distances between elements in a grain elevator facility

Is there any standard for the setting of minimum distances between the silos, the bucket elevators and other components of a typical grain elevator facility?

I can imagine it is smart to keep aisles wide enough to allow for the transit of forklift trucks, but then OSHA sets some regulations for an area about 10 meters around a bucket elevator, and still, in most facilities I have seen there is barely any space at all; conveyors, silos and processing machines are cluttered in the area.

Have you heard of, or do you practice, any good recommendations on these distances? ■