such as evaluation of materials used in hip joint components.
Applications of RATT corrosivity testing include versatile oil corrosivity measurement, database development, model development, crude oil blend optimization and corrosion inhibitor research. It also can aid in materials selection by measuring corrosion resistance of various materials, and in research involving operating conditions by testing under varying temperatures, shear stresses and pressures.
For more information on RATT and corrosivity measurement contact Treuhaft at (210) 522-2626, fax (210) 522-5720 or e-mail martin.treuhaft@swri.org.
For more information, contact Joe Fohn, Communications Department, (210) 522-4630, PO Drawer 28510, San Antonio, TX 78228-0510.
