Detection of defects in steel ropes using dynamical methods

Abstract

Early defect detection and monitoring of rope systems constitute important safety requirements for equipment that employs ropes as single driving component, e.g. lifts, rope trains, etc. Quality characteristics of ropes are regulated by procedures of safety standards and are prescribed in safety standards of transportation machines, which are particularly stringent in the case of human elevating equipment. Many types of rope quality control are applied in practice but standard control procedure of such nonhomogeneous structures as ropes with electromagnetic methods are still not fully reliable, particularly in the case of broken wires in rope strands. The paper presents a method for detection of the aforementioned rope defects using dynamic properties of a rope that is treated as a dynamic system. The proposed method enables to measure dynamic characteristics of a rope system and, based on obtained results, evaluate rope quality, determine the presence of broken strands and define cross-section of the defects. Analysis of dynamic properties is used in order to establish existence of a defect. Aim of such analysis is to determine some characteristic natural frequencies corresponding to broken strand and change of the lowest natural frequencies that represent the rope as a constrained system. The paper also addresses the issues of equipment and methodology required for defect detection in ropes together with the necessary conditions. Final conclusions are formulated with regard to possibility of implementing the proposed method in real working conditions.