Wire Ropes Under Bending and Tensile Stresses - Wire Ropes: Tension, Endurance, Reliability - page 295

Table 3.18 Constants for calculating the discarding number of wire breaks or the discard lim-
iting force, ( 3.83 )or( 3.94 )
Rope g 0 g 1 g 2 g 3

FC-8 9 19-sZ a,b
zZ b,c

Filler Warr. Seale 18 0.000174 1,550 0.026

WRC-8 9 19-sZ a,b
zZ b,c

33.3 0.000184 1,830 0.0447

FC-8 9 38-sZ a,b
zZ b,c

Warr.-Seale 29 0.000271 2,400 0.0403

WRC-8 9 36-sZ a,b
zZ b,c

44.5 0.000222 2,200 0.0536

18 9 7 b,c

Spiral round strand rope 14 0.000160 -350 0.0350

34 9 7 b,c 20 0.000230 -500 0.0500

For reverse bendings the number of wire breaks has to be calculated with a specific tensile force,
increased by DS/d 2 = 50 N/mm 2 . For six strand ropes the number of wire breaks 0.75 of that for
the eight strand ropes
a Outside visible wire breaks
b Magnetic detected wire breaks
c Half of the calculated number of wire breaks as visible wire breaks if confirmed by bending
fatigue tests for the considered wire rope

The discarding number of wire breaks on the small reference length L = 6 d—
which has been chosen to detect break concentrations—is given by definition as

B A6 ¼ 0 : 5 B A30 :

ð 3 : 84 Þ

It should be noticed that these discarding numbers of wire breaks generally
differ from those in existing technical regulations.

(b) Discard Limiting Force

As an alternative design limit to the discarding number of wire breaks, the wire rope
tensile force S must be smaller than the discard limiting force S G . This discard limiting
force S G can be calculated by an equation regrouped from ( 3.83 )forarequireddis-
carding number of wire breaks B A30min . The discard limiting force is then

t

2

d
D

B A30 ; min þ g 0 g 2

S G ¼ d 2

: ð 3 : 94 Þ

2

d
D

g 1 þ g 3

In ( 3.83 ) and ( 3.94 )

S is the rope tensile force in N

d the rope diameter in mm, and

D is the sheave diameter.