Approach for the Dimensioning of Bolted Joint Connections With Threaded Flanges for High Pressure Applications

High pressure flange connections for LDPE plants are commonly designed using lens ring gaskets and bolted flange connections. The rules given in the ASME Code Sections B31.3, VIII Div. 2 or VIII Div. 3 for bolted-flange joints offer no guidance for the calculation of threaded flanges. In this paper, an approach is presented that considers internal pressure and external loads on a flange connection and fulfills the requirements of ASME Section VIII Div.3 and ASME B31.3. Of specific interest is the dimensioning of bolts due to the bending moment with a method that avoids the over-conservatism of the rules given in ASME VIII Div.2 and ASME B31.3. Furthermore, a simplified calculation for threaded flanges considering the stress classification and stress limits given in ASME VIII Div. 3 and using Finite Element Analyses is described.