Wire Ropes Under Bending and Tensile Stresses - Wire Ropes: Tension, Endurance, Reliability - page 300

The rope safety factor is

v ¼ F min
S

¼ 179

30 ¼ 5 : 97

The rope safety factor is—as it should be—bigger than 2.5.
Discard limit:

(a) Discarding number of wire breaks

According to ( 3.83 ) and using the constants listed in Table 3.18 and the factor 6/8
for the six strand rope, the discard number of wire breaks for simple bendings is

" #

2
g 2

2
g 3

2 2

B A30 ¼ 6

S
d 2

d
D

S
d 2

d
D 8

g 0 g 1

" #

2
0 : 0447 ð 117 : 2 Þ 2

2

B A30 ¼ 6

1
25

1
25

33 : 3 0 : 000184 ð 117 : 2 Þ 2 1 ; 830

8

B A30 ¼ 20 :
For reverse bending, the specific rope tensile force has to be set S rev /d 2 =
S/d 2 + 50 N/mm 2 . Then the discard number of wire breaks for reverse bendings is
B A30 ; rev ¼ 17

and B A30 ; com ¼ 17 :

According to ( 3.84 ), the discard number of wire breaks on the small reference
length L = 6d is
B A6 ¼ 0 : 5 B A30 ¼ 0 : 5 20 ¼ 10 and B A6rev ¼ 9 :

(b) Discard limiting force (alternatively)

According to ( 3.94 ) the discard limiting force is

t

2

d
D

B A30 þ g 0 g 2

S G ¼ d 2 :

2

d
D

g 1 þ g 3

With the constants listed in Table 3.18 , the factor 6/8 for the six strand rope and
a required number of wire breaks B A30 = 15, the discard limiting force for simple
bendings is

t

8

2

1
25

6 15 þ 33 : 3 1 ; 830

S G ¼ 16 2 ¼ 51,600 N = 51 : 6kN :

2

1
25

0 : 000184 þ 0 : 0447

For reverse bending, the discard limiting force S G,rev is DS = 50 d 2

smaller