The Flexibility of Slings
Wire rope for slings comes in many different constructions. For the user the most important difference is “flexibility”, that is the ease with which a sling can be bent by hand. Flexibility of a wire rope sling is dependent on the total number of single wires in the rope, and whether the rope has a steel core or a fiber core.
Generally, a “stiffer” wire rope will withstand more crushing and abrasion than a wire rope which is “flexible” but has rather “fine” and “thin” single wires. The “thinner” the strand wires become, the easier it is to damage them.
The more flexible a sling is, the higher the number of individual wires. The total number of individual wires in a sling can vary between 114 and more than 2,000 wires.
|Wire rope is made from hundreds of individual load carrying members.
The failure of one wire will not cause the entire sling to fail.
|Chains rely on EACH individual link.
If ONE link fails, the entire sling system fails.
Furthermore, flexibility is a somewhat subjective term. A 3/8″ diameter 6×19 wire rope has the same “construction flexibility” as a 1″ diameter 6×19 rope yet, for us humans, the 1″ diameter rope appears to be far “stiffer”; it just requires more “muscle” to bend it around an object.
The requirement for wire rope sling “flexibility” may also depend on the application and may even be dependent on the sling type. A simple single leg sling which is constantly used in a choker hitch requires more “flexibility” than a multiple leg sling with a master link which may get used in a straight connection between the hook and the load only. On the other hand a “stiffer” sling can easily be pushed though under loads, steel bundles, pallets, etc.
Unirope slings come in the following flexibility grades (in order from “flexible” to “stiff”):
54 strands, GATOR-FLEX®, 3x3x6x19/36 (Steel Core)
18 strands, TRI-FLEX®, 3x3x6x19/36 (Steel Core)
6 strands, 6×37 Fiber Core
6 strands, 6×36 Steel Core
6 strands, 6×19/26/25 Fiber Core
6 strands, 6×19/26/25 Steel Core
Depending on sling diameter we also carry 8×19 Steel Core, 19×7 and 34×7 rotation resistant types, and various high strength Python® constructions.
Aside from flexibility the other difference between sling rope constructions is the way the end terminations (or splices) are done. See next page for details.
Slings made from Wire Rope
Wire rope slings have become the workhorse in the sling field. Although they have sound safety features, they must be chosen carefully for the service in which they are to be placed since that they also have certain limitations.
Their most outstanding feature is the ease of inspection. They do not deteriorate without ample warning, nor do they rely on a single load bearing system like chains. They withstand a large amount of physical abuse and, unlike web slings, are not easily cut nor do they deteriorate in sunlight. Wire rope slings are constructed from a large number of individual load bearing components, the single wires. If one of the hundreds of individual wires fails, the wire rope sling itself will not fail in a so called “catastrophic” manner. This is what sometimes is referred to as a “redundant” system. The only other sling type which has a similar “redundancy” characteristic is the Twin-Path® sling which is composed from two totally independent load carrying systems.
|The choice for ultimate flexibility and strength. Ideal for tight choker hitches. Capacities to over 300 tons. Maximum diameter is 10″.|
|A 300% increase in flexibility over the regular 6×19 steel core rope. Best compromise between ease of handling, strength, cost, and crush resistance.|
|6×37 Fiber Core|
|The MOST flexible 6-strand sling. Same strength as 6×19 Fiber Core, but handles far better. Available in selected sizes only. Ask for details.|
|6 x 36 Steel Core|
|More flexible than even 6×19 Fiber Core, same strength as 6×19 Steel core, good resistance to kinking, good crush resistance.|
|6 x 19 Fiber Core|
|A little more flexible, less expensive, but Rated Capacities (WLL’s) are 10% lower than slings made with Steel Core.|
|6 x 19 Steel Core|
|The standard construction for Unirope slings. Very good crush and abrasion resistance, but larger diameters are not very flexible.|