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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.

Fluid-Structure Interaction Under Seismic Loading Using Finite Element Analysis

Fluid-Structure Interaction Under Seismic Loading Using Finite Element Analysis
Becht Nuclear Services recently applied ANSYS ® multi-surface, with fluid-structure interaction (FSI) capabilities to evaluate the effects of seismic loading on vessel internals that are immersed in the fluid.  Before proceeding with the analysis of the actual vessel, the FSI capabilities were benchmarked to an analytical solution of a simpler liquid-filled flexible tank under seismic loading.   Benchmark Model A fixed-base, flat-bottom, cylindrical tank, with a height/radius ratio (H/R) similar to the vessel to be analyzed, is modeled in ANSYS ® as shown in Figure 1.  The tank is filled with an inviscid liquid that is free to slosh, without impacting a roof.  SOLID186 (3-D 20-node) structural solid elements are used for the vessel.  The use of shell structural elements is also investigated and the performance compared with solid elements.  FLUID220 (3-D 20-node) acoustic elements are used to simulate the fluid.  A characteristic of the acoustic equations is that there is...
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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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Brittle Fracture Resistance Workbook API 579-1/ASME FFS-1 Approach (Fitness-For-Service)

Brittle Fracture Resistance Workbook API 579-1/ASME FFS-1 Approach (Fitness-For-Service)
Description Process vessels such as towers, drums and heat exchangers may be exposed to low temperatures as a part of normal operation or as the result of an upset condition. Carbon and low alloy steels typically used in process vessels undergo a transition from ductile to brittle behavior as temperature is reduced and are at increased risk of brittle fracture at low temperature. To reduce this risk, the ASME Boiler & Pressure Vessel Code contains requirements for vessels and vessel components with respect to low temperature operation. While these rules are applicable to new construction, API 579-1/ASME FFS-1 Fitness-For-Service uses the Code rules as the basis for evaluating the brittle fracture resistance of existing vessels. This article discusses an approach and spreadsheet tool that was used to provide a client with operating pressure limits as a function of decreasing vessel metal temperature. These limits were used as part of the client’s...
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