Wall friction

Two parameters shall be used:

— Angle of wall friction jw for the evaluation of flow;

— Coefficient of wall friction for the determination of pressures. B7.1 Angle of wall friction ww for the evaluation of flow

B7.1.1 Principle of the test

A sample of the particulate material is sheared along a surface representing the hopper wall, and the friction force at the sheared surface is measured. The reference pressure is kept low to simulate the low pressures occuring during discharge near the outlet of the silo.

B7.1.2 Apparatus and test procedure

The test may be carried out using the apparatus described in B7.2 and in accordance with the test procedure given in "International Standard Shear Testing Technique", Report of the European Federation of Chemical Engineering, EFCE, Working Party on the Mechanics of Particulate Solids, The Institution of Chemical Engineers, 1989 (or revisions).

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