For engine service facilities that were not equipped to dry their own sand the B&O had box cars that brought in pre-dried sand. Some of the cars had a bin at each end and hose connections to deliver sand to the engines. Other cars just had sand piled loose at each end and a plank across the doorway, and the sand would be carried in buckets to the engines. These cars were used at least into the late 1970s.
Not only do railroads use covered hoppers to transport sand, but they have been known to use them as sanding towers, too:
http://wc6524.tripod.com/sitebuildercontent/sitebuilderpictures/wc7520.jpg
Edit: Oops, forgot to make the link clickable. Fixed!
And let's not forget tank cars were occasionally used for dry sand, too:
http://www.trainweb.org/mccloudrails/Equipment/MR503.html
SP&S had several, also.
Ed
Modeling BNSF and Milwaukee Road in SW Wisconsin
Lots of railroads used older covered hoppers to ship company service sand around.
These would generally be older cars retired to work service.
Chris van der Heide
My Algoma Central Railway Modeling Blog
Was/is there a specific way that railroads delivered sand to their yard facilities? I am trying to figure out the right kind of car for my railroad. I have seen gondolas used with proper drying facilities. However, I don't foresee having the proper room for such a facility. (The yard is built around an Atlas 305 turntable. I model HO in case you hadn't figured that out.) As a result, I wonder if a covered hopper could be used for sand service in order to keep the sand dry. I model the early to mid-70s if that helps determining the proper car. Any ideas that anyone would have would be welcomed.