Scope of this paper is to study the flange to gasket joint under bolt tightening and operating conditions as per the guidelines specified in ASME PCC-1 Appendix O using FEA approach with ANSYS as the FEA tool. Contact pressure for various transient loading conditions is obtained and compared against the required minimum contact pressure for the leak proof joint. ASME-PCC 1 gives the guidelines for bolted flange assembly for pressure vessel and piping joints in a standardized manner. With the help of FEA tools simulation can be done and broad picture of the assembly can be looked upon so that a designer engineer can have better insights for the stress and deformation during seating and operating conditions. Thorough investigation of the flange joint has been carried out by finite element analysis in this paper and acceptance criteria as recommended in ASME PCC-1 Appendix-O have been used to establish the design in a safer and optimized way.