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Terminology concerning steel wire ropes « back

Nominal diameter - d [mm]

rope’s diameter stated in the standard corresponding to relevant rope’s construction, calculated as the average theoretical value rounded to integer. This value is used to define specification and ropes description while making inquiries, strength calculation of the ropes and issuing certificates.

 

Actual diameter of the rope [mm]

value received as the result of rope’s measurement made by an appropriate measuring instrument (slide caliper or micrometer). Rope measurement is obtained by measuring the diameter in two perpendicular planes one to another, two measurements for each of them. The obtained by means of this method is averaged and the achieved outcome is the actual diameter of the rope. In questionable cases it is allowed to measure the rope under a load.


Correct way of measuring rope diameter by caliper. Improper way of measuring rope diameter.

Diameter tolerance

acceptable deviation of rope’s nominal diameter or in other words: acceptable dimensional range of actual rope diameter measured without a load.

 

Minimum breaking load [kN]

a magnitude corresponding to the guaranteed breaking load, a value required by particular subject standards which a manufacturer must absolutely fulfil. Actual breaking
load cannot be lower than the nominal breaking load stated in the appropriate standard specification.

 

Class of the rope strength [MPa] 

a level of required strength for which the value of the ropes breaking load is determined, specified by values 1370, 1570, 1770, 1960, 2160, etc. The class of strength corresponds
to the wires strength Rm in the rope which is quantified by ratio of wire breaking load to its cross-section. Strength class of the rope needn’t exactly correspond to strength of the wires used to its production.

 

Nominal weight of 1 m of rope [kg]

weight of 1 m of rope appointed for a subject standard as a result of theoretical calculations.

 

Actual weight of 1 m of rope [kg]

weight obtained as a result of measurement.

 

Length of lay of wires in the strand (analogically to the strands in the rope) 

it is the distance in which idem wire (strand) is repeated at winding strands on the central wire (core of the rope) and we denote it by the letter h.

 

Way of measuring the length of lay.

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