I am bit confuse,

I do manual calculation of Branch pipe with collar pad based on ASME B31.4.

On following consideration:

1. Header pipe OD 2134mm and thickness 15.88mm.
2. Branch Pipe OD 1321mm and Thickness 10.31mm.
3. Width of the collar plate 550mm and thickness 15.88. 
4. All are X42 grade carbon steel pipe

As per ASME B31.4 my proposed collar plate is sufficient but when i model it on solid works it shows that