Finite Element Analysis of Flange Joint With Single and Twin Gaskets Under External Bending Load

Gasketed flange joint is a vital component in pressure vessels and piping systems. Flange joint is usually subjected to bending load due to expansion, wind load, self-weight, etc. Most of the flange design methods use equivalent pressure to include the effect of external bending loads. It becomes complex when the joint is subjected to bending load at elevated temperatures, due to the nonlinear behavior of gasket material. In the present work, performance of the flange joint has been studied under external bending load at elevated temperatures. A 3D finite element model is developed, considering the nonlinearities in the joint due to gasket material and contact between its members along with their temperature dependent material properties. The performance of the joint under different bolt preloads, internal fluid pressures and temperatures is studied. Flange joint with two gaskets (twin gasketed joint) placed beside each other radially, is also analyzed under external bending moment. The maximum allowable bending moments at different internal temperatures, for single and twin gasketed joints with spiral wound gasket are arrived.

Further Studies on Predicting Leak Rates Using an Emissions Calculator for Bolted Flanged Connectors

Work on the development of a practical tool, the “Fugitive Emissions Calculator” (FEC) has been previously reported. This tool, based in Microsoft® Excel® has been used to help predict anticipated fugitive emissions of various gasket materials with the proposed ASME / PVRC method for estimating leak rates using standard Room Temperature Testing (ROTT) data, the operating pressure, the pipe diameter, gasket stress, and other inputs. To further test the performance of the FEC, a sensitivity analysis has been conducted, focusing on several parameters, including system pressure, assembly efficiency, and gasket stress and their relative degree of significance on the predicted gasket tightness and leak rate. In addition, work has been conducted for developing a method for estimating the stress retention coefficient previously reported as a proposed modification to the PVRC leak rate method. The findings and conclusions of these studies are presented.

Initial Investigation on the Effect of Bolt Loading Rate on the Need to Re-Torque PTFE Gaskets in Bolted Flanged Connections

Industry practice dictates that there is a minimum level of assembly stress to obtain gasketed joint tightness. In addition to the initial stress placed upon the gasket, it is maintained that a re-torque is often necessary with PTFE based gaskets to insure proper operating stress levels on the joint and gasket material system. This paper and research will explore the effect of bolt loading and flange assembly rate in bolted flanged connections utilizing PTFE gaskets.

Effect of the Shapes of Diversion Umbrellas on Temperature Field in a Large Spherical Tank During Heat Treatment Processes

Internal combustion method is widely used to reduce residual stress of large spherical tanks in China, when post weld heat treatment of the spherical tanks is required. During the heat treatment processes diversion umbrellas set in the spherical tanks can be utilized to drop the maximal difference of wall temperatures of the spherical tanks. Numerical simulation based on Fluent software was carried out to study the effect of an A-shaped diversion umbrella and three V-shaped diversion umbrellas with different angles on internal flow and wall temperatures of a 10000 m3 spherical tank. The results show that the V-shaped diversion umbrellas have better performance than the A-shaped one, but the angles of the V-shaped diversion umbrellas from 100° to 140° have little effect on maximum wall temperature differences of the spherical tank during the heat preservation stage of the heat treatment processes.

High Fidelity Simulation of Safety Relief Valve Internal Flows

This paper presents a numerical methodology and simulation for three-dimensional transonic flow in Safety Relief Valves. Simulation of safety relief valve flows is very challenging due to complex flow paths, high pressure variation, supersonic flow with shock and expansion waves, boundary layers, etc. The 3D unsteady Reynolds averaged Navier-Stokes (URANS) equations with one-equation Spalart-Allmaras turbulence model is used. A fifth order WENO scheme for the inviscid flux and a second order central differencing for the viscous terms are employed to discretize the Navier-Stokes equations. The low diffusion E-CUSP scheme used as the approximate Riemann solver suggested by Zha et al. is utilized with the WENO scheme to evaluate the inviscid fluxes. Implicit time marching method with 2nd order temporal accuracy using Gauss-Seidel line relaxation is employed to achieve a fast convergence rate. Parallel computing is implemented to save wall clock simulation time. The valve flows with air under different inlet pressures and temperatures are successfully simulated for the full geometry with all the fine leakage channels. A 3D mesh topology is generated for the complex geometry. Detailed simulations of air flow are accomplished with inlet gauge pressure 0.5MPa and 2.1MPa. The simulated air mass flow rate agrees excellently with the experimental results with an error of 0.26% for the inlet pressure of 0.5Mpa, and an error of 2.5% for the inlet pressure of 2.1MPa. The shock waves and expansion waves downstream of the orifice are very well resolved.

Technical Basis for the Assessment of Small Bore High Energy Piping With Lower Than Code Specified Design Minimum Thickness

Wall thinning by Flow Accelerated Corrosion (FAC), Erosion-Cavitation (E-C), and fretting has been observed in carbon steel piping. At some locations, the predicted end-of-life wall thickness could be below the design minimum thickness required by ASME B&PV Code Section III, which is an extremely conservative analysis method. To support the life extension without replacement or repair, it is essential to demonstrate the fitness for service of degraded piping components that satisfy the mandatory structural factors with uncertainties explicitly identified and addressed in an integrated manner. The present paper discusses the key technical basis for a sound assessment of small bore high energy Class 1 piping with lower than Code specified design minimum thickness, and proposes some future research activities to further enhance the technical basis.

Effect of Adhesive Nano-Additives on Static Load Transfer Capacity and Failure Mode of Bonded Steel-Magnesium Single Lap Joints

An experimental procedure and test setup is used for investigating effect of using nanoparticle additives to the adhesive on the load transfer capacity (LTC) of bonded magnesium (Mg)-steel (St) single lap joints (SLJ). Investigated variables include the nano-powder material (Alumina vs. Silica), particulate size (20 nm vs. 80 nm), and concentration in the adhesive (2.5% wt. vs 5.0 % wt.). Two different levels of surface roughness on the bonded area are used; namely, sanding the bond area with G60 or G180 sand paper. Test data and SEM failure mode analysis are provided.

Effect of Scatter in Axial Bolt Force on the Sealing Performance of 20” Inch Pipe Flange Connections With CSG Under Internal Pressure

Since a scatter in axial bolt force exists in assembling the pipe flange connections, it is important to evaluate the effect of scatter in axial bolt force on the sealing performance of pipe flange connection. The FE and experimental analyses were done to evaluate the effect of scatter in axial bolt force on the sealing performance of pipe flange connection with 20 “nominal diameter. The results revealed that the large diameter pipe flange connection was sensitive to the scatter in axial bolt force. Besides, the large diameter pipe flange affected more by flange rotation when internally pressurized. As a result, a larger diameter pipe flange connection with scattered bolt preload showed poor sealing performance. The experimentally obtained scatter in axial bolt force as assembled was taken into account in FE analyses and the effect of the scatters on the contact gasket stress distributions was shown numerically. FE results show that the sealing performance is reduced due to the distributed gasket stress and bolt force scatter in the axial direction.

Things to Concern for Finite Element Analyses

Recently FEA (Finite Element Analysis) is used in various engineering fields such as for design, verification, validation trouble-shooting and other applications. As the more users are treating FEA, the quality of analyses has become the larger issue. Finite Element Method (FEM) is just a calculation method to reproduce physical phenomena, and it has functional limitation in nature. As the software becomes more and more user-friendly, the limitation is hidden in the operation. However, as the limitation still exists in principle, users must be aware of it when using the FEA software. This paper will address about the issues that we are easily trapped in modeling, such as element selection, boundary conditions and other conditions.