Inspecting Wire Ropes

by Lynn Larsen

Wire ropes are an integral part of many hoists. Most wire ropes are easily inspected�once you know what to look for.

There are strict rules for the quantity of broken wires in a strand and other defects in wire ropes. However, the procedure for doing the inspection is not as well known.

Let�s define exactly what the wire rope terms are:

� Wire�individual metal threads in wire rope.

� Strand�a bundle of wires twisted together.

� Core�Multiple strands are spiraled around the core to make the wire rope.

� Lay�one complete wrap of a strand around the core.

You want to inspect the wire rope before installing it on a hoist and at regular intervals dependent on frequency of hoist use.

Also keep in mind that the atmosphere and environment may accelerate wear on the wire rope, so take this into consideration when adopting an inspection schedule.

When you inspect wire rope, wear gloves! Any broken wire is sure to find your flesh and you will have a nasty puncture wound as a result.

Take a shop rag and run it down the length of the wire rope as the cloth will snag on broken wires.

But don�t just rely on the cloth. Look at the rope as you are checking for broken wires. Be sure to check the entire length of the rope including where the rope wraps around the sheaves and connects to the hoist.

Sometimes the most excessive wear is at the most inaccessible points.

What to Look For

When you find a broken wire you need to inspect that strand for one full rotation (a lay) around the core.

Take a piece of tape and wrap it below the broken wire and mark the tape with an arrow indicating where the broken wire is located.

Follow that strand as it spirals around the rope 360 degrees, then tape the point that marks one complete rotation (a lay).

Now, carefully inspect the rope between the pieces of tape looking for two things:

1. If there are more than three broken wires in the strand, the wire rope fails inspection.

2. If there are six randomly distributed broken wires in the lay, the wire rope fails inspection.

Also look for signs or misuse: pinching or kinking of the rope or a pattern of wear.

Keep inspecting the entire rope with this procedure.

Not All Breaks are the Same

Not all broken wires indicate the same problem. If the broken wires have a clean, square break, it is usually normal wear and tear.

If the wire looks pinched (this is called a cup and cone) it indicates a load was lifted in excess of the wire rope strength rating.

Look for wear to the crown (the highest point of the wire rope).

There are other defects to look for in a wire rope, many of these are obvious and are a result of misuse.

�Bird caging� is where the wire rope is actually expanded from the core so that you could keep a small bird in the center.

This is a result of the rapid release of a load, usually a near-miss type accident.

Kinks in the rope may indicate the wrong size rope for the hoist or poor installation.

Wire ropes riding over the sheaves results in severe damage to the wire rope�it looks like someone cut the rope with a hot knife�and is usually a result of side lifting a load or other improper lifting techniques.

If you find these defects it indicates misuse of the hoist and the need to review proper hoist use with your employees.

If your rope passes this inspection, document the findings and file it for comparison to future inspections.

Always compare the current inspection to the previous. A sudden increase in wire damage or breaks indicates that the wire rope is getting fatigued and it is time to order a replacement rope.

Catastrophic Damage

Explaining how to inspect wire rope can be just as twisted as the strands on the rope itself. It does sound complicated and is time-consuming the first time you do a complete inspection.

However, with each inspection the process becomes more routine as you become familiar with the types of damage.

If you have ever seen the catastrophic damage caused by a hoist failure, you understand why this inspection is needed.

When you take the time to keep your equipment in good working order, you can prevent accidents.

Lynn Larsen is president of Safety Solutions Inc., a safety and equipment consulting firm in Christine, ND; 701-469-2315.