Abstract

Steel wire rope was breaked in exploratory conditions i.e. during hoisting the load. The requirement of the purchaser of the investigations was to find a reason which caused breaking the steel rope. In other words to check fitness for purpose of the used steel wire rope. Because of that all necessary investigations to solve this problem were performed. As first, quality of delivered rope was checked. More concretely it was checked chemical composition of the base material (steel strands and wires). Besides, quality of the base material i.e. presence of non-metallic inclusions, microstructure, segregation and decarburation of the rope wires was done. This investigation showed that base material is high carbon steel. Its quality fulfill necessary requirement. Therefore, the next step was to make failure analysis of the rope after long period of exploitation. These investigations contain visual inspection of the rope, metallographic investigations, fractographic analysis and tensile test.
Visual inspection was performed according ISO 4309 and ASME B30.30. Standards [1-3]. This inspection was performed to all segments of the rope. To perform visual inspection segments were unwinded and separately tested. It was found that the most serious damaging was detected near the breaking point of the rope.
Performed investigations clear confirmed that wear of the rope is the most often detected type of failure. Besides corrosion of the rope was detected at many locations too. Metallographic investigation detected the wear damage too. Scaning electron microscope (SEM) confirmed that shear and fatigue are the most often found types of fracture in the rope wires.
It was concluded from the investigation to too that lubrication of the rope is different at different locations. It means that at some position there is no lubrication.
It is obvious that defects (failures) which caused breaking of the rope appeared in the rope during exploitation.
Metallographic investigations of the wires and visual control of the ropes segments and strands confirmed that all defects in the ropes are results of improper installation, manipulation and handling of the rope.
Nominal value of the load, which can be hoisted by steel rope, became lower during exploitation. More concretely remained load, which can be hoisted, is in relationship 5:1 with nominal load [4-6]. So if higher load was hoisted, the rope will be breaked as it happened in our case.