Thumb rule to decide reinforcing pad

[ify09]

Can anybody throw light on this matter.

[ben]

Reinforcing pad is not required for intersections using couplings whose size does not exceed 2" NPS nor one-fourth the nominal diameter of the running pipe. Similarly in case of pressure vessels, every nozzle above 2" NPS (sometimes may be 3" NPS) shall be reinforced.

[mechcolor]

I doubt if there is any alternate / thumb rule to code calculations for reinforcing pad.