Why wire ropes should be inspected and examined with MRT (Magnetic Rope Test)
Wire ropes are consumable items with limited life. During service the physical properties of a wire rope will change. A visual inspection of the entire wire lenght will in most cases be too time consuming. A crane wire of 70-140mm x 3-4000m would take days to complete, in addition it is almost impossible to detect internal wire breaks and corrsion without opening the wire up.
According to ISO 4309:2017, MRT should be used as an aid to periodic inspection. If intended to carry out MRT during periodic inspections, the wire rope should be subjected to an initial examinination (SIGNATURE). One objective of inspecting a wire rope is to supervise the normal process of deteraiation in order to remove the wire rope from service before becoming a safety hazard.
Another objective is to prolong the life time of the wire rope. With proper maintenace and surveillance, the life time could be increased from normally 3-5 years up to 10 years and longer.
Internal Wire Breaks
Complete rope shown on left and same rope with outer strands removed shown on right. Illustrates absence of external wire breaks, but presence of internal wire breaks
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