Manoj,
This is one (Momentum criteria)of the methods used for sizing the pipe / pipe line . I do not know why process engr. thrown this issue to a stress engineer whose involvement is NIL in this case . If ρV2 exceeds the limit, let him(process) check if velcoity is within the "erosion" limit.
It is his baby , not yours so throw back to him.

However, Keep in mind that the higher fluid velocity might induce vibration hence, try to keep this line with minimum natural frequency of 4HZ.at least .