Dimensioning of rope drives and operating time of wire ropes

The purpose of the dimensioning of rope drives is, by application-specific interactions of safety factors and diameters of the rope drive elements, to ensure sufficient operating life of the wire ropes. For hoisting gear and cranes, this is done according to the DIN 15020 standard with mechanism groups and the direct calculation of the rope diameter. Using the “Leipzig” method simplified for the TGL 34 022 standard, it was possible to mathematically estimate the bending cycles of wire rope constructions for visible and non-visible wire breaking development in rope drives generally. The rope diameter was defined from the safety factor in conjunction with the required operating life. This was the first time that the “sufficient time of bearing” could be calculated for rope drives according to DIN 15020. The “Leipzig” method integrates the experimental results of the former WBK rope testing body Bochum. Comparisons with the “Stuttgart” method showed both differences and extensive agreement of bending cycles tolerated with mathematical probability. Rope drive analysis by means of a “rope harp shape” is a way of calculating the bending cycles acting in rope drives and other stresses from the operating conditions of the ropes. In the new preliminary standard DIN CEN/TS 13001-3-2, the rope diameter is defined from one of two limit design rope forces. The interactions resulting from the proof procedure continue the tradition of dimensioning according to DIN 15020. However, the method of calculating the total bending cycles could raise excessively optimistic expectations on the service life of the wire ropes in the interactions of dimensioning, and signs of fatigue not detected in time may cause risks or even rope breakage.

Author(s): O. Gronau and G. Steinbach