The sand furnace was typically adjacent an access road between the coaling, watering and turntable area, and the shed roads or sidings where locos were parked awaiting their next turn, so that supply was near where the locos were standing; and in some cases so that a flange actuated treadle could also give the sand drying hopper a wallop as locos moved past, to help the sand drop through the riddles as it dried. Drying was essential for free flow in the loco sanding system, but the grading through the riddles if anything even more important. A stone jammed in a sand hopper gate or the sanding pipe might mean replacement or 'surgery'.
Some locations ceased using sand before the end of steam, BR taking up use of abrasive fines sourced from Scunthorpe steelworks. Among the benefits was that it was both ready graded and needed no drying, and could be brought in using Presflo type wagons eliminating the manual handling . ('Top Shed' by Peter Townend pub. Ian Allan, p79.)
There is continuing research into the best material to use for this purpose, my late Father in law who was a considerable authority on abrasives and tribology, only a couple of years past drew my attention to a quite recent paper from his alma mater:
https://eprints.whiterose.ac.uk/139102/ ... %20ARC.pdf
