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It is well known that the scatter of bolt loads occurs when bolting up a pipe flange connection with a number of bolts. In general practice, two factors presumably have dominant effects on the non-uniform loads. One is due to the scatter of bolt clamping force when adopting a torque control method. The second is elastic interaction due to the flange deformation occurring in the process of successive bolt tightening. In this study, bolt-up finite element simulations of the pipe flange connection are conducted by considering the scatter of bolt clamping force when using the torque control method. The interrelationship of the effects of the scatter of clamping forces and the elastic interaction on the preload scatter occurring in the bolt-up process is investigated.Copyright © 2004 by ASME

In the pipe flange connection with a raised face, the non-uniform gasket contact stresses in the radial direction are occurred due to the flange rotation. The gasket contact stress distributions have dominant effects on the sealing performance of the pipe flange connection. However, the leak testing of a gasket is usually performed under the uniform gasket contact stress using the rigid platen. It is very important to establish a method which predicts the leak rate from the actual pipe flange connection using the results of the leak test conducted under the ideal condition. To do so, there is a need to know the sealing performance of the actual pipe flange connection. In this study, the leakage tests and the finite element simulations are conducted for some pipe flange connections with different gasket width and different flange thickness, which might cause different flange rotation angle. The effects of the flange rotations on the sealing performance and the mechanical behavior of the pipe flange connection are examined.Copyright © 2004 by ASME

Various clamping methods are used to tighten bolted joints and the selection is made according to its configuration, bolt size, etc. Angle control method is commonly used among them and it is usually applied when tightening bolts to the plastic region. However, elastic angle control method is sometimes used to tighten important structures, e.g., for the case where the clamping bolts are to be disassembled in a periodical inspection. In this paper, the tightening process of elastic angle control method is studied and the expression relating axial bolt force and nut rotation angle is proposed, in which the effects of surface roughness of contact surfaces and the inclined angle existing around nut loaded surface are incorporated. The validity of the proposed equation is demonstrated by experiment. It is shown that the elastic angle control method is preferably applied to the case of a bolted joint with large grip length being tightened with high bolt stress.Copyright © 2004 by ASME

Achieving uniform bolt preloads is an important and difficult issue, when bolting up a pipe flange connection with a number of bolts. Repeated bolt-up operations are, therefore, commonly conducted to get uniform bolt loads. In this study, an effective one-pass bolting up procedure to get uniform bolt loads is proposed by using finite element analysis with elastic interaction coefficient method being incorporated. Furthermore, multi-pass bolting up procedure is also examined to avoid high initial bolt clamping forces that might be generated in the one-pass tightening. These procedures are applied to class 300 lb 20 inch flanges with solid-metal flat gasket and compressed asbestos sheet gasket. The validity of the procedures is substantiated by conducting bolting up experiment using calculated initial clamping forces.Copyright © 2004 by ASME

The purpose of this study is the proposal of guidelines for bolt-up operation of pipe flange connections with joint sheet gasket or spiral wound gasket. Numerical calculations are systematically executed for pipe flanges with wide variety of nominal size by using finite element analysis, which can simulate the bolt-up process of a pipe flange connection, because the tightening performance of the pipe flange connection largely depends on the bolt-up process. Gaskets also have dominant effects on the tightening performance. It is, however, impossible to determine the number of tightening passes to get uniform bolt preloads for all kinds of gaskets. A simplified modeling method of nonlinear stress-strain relationship of gasket is, therefore, evaluated and a representative material property of gasket is selected to develop the bolt assembly guideline. The bolt-up procedure, in which four bolts located 90 degrees from each other are tightened with the same magnitude of preload at the installation process, is investigated.Copyright © 2003 by ASME

In bolt assembly process of pipe flange connections, repeated bolt-up operations are conducted to achieve uniform preloads. Nobody, however, knows how many times of bolt-up operation is required to achieve uniform preloads. It is important for practicing workers to know the number of bolt-up operations. The number of bolt-up operation required to get uniform bolt preloads depends on the nominal diameter of pipe flange, the number of bolts, the types of gasket, etc. In this study, systematical finite element analyses of bolt-up operation are conducted for JPI class 150in and 300in flanges with a compressed asbestos sheet gasket. The number of bolt-up operations required to achieve uniform preloads is estimated for each pipe flange connection.Copyright © 2002 by ASME

The most important factor for the leakage problem of pipe flange connections is considered to be contact pressure distribution at the gasket bearing surface in service. In this study, the mechanical behaviors of the pipe flange connection are evaluated using FEM as a three-dimensional contact problem, in which a gasket is modeled as a nonlinear one-dimensional gasket element. Here, the contact pressure distributions at the gasket bearing surface and the variations of the bolt stress are estimated under uniform bolt preloads or nonuniform ones due to the elastic interaction during bolting up. The numerical procedure proposed here can successively deal with the processes of bolt-up, applying inner pressure and applying bending moment. The analytical objects are pipe flanges specified in JIS B 2238 with compressed asbestos sheet gaskets being inserted. The validity of the numerical method is ascertained by experiment.

Elastic interaction between bolts occurs in pipe flange connections during not only the bolt assembly process but also the disassembly process. In this study, the mechanical behaviors of pipe flange connections during the disassembly process have been systematically examined by using finite element analysis. As a result, it is shown that the increase in the rating class and nominal size of pipe flange increases the maximum value of bolt loads occurred during the bolt removing process. The effects of the bolt removing sequence are also analyzed in order to estimate the redistributions of bolt loads and the variations of contact pressure distributions on the gasket bearing surface. Furthermore, it is simulated how a pipe flange connection behaves when the clamping forces of some bolts are lost due to failure or loosening.Copyright © 2002 by ASME