Experiences during the magneto-inductive rope testing under application of LF and LMA sensors
Since about 1983 DMT has used sensors with which the reduction of the metallic cross section area (LMA) can be determined along with the classic sensors for detection of local faults (LF). The LMA data not only yields information about losses due to corrosion and/or abrasion; it also provides a means to determine the number of wire breaks at a certain rope position. Several wire breaks close to each other superimpose their stray fields and make an exact conclusion as to their number impossible if using only LF data. The LMA caused by corrosion and/or abrasion leads to a reduced breaking strength of hoisting ropes. However this reduction is not equal to the value indicated by the LMA data. Tests on discarded hoisting ropes have made it possible to develop correlations between the measured LMA data and the loss of the breaking strength.
Author: O. Gronau