Wire Rope is one of the most complex products to understand in the rigging industry. There are many variations and different components to consider when choosing the best wire rope. In this article, we want to give an overview of some wire rope basic terminology and information.
Basic Wire rope terminology
Below you can find the break down of the parts of a wire rope as well as an illustration:
- Core: The core is the center element made of either steel or fiber. The core maintains the circular section of the rope by supporting the strands around it.
- Wire: The wire is a single element.
- Strand: A number of single wires twisted together make a strand.
- Rope: A number of strands twisted around a central core of steel or fiber created the wire rope.
Additionally, there are three basic types of Stranded Rope:
- Single Layer: A single layer stranded rope consists of one layer of outers strands laid helically over a central core.
- Rotation Resistant: Three-layered strand ropes tend to be classed as “low rotation.” The aim of low rotation rope is to provide stable, balanced rope that offers greater load control than other constructions. They are typically used as hoist ropes for mobile, tower, crawler, deck and offshore pedestal cranes where strength, greater heights of lift and durability are dominant requirements.
- Parallel-Closed: These ropes can also be referred to as double seal closed “DSC” or parallel laid. They are widely used for overhead cranes. Parallel closed ropes possess poor rotational characteristics, and should therefore only be used where there are minimum fleet angles and where both ends of the rope are fixed.
Rope characteristics & Properties
Design inputs and outputs play a role in wire rope selection as well. Some design inputs, or rope characteristics, include rope diameter, rope grade, wire finish, core type, construction, lay direction, compaction, and lubrication. While design outputs, or the rope performance properties, include strength, bend fatigue resistance, rotation resistance, abrasion resistance, crush resistance, and corrosion resistance.
The choice of design inputs determines the design outputs. For example, smaller wires tend to have better bending fatigue than larger wires because their bending radius is larger. Additionally, ropes with a smooth surface, like Dypac ropes, improve abrasion resistance with increased contact area. There are countless other factors, such as the core type effecting strength, lubrication effecting corrosion resistance, and more.
Refer to Crane Manual
While this information barely scratches the surface on all the details that go into choosing and understanding wire rope, we hope it serves as a basic guide for those first diving into wire rope. It is important to always refer to the crane manufacturer and manual to ensure you are purchasing the correct type of rope. Equipment, like cranes, are engineered to use certain types of rope and it can be detrimental to use incorrect crane rope.
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