820 Cranes and Derricks Safety I

Selection and Installation Criteria

It establishes a classification system for rotation resistant rope and specifies design factors for the different classes of such rope.

Wire rope is classified as either "standard rope" or "rotation resistant rope." Rotation resistant rope, in turn, can be constructed in various ways, and the standard lists three different "types" that vary in their construction.

2. Type II rotation resistant wire rope: This type of wire rope constructed to have significant resistance to rotation. It has at least ten outer strands and comprises an assembly of two or more layers of strands laid helically over a center in two or three operations. The direction of lay of the outer strands is opposite to that of the underlying layer.
3. Type III rotation resistant wire rope: This type of wire rope is constructed to have limited resistance to rotation. It has no more than nine outer strands and comprises an assembly of two layers of strands laid helically over a center in two operations. The direction of lay of the outer strands is opposite to that of the underlying layer.

For all three types of rotation resistant ropes, internal design resists twisting better than standard rope. Rotation resistant rope, therefore, enables better control of the load because it tends to keep the load from rotating while it is being hoisted or suspended. However, the design of rotation resistant rope makes it more susceptible to internal damage than standard rope, and such internal damage can be hard to detect. Because of the chance of hidden damage, this section restricts the use of rotation resistant rope for boom hoist reeving and duty cycle/repetitive lifts.

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