Rotation resistant steel wire ropes
Rotation resistant steel wire ropes are needed any time it is involved a not guided operation and in case of relevant lifting height (i.e. tower crane, mobile cranes, drilling rigs etc.).
There are several rope constructions that reduce the natural tendency of a rope to rotate under load.
The very basic construction corresponds to the Class 17 x 7, this is for sure the less performing rope option in the market and it should be defined “rope with a reduced rotation” and not really a rotation resistant one.
The next step is the 24 x 7 W, a rope with more strands combined differently, more flexibility and resistance to rotation respect to the 17 x 7.
It is manufactured with parallel sense of lay (Lang’s lay)to increase flexibility and facilitate the multi-layer reeving.
The only rope construction that can be correctly defined “rotation resistant” is the 35 x 7 one. The high number of strands allows to draw a construction made of 3 different layers with alternate sense of lay. This is the way to compensate the different torque factors of the layers and made the construction stable under load.
This construction guarantees a very high flexibility and breaking load, besides that it has an excellent reeving behavior on multi layers spooling.
This rope construction it is usually manufactured in parallel sense of lay (Lang’s lay) too.
The 35 x 7 class in compacted version (35 x K7) it is the most used rope by the crane manufacturers.
In order to choose the most suitable rope for your application :
- Low rotation rope 17 x 7 class round and compacted ( pag.12)
- Rotation resistant for low-medium height 24 x 7 (pag.13)
- Multi layers Rotation resistant 35 x 7 Flexo ( pag.14)