YOU CAN DO THE CALCULATIONS FOR AREA REPLACEMENT METHOD. FOR OPENINGS ON BLIND FLANGE YOU HAVE TO REPLACE HALF THE AREA OF OPENING. THE THICKNESS OF BLIND FLANG FOR CALCULATING REINFORCEMENT TO BE DONE IN OPERATING CONDITION ONLY. BOLTUP CONDTION IS NOT REQUIRED. AS THE THICKNESS OBTAINED IN BOLTUP CONDITION IS NEAR THE ENDGE OF THE FLANGE. YOU CAN FIND THE CALCULATION IN A BOOK CALLED "PRESSURE VESSLE DESIGN MANUAL " BY DENNIS.R.MORE<br><br>K.V.RAMANA