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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.

Five Keys to a Cost-Effective Repair/Modification Package for Tanks-Vessels-Piping

becht_nuclear_5_keys
: Process : Does the repair change the process chemistries, physics (fluid phase), and thermo-hydraulics (flow rates, pressures, temperatures)? Does the modification change the control room indications and the operating envelopes? Material : Are the selected metallic materials (base metal and welds) and non-metallic materials (gaskets, packings, etc.) compatible with the existing materials, with the environment, and with the service, for the design life of the repair? Is the material compliant with (a) the material specification (ASTM or ASME II), (b) the supplementary Code requirements, and (c) the supplementary plant-specific requirements? Will the material be procured from an approved supplier; does it require supplementary Quality Controls? ASME Code design : Does the modification alter the system layout? If yes, has the layout been checked for good practice and consistency with the process design (item 1 above)? Are the loads and load combinations well defined and categorized as Service Levels A, B,...
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Reduced Toughness Properties of Some Modern Carbon Steels Create Brittle Fracture Risk

Reduced Toughness Properties of Some Modern Carbon Steels Create Brittle Fracture Risk
Changes in steelmaking practice are reported to be causing some carbon steel piping components that are assumed by ASME Codes to behave in a ductile manner at ambient temperatures, to behave instead in a brittle manner.  Barry Messer from Fluor made a presentation on this subject at the Spring 2016 meeting of the ASME B31.3, Process Piping Code Committee to alert committee members to this issue.   Having steel components that behave in a ductile fashion is an important aspect in the safety of pressure equipment.   ASME B31.3 requires impact testing to confirm ductile behavior unless the material is exempted from such testing by various code rules.  These exemption rules have been based on the historic properties of the materials.   A105 carbon steel flanges are generally exempted down to -20°F (-29°C) as is A106 Gr B carbon steel pipe with a wall thickness ½ inch (13 mm) and less.  The issue has...
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7986 Hits
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Changing Your Crude Slate – Short and Long Term Consequences

Changing Your Crude Slate – Short and Long Term Consequences
There are many reasons why a refinery may want to change their crude slates. However, all of them boil down to economics. Whether a cheaper crude is available or there is a desire to manufacture specific products to increase profitability - money is the driver. However, in deciding to change your crude slate, the long term effects of those changes can go overlooked, costing significantly more money in the long run. Whatever the reasons for the crude slate change may be, it is important to keep in mind the processabilty of the crude. For example, perhaps a refinery wants to process more of the shale crudes (Bakken, Marcellus, or Eagle Ford) due to pricing advantages. Or the refinery wants to bring in large shipments of foreign crudes, again because of price advantages. A common, significant aspect of both of these crudes is that they can be very high in hydrogen sulfide...
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Fatigue Evaluation of Welded Joints

In welded structures, fatigue failures typically occur at the welded joints. Stress concentrations and small flaws in the welds are key parameters in determining the fatigue life of weldments. Traditionally, fatigue analysis of welded joints has been performed by attempting to determine the peak stress at the welded joint and then entering an appropriate “S-N curve” to estimate the fatigue life of the joint. The determination of the peak stress is required because the S-N curves are based on smooth bar specimens that do not include the effect of any stress concentrations. There are two methods to estimate or account for the peak stress in the welded joint. One method is to assign a fatigue strength reduction factor (FSRF). The FSRF correlates the fatigue behavior of a specimen with a notch stress to a specimen without a notch stress and thus accounts for the stress concentration effects of the notch in the fatigue evaluation. That is, the FSRF...
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