Figure 1-5. - Correct and incorrect methods of measuring wire rope.
places on a six-stranded, and four places on an eight- stranded wire rope. Use the average of the three measurements as the diameter of the wire rope.
The term safe working load (SWL), as used in reference to wire rope, means the load that you can apply and still obtain the most efficient service and also prolong the life of the wire rope. Most manufacturers provide tables that show the safe working load for their wire rope under various conditions. In the absence of these tables, you may apply the following rule-of- thumb formula to obtain the SWL:
SWL (in tons) = D
2 x 8
This particular formula provides an ample margin of safety to account for such variables as the number, size, and location of sheaves and drums on which the wire rope runs and such dynamic stresses as the speed of operation and the acceleration and deceleration of the load, all of which can affect the endurance and breaking strength of the wire rope. Remember this formula is a general computation, and you should also consider the overall condition of the wire rope.
In the above formula, D represents the diameter of the rope in inches. Suppose you want to find the SWL of a 1/2-inch-diameter wire rope. Using the formula above, you would solve the problem as follows:
SWL = (1/2)2 x 8
SWL = 2 tons
Wire rope can be attached to other wire ropes, chains, pad eyes, or equipment by splicing, which is permanent, or by any of a number of wire-rope attachments. These include sockets and wire-rope clips. In general, these attachments permit the wire rope to be used with greater flexibility than would be possible with a more permanent splice. The attachments allow the same wire rope to be made up in a variety of different arrangements.
A temporary eye splice may be put in wire rope by using clips. A single clip (fig. 1-6) consists of three parts: U-bolt, saddle, and nuts. The correct and incorrect methods of applying these clips to wire rope are shown in figure 1-6; the second incorrect method shown is the most common. Notice that the correct way is to apply the clips so that the U-bolts bear against the bitter end; that is, the short end of the wire rope. If the clips are attached incorrectly, the result will be distortion or mashed spots on the live end of the wire rope. After a wire rope is under strain, tighten the clips again. On operating wire ropes, tighten the clips daily and inspect the wire ropes carefully at points where
Figure 1-6. - Use of wire-rope clips.Continue Reading