Strength
Wire rope strength is normally refered to as minimum breaking force or minimum breaking load. The minimum breaking load of any given rope diameter can be increased in two basic ways;
- An increase in the tensile strength of the wire used to manufacture the rope will increase the minimum breaking load of the final rope. Typical tensile grades of wire used for crane rope manufacture are 1770N/mm2, 1960N/mm2 and 2160N/mm2.
- Additionally it is possible to increase the steel fill factor of the wire rope. Fill factor means the ratio between the sum of the nominal cross sectional areas of all the wires in the rope and the circumscribed area of the rope based on its nominal diameter. More simply it measures the metallic cross sectional area of the rope.
It is possible to marginally increase the fill factor by varying the construction i.e. adding smaller filler wires. More effectively the individual strands of the rope can be compacted.
The resultant rope has a very high steel fill factor and consequently a relatively high minimum breaking load for any given diameter when compared with a conventional rope.
The high breaking load to diameter relationship offered by compacted ropes can allow crane manufacturers to optimise the design of crane components such as winding drums and sheaves whilst still complying with international crane design standards.
Lower stress levels which occur when crane operators replace a conventional rope with an identical diameter of high strength compacted rope can lead to more ‘comfortable’ operation and longer rope life.