A wire rope with a decent breaking strength must be chosen and used with caution by lifting and rigging workers. You must choose slings based on the amount and kind of weight and the workplace’s ambient circumstances. Before using wire rope slings, you must visually examine them. Slings with many broken wires, significant corrosion, localized wear, end-fitting damage, or structural rope damage must be eliminated and scrapped.
In general, a wire rope sling with good strength is available in various sizes, the most common of which are 6×19 and 6×37 and those bearing an eye loop swaged with both ends of the sling. A smaller number of large exterior wires results in better wear, corrosion resistance, and breaking strength. Meanwhile, a more significant number of tiny wires gives more flexibility and fatigue resistance.
For a more secure use, the wire rope sling’s flexible design may adjust to the structure of a load. In this article, we will discuss what wire rope sling and breaking strength wire rope is.
Wire Rope: Safe Load, Minimum Breaking Strength, and Weight
The safe working load varies with the diameter of the wire rope slings and the weight per foot—the smaller the wire rope, the lower the SWL. The SWL is also affected by the safety factor ratio. However, because this is not clearly stated on wire ropes, it is critical to grasp this word. Fortunately, most endless wire rope sling manufacturers will do this estimate for you. (1)
Shown below is the table for safe working load, minimum breaking strength, and equivalent weight for each rope diameter.
| Rope Diameter | Minimum Breaking Strength | Safe Load | Weight | ||||
| (in) | (mm) | (lbf) | (kN) | (lbf) | (kN) | (lbm/ft) | (kg/m) |
| 1/4 | 6.4 | 5480 | 24,4 | 1100 | 4.89 | 0.11 | 0.16 |
| 5/16 | 8 | 8520 | 37,9 | 1700 | 7.56 | 0.16 | 0.24 |
| 3/8 | 9.5 | 12200 | 54,3 | 2440 | 10.9 | 0.24 | 0.36 |
| 7/16 | 11.5 | 16540 | 73,6 | 3310 | 14.7 | 0.32 | 0.48 |
| 1/2 | 13 | 21400 | 95,2 | 4280 | 19.0 | 0.42 | 0.63 |
Wire Rope Strength (Table Chart)
Most wire rope cores have six strands, each with 15–66 wires. The stronger the strand, the greater the wire count. The breaking strength of wire rope has been measured through testing by line sling manufacturers, and charts have been created to present this information.
The table shown below is the equivalent breaking strength wire rope per diameter for the Independent Wire Rope Core (IWRC) for the 6×19 and 6×37 Improved Plow Steel (IPS).
Dia. (in.) | Weight per ft. | Breaking Strength (tons) Stainless Steel (6×19) | Breaking Strength (tons) Stainless Steel (6×37) | Breaking Strength (tons) Galvanized IPS | Breaking Strength (tons) Bright IPS |
| 1/4″ | 0.11 | 2.7 | 2.65 | 2.94 | |
| 5/16″ | 0.18 | 4.5 | 4.15 | 4.12 | 4.58 |
| 3/8″ | 0.26 | 6.0 | 5.85 | 5.9 | 6.56 |
| 7/16″ | 0.36 | 8.15 | 7.9 | 8.0 | 8.89 |
| 1/2″ | 0.46 | 11.4 | 10.02 | 10.35 | 11.5 |
| 9/16″ | 0.59 | 14.25 | 12.8 | 13.05 | 14.5 |
| 5/8″ | 0.72 | 17.5 | 15.7 | 16.1 | 17.9 |
What is Wire Rope Sling?
Wire rope slings are an essential piece of rigging material used in lifting and hoisting operations and are commonly utilized in a wide range of industries. These slings attach the load to the machine and come in various designs to suit several needs. To increase the strength of wire ropes, they are gathered and coiled together to form cables, increasing their importance in support, lifting ability, and structural stability. (2)
Though the construction of endless wire rope slings is generally similar for all kinds, certain variations are used to adapt slings to multiple uses. Slings may be arranged in several ways to accommodate distinctive types of loads. These modifications are known as hitches.
Types of Hitches
These are the different types of hitches commonly used by a number of industries:
Choker Hitch
With a choker hitch, one eye of the sling is hooked to the lifting hook in the choker arrangement. The second sling eye is looped over the first to produce a noose or choke. The choke loop is packed with the load.
Basket Hitch
A basket hitch is made when both sling eyes are wrapped over the lifting hook.
Bridle Hitch
A bridle hitch is a multiple-leg hitch with more than one wire rope sling hooked to equalize the weight and control balance. They allow easier rigging once attached to permanent lifting points and decrease load damage by employing fixed locations on the load.
Vertical Hitch
It is formed by attaching one eye of the wire rope to the hook and the other eye to the weight.
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References
(1) safe working load – https://www.sciencedirect.com/topics/
engineering/safe-working-load
(2) structural stability – https://www.sciencedirect.com/book/
9780750678759/fundamentals-of-structural-stability