Figure 5-4. - Lays of wire rope.

strand. Lay length measurement is shown in figure 5-5.

CLASSIFICATION OF WIRE ROPE

The primary types of wire rope used by the NCF consist of 6, 7, 12, 19, 24, or 37 wires in each strand. Usually, the wire rope has six strands laid around the core .

The two most common types of wire rope, 6 by 19 and 6 by 37, are shown in figure 5-6. The 6 by 19 type (having six strands with 19 wires in each strand) is the stiffest and strongest construction of the type of wire rope suitable for general hoisting operations. The 6 b y 37 wire rope (having six strands with 37 wires in each strand) is flexible, making it suitable for cranes and similar equipment where sheaves are smaller than

Figure 5-5. - Lay length of wire rope.

Figure 5-6. - A. 6 by 19 wire rope; B. 6 by 37 wire rope.

usual. The wires in the 6 by 37 are smaller than the wires in the 6 by 19 wire rope and, consequently, will not stand as much abrasive wear.

WIRE ROPE SELECTION

Several factors must be considered when you select a wire rope for use in a particular type of operation. Manufacture of a wire rope that can withstand all of the different types of wear and stress, it is subjected to, is impossible. Because of this factor, selecting a rope is often a matter of compromise. You must sacrifice one quality to have some other more urgently needed characteristic.

Tensile Strength

Tensile strength is the strength necessary to withstand a certain maximum load applied to the rope. It includes a reserve of strength measured in a so-called factor of safety.