Becht Engineering Blog
In this section of the site contributing authors submit interesting articles relating to the various services, industries and research & development efforts of Becht Engineering.
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How To Quantify And Evaluate Oil Storage Tank Annular Plate Corrosion
Sunday, 18 November 2018
Nadarajah "Ranjan" Chithranjan
Materials Degradation and Corrosion
Failure of Oil Storage Tank Annular Plate
In the past ten years, there have been a few oil storage tank annular plate failures due to soil side corrosion and fatigue loading (filling and emptying) which has led to large spills. The corrosion tends to be localized in a groove fashion and the size of the flaw could vary from 3 feet to 12 feet in the circumferential direction. The location of the corrosion is also where the highest bending stress will occur during filling and emptying of tanks. See Figures 1 and 2 for the location of the failure on the annular plate. Since the location of failure is under the tank, the corrosion flaws cannot be detected easily from the outside of the tank. It can only be detected if an internal inspection is done which would require the tank to be emptied and cleaned and this is very expensive. However, with UT shear wave...
Storage Tanks Floating Roofs - Challenges In Aging Tanks When Exposed To Extreme Weather Conditions
Friday, 01 December 2017
Arcot ("Radha") Radhakrishnan
Turnaround Services/Inspection Planning
Over one hundred thousand floating roofs have been used in hydrocarbon (oil) storage tanks since the 1950s. A majority of these tanks continue to be in service and are critical to meet strategic storage needs. An earlier article in this blog category describes Industry Best Practices for inspection and maintenance of such tanks. View Maintenance & Reliability of Floating Roofs . The article below responds to multiple inquiries - from domestic and international refiners - who are confronted with challenges to safely operate and maintain large diameter (200-350 feet diameter) floating roofs in service for 30-35 years. In addition to age, these tanks may be exposed to extreme weather conditions such as hurricane winds above 100 mph and/or excessive rainfall. For example, Hurricane Harvey dumped in excess of 50 inches of rain in the Houston, TX area with sustained winds of 130 mph in 2017. Under these extreme conditions, catastrophic...