Summary of PVRC research on bolted flange assembly
- Univ. of North Dakota, Grand Forks, ND (United States). Dept. of Mechanical Engineering
Responding to a request from the ASME, the Pressure Vessel Research Council (PVRC) Design Division established the Sub-committee on Bolted Flange Connections (BFC) in 1965. Their goal is the improvement of ASME design rules for bolted flange connections. Another major focus has been gasket performance testing. More recently it has been recognized that considerable bolt-to-bolt preload variation occurs in a bolted flange assembly during normal bolt-up procedures. Variation in bolt preload during torquing due to frictional variation has been previously studied. Considerably greater variation occurs because of elastic interaction. Elastic interaction can be explained in terms of a progressive compression of the joint. Most of the compression occurs in the gasket, but elastic interaction is also effected by the distortion of the flange under the bolt. When the first bolt is tightened the gasket compresses and the flange distorts. (Assume all bolts are hand tight to prevent flange rocking that would occur if only one bolt was tightened.) When an adjacent bolt is tightened, the gasket compresses and the flange distorts further. This additional compression and distortion reduces the preload in the first bolt. Tightening the second adjacent bolt results in a further reduction in preload. Elastic interactions are additive and vary greatly with flange size, joint stiffness, number of bolts, bolt size, bolt length, and gasket stiffness. Elastic interactions will even vary with changes in the bolting pattern and sequence. Tightening groups of bolts in a bolted flange assembly results in significant elastic interaction. Individual bolts can lose up to 95% of their initial preload. Final bolt load can be as low as 45% of design even after a three pass bolt-up procedure. Elastic interaction is defined and typical data are given. An improved method of flange assembly is presented. Uniform preload ({+-}2%) is obtained in a single pass bolt up operation.
- OSTI ID:
- 116278
- Report Number(s):
- CONF-950740-; ISBN 0-7918-1338-X; TRN: IM9545%%247
- Resource Relation:
- Conference: Joint American Society of Mechanical Engineers (ASME)/Japan Society of Mechanical Engineers (JSME) pressure vessels and piping conference, Honolulu, HI (United States), 23-27 Jul 1995; Other Information: PBD: 1995; Related Information: Is Part Of Transport and storage of radioactive materials 1995. PVP-Volume 307; Carlson, R.W.; Hafner, R.S. [eds.] [Lawrence Livermore National Lab., CA (United States)]; Lake, W.H. [ed.]; PB: 191 p.
- Country of Publication:
- United States
- Language:
- English
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