Lifting Slings - Some Important Factors to Consider

Looking into getting a lifting sling for lifting/ transporting some heavy loads or goods?

There are 3 common types of lifting sling typically used by the industry for attaching on their lifting machines/ equipment to carry and/or transport the heavy loads:

• Synthetic Sling
• Alloy Chain Sling
• Wire Rope Sling   

Let's look at each of them briefly:

Synthetic Sling ( Usually Polyester /Nylon )

Generally, it is the preferred choice of sling for lifting loads that could be subjected to crushing damages, as such requiring the lifting sling to be of a softer, and more flexible material that could mold to the dedicate shape of the load to be lifted. It can be used in vertical, choker & basket hitch lifting, making it extremely versatile.

The key advantages being lightweight, flexible and lower in cost as compared to the wire rope, or chain variants; usually in nylon or polyester build.

It should be noted by the user that synthetic slings are generally low in heat resistance (although some manufacturers do produce special high heat resistant grade), as such should be avoided in applications / environment involving excessive heat or very high temperature.

Alloy Chain Sling

The preferred choice of sling for lifting heavy loads in harsh environment; due to its durability to chemical exposure, as well as extreme temperature conditions, where it stands out against general wire rope & synthetic slings.

Another of its key advantages over other sling variants, is that the chain slings can be repaired if part of the chain link segment is damaged, thus having the benefit in repairability & higher reusability.

It should be noted by the user that due to its robust nature, it could subject the more dedicate lifting loads to damages, as such should be taken into consideration, or avoided if the lifting subject/ loads are crush sensitive in nature.

Wire Rope Sling

Its acquired quality of being abrasion resistance, and/or fatigue resistant, yet maintaining strength and flexibility in its sling,  are the main reasons for the popular use wire rope sling  in most manufacturing, construction and oil & gas industries; Typically, of lower initial cost & weight as compared to an equivalent alloy chain sling, is another plus point which  adds to its benefits.

It should be noted that the wire rope construction, could make it difficult for inspection purposes especially in the core area; it is also non-repairable if taken out of service.

Factors to consider...

A couple of important questions to ask that helps determine the required sling... 

• Load to be lifted
  • weight & size
  • lifting points
• Working environment & conditions
• Sling features
  • rated capacity of sling
  • number of sling legs
• Other requirements, etc.

Note that the above provides quick self check list and is not exhaustive. 

Lifting Sling Tension...What is it about?

With the important factors considered, we need look into the way in which the load is being carried/ lifted, as loads that are being carried at an angle will affect the sling tension directly.  A general visualization is when the sling angle ( from the horizontal plane) gets smaller ( for example: angle drop from 60⁰ to 30⁰), the load is being "crushed" by the sling and thus the slings work harder.

It can be seen from the table below ( see picture insert),  L.A.F. ( Load Angle Factor ) / L.A.M. ( Load Angle Multiplier) increases, as the lifting sling angle drops; which implies the sling tension increases as the sling angle decreases.

The lifting sling angle gets undesirable at 30⁰ and below as the sling tension doubles...! 

Check out the sample lifting sling tension calculation  ( using L.A.F./L.A.M. table ) below:

Quick look into lifting sling capacity  ( using Synthetic Webbing Sling as example)

Consideration for getting Webbing Slings:

Any other queries on your sling requirements and needs? Feel free to contact us for more information.