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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.

Changes In the 2012 Edition of ASME B31.3

In addition to the many clarifications, updated references to codes and standards, updates to basic allowable stresses, and added listed materials, there are several substantive changes to the 2012 Edition of ASME B31.3, Process Piping. These changes are: Category D Fluid Service The definition was revised to include piping with design minimum temperatures below -29⁰C (-20⁰F) if the cause of the lower temperature is from ambient conditions. Allowable Displacement Stress Range The allowable displacement stress range was limited to 60,000 psi (414 MPa) in the 2012 edition. High strength steels have higher yield and tensile strengths and thus higher allowable stresses. Therefore, they also have higher calculated allowable displacement stress ranges when calculated using the old formula. However, these materials have fatigue strengths similar to the more common steels, which is why the limit was added. Flexibility Stress Equation The axial stress was added to the flexibility stress equation. While axial...
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Don Frikken

Summary of substantial changes...

Yes, I can provide that. Just send me an email request at dfrikken@becht.com.
Friday, 08 March 2019 09:48
Don Frikken

RE:Allowable Displacement Stre...

Limiting Sc and Sh to 138 MPa applies no matter what the value of f is. Without this limit, the allowable stress range could be hi... Read More
Sunday, 03 May 2015 09:03
Don Frikken

RE:Allowable Stress Sc & Sh fo...

High strength steels have about the same fatigue resistance as low strength steels, especially for low cycle fatigue. Using the hi... Read More
Monday, 16 March 2015 09:51
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Demister Pads—A simple device until they don’t work

Demister Pads—A simple device until they don’t work
A demister pad is similar to an air filter except instead of removing dust particles from a stream of air for example, it removes micron-size liquid particles from a liquid/vapor stream often found in many industrial processes. An air filter prevents dust particles from entering downstream equipment; similarly a demister prevents liquid droplets from entering downstream equipment where they may affect operation or cause damage. In general, a duty specification is prepared by the process designer and given to demister vendors to recommend a demister that meets the duty requirements. Or today, knowing the required duty you can select a demister from the vendor's online catalog. The demister is installed, performs as intended and is never heard about again. On occasion, problems arise as the case in which Bob Fiocco, a Becht Sr. Advisor, provided technical support to a refining client on demister design and selection. An existing demister installed in...
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Risk-Based Work Selection - Key to Optimized Turnaround Workscopes

Risk-Based Work Selection - Key to Optimized Turnaround Workscopes
Operations and Maintenance Practices in refineries focus on maximizing safety, reliability and profitability, in a highly competitive industry, with tight margins. A key consideration is to effectively manage annual maintenance costs which can be as high as 40-50 MM$/year for a medium size refinery. These costs can escalate to several hundred million dollars, if unplanned shut downs occur, resulting in loss of production. Risk-based work selection (RBWS) is used to plan, schedule and execute maintenance work and is an industry Best Practice for improved reliability. The result is a risk-justified, optimized work list which uses maintenance resources cost effectively while mitigating unacceptable business and S/H/E risks. For TAs which require 200,000 to 1,000,000 person-hrs, the process has identified potential savings of 15-30% on estimated direct costs for the planned work scope. RBWS is used for task prioritization for turnaround (TA) work scopes and routine maintenance work. Rigorous use of RBWS enables...
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Piping Vibration Screening Rule

It is useful to have a screening rule for evaluation of piping vibration in order to determine if the vibration is potentially harmful (can lead to damage or fatigue failure) or if it is simply a nuisance and can be accepted without doing a more detailed assessment or anything to mitigate it. A very useful screening rule is provided in ASME OM-3 , “ Requirements for Preoperational and Initial Start-up Vibration Testing of Nuclear Power Plant Piping Systems;” however, it is first important to understand when it is appropriate to use this rule. It is not uncommon to have people use tools they are familiar with to address problems the tools are not suited for, yielding meaningless results. To understand where the OM-3 screening rule is applicable, it is useful to understand different categories of piping vibration. The first division is transient versus steady state. The screening rule is for steady...
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