Per NFPA, the only maximum velocities are noted for the piping 10 pipe diameters up stream of the suction side of a fire pump. You can refer to NFPA 20 for the fire pump suction and discharge requirements. However, the maximum velocity for the upstream pipe (10 pipe diameters in length) is 15 FPS. For the remainder of the system there are not any limitations to velocity. Refer to the technical report by Roland Huggins, PE of AFSA for more information on the relative non-impact of velocity in fire sprinkler systems
As far as FM, I think they have also removed the velocity requirements. They used to mandate 32 fps in "tree mains", and 20 fps in gridded branch lines. However, I have not had problems in the last 5 years or so when I have exceeded those values.
