Have you wondered why rigging experts always suggest a sling that has a significantly higher breaking strength than the actual weight of the load you are lifting? The manufacturers know that the rigging used in overhead applications need to have room for error. This is known as the Safety Factor.

Northern Strands manufactures wire rope slings rated up to 36,000 lbs and sells round synthetic slings that are rated up to 140,000 lb capacity. This capacity is the Working Load Limit of the sling, which is the maximum amount of weight or force that the sling's user is allowed to put on the sling. Note: These slings do not break at the working load limit. These slings are designed with a safety factor of 5:1. This means that 5 times as much force as the working load limit has to be applied to the sling before it potentially fails. This means the wire rope slings have a Breaking Strength of up to 180,000 lbs and the round synthetic slings can withhold up to 700,000 lbs.

Why are these capacities reduced by such a drastic degree?

Among others, here are 3 good reasons:

1. Shock Loading - Unexpected drops where the load can accelerate and then must be 'caught' by the slings.
2. Wear - Working load limits are based on slings in brand new condition and a safety factor can help account for normal wear and tear until it is deemed unfit for further use.
3. Uneven loading - Slings are made up of either wires or fibers that must all share the weight of the load evenly. If any situation arises where the sling is bent or wrapped around an object, there is potential that some of the wires or fibers will be taking on a greater share of the load than others.

Visit Northern Strands website to use the sling tension calculator. The Northern Strands Sling Calculator has been designed to assist you in selecting slings with enough load carrying capacity for your lifting applications. It is your responsibility to assure that the slings you use are appropriate for your application.  http://www.northernstrands.com/sling-calculator.aspx

To inquire about Rigging and Safety Factors, contact:

Northern Strands @ 306-242-7073

or Email info@northernstrands.com

Being a company that specializes in rigging, we are often asked for working load limits for wire rope slings, synthetic slings, chain slings and polyester round slings.   We have attached a Sling Ratings Chart for the convenience of our valued customers.

Sling Ratings Chart.pdf (324.61 kb)

Trivia:  Did you know that Northern Strands is the largest supplier of wire rope and rigging in Saskatchewan?

Northern Strands is proudly Saskatoon, Saskatchewan owned and operated.

Northern Strands delivers presentations on Safety with Rigging at the Agrium Safety Fair.  These presentations included aspects of rigging inspections, examples of rejections and the do's and don'ts of rigging safety.  Northern Strands provided a test bed to perform breaks on lifting slings as part of the presentation.

The test bed demonstration:

New web and wire rope slings ( 3/8 x 6ft and 1” 1ply and 2ply ) were supplied for demonstration. Agrium also supplied Northern Strands with 10-12 used wire rope and web slings in varying degrees of degradation. All new slings were benchmarked to have breaking load 5 x Working load limit. All new slings broke above this benchmark. The used slings broke all over the map. Some of the new slings were given a knot and then tested with an expected 50% reduction in breaking load. Slings with knots were 40% to 60% of benchmark. Hitches were also tested ( Choker style ) there were consistent breaks near calculated load. We did have a number of eye breaks on new web and wire rope slings but above projected breaking point.

Approx. 300 people attended the presentations and were very interested in the demonstration results

Some of the comments overheard were along the lines of: Who'd of thought...I didn't know that...great to see what we only read about before....guess we don't do that anymore.

The comments were very positive and it's very likely Northern Strands will be asked by Agrium to give additional presentations on Safety with Rigging at the Agrium Safety Fair next year. 

Northern Strands is proudly Saskatoon, Saskatchewan, Canada owned and operated.