Determination of structural and technological parameters of detachable joints

Abstract

A procedure for calculating forces acting at various stages of operation (tightening of fastening parts, rise and fall of pressure, etc.) on parts and units of detachable joints with radial self-sealing is discussed. The procedure allows determination of forces axial and perpendicular to seal surfaces, taking account of pliability of fastening dowels, seal rings, cover, and flange as well as of reversal of frictional forces on seal surfaces.Manufacture of high-pressure vessels, increasing their overall dimensions, and raising operational parameters are always accompanied by investigations of detachable joints (DJ) to ensure their reliability and to broaden the range of operating parameters.The major lines of investigations are:• creation and development of new reliable DJ;• development and refinement of procedures for calculating strength and tightness of parts and units of DJ;• investigation of various types of DJ at higher operating parameters;• selection of optimum DJ making technology, development and refinement of technical specifications;• development of equipment for use of DJ; and • development of normative documents to appraise the technical state of the DJ during their use. Based on analysis of published data and on the experience of use of high-pressure vessels, apparatuses, and pipelines, it has been concluded that at high parameters DJ's are most widely used with double-cone (double-wedge), triangular, octagonal, and undulating seals, with flat metallic gasket, and with ground seal unit [1].Based on investigations into the mechanism of operation of the above-listed DJ's, procedures have been developed to calculate joints having triangular and undulated sealing rings and having ground units [2][3][4], and procedures for calculation of structures having soft metallic gasket and double-wedge sealing rings have been refined.The developed procedure for calculation of forces acting at various stages of operation (tightening of fastening pieces, rise and fall of pressure, etc.) on parts and units of the DJ with radial self-sealing can be used to determine forces axial and perpendicular to the seal surfaces with due regard for the pliability of the fastening dowels, seal rings, cover, and flange as well as with due regard for the reversal of the frictional force on seal surfaces [5]. This procedure is usable for determining the force acting on the dowel Q d and the normal contact forces q N acting on the seal surfaces. It has been observed that sections of reversal of frictional force appear with rise and fall of pressure (Fig. 1).