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Nadarajah ("Ranjan") Chithranjan's career has spanned over 18 years of worldwide involvement in petrochemical industries for ExxonMobil Research and Engineering. Prior to joining Becht Engineering, he worked as a fixed equipment specialist at ExxonMobil Research and Engineering and he has worked in more than a dozen countries worldwide to solve complex mechanical plant problems as well as mechanical support for large scale projects. He has extensive knowledge in pressure vessels, piping, and storage tanks, design and maintenance codes.

How To Quantify And Evaluate Oil Storage Tank Annular Plate Corrosion

annular_plates_cover-imag_20181008-172036_1 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 technology...
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Design/Specification of FCC Replacement Parts and Upgrades

Design/Specification of FCC Replacement Parts and Upgrades
Overview Fluid Catalytic Cracking (FCC) units were first developed in the 1930s. Over the years this technology has evolved and it is one of the most important processes used in refineries. The FCC units are used to convert high boiling point, high molecular weight hydrocarbon fractions of crude oils to gasoline, olefinic gases, and other products. There are a number of process technology providers who license proprietary FCC technology; however, the equipment is basically the same ─ a reactor vessel where the hydrocarbon feed and hot catalyst contact and react (~950F) producing hydrocarbon vapors for further processing, and a regenerator vessel where the carbon laid down on the surface of catalyst from the reaction is burned off (regenerated and heated) in a fluidized bed (~1350F). The regenerated catalyst is returned to the reactor. The catalyst circulation between the reactor and regenerator is continuous. Large diameter refractory lined piping (transfer lines) circulate the...
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Determining “Life” of Bulged Coke Drum

Determining “Life” of Bulged Coke Drum
My previous blog on Equipment Health Monitoring (EHM) explains why EHM can be used to improve fatigue life of a coke drums. As explained in this blog, one of the critical locations to be monitored are the circumferential weld seams  - where high thermal stresses occur during the operation of the drum. These high stresses over time can cause localized bulges to occur and eventually fail due to fatigue. One way to quantify the amount of bulging and deformation is to do a laser scan of the drum. Once you get the laser scan data, analysis of the data can be done to determine the life of the drum Laser Scanning Some in the industry simply create a model of the deformed shape from the laser scan data, and calculate the amount of plastic strain at the bulges and put a limit on the plastic strain to determine whether failure is...
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5137 Hits
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Why Do Coke Drums Tilt Over Time?

Why Do Coke Drums Tilt Over Time?
Background Refinery coke drums experience fatigue induced issues which can be attributed to the coke drum operating cycle; rapidly heating the drum with hot coking feed, and, following the completion of coking process, rapidly quenching of the drum contents with water prior to cutting.  Rapid temperature changes as the drum transitions between steady state temperatures impart a measurable stress gradient on the drum wall and through the skirt and baseplate resulting in long term effects which will cause coke drums to tilt. The tilting of the drum will cause misalignment of the top nozzle and cutting tool. In some cases the misalignment may prevent the drilling operation. The cause of the tilt can be attributed to these uneven temperature distributions which result in the failure of the base plate, grout, construction shims, anchor bolts and drum bulging as noted below: Base Plate, Grout, Shim and Bolt Failure A mechanism which will...
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8058 Hits
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