Wire
Ropes
Wire
Rope Construction
Essentially,
it is made of a number of strands laid helically about a metallic or
non-metallic core. Each strand composed of a number of wires also
laid helically . Various types of wire rope have been
developed to meet a wide range of uses and operating conditions.
These types classified by the kind of core; number of strands; the
number, sizes and wire arrangement in each strand.
Wire
Rope Materials
Materials
used in the manufacture of wire ropes are, in the order of
increasing strength: iron, phosphor bronze, traction steel, plow
steel, improved plow steel and bridge rope steel. Iron wire
rope is largely used low strength applications such as elevator
ropes not used for hoisting and for stationary guy ropes.
Phosphor
bronze wire rope is used occasionally for elevator
governor-cable rope and marine applications as life lines, clearing
lines, wheel ropes and rigging.
Traction
steel wire rope is primarily used as hoist rope for
passenger and freight elevators of the traction drive type, an
application for which it was specifically designed.
Galvanized
wire or coated with zinc by the electrode position process are
used in certain applications where additional protection against
rusting is required.
Galvanized
carbon steel, tinned carbon steel and stainless steel are used
for small cords and strands ranging in diameter from 1/64” to 3/8”
and larger.
Properties
of Wire Rope
Important
properties of wire ropes are strength, wear resistance, flexibility
and resistance to crushing and distortion.
Strength:
The strength of a wire rope depends upon its size, material,
number, type of core and whether the the wire is galvanized or not.
Strengths of various types and sizes of wire ropes are
given in the accompanying tables together with appropriate factors to
apply for ropes with steel cores and galvanized wire ropes.
Wear
Resistance: Wire rope which in use must pass back
and forth over surfaces which subject is too unusual wear or abrasion
must be specially constructed for reliable service.
Flexibility:
Wire rope which undergoes repeated and severe bending, such as
in passing around small sheaves, must have a high degree of
flexibility to prevent premature breakage due to over fatigue.
Resistance
to Crushing and Distortion: Where wire rope is to
be subjected to transverse loads that may crush or distort it, care
should be taken to select a type of construction which can withstand
that operating conditions.
Standard
Classes of Wire Rope
Wire
rope is commonly designated by two figures, the first indicating
the number of strands and the second, the number of wires per strand.
6
x 7 Class ( Standard Course Laid Rope ): Wire
ropes in this class are for use where resistance to wear, as in
dragging over the ground or across rollers, is an important
requirement. Heavy hauling rope transmissions, wheel drilling are
common applications.
Diameter, inches
|
Weight per Foot,
lbs.
|
Breaking
Strength, Tons of 2000 Pounds
|
||
Improved Plow
Steel
|
Plow Steel
|
Mild Plow Steel
|
||
1/4
|
0.094
|
2.64
|
2.30
|
2.00
|
5/16
|
0.15
|
4.10
|
3.56
|
3.10
|
3/8
|
0.21
|
5.86
|
5.10
|
4.43
|
7/16
|
0.29
|
7.93
|
6.90
|
6.00
|
1/2
|
0.38
|
10.3
|
8.96
|
7.79
|
9/16
|
0.48
|
13.0
|
11.3
|
9.82
|
5/8
|
0.59
|
15.9
|
13.9
|
12.0
|
3/4
|
0.84
|
22.7
|
19.8
|
17.2
|
7/8
|
1.15
|
30.7
|
26.7
|
23.2
|
1
|
1.50
|
39.7
|
34.5
|
30.0
|
1 1/8
|
1.90
|
49.8
|
43.3
|
37.7
|
1 1/4
|
2.34
|
61.0
|
53.0
|
46.1
|
1 3/8
|
2.84
|
73.1
|
63.6
|
55.3
|
1 1/2
|
3.38
|
86.2
|
75.0
|
65.2
|
6
x 19 Class ( Standard Hoisting Rope ): This is the most
popular and widely used class. This class are furnished in regular
or lay and may be obtained preformed or not preformed. Cores may be
of fiber, independent wire rope or wire strand.
Diameter, inches
|
Weight per Foot,
lbs.
|
Breaking
Strength, Tons of 2000 Pounds
|
||
Improved Plow
Steel
|
Plow Steel
|
Mild Plow Steel
|
||
1/4
|
0.10
|
2.74
|
2.39
|
2.07
|
5/16
|
0.16
|
4.26
|
3.71
|
3.22
|
3/8
|
0.23
|
6.10
|
5.31
|
4.62
|
7/16
|
0.31
|
8.27
|
7.19
|
6.25
|
1/2
|
0.40
|
10.7
|
9.35
|
8.13
|
9/16
|
0.51
|
13.5
|
11.8
|
10.2
|
5/8
|
0.63
|
16.7
|
14.5
|
12.6
|
3/4
|
0.90
|
23.8
|
20.7
|
18.0
|
7/8
|
1.23
|
32.2
|
28.0
|
24.3
|
1
|
1.60
|
41.8
|
36.4
|
31.6
|
1 1/8
|
2.03
|
52.6
|
45.7
|
39.8
|
1 1/4
|
2.50
|
64.6
|
56.2
|
48.8
|
1 3/8
|
3.03
|
77.7
|
67.5
|
58.8
|
1 1/2
|
3.60
|
92.0
|
80.0
|
69.6
|
1 5/8
|
4.23
|
107
|
93.4
|
81.2
|
1 3/4
|
4.90
|
124
|
108
|
93.6
|
1 7/8
|
5.63
|
141
|
123
|
107
|
2
|
6.40
|
160
|
139
|
121
|
2 1/8
|
7.23
|
179
|
156
|
….
|
2 1/4
|
8.10
|
200
|
174
|
….
|
2 1/2
|
10.0
|
244
|
212
|
….
|
2 3/4
|
12.1
|
292
|
254
|
….
|
6
x 37 Class ( Extra Flexible Hoisting Rope ): For given
size of rope, the component wires are of smaller diameter than those
in the two classes previously described and hence have less
resistance to abrasion.
Diameter,
( inches )
|
Weight per Foot,
( lbs. )
|
Breaking
Strength, Tons of 2000 Pounds
|
|
Improved Plow
Steel
|
Plow Steel
|
||
1/4
|
0.10
|
2.59
|
2.25
|
5/16
|
0.16
|
4.03
|
3.50
|
3/8
|
0.22
|
5.77
|
5.02
|
7/16
|
0.30
|
7.82
|
6.80
|
1/2
|
0.39
|
10.2
|
8.85
|
9/16
|
0.49
|
12.9
|
11.2
|
5/8
|
0.61
|
15.8
|
13.7
|
3/4
|
0.87
|
22.6
|
19.6
|
7/8
|
1.19
|
30.6
|
26.6
|
1
|
1.55
|
39.8
|
34.6
|
1 1/8
|
1.96
|
50.1
|
43.5
|
1 1/4
|
2.42
|
61.5
|
53.5
|
1 3/8
|
2.93
|
74.1
|
64.5
|
1 1/2
|
3.49
|
87.9
|
76.4
|
1 5/8
|
4.09
|
103
|
89.3
|
1 3/4
|
4.75
|
119
|
103
|
1 7/8
|
5.45
|
136
|
118
|
2
|
6.20
|
154
|
134
|
2 1/8
|
7.00
|
173
|
150
|
2 1/4
|
7.85
|
193
|
168
|
2 1/2
|
9.69
|
236
|
205
|
2 3/4
|
11.72
|
284
|
247
|
3
|
14.0
|
335
|
291
|
3 1/4
|
16.4
|
390
|
339
|
3 1/2
|
19.0
|
449
|
390
|
8
x 19 Class ( Special Flexible Hoisting Rope ): This is a
stable smooth running rope, specially suitable, because of its
flexibility, for high speed operation with reverse bends. This class
are available in regular lay with fiber core.
Diameter,
( inches )
|
Weight per Foot,
( lbs. )
|
Breaking
Strength, Tons of 2000 Pounds
|
|
Improved Plow
Steel
|
Plow Steel
|
||
1/4
|
0.09
|
2.35
|
2.04
|
5/16
|
0.14
|
3.65
|
3.18
|
3/8
|
0.20
|
5.24
|
4.55
|
7/16
|
0.28
|
7.09
|
6.17
|
1/2
|
0.36
|
9.23
|
8.02
|
9/16
|
0.46
|
11.6
|
10.1
|
5/8
|
0.57
|
14.3
|
12.4
|
3/4
|
0.82
|
20.5
|
17.8
|
7/8
|
1.11
|
27.7
|
24.1
|
1
|
1.45
|
36.0
|
31.3
|
1 1/8
|
1.84
|
45.3
|
39.4
|
1 1/4
|
2.27
|
55.7
|
48.4
|
1 3/8
|
2.74
|
67.1
|
58.3
|
1 1/2
|
3.26
|
79.4
|
69.1
|
18
x 7 Class ( None Rotating Rope ): This wire rope
specially designed for use where a minimum of rotating or spinning is
called for, especially in the lifting or lowering of free loads with
a single part line. The combination of opposing lays tends to prevent
rotation when the rope is stretched.
Diameter,
( inches )
|
Weight per Foot,
( lbs. )
|
Breaking
Strength, Tons of 2000 Pounds
|
|
Improved Plow
Steel
|
Plow Steel
|
||
3/16
|
0.061
|
1.42
|
1.24
|
1/4
|
0.108
|
2.51
|
2.18
|
5/16
|
0.169
|
3.90
|
3.39
|
3/8
|
0.24
|
5.59
|
4.86
|
7/16
|
0.33
|
7.58
|
6.59
|
1/2
|
0.43
|
9.85
|
8.57
|
9/16
|
0.55
|
12.4
|
10.8
|
5/8
|
0.68
|
15.3
|
13.3
|
3/4
|
0.97
|
21.8
|
19.0
|
7/8
|
1.32
|
29.5
|
25.7
|
1
|
1.73
|
38.3
|
33.3
|
1 1/8
|
2.19
|
48.2
|
41.9
|
1 1/4
|
2.70
|
59.2
|
51.5
|
1 3/8
|
3.27
|
71.3
|
62.0
|
1 1/2
|
3.89
|
84.4
|
73.4
|
1 5/8
|
4.57
|
98.4
|
85.6
|
1 3/4
|
5.30
|
114
|
98.8
|
Safety
Working Loads and Factors of Safety
The
maximum load for which a wire rope is to be used should take
into account such associated factors as friction, bending load around
each sheave, acceleration and deceleration and if a long length of
rope is to be used for hoisting, the weight of the rope at its
maximum extension. The condition of the rope, whether new or old,
worn or corroded and type of attachments should be considered.
Factors of safety for standing rope usually range from 3 to 4; for
operating rope from 5 to 12. Where there is the element of hazard to
life and property, higher values are used.
Installing
Wire Rope
The main
precaution to be taken in removing and installing wire rope is
to avoid kinking which greatly lessens its strength and service life.
Thus, it is preferable when removing wire rope from the
reel to have the reel with its axis horizontal position and if
possible, mounted so that it will revolve and the wire rope
taken off straight. If the rope is in the coil, it should be unwound
with the coil in vertical position as by rolling the coil along the
ground. Where a drum is to be used, the rope should be run directly
into it from the reel, taking care to see that it is not bent around
the drum in a direction opposite to that on the reel, thus causing it
to be subject to reverse bending. On flat or smooth faced drums it is
important that the rope be started from the proper end of the drum. A
right lay rope that is being over wound on the drum, that is, it
passes over the top of the drum as it is wound on, should be started
from the right flange of the drum and left lay rope from the left
flange.
Lubrication
of Wire Rope
Although
wire rope is thoroughly lubricated during manufacture to
protect it against corrosion and to reduce friction and wear, this
lubrication should be supplemented from time to time. Types of
lubricant varies as the kind of ropes and operating conditions.
Maintenance
of Wire Rope
Heavy
abrasion, overloading and bending around sheaves or drums which are
too small in diameter are the practical reasons for the rapid
deterioration of the wire rope. Wire rope in use should
be inspected periodically for evidence of wear and damage by
corrosion. Such inspection should take place at progressively shorter
intervals over the useful life of the rope as wear tends to
accelerate with use. If there is any hazard involved in the use of
the rope, it may be prudent to estimate the remaining strength and
service life.
