![]() In this post we will study WRC Bulletin 297 to better understand the variables used in the bulletin to determine stresses in the vessel/nozzle intersection. Findings from this study will then be applied to WRC Bulletin 107 to estimate the stresses in the nozzle region. Background WRC 297 is a very important bulletin for piping design engineers. It provides formulas for calculating stresses at a cylindrical vessel to a radially outward pipe nozzle connections. Aug 27, 2015 - WRC Bulletin 107, 'Local Stresses in Spherical and Cylindrical. Provided here in Bulletin 297 that broadens the coverage of Bulletin 107. Dear Members, I would like to know which paragraph in WRC 107 297 says allows the use of reinforcing pad thickness while calculating the local stresses in a nozzle to shell junction in. Buy batman arkham city pc. Why is the proper evaluation of a nozzle-vessel interaction so important? Because if we don’t, estimation of the stresses can be highly inaccurate. To illustrate this point, Sample example A-2 given in the bulletin has the bending stresses generated in the vessel due to self-equilibriating internal forces that are more than 9 times the membrane stresses. Why are the bending stresses so high? This occurs because the vessel is a very thin shell structure with large Diameter/Thickness (D/T) ratio of the order of 100. Such vessels away from any discontinuities (geometry or load) can only carry load in membrane direction along the plane of the shell. It’s unable to carry transverse loads. So, when a shell is loaded transversely, or meets another shell with different orientation or thickness the membrane stresses alone cannot address the required equilibrium equation, and high bending stresses are generated at the discontinuity to transfer loads and ensure kinematic constraints are met. These bending stresses, however, dampen out in a short distance away from the discontinuity. Calculating the various stress components at the intersection is tedious and complex or may not be feasible. WRC 297 simplifies the stress calculations by providing figures based on existing analysis and best-fit techniques. Stress Calculations The bulletin provides stress formulas for the inside and outside surface at 4 locations around the circumference of the intersection for both the vessel and the nozzle. The longitudinal direction is along the axis of the vessel and the transverse direction is orthogonal to it along the circumferential direction. Normal Stress For vessels, the stresses are calculated using the unit edge membrane forces (Nr, Nθ) and bending moments (Mr, Mθ). These unit forces and moments are normally used for stress analysis of shell structures. Axial piping load (P) and bending moments (ML and MC) applies transverse loads on the vessel shell and are normally the main contributors of the stresses at the intersection. WRC 297 provides tables to transform these loads edge forces and moments on the vessel shell Eq. WRC 297 provides a stress equation containing two terms for each of the above three piping loads components. The first term in the stress equation is for membrane stress and the second term is for bending stress. The bending stress has +/- prefix. The + prefix is for outside surface and the – prefix is for the inside surface. For unit edge membrane force, stress = For unit edge moment, stress = At the intersection, the edge moments on the vessel are also acting on the nozzle. So, the moment values used for vessel at the intersection can also be used to estimate stresses in the nozzles as was done in Eq. The shell at the interface has a membrane component.
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