before starting calculation and stress use:
1/ -Location of structures, beams, colums ..and try to place your pipe supports there.
2/- There is a specific table in ASME B31.1 (power code) , for GUIDANCE on maximum spans for pipes full of water or full of air..
3/- Think also about maximum stress in pipe, but do not forget to watch out the maximum defelection at mid span ..because you can exacerbate the corrosion if the product is left there and not drained.

4/ Pipe stress is to confirm the rest ; nozzle loads, maximum horizontal deflection, flange loads (= maximum moment to be converted in an equivalent additional pressure...), etc