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, mainte- nance,  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. 13-1