Analytical Study of Thermomechanical Strength of Assemblies with Optional Plane Flanges. The Effect of the Flange Ring Rotation Around the Median Circumference

Abstract

This paper describes the analytical evaluation of the thermo - mechanical stresses developed in the circular flange assemblies, of optional type, welded to the cylindrical shell of a pressure vessel. In this case, the structure is formed by welding the cylindrical shell on the inner circumference of the flange ring. Based on the theory of deformation compatibility (radial displacements and rotations), the expressions for the evaluation of radial unitary bending moments and the unitary shear forces are deduced. Subsequently, stress values can be calculated and their concentration can be evaluated along the cylindrical shell, below the separation plane of the flange ring.

Analytical Study of the Static Thermomechanical Stresses of the Assemblies With Optional Ring Flanges. Rotation of the Flange Ring Around the Circumference of Centers for Bolt Holes

“…7. The value of the rotation angle of the flange ring is conditioned by the intensity of the internal connection loads, together with the effect of the external loads: a) the unit force resistant to the tendency of the expulsion of the gasket [27,39]; b) by the bending, resistant unit moments, mg, by the eccentric compression of the gasket, respectively ms present due to the curvature of the screws [7, 9, 40 -42], all related to the inner circumference of the ring; 8. A uniform radial compression of the gasket for sealing and, at the same time, an identical tightening of the screws, by using a specific methodology and suitable systems is considered [31,35,[80][81][82];…”

“…The choice of the material of a sealing gasket is a difficult problem, because it must meet a number of extremely important conditions, such as: a) be stable at working temperature, pressure and chemical and mechanical aggressiveness of the technological environment, while maintaining its economic characteristics; c) have resistance to friction and wear; e) deform elastoplastic, when the gasket is tight, in order to completely fill the micro-asperities of the sealing surfaces. For its importance, recognized experimental research has been carried out over time [61 -67], as well as appropriate theoretical studies [39,68,69], for example, for the evaluation of the sealing pressure between the flange rings, in the radial and circumferential direction.…”