Lifting Slings

Wire Rope Lifting Slings

Nobles have been making wire rope slings for almost 100 years, and can test slings up to 1,000 tonne. 

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Types of wire rope slings

Types of wire rope slings

 

Aluminium Ferrule Secured

= Ferrule secured splice
+ Proof load testing of each sling
+ WLL markings
+ Sling production site marking
+ Test Number for easy matching with test certificate


Aluminium

Cross section of a splice showing how rope and ferrule form one strong, homogenous mass.

Ferrule Secured Flemish Eye


Flemish Eyes


Flemish eyes with steel sleeves are recommended for corrosive conditions where a steel ferrule or sleeve is able to withstand electrolytic reactions, which can affect other metals. In hot working areas the steel retains its strength at higher temperatures.

In abrasive conditions steel can withstand more mechanical stresses than other ferrules. In the above situations the Flemish eyes with steel sleeves have the back up strength of a Flemish eye even if by some means the ferrule is damaged.
 

Hand Spliced


Hand Spliced


Although aluminium ferrule secured has become the most popular type of wire rope sling there is still some demand for Hand-spliced slings which have more flexibility at the splice.

 

Wire Rope Sling Types


wire rope
soft eye

 

Inspection before use

Inspection before use

 

A sling will eventually deteriorate as a result of abrasive wear, wire breaks, loss of lubrication, corrosion and consolidation of the core and rope strands. Damage is not always readily evident. The normal types of damage are described in this section.

The pre-use inspection for wire rope slings shall give particular emphasis to:

  1. Check the identification stamp or tag and ensure the WLL of the sling is clearly legible.
  2. Check load-bearing points for excessive wear, kinking, broken wires and corrosion.
  3. Check each strand along its length, opening the rope as much as practicable to enable examination of the surfaces of the strands towards the inside of the rope.
  4. Check end fittings and attachments for any signs of deformation, excessive wear or corrosion.
  5. Check the sling for heat damage. This is usually obvious through the discolouration of the wires.

Types of Damage

Wire rope can be damaged in different ways and the resulting damage can take the forms of external wear, local abrasion, broken wires, internal wear, physical deterioration, corrosion, kinking and flattening of eyes.


Severe overloading of wire ropes is evidenced by an increasing rate of fracture of the wires and excessive stretch under load accompanied by marked reduction in diameter.

External wear can be caused by dragging the sling over rough surfaces and is the most readily noticeable cause of weakness, particularly if a new sling is available for comparison. In the extreme, the outer strands become worn as the outer wires within the strands are flattened and worn.

Local abrasion, as distinct from external wear, can be caused by the passage of the sling over sharp edges whilst under tension and can cause a serious loss of strength. It is good economy to protect slings at points where excessive local abrasion can occur. Cuts, bruises and similar damage can be internal as well as external. This type of damage is indicated by local rupturing or loosening of wires or strands. It is caused by lack of care in use such as hammering of the slings and careless placement of the load. Internal wear is caused by repeated flexing of the sling and by particles of grit picked up in service. Internal wear is accelerated by lack of lubrication and by corrosion.

Corrosion is caused by dampness and exposure to acids, alkalis, other chemicals, flue gases, industrial dusts, ashes and similar substances.

High temperatures, such as those found in foundries, steel works and like applications, reduce both the strength and the safety of a sling.

Distortion, permanent set or any physical deformation of end fittings, particularly at load bearing points should be regarded as dangerous and the sling should not be used.

Discarding Slings

The decision whether or not to withdraw a sling from use shall be based on an assessment of the general condition of the sling. After examination, if any doubt exists about the safety of a sling, it shall be withdrawn from service.

Slight damage to the outer wires of a wire rope sling may be disregarded. Serious damage of one strand or somewhat less serious damage to more than one stand however, merits rejection of the sling.

Slings that have been subjected to impact loads, overloaded or loaded in a kinked condition shall be destroyed and discarded.

Where kinking is such that it creates a hazard in taking up loads through hand injuries or causing unevenness or jerking during loading, the kinked slings shall be discarded.

 

Care In Use

Care In Use

 

Wire rope slings are particularly susceptible to kinking, local abrasion and mechanical damage and care should be taken to ensure they are protected as much as is practical to prevent or lessen the extent of such damage. Some common safe use practices for wire rope slings are:

  1. Never exceed the WLL of a wire rope sling. Always ensure you know the lifting capacity of the sling in the configuration you intend to use it.
  2. Ensure that wire rope slings are not used on sharp corners of a load. This will almost certainly kink the sling and render it unusable. If a load with sharp corners is to be lifted the corner should be packed or a protective sleeve placed over the sling.
  3. Splices in rope slings shall not be bent around corners or edges whether sharp or curved.
  4. The inside radius of any bend in a wire rope around a corner of a load, (except at the point of reeving in choke hitches) shall be not less than the rope diameter where the included angle of the bend of the rope is more than 90 degrees or five times the rope diameter where the included angle of the rope is less than 90 degrees.
  5. Practice such as hammering or "battening down" of slings to force the sling down in a choke hitch configuration is dangerous. The wire rope sling should be left to find its natural angle. If positive choking is required a synthetic sling may better serve the application.
  6. Never lift a load over people or dangerous parts of plant.
  7. Do not use slings that are knotted or kinked.
  8. Wire rope slings should not be exposed to welding or cutting operations.
  9. Careless placement of the load is a sure way to damage a sling and must be avoided. Loads should always be placed on battens.
  10. When using multi leg slings ensure that the load is as evenly balanced as possible in order for all sling legs to take an equal amount of load.
  11. Never shorten a sling be tying a knot in it. If the load is unequal and varying leg lengths are required a specially designed wire rope sling shall be used or an alternative slinging method.