Causes for Hoist Wire Rope Failures

A hoist wire rope is a machine in and of itself that requires proper selection, installation, and maintenance.  As a wire rope is used in a hoisting application, the individual wires move and allow the rope to bend around the drum and sheaves.  This movement causes friction and abrasive forces that require proper lubrication.  If selection, installation, operation, or maintenance is improper, the rope life will be shortened dramatically.  Even under the optimum conditions and usage, every wire rope used in a hoisting application will eventually fail. Therefore, routine periodic inspections, by a trained and qualified inspector must be employed to determine the condition of the wire rope so that replacement made before the rope fails.

When we look at wire rope wear and failure, there are numerous possible causes.   Possible causes include:

  • Abrasion Caused Failure
  • Core Protrusion
  • Corrosion Caused Failure
  • Cut or Shear Caused Failure
  • Fatigue Caused Failure
  • Tension Caused Failure (Overloading of Rope)

Abrasion Breaks (Externally Induced Damage)

Abrasion wire breaks of hoist wire ropes are located at points where the rope has been damaged by improper contact with hoist sheaves and drums or has struck an external object such as the crane girder or shelving.  Improperly grooved sheaves and drums or improper fleet angle into the sheaves can often cause this kind of damage.  Wire breaks caused by abrasion show broken wire ends worn to knife-edge thinness.

Core Slippage or Protrusion (Shock Load or Improper Installation)

Core protrusion can be caused by shock loading as well as improper installation.
Rotation-Resistant wire ropes on hoists must be installed with extra care and proper handling to prevent rope damage during installation. The lay length of a rotation-resistant rope must not be disturbed during the various stages of installation.  By introducing twist or torque into the rope, core slippage may occur—the outer strands become shorter in length, the core slips and protrudes from the rope. In this condition, the outer strands become overloaded because the core is no longer taking its designed share of the load. Conversely, when torque is removed from a rotation-resistant rope core slippage can also occur. The outer strands become longer, and the inner layers or core become overloaded, reducing service life and causing rope failure.

Corrosion Breaks (Poor Lubrication)

Wire ropes that fail due to corrosion are usually indicative of improper lubrication.  Corrosion is easily identified by the pitted surface on individual wires of the rope.  Broken wires do not usually show evidence of tension, abrasion, and fatigue. The extent of the damage to the interior of the rope is extremely difficult to determine; consequently, corrosion is one of the most dangerous causes of rope deterioration.

Cut or Shear (Externally Induced Damage)

In this type of wire rope damage, the wire will be pinched down and cut at broken ends or will show evidence of a shear-like cut. This condition is evidence of mechanical damage cause from an external source or wear or damage on equipment components such as a broken flange on a sheave or sharp drum grooves.

Fatigue Breaks (Repetitive Bending Wear)

Hoist wire ropes are subject to a lot of repetitive bending over sheaves, which causes the wire to develop cracks in its individual wires. These broken wires often develop in the sections that repetitively move over sheaves. The smaller the sheave is in relationship to the diameter of the wire rope, the higher the bending fatigue.  This process will become escalated as a rope travels on and off of a grooved single layer drum, which also causes a bending cycle.

Fatigue breaks often develop in segments as stated before these segments are usually the part of the rope surface that comes into direct contact with a sheave or drum. Because this is caused by external elements rubbing, often these breakages are external and visible for the eye to see. Once broken wires start to appear, it creates a domino effect and quickly much more will appear. Square ends of wires are common for fatigue breaks. These breaks are considered a long term condition and are to be considered part of the normal to the operating process. 

Tension Failure (Overload / Shock Loading)

Tension failure is caused by overloading of the wire rope.  The overloading can be based upon the original strength of a new wire rope or for the remaining strength of a used wire rope.  When a wire rope has failed due to excessive tension, the broken rope will show one end of broken wire coned and the other cupped. Necking down of the broken ends is typical of this type of break.  Tension breaks are often caused due to shock loading a slack rope that induces excessive impact stress on the rope.

CRANE 1 provides experienced wire rope analysis and recommendations:
We have included a troubleshooting checklist of the possible causes for early wire rope failure below.  Call your nearest CRANE 1 office for expert analysis, lubrication and replacement ropes that are installed by trained professionals.   


Troubleshooting Checklist

ABRASION DAMAGE

  • Frozen sheaves or rollers
  • Tight grooves
  • Excessive fleet angle
  • Oversized or undersized rope
  • Corrugated sheave or drum
  • Rope overspin caused by improper sheave rotation (bad bearing)
  • Rope jumping the sheave
  • Poor spooling
  • Misaligned sheaves
  • Site contaminants

CORE PROTRUSION/SLIPPAGE

  • Shock or snag loading
  • Poor seizing techniques, particularly on rotation resistant rope
  • Poor installation techniques placing undesirable twist in the rope

CORROSION DAMAGE

  • Poor lubrication
  • Environmental damage (acid, caustic)
  • Improper storage

CRUSHING

  • Poor installation techniques
  • Cross winding
  • Improper spooling
  • Incorrect wire rope diameter or construction
  • Poor break-in procedure
  • Excessive fleet angle
  • Excessive rope length (drum overwrap)

DIAMETER REDUCTION

  • Lack of lubrication (fiber core)
  • Excessive abrasion
  • Corrosion, internal and external Inner wire or core failure

FATIGUE

  • Out of round sheaves
  • Tight grooves (Improper Rope Diameter)
  • Misaligned sheaves
  • Undersized sheaves
  • Worn bearings
  • Vibration, Slapping, Whipping
  • Reverse bends

HIGH STRANDING

  • Poor wire rope end seizing techniques
  • Tight grooves
  • Undersized sheaves
  • Poor installation techniques

JUMPING THE SHEAVE

  • Poor spooling
  • Excessive rope length
  • Broken flange
  • Slack rope (Operation)

KINKING

  • Poor new rope unreeling procedures
  • Poor installation techniques
  • Undersized sheaves

LAY LENGTHENING/TIGHTENING

  • Poor installation techniques
  • Poor unreeling procedures
  • Corrosion
  • Core failure

LOOPED WIRES

  • Poor installation techniques
  • Undersized sheaves

UNBALANCED ROPE

  • Oversized sheaves
Causes for Hoist Wire Rope Failures | Crane 1 Services

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