Controller for bulk solid handling equipment

A controller for 1100 the motor of bulk solid handling equipment (Figs 1 & 4) receives a signal 1110 associated with power supplied to the motor when rotating at a base speed. Controller 1100 determines if this is within a predetermined range 1120 and if not then causes at least two temporary changes in electric motor speed 1130; either increasing or decreasing the speed accordingly by between 2-15%. Once allowed to return to the base speed, controller 1100 redetermines with the predetermined range 1140, 1150 and if this is then outside the range inducing vibration 1160 of the equipment or part thereof. An associated piece of equipment, method and associated computer program are also disclosed.