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  Return to Wire Rope Main Page and Detailed Wire Rope Data  
    Technical Information  
  Use and Care of Wire Rope  
  Wire Rope is a Machine  
    Installation of Wire Rope:  
  Foreword, Measuring the rope diameter  
  If you have to cut a rope  
  Unreeling the rope  
  Connecting the old rope to the new rope  
  Rope lay direction versus Drum Grooving  
  Winding on to the drum  
  Installation of Wedge Sockets  
  Using your rope for the first time  
  Efficiency ratings of end terminations  
    Inspection of Wire Rope:  
  How to inspect Wire Rope  
  Crown- and Valley Wire Breaks  
  Number of broken Wire Discard Tables  
  Reduction of diameter, Rope Wear  
  Rope Stretch, Core Wire breaks  
  Mechanical damages  
  Corrosion, Rope Removal and Cause  
  Inspection of Sheaves and Drums, Dimensions of Groove Radius  
  Cut and Slip Procedure, Lubrication  
    Rope Properties & Data:  
  Tensile Strength and Fill Factor  
  Strand- and Swage Compaction  
  Rotation Resistant and Non-Rotating Wire Rope  
  Sheave and Drum Dimensions  
  Relative Service Life, Loss of Strength over Pins, Why Multistrand Ropes  
Technical Information – Rope Properties & Data
  to Technical Information Main Page

  Relative Service Life

The ability of wire rope to withstand repeated bending work over sheaves and onto drums is also called the 'fatigue resistance'. This terms does NOT describe the ability to withstand mechanical damages nor the crush resistance of the rope.

The fatigue resistance of a rope is not time but cycle dependent. Bending fatigue is the ability to withstand repeated bending over sheaves and drums and such ability is depending on factors such as drum diameter, groove dimensions, rope tension, line speed, rope construction, fluctuation between highest and lowest loads etc.

For further information on this topic, please contact us for technical assistance and advice.
The tables show relative expected rope service life in relationship to D/d ratios and Design Factors.
If the shackle or object has 2 times the diameter of a 6-strand wire rope sling (D/d 2:1) the basket sling capacity must be reduced by 40%
If the object lifted with a 6-strand wire rope sling in a basket hitch is at least 25 x larger than the sling diameter (D/d 25:1) the basket hitch capacity need not to be adjusted.  
  Loss of Strength over
Sheaves and Pins

Rope breaking strength is determined in a standard test wherein fittings are attached to the ends of the rope and the rope is pulled in a straight line. If however, the rope passes over a curved surface (such as a sheave or pin) its strength is decreased. The amount of such reduction will depend on the severity of the bend as expressed by the D/d ratio.

For example, a rope bent around a pin of its own diameter will have only 50% of the strength attributed to it in the standard test. This is called '50% efficiency'. Even at D/d ratios of 40, there may be a loss of up to 5%.

At smaller D/d ratios, the loss in strength increases quite rapidly. The angle of bend needs not to be 180°, 90°, or even 45°; relatively small bends can cause considerable loss.

The table shown derived from standard test data as published by the 'Wire Rope Technical Board', is based on static loads only, and is a weighted average of 458 tests over pins and thimbles on 6x19 and 6x37 class ropes.
  Why multi-strand Wire Rope?

The number of outer strands determine the contact area between the rope and the sheave groove. If this area is increased the points of contact are multiplied and contact pressures are reduced.

At the same time lateral notching stresses between strands and wires are reduced, resulting in increased fatigue life.

Extensive tests programs at the University of Stuttgart, Germany, have proven conclusively that the bending fatigue life of wire rope improves with an increasing number of outer strands.

Based on that research we have developed Python® High Performance Wire Rope with 8-, 9-, and 10 outer strands.
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