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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.

Purpose of the Flange Bolt Rules in ASME VIII and ASME III

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The partial objective of the ASME Appendices ASME VIII Div.1 Appendix 2, and ASME III Div.1 Appendix XI provide “Rules for Bolted Flange Connections” with ring-type gaskets. One of the rules provided applies to the calculation of the minimum required bolt area. In other words, what should be the minimum combined cross-section area of the flange bolts to (a) seal the gasket, while (b) not exceeding the bolt allowable stress? The two force components W m1 and W m2 The rules are intended to provide bolts with sufficient pre-tension to achieve two objectives: (1) Counter a pressure-induced force W m1 which tends to pry open the flange in operation, and (2) provide a compressive force W m2 which is needed to seat the gasket during initial assembly of the flange joint. The at-pressure force W m1 The W m1 force is in turn comprised of two contributions, illustrated in the...
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Differential Thermal Expansion: A Challenge to Flange Joints

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by George Antaki and Jeremy Lundquist It is not uncommon to use B7 low alloy high-strength bolts on stainless steel flanges. If that is the case, and if the flange operates at high temperature, then the thermal expansion-induced stress in the bolt should be checked. Consider, for example, a stainless steel flange SA-182 Grade F304, with SA-193 Grade B7 bolts, in a line that operates at 600 o F. The line is insulated, so both the flange and its bolts will be at 600 o F during steady-state operation. In hot operation, the stainless steel flange wants to expand more than the low alloy steel bolt. This will induce a tensile stress in the bolt equal to: σ bolt  = E b  × (α flange  - α bolt ) × ∆T Where E b = modulus of elasticity the bolt at 600 o F = 26.9E6 psi; a flange = coefficient...
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George Antaki

Avoiding Leakage

If the flange is in a service where delta-T is sufficiently large so that stress-preload (depends on the initial torque) + stress-... Read More
Saturday, 13 January 2018 09:37
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ASCE 43 - Changes to the Upcoming Revision 2018

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ASCE/SEI Standard 43, “Seismic Design Criteria for Structures, Systems, and Components in Nuclear Facilities,” is a consensus US national standard developed by the American Society of Civil Engineers.  It provides design criteria for nuclear structures and should be used in conjunction with ASCE/SEI Standard 4 - “Seismic Analysis of Safety-Related Nuclear Structures”.  The two standards are performance based and are written to ensure that structures, systems, and components (SSCs) designed and evaluated in accordance with their provisions meet target performance goals that vary as a function of the seismic design basis.  ASCE/SEI 43 was published in 2005 and is currently being revised with the goal of issuing the updated Standard in 2018. ASCE 43-05 was initiated at the behest of the US Department of Energy (DOE), as were ANS 2.26, ANS 2.27, and ANS 2.29, to integrate the various steps of the seismic design process. Thus, criteria and methods of Seismic Design Categorization...
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Storage Tanks Floating Roofs - Challenges In Aging Tanks When Exposed To Extreme Weather Conditions

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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...
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