FURTHER
EXPLANATIONS AND CAUTIONS IF LIFTING ANGLES ARE INVOLVED
Numerical
values published for Breaking Strength and Working Load Limit
in the catalog are very specific in one point: They refer to
straight, in-line pull or force and are obtained under laboratory
conditions.
There are,
however, many applications where a straight line pull is not
possible or even desirable. When a tackle block system is reeved,
wire rope may be bent over many sheaves; multiple leg wire rope
or chain slings involve differing lifting angles; angular loads
on shackles or eyebolts alter Working Load Limits of the equipment
used.
All these
and other factors influencing the Working Load Limit must be
taken into account when systems are designed and used.
The following
examples and tables are intended to highlight and demonstrate
the effects of angles on the Working Load Limit.
|
CHAIN
SLINGS, Fabricated
entirely from grade 80 alloy components.
|
WORKING
LOAD LIMITS - POUND
|
| |
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Chain
Size
|
|
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|
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|
|
|
|
| 9/32" |
3,500 |
3,500 |
4,900 |
6,100 |
5,200 |
7,400 |
9,100 |
| 3/8" |
7,100 |
7,100 |
10,000 |
12,300 |
10,600 |
15,100 |
18,400 |
| 1/2" |
12,000 |
12,000 |
17,000 |
20,800 |
18,000 |
25,500 |
31,200 |
| 5/8" |
18,100 |
18,100 |
25,600 |
31,300 |
27,100 |
38,400 |
47,000 |
| 3/4" |
28,300 |
28,300 |
40,000 |
49,000 |
42,400 |
60,000 |
73,500 |
| 7/8" |
34,200 |
34,200 |
48,400 |
59,200 |
51,300 |
72,500 |
88,900 |
| 1" |
47,700 |
47,700 |
67,400 |
82,600 |
71,500 |
101,200 |
123,900 |
| 1.1/4" |
72,300 |
72,300 |
102,200 |
125,200 |
108,400 |
153,400 |
187,800 |
|
| Effect
of Angles on Sling Capacities |
|
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 |
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| |
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|
Sling
Angle
|
Load
Angle Factor
|
|
90° (vertical)
|
1.000
|
|
75°
|
.966
|
|
60°
|
.866
|
|
45°
|
.707
|
|
30°
|
.500
|
|
|
Example: |
|
| The
rated capacity of a multiple leg sling is directly affected by the
angle of the sling leg with the load. As this angle decreases, the
stress on each leg increases with the same load. If the sling angle
is known, the capacity can be readily determined by multiplying
the sling's vertical capacity by the appropriate load angle factor
from the table at right. |
A
multiple leg sling with a rated capacity of 2000 lb. will have a
reduced capacity of 1000 lb. (2000 x .500) when sling legs are at
an angle of 30° with the load. |
|
