Rotation Resistance and Low Torque Wire Rope
A common problem with using wire rope is rotation. Comcoming this issue requires that rotation resistant wire ropes be employed. Standard cable can twist and turn when handling a load, and so special considerations must be made when constructing rotation resistant wire ropes. These ropes are Contra-helically laid, and they are designed to lessen the torque on lines. As rotation resistance increases, other characteristics of wire rope begin to suffer. Specialized wire ropes must be treated and maintained properly.
There are several standard types of rotation resistance, which are broken down into categories. These categories are:
Category 1: has a minimum of 15 outer strands with three layers over the center. It has almost no tendency to rotate, and when it is guided, it will transmit little torque.
Category 2: has ten or more strands and two or more over the center. These ropes have substantial resistance to rotation.
Category 3: has nine or less outside strands and two more layers over a center. This version has a limited amount of resistance against rotation. Do not use category three ropes with a swivel.
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