5 Knowledge 5 Terminology related to steel wire ropes

Terminology related to steel wire ropes

Nominal diameter – [d] mm

A diameter of the rope accepted in the standard applicable for the given rope construction, calculated as a theoretical mean value rounded to nearest integer. This value is used for specification and description of the ropes while making a request for proposal, issuing attests and calculating the strength of the ropes.

Rope real diameter [mm]

A value obtained as a result of rope measurement with a measuring instrument designed for this purpose (a caliper or micrometer). The rope measurement is done by measuring its diameter in two planes perpendicular to each other, two measurements for each of them. Obtained in this way results are averaged and the obtained result is the real diameter. In dubious cases it is allowed to make a measurement of the rope loaded.

Diameter tolerance

The allowable deviation from the nominal diameter of a rope, or, in other words: allowable measurement range of the rope real diameter measured without load.

Minimum braking force [kN]

A value equivalent to the guaranteed breaking force, required by individual standard specifications to be strictly met by a ropes producer. The real force breaking the rope must not be lower than the minimum breaking force provided in the standard.

Rope strength classes [MPa]

The level of the required strength for which the value of rope breaking force is determined, denominated with values 1370. 1570. 1770. 1960. 2160 etc. The strength class corresponds with the strength of the Rm wires per rope, which is expressed by the ratio of breaking force to its cross-section area. Rope strength classification does not have to respond exactly to the strength of wires per rope.

Nominal mass of 1 m of a rope [kg]

Mass of 1 m of a rope is determined for the standard specification as a result of theoretical calculations.

Real mass of 1 m of a rope [kg]

A mass obtained from the measurement.

Length of wires lay in a strand (and strands in a rope)

It is a distance of which the same wire (strand) repeats while winding around the core wire.