CHAPTER 13 RIGGING

Rigging is a technique of handling materials using wire rope, fiber rope, chains, slings, spreader bars, and so forth. Rigging is a vital link in the weight-handling process.

In the Naval Construction Force (NCF), an in-depth management program for maintenance and use of all rigging gear is required to ensure the entire weight-handling operations are performed safely and professionally. These guidelines are outlined in the COMSECOND/COMTHIRDNCBINST 11200.11,

Use of Wire Rope Slings and Rigging Hardware in the Naval Construction Force.

This chapter covers the characteristics, maintenance, usage, and storage of rigging gear used in weight-handling operations.

WIRE ROPE

Many of the movable components on cranes and attachments are moved by wire rope. Wire rope is a complex machine, composed of a number of precise, moving parts. The moving parts of wire rope are designed and manufactured to bear a definite relationship to one another to have the necessary flexibility during operation.

Wire rope may be manufactured by either of two methods. If the strands, or wires, are shaped to conform to the curvature of the finished rope before laying up, the rope is termed preformed wire rope. If they are not shaped before fabrication, the wire rope is termed non-preformed wire rope.

The most common type of manufactured wire rope is preformed. When cut, the wire rope tends not to unlay and is more flexible than non-preformed wire rope. With non-preformed wire rope, twisting produces a stress in the wires; therefore, when it is cut or broken, the stress causes the strands to unlay.

NOTE: When the wire is cut or broken, the almost instantaneous unlaying of the wires and strands of non-preformed wire rope can cause serious injury to someone that is careless or not familiar with this characteristic of the rope.

PARTS OF WIRE ROPE

Wire rope is composed of three parts: wires, strands, and core (fig. 13- 1). A predetermined number of wires of the same or different size are fabricated in a uniform arrangement of definite lay to form a strand. The required number of strands are then laid together symmetrically around the core to form the wire rope.

Wire

The basic component of the wire rope is the wire. The wire may be made of steel, iron, or other metal in various sizes. The number of wires to a strand varies, depending on the purpose for which the wire rope is intended. Wire rope is designated by the number of strands per rope and the number of wires per strand. Thus an 1/2-inch 6 x 19 rope has six strands with 19 wires per strand. It has the same outside diameter as a 1/2-inch 6 x 37 rope that has six strands with 37 wires (of smaller size) per strand.

Strand

The design arrangement of a strand is called the construction. The wires in the strand maybe all the same size or a mixture of sizes. The most common strand

Figure 13-1.-Parts of wire rope.

Figure 13-2.-Common strand construction.

constructions are Ordinary, Seale, Warrington, and Filler (fig. 13-2).

. Ordinary construction wires are all the same size.

. Seale is where larger diameter wires are used on the outside of the strand to resist abrasion and smaller wires are inside to provide flexibility.

l Warrington is where alternate wires are large and small to combine great flexibility with resistance to abrasion.

l Filler is where very small wires fill in the valleys between the outer and inner rows of wires to provide good abrasion and fatigue resistance.