Control of friction hoist head rope tensions revisited

ABSTRACTMatching of head ropes and drum grooves in multi-rope friction winding systems is essential for effective load sharing between the winding ropes. Analytical methods were developed in the 1960s to evaluate rope load disparity when rope groove depths are mismatched. Although this historical analysis ignored flexibility in rope groove lining materials, it is widely accepted that rope groove flexibility has the effect of reducing the disparity in load sharing. This paper recounts the original 1960s work in which rope load disparity was analyzed to provide rope groove depth tolerances of rigid grooves and provides a new rope groove depth tolerance for flexible grooves. Both rigid and flexible groove analyses show the importance of an adequate distance between the conveyance at its uppermost normal position in the shaft and the head ropes’ tangent point on the hoist drum. They also show that ground-mounted hoists are more tolerant to groove depth mismatch. Maintenance methods, including the collar-to-collar test, are revisited to reflect this latest analysis.