Lifting Slings

Grade 80 Chain Slings

Nobles is a leading manufacturer of Grade T chain slings in Australia. Nobles chain slings comply with AS 3775 and all chain slings manufactured by Nobles are proof load tested to twice the WLL.

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Types of slings

Types of slings

 

With the exception of endless slings as described below the configurations are based on sling legs. The most commonly used chain assemblies are illustrated here but also illustrated are special assemblies that may be devised for lifting specific or unusually shaped loads.

Sling Selection

The following factors should be considered before making a selection:

  1. Load - mass
  2. Headroom
  3. Type of load - steel, shipping containers, timber, fabricated sections or vessels
  4. Length of sling
  5. Method of slinging
  6. Environmental elements such as corrosion or heat

Geometry

The geometry of the sling is the number of chain legs of multi-leg slings and the angles between the legs and vertical. Angles should be assessed as shown in the figures below. The 'included angle' = 2B. Example below B = 30°. When calculating angles the apex of the angles should not include the length of the oblong link or master link.

Sling selection - Geometry Diagram

Multi-Leg Slings

The WLL of slings comprising two or more legs shall not be more than the calculated WLL of the sling while it is supporting the load with two of its legs having a symmetrical configuration with an included angle between the two legs of 60°. The included angle shall never be greater than 120°.

Sling selection - Multi-leg slings Diagram

Headroom & slinging methods

Headroom & slinging methods

 

Use of lifting beams or spreader beams assist in overcoming headroom problems and these can be purpose built by Nobles to comply with all relevant standards and regulations.

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Endless Slings

An endless sling shall never have a working load limit greater than 1.5 times the WLL of a sling leg sling.

Types of chain slings - Endless Slings Diagram

Reeved Slings

In the examples shown the WLL shall not be greater than 0.75 times the WLL of the chain to which it is attached.

Types of chain slings - Reeved Slings Diagram

Adjustable Slings Using Shortening Hooks

Nobles can incorporate shortening hooks into all sling assemblies rendering them adjustable.

Shortening hooks in multi-leg slings will adjust the leg length but care must be taken to ensure that no one leg is overloaded as a result. Bear in mind that if the legs are not equally disposed about vertical, the leg making the smallest angle to the vertical will carry a larger share of the load.

Shortening hooks are the preferred devices for adjusting leg length as they maintain the correct 'in line loading' of the chain
so that the rating is not affected.

Some grab hooks that lock onto a link of the chain for this purpose require a 25% deration. Cradle grab hooks, which fully support the chain link, do not require a deration.

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Inspection before use

Inspection before use

 

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wear-and-stretch.jpg
 
The pre-use inspection for chain slings should take note of the following:
  1. Clean sling before inspection.
  2. Ensure the sling is correctly tagged and certified.
  3. Every chain link should be individually inspected for any signs of wear, twisting, stretching, nicks, gouging, heat damage, chemical attack or excessive corrosion.
  4. Any worn links should be measured to determine the degree of wear, which should not exceed 10% in any plane.
  5. Upper and lower terminal links, hooks, etc. should be inspected for any signs of distortion, e.g. widening of any hook throat opening.
  6. Connecting links or chain connectors should be inspected for any signs of wear at their load-bearing points and for any excessive play of the load pin.
  7. Wear may be tolerated until the thickness of any worn section has been reduced by 10% of the nominal section in any plane.
  8. Chain links or fittings having any defects should be clearly marked to indicate rejection, and the sling should be withdrawn from service until properly repaired.
  9. Slings with damaged fittings may be repaired by replacing the fittings but the entire chain assembly must be proof load tested before being returned to service. Any damaged chain must be destroyed.

Care In Use

Care In Use

 

  1. The operator should establish the weight of the load to be lifted as accurately as possible.
  2. Ensure that the crane or other lifting equipment and the liftiing points are adequate to lift the load.
  3. Prepare the site where the load is to be landed in advance. Ensure that the sling is not trapped by the load in such a way that removal of the sling cannot be made by hand.
  4. Check compatibility of the chain sling to the crane hook and the lifting points on the load.
  5. Ensure the chain is free from twists and is protected from any sharp corners on the load.
  6. Ensure the load is evenly distributed on all sling legs. This can be facilitated through the use of shortening hooks.
  7. When using a choke hitch, the bite should be allowed to assume its own position.
  8. Commence the lift slowly, taking up the slack gradually.
  9. Care must be taken to ensure that the load remains stable throughout the lift.
  10. A trial lift should be made prior to the full lift operation. If the load is not balanced it should be lowered and the slings re-positioned.
  11. Sling hooks of a multi-leg sling should be positioned so that they face outward from the load.

 

Storage & Handling

  • Chain slings should be kept on a properly designed rack in a clean, dry place.
  • Lightly oil slings before any prolonged storage.
  • Never heat or heat-treat slings.

 

Heat

As the temperature which a sling attains in-service increases, its strength decreases. Care must be taken to account for the maximum temperature that can be reached by the sling in service.
 
Temperature of sling Strength of sling
up to 200ºc Nominal strength of sling
200ºc - 300ºc 90% of strength rating
300ºc - 400ºc 75% of strength rating
Over 400ºc DO NOT USE

Note: The use of a sling within these temperature ranges does not imply any permanent reduction in strength when the sling is returned to normal temperatures. If slings are accidentally exposed to temperatures indicated in excess of the maximum permissible temperatures indicated above, they should be withdrawn from service and returned to A. Noble & Son Ltd for inspection, testing and or repair or replacement.