A few years back I worked on conveyor bridge for power station. They provided all loads like weight of parts, belt and material (depending on width of belt height of material will change). In addition they provided loads for tension of belt transferred to end supports, forces on pulleys for pulley frame design. Force for emergency stop was assumed as tension force times impact ratio of 2.
Talk to conveyor supplier. They will tell you exact numbers.
In additon to this use wind, seismic and snow load as well as load of maintenence people with parts and tools.
Good luck.