WIRE ROPE SAFE WORKING LOAD

The term safe working load (SWL) of wire rope is used to define the load which can be applied that allows the rope to provide 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 numbers 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.

Figure 5-7.-Correct and incorrect methods of measuring wire rope.

CAUTION

Do NOT downgrade the SWL of wire rope because it is 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:

Using incorrect size, construction or grade

Dragging over obstacles

Improper lubrication

' Operating over sheaves and drums of inadequate size

' Overriding or cross winding on drums

' Operating over sheaves and drums with improperly fitted grooves or broken flanges

' Jumping off sheaves

' Exposure to acid fumes

' Use of an improperly attached fitting

Grit being allowed to penetrate between the strands, causing internal wear

Being subjeted to severe or continuing overload WIRE ROPE ATTACHMENTS

Attachments can be put on a wire rope to allow it to be attached to other ropes; for example, pad eyes, chains, or equipment.

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