Worn and abraided wires

Wear, due to friction on sheaves, rollers, drums, etc., eventually causes outer wire abrasion.

Before any inspection is made, determine what type of wire rope you have in service. Many of today’s wire ropes are ‘compacted’, ‘calibrated’, or ‘die formed’. This manufacturing process purposely flattens the outer wires and for an inexperienced inspector these ropes may appear to be already abraded when indeed they are brand new. If you are in doubt about what type of rope you are about to inspect, have a look at a section of the rope which was not subjected to any abrasive work; e.g. like the safety wraps on the drum or a section just behind the end connection.

The round outer wires of standard wire rope will become flat on the outside due to friction when in contact with drums, sheaves, or other abrasive matter like sand or gravel. This is part of normal service deterioration and in most crane installations relatively even abrasion will occur. The rope must be replaced, however, if this wear exceeds 1/3 of the diameter of the wire.

It is good practice to compare a section of the rope which was NOT subjected to any bending work (e.g. the safety wraps, or a short section behind the end fitting) to the rope section to be inspected.

The same applies when evaluating any possible reduced rope diameter during service. (See next column.)

Reduction in Rope Diameter

As already discussed on the ‘Measuring the rope diameter‘ page and on the ‘Break-In-Period‘ page, shortly after installation, the wire rope diameter will slightly decrease. This is normal and is caused by the adjustment of all rope elements when loaded the first time. To evaluate the diameter reduction, you have to measure the rope when new, and you also have to measure the rope after the break in period at a specified load. This gives you a good indication of the magnitude of the initial diameter reduction in your specific application. The diameter reading you took after the break in period should now become your ‘gauge’. Do not compare the rope diameter you are about to take with the ‘catalogue’ diameter. It may give you a false indication, since wire rope may have a plus tolerance of up to 4% to 5% over the ‘catalogue’ diameter.

If you detect a further diameter reduction when measuring the rope under the same load condition as after the break in period, it is often due to excessive abrasion of the outside wires, loss of core support, internal or external corrosion, inner wire failures, and/or inner wire abrasion. However, there will always be a normal continuous small decrease in diameter throughout the rope’s service life.

Core deterioration, when it occurs, is revealed by a more rapid reduction in diameter, and when observed, it is time for removal.

Deciding whether or not a rope is safe is not always a simple matter. A number of different but interrelated conditions must be evaluated. It would be dangerously unwise for an inspector to declare a rope ‘safe’ for continued service simply because its diameter had not reached a certain minimum diameter if, at the same time, other observations led to a different conclusion.

However, ASME, ISO 4309, CSA, other Canadian Provincial H&SA and USA OSHA Regulation have various values published for maximum allowable diameter reductions. They are somewhat confusing as they show diameter reduction values from 3.5% to 9%, and some give reduction values in inch fractions depending on rope nominal diameter.

Take measurement of rope diameter AFTER the
Run In Period.

General

It is essential to maintain a well planned program of periodic inspections. In most cases there are statutory and/or regulatory agencies whose requirements must be adhered to.

Whether or not such requirements exist in your specific environment, you can be guided by the suggested procedures that follows.

Abrasion, Bending and Crushing represent the ABC‘s of wire rope abuse, and it is the primary goal of good inspection practice to discover such conditions with minimum effort. When any degradation indicates a loss of original rope strength, a decision must be made quickly to allow the rope to remain in service. Such a decision can only be made by an experienced inspector. His determination will be based on:

1. Details of the equipment’s operation
2. Frequency of inspection
3. Maintenance history
4. Consequences of failure
5. Historical records of similar equipment

Broken Wires

Shortly after installation
The occasional premature failure of a single wire may be found early in the rope life and in most cases it should not constitute a basis for rope removal. Note the area and watch carefully for any further wire breaks. Remove the broken ends by bending the wire backwards and forwards. In this way the wire is more likely to break inside the rope where the ends are left tucked away between the strands. These infrequent premature wire breaks are not caused by fatigue of the wire material.

During wire rope service (Fatigue Breaks)
The rope must be replaced if a certain number of broken wires are found which indicate that the rope has reached its finite fatigue life span.
See Broken Wire Discard Tables.

This page lists several types of end terminations used for overhead lifting applications.

All efficiency ratings are based on the difference between the actual breaking strength of a rope and the attained breaking strength with that specific fittings. The only fitting which will attain a 100% efficiency are spelter sockets; provided they are properly attached.

The initial stretch (constructional stretch) is a permanent elongation that takes place due to slight lengthening of the rope lay and due to a slight decrease in rope diameter.

Constructional stretch generally takes place during the first 10-20 lifts, and increases the rope length by between 1/2% for fiber core rope, approx. 1/4% for 6-strand steel core rope, and approaches zero for compacted Python® ropes.

If you have the chance and the equipment configuration allows this, disconnect the rope end after the run-in-period to allow any possible torque and twists which may have developed during installation and the run-in-period to be released at the end connection.

Under NO circumstances must the crane be tested prior to the break in procedure of the wire rope. If you overload a rope which has not yet been broken in, you may inflict permanent damage to the rope.

Equipment with multiple layer windings call for additional caution. As mentioned before, severe overloads of the top layers may damage the lower ones or may crush the rope. If possible, test the crane with the rope spooled in the first drum layer only.

If the crane is equipped with a smooth drum, special care must be taken to ensure that the rope does not cross-wind over itself when testing the crane. After testing (overloading) you have to repeat the spooling procedure as outlined here ‘Winding on smooth or flat faced drums’.

Depending on rope construction and type, their efficiency rating ranges between 75% and 80%. For detailed information ask the manufacturer of your wedge socket.

The installation of Python® rope into wedge sockets is similar to that of 6- or 8-strand wire rope. Here’s a quick run down of some of the do’s and dont’s:

• Always inspect socket, wedge and pin before installation.
• For intermediate rope sizes use next larger socket size (e.g. use a 3/4″ socket for a 18 mm rope)
• Align live end of rope with center line of pin.
• Use a hammer to seat Wedge and rope as deep into the socket as possible.
• Apply first load to fully seat the wedge and wire rope in the socket.
• Ensure that the rope end is welded and/or properly seized before inserting the rope into the socket. Failing to do so may cause the core to slip and/or the strands to loosen inflicting serious rope damage.

• The tail length should be a minimum of 6 x rope diameter but NOT less than 6 inches.
• Secure the dead end section of the rope. Several accepted methods are available and illustrated on this page.
• DO NOT CLAMP OR CLIP THE DEAD END OF THE ROPE TO THE LIVE END.
• During use, do not strike the dead end section with any other elements of the rigging (called Two-Blocking).
• When using with 34×7 and all Python non-rotating types attach a hose clamp approx. 3-5 ft above the socket to the LIVE END of the rope BEFORE ATTACHING THE SOCKET. The clamp will prevent any looseness of the outer strands, which may have occurred during installation, from travelling along the entire rope length. If this happens you have to shorten the rope slightly but you will have contained the damaged zone to a very short rope portion. 

Winding on smooth or flat faced drums
Start winding the rope in a straight helix angle. To assist with this, some drums have a tapered steel part attached to one flange which ‘fills’ the gap between the first turn and the flange (see picture 7).

The first layer must be wound tight and under tension. Take a mallet or a piece of wood and tap the wraps tightly against each other (see picture 1); but not so tight that the rope strands interlock (see picture 2), but tight enough that the rope can’t be shifted on the drum. If the first layer is wound too loose, the next layer will wedge a gap into the first layer causing that layer to ‘pull in’ (see picture 3). A too tightly wrapped first layer will not allow the next layers enough space between wraps (see picture 2).

In any case, the first layer, as well as all of the layers, must be wound on to the drum with sufficient pre-tension (5-10% of the rope’s WLL is a good measure). If wound with no tension at all, the rope is subjected to premature crushing and flattening caused by the ‘under load’ top layers (see picture 4).

Even if wound on properly during installation, the first layer will loosen somewhat during service. When the first layer becomes slack (the pre-tension is gone), this initial procedure MUST be repeated in regular intervals.

Otherwise, the tensioned ‘hard’ wraps will severely crush the bottom layers (picture 5).

Winding on grooved drums
Basically, follow the same procedure as for smooth drums. Also here, pre-tension is of utmost importance.

If the first layer, or layers, are only used from time to time, they will loose their tension on the drum and start to flatten out due to the high pressures of the loaded layers. Repeat this pre-tensioning procedure regularly.

As with tower cranes, for example, which have a long rope length installed and rise as the building goes up, pre-tensioning will not be possible. In these cases it may be advisable to install a shorter rope length first. Otherwise, you may have to replace the entire rope length because of crushing and flattening of the bottom layers. If this not possible, extra care must be taken to pre-tension the rope on the drum during installation.

Whatever you do, DO NOT run the rope through a ‘tightening’ device (see picture 6), e.g. two wooden blocks clamped together. YOU WILL DESTROY
THE ROPE!

Be sure to use the correct rope lay direction for the drum. This applies to smooth, as well as to grooved drums.

Many crane models have a two sided grooved drum, one part of it is left, the other right lay grooved. Some wire ropes are more sensitive to this type of design than others; it depends on lifting height, frequency of use, and even the rope diameter as to the type of wire rope most suitable for that application.

In some applications it may be advisable to select the rope lay direction according to the most frequently used drum layers. If the first rope layer on a drum is used as a ‘guide layer’ only, it may be advisable to select the rope lay direction according to the second layer.

Left Lay Rope	Right Lay Rope
Right Hand Grooved: Use Left Hand Rope	Left Hand Grooved: Use Right Hand Rope
Right Lay Rope	Left Lay Rope
Left Hand Grooved: Use Right Hand Rope	Right Hand Grooved: Use Left Hand Rope

Depending on the type of rope several accepted methods are available.

Welding
Welding two ropes together is common in the steel industry. If properly done, welding may develop sufficient strength to complete the rope installation. However, the welded portion of the rope is rather stiff, and the welded steel wire material may become brittle. Since the welded portion has to pass over sheaves, there is the danger that the weld may break.

If installing Python® wire rope as well as all non-rotating types we do not recommend the welding procedure. Welding might damage the seizings and the rope may unravel getting damaged beyond repair.

Becket Loops
A common method for heavy crane rope installations. A steel sleeve only slightly larger than the rope diameter is swaged on to the rope end and a small auxiliary cable protrudes from the sleeve. Either, the old rope is furnished also with a becket loop, or the old rope will be connected to the becket loop with a cable grip.

Use of Cable Grips

The most common method to install a wire rope. The type of cable grip depends on the rope type and construction.

Non-rotating rope must be installed with a swivel between old and new ropes. The old rope may have developed torque during it’s working life and we must ensure that this torque is not transferred to the new rope.

Python® types Multi and Super 8 may be installed with a swivel. In fact, if you have to change either of these constructions for a 6-strand rope, particularly when this rope has a different lay direction, a swivel is of definite benefit.

Python® Power 9 and Python® Ultra must not be installed with a swivel. Doing so will unlay the rope and damage it beyond repair. Use two cable grips and connect them with an auxiliary cable.

When using cable grips, the end of the grips have to be tightly seized on to the rope body to prevent accidental slip-out of the rope. Alternately, you may wrap the grip end with a strong reinforced industrial strength adhesive tape.