Sling and Hoist Selection Guide
Document Number: 104
Introduction
Slings and hoists are tools used in many industries for moving large heavy loads in the workplace. Slings and hoists are available in hundreds, if not thousands, of options and styles. This tremendous selection can make the job of choosing the correct sling or hoist very challenging. The wrong choice has led to thousands of accidents and even deaths each year in the United States. This document is a basic guide to help the individual in charge of rigging select the correct sling or hoist for a job. It also addresses basic rigging applications. Other applications not addressed here should always be referred to an expert.
Hoist Selection
Before a hoist can be selected, careful consideration should be given to duty cycle, lift, headroom, atmosphere, speeds, distance, efficiency, safety, and economy. The best way to select the proper hoist is to consider the working conditions the hoist will be subjected to and the type of application it will be required to perform. The primary concern will be the capacity required for the load to be lifted. Not only must you consider the largest load you intend to handle, but you must include the weight of any hook lifting devices such as spreader bars, grabs, slings, etc. Hoists are typically used in combination with other equipment, i.e. trolleys and boom cranes. It is important to remember to check this ancillary equipment as well as the hoist. Both devices should have an engineer verify that they will tolerate the stress applied to them. Despite the fact that most hoists do have a safety factor allowance, never exceed the rated capacity stamped on the hoist for any reason. Exceeding the rated capacity, even for a short period, will cause equipment damage and can result in serious injury.
Sling Selection
Slings are used in combination with a lifting device. The most common lifting devices are overhead cranes, hoists, and forklifts. To select the correct sling, two questions must be answered: what type of sling and what size (diameter or thickness)?
The four main types of slings and their applications are:
- Chain: Combines superior strength, east of handling and durability. The combination of heavy loads, elevated working temperatures and severe lift conditions usually dictate that an alloy chain sling be used. Typically used in steel mills, foundries, and heavy machining operations that require repetitive lifts.
- Wire Rope: The most commonly used sling. It also has the lowest cost per ton of lift. Used in the construction industry and other industries where heavy loads and rugged conditions exist.
- Mesh: Wire and Chain. Excellent in lifting objects that are hot or have sharp edges, such as bar stock or plate steel. Mesh slings usually have wide load bearing surfaces that greatly enhance load balancing. Machine shops and steel warehouses typically have applications requiring mesh slings.
- Synthetic Both web and roundslings are used where loads must be protected from damage. The light weight and flexibility reduce fatigue and strain on the rigger.
The size of the sling is determined by the weight, shape, and size of the load. When determining the stress that will be applied to a sling, the length of the sling is divided by the vertical distance from the top of the load to the lifting device. The resulting quotient is multiplied by the shared weight of the load.
Tension in "c" = length "c" divided by length "a" multiplied by share of load wt.
"c"/"a" = Load Factor
Given: length "c" = 10' and length "a" = 8', what is tension in "c"?
Solution: Tension in "c" = 10/8 x 5,000, Tc = 1.25 x 5,000, Tc = 6,250#
Once the stress is determined, use the Rigger's Reference Charts (Figures 2 and 3) to determine the diameter necessary to safely lift the load.
Figure 2 - Sling Capacities
MECHANICAL SPLICE IN POUNDS ---- DESIGN FACTOR - 5:1
Wire Rope IPS IWRC |
| Size in inches |
VERTICAL |
CHOKER |
2-LEGS OR BASKET 90° |
60° |
45° |
30° |
Color Code (Optional) |
Size in inches |
| 1/4 |
1,100 |
840 |
2,200 |
1,940 |
1,580 |
1,100 |
White |
1/4 |
| 5/16 |
1,700 |
1,300 |
3,400 |
3,000 |
2,400 |
1,700 |
Lt. Green |
5/16 |
| 3/8 |
2,400 |
1,860 |
4,800 |
4,200 |
3,600 |
2,400 |
Red |
3/8 |
| 7/16 |
3,400 |
2,500 |
6,800 |
5,800 |
4,800 |
3,400 |
Yellow |
7/16 |
| 1/2 |
4,400 |
3,200 |
8,800 |
7,600 |
6,200 |
4,400 |
Lt. Blue |
1/2 |
| 9/16 |
5,500 |
4,200 |
11,000 |
9,600 |
7,700 |
5,500 |
Black |
9/16 |
| 5/8 |
6,800 |
5,000 |
13,600 |
11,800 |
9,600 |
6,800 |
Orange |
5/8 |
| 3/4 |
9,700 |
7,200 |
19,400 |
16,800 |
13,600 |
9,700 |
Tan |
3/4 |
| 7/8 |
13,000 |
9,800 |
26,000 |
22,000 |
18,300 |
13,000 |
Dk. Green |
7/8 |
| 1 |
17,000 |
12,800 |
34,000 |
30,000 |
24,000 |
17,000 |
Purple |
1 |
| 1-1/8 |
20,000 |
15,600 |
40,000 |
36,000 |
30,000 |
20,000 |
Dk. Blue |
1-1/8 |
| 1-1/4 |
25,000 |
18,400 |
50,000 |
42,000 |
34,000 |
25,000 |
Gold |
1-1/4 |
|
|
Multiplier ---> |
1.00 |
.75 |
.60 |
<--- Multiplier |
Formula to find sling length ---> Load width x Multiplier = Sling Length
Figure 3 - Sling Capacities
|
Size in inches |
VERTICAL |
CHOKER |
2-LEGS OR BASKET 90° |
60 degrees |
45 degrees |
30 degrees |
Color Code (Optional) |
Size in inches |
| Chain G-8 |
9/32
3/8
1/2
5/8 |
3,500
7,100
12,000
18,100 |
2,620
5,300
9,000
13,500 |
7,000
14,200
24,000
36,200 |
6,050
12,300
20,800
31,300 |
4,950
10,000
17,000
25,600 |
3,500
7,100
12,000
18,100 |
Must be tagged for length & strength |
9/32
3/8
1/2
5/8 |
| Web |
1-9-1
1-9-2
1-9-3
1-9-4
2-9-3
2-9-4 |
1,600
3,200
4,800
6,400
8,880
11,520 |
1,280
2,560
3,840
5,120
7,100
9,210 |
3,200
6,400
9,600
12,800
17,760
23,040 |
2,770
5,540
8,320
11,090
15,390
19,960 |
2,260
4,452
6,780
9,040
12,540
16,270 |
1,600
3,200
4,800
6,400
8,880
11,520 |
Must be tagged for type, length & strength |
1-9-1
1-9-2
1-9-3
1-9-4
2-9-3
2-9-4 |
| Polypro Rope |
1/2
9/16
5/8
3/4
7/8
1 |
645
780
950
1,300
1,760
2,140 |
325
390
475
650
880
1,070 |
1,290
1,560
1,900
2,600
3,520
4,280 |
1,120
1,350
1,650
2,250
3,050
3,700 |
910
1,100
1,340
1,840
2,490
3,030 |
645
780
950
1,300
1,760
2,140 |
Should be tagged for length & strength |
1/2
9/16
5/8
3/4
7/8
1 |
Terminology
Lubrication free load brake: low friction materials are used in the brake mechanism so lubrication is not necessary.
10' lift hoist or 20' lift hoist: This is the maximum lifting height for a load.
The term 1' overhaul lift/ft. means the hoist uses a loop of chain in the lifting mechanism. If a hoist has a rating of 30 for the 1' overhaul lift/ft., then 30' of chain would need to move in order to raise an object 1'. To raise an object 2', 60' of chain would need to be moved.
Regulation
OSHA regulates slings in 29 CFR 1910.184. The regulation covers general requirements, basic definitions, safe operating practices, inspections of the various types of slings. OSHA regulates hoists in 29 CFR 1910.179.
Commonly Asked Questions
| Q. |
|
What does angle factor mean in rigging? |
| A. |
|
Angle factor deals with the stress the sling is subjected to at different slinging angles. As the angle increases (degree number gets smaller) the stress applied to the sling increases, which results in a decrease in capacity of the sling, i.e. A thirty degree sling angle would result in a 50% reduction in the sling capacity. |
|
| Q. |
|
How do I get more life out a synthetic sling? |
| A. |
|
Use a wear-pad, either sliding or sewn-on. |
|
| Q. |
|
Can you tie knots in a sling? |
| A. |
|
No, it will reduce the lifting capacity by a minimum of 50%. |
References
M. Brett, Phone interview, 24 June 1998.
Accident Prevention Manual for Industrial Operations, Engineering and Technology, ninth edition.
American National Standards Institute, 1430 Broadway, New York, N.Y. 10018. "Safety code for Cableways, Cranes, Derricks, Hoists, Hooks, Jacks, and Slings," B30 Series
29 CFR 1910.179
29 CFR 1910.184
AISI Wire Rope Users Manual, 2nd editions.
Wire Rope & Rigging Consultants, 1992 edition.