Q. Show the Procedure of Compute flange stresses?
Compute flange stresses and the actual bolt stress using:
- COLT values for gasket seating stress, ‘y' and the gasket factor, ‘m'.
- ASME Code allowable stress as initial values for Sa and Sb.
Repeat the calculation, substituting actual seating and operating bolt stresses for the original values of Sa and Sb.
For steps 1 and 3 of calculations, the iteration may be stopped at this point and the stresses and bolt loads determined.
For steps 2, 4 and 5, continue as follows:
- If value of stress or bolt load is incorrect, adjust gasket seating stress, ‘y'.
- Substitute resulting actual operating and seating bolt stresses for Sb and Sa.
- Review results and continue this process of alternately adjusting gasket seating stress and actual bolt stresses until the desired flange stress or bolt load is achieved.
If above procedures are followed correctly, the subsequent observations will be made:
- The required bolt area Am will equal the actual bolt area, Ab.
- Bolt load, W will equal the greater of Wm1 or Wm2.
When a closure involves two flanges of different dimensions, separate calculations for each flange are initially required. One single bolt load will be common to both flanges when the joint is tightened. Therefore, highest value of Wm1 and Wm2 must be transferred between the calculations of each flange.