MEASURING WIRE ROPE

Wire rope is designated by its diameter in inches, as shown in figure 13-7. The correct method of measuring the wire rope is to measure from the top of one strand to the top of the strand directly opposite it. The wrong way is to measure across two strands side by side.

To ensure an accurate measurement of the diameter of a wire rope, always measure the rope at three places,

Figure 13-7.-Correct and incorrect methods of measuringwire rope.

at least 5 feet apart. Use the average of the three measurements as the diameter of the rope.

NOTE: A crescent wrench can be used as an expedient means to measure wire rope.

WIRE ROPE SAFE WORKING LOAD

The term safe working load (SWL) of wire rope means the load that can be applied and still obtain the most efficient service and also prolong the life of the rope.

The formula for computing the SWL of a wire rope is the diameter of the rope squared, multiplied by 8 (D x D x 8 = SWL in tons).

Example: The wire rope is 1/2 inch in diameter. Compute the SWL for the rope.

The first step is to convert the 1/2 into decimal number by dividing the bottom number of the fraction into the top number of the fraction: ( 1 divided by 2 = .5).

Next, compute the SWL formula: (.5 x .5 x 8 = 2 tons). The SWL of the 1/2-inch wire rope is 2 tons.

NOTE: Do NOT downgrade the SWL of wire rope due to being old, worn, or in poor condition. Wire rope in these conditions should be cut up and discarded.

WIRE ROPE FAILURE

Some of the common causes of wire rope failure are the following:

l Using incorrect size, construction, or grade

l Dragging over obstacles

l Lubricating improperly

l Operating over sheaves and drums of inadequate size

l Overriding or crosr winding on drums

. Operating over sheaves and drums with improperly fitted grooves or broken flanges . Jumping off sheaves l Exposing to acid or corrosive liquids or gases . Using an improperly attached fitting . Allowing grit to penetrate between the strands, promoting internal wear . Subjecting to severe or continuing overload l Using an excessive fleet angle

HANDLING AND CARE OF WIRE ROPE

To render safe, dependable service over a maximum period of time, you should take good care and upkeep that is necessary to keep the wire rope in good condition. Various ways of caring for and handling wire rope are listed below.

Coiling and Uncoiling

Once a new reel has been opened, it maybe coiled or faked down, like line, The proper direction of coiling is counterclockwise for left lay wire rope and clockwise for right lay wire rope. Because of the general toughness and resilience of wire, it tends now and then to resist being coiled down. When this occurs, it is useless to fight the wire by forcing down the turn because it will only spring up again. But if it is thrown in a back turn, as shown in figure 13-8, it will lie down properly. A wire rope, when faked down, will run right

Figure 13-8.-Throwing a back turn.

off, like line; but when wound in a coil, it must always be unwound.

Wire rope tends to kink during uncoiling or unreeling, especially if it has been in service long. A kink can cause a weak spot in the rope that wears out quicker than the rest of the rope.

A good method for unreeling wire rope is to run a pipe, or rod, through the center and mount the reel on drum jacks or other supports so the reel is off the ground, as shown in figure 13-9. In this way, the reel will turn as the rope is unwound, and the rotation of the reel helps keep the rope straight. During unreeling, pull the rope straight forward, and avoid hurrying the operation. As a safeguard against kinking, NEVER unreel wire rope from a reel that is stationary.

Figure 13-9.-Unreeling wire rope (left); uncoiling wire rope (right).

To uncoil a small coil of wire rope, simply stand the coil on edge and roll it along the ground like a wheel, or hoop, as also shown in figure 13-9. NEVER lay the coil flat on the floor or ground and uncoil it by pulling on the end, because such practice can kink or twist the rope.