The answer is that this value has to be measured for the particular circumstances of the application. For example, what compostion, finish and state of the steel surface? How wet is the product? What in the type and condition of the sugar?

It is dangerous to use data relating to the physical properties of bulk material for any published data for design purposes and tests should be carried out on represntative samples of the roduct and the operating circumstances. Ajax make a wall friction tester that allows the value to be easily determined. Crude measurements of static friction can be made by progressively inclining a plate on which a pile of the material is resting it is far better to determine static and dynamic friction uder various normal pressures of contact and sliding speeds by varying the normal load and using a force guage, then pltting the results. The reluting graph will highlight any surface cohesion or variaon of friction with load. ■