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INSPECTION & MAINTENANCE

What is the difference between WLL/ SWL & MRC and when should they be used? Over the past few months Cranemec has received several requests to explain the difference between Safe Working Load (SWL) and Working Load Limit (WLL). We have set out in this article to explain the difference. The term Safe Working Load, (SWL) has been a term used by the engineering fraternity particularly with respect to load carrying equipment for many years. It was generally considered to be the minimum breaking load of a component divided by an appropriate factor of safety giving a ‘safe’ load that can be carried or lifted. Throughout the world the use of Safe Working Load (SWL) for cranes,

hoists, winches and lifting gear was universally used throughout industries and referenced in the relevant legislation and standards. Since the definition of “Safe Working Load” is not very specific and there are legal implications, the USA standards stopped using this term. A few years later the European and ISO standards began to follow suit. The Americans, Europeans and ISO then developed a more

appropriate term and definition for the maximum load capacity of a particular lifting device. All parties agreed to the use of the term “Working Load Limit” or WLL. So, what is Working Load Limit (WLL)? It is the most frequently used terminology used by manufacturers now tagging all load carrying equipment, rigging and its components with the abbreviation WLL (Working Load Limit). A simple definition of WLL is the maximum load that includes mass or force that should ever be applied to the load carrying equipment in a specified condition or application. Any rigging device or configuration is only as strong as its weakest or lowest WLL rated part. Remember, the WLL provides a safety margin to compensate for the weakening of the lifting equipment during normal use due to wear, ageing, dynamic loading, jolting during lifting and inaccuracies in load weight estimations.

FIGURE 1

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Lifting Africa - Nov/Dec 2019

It is the lifting equipment’s manufacturer that recommends the maximum load capacity of his lifting equipment. The lifting equipment

Profile for Lifting Africa

Lifting Africa Nov-Dec 2019  

The Lifting Africa Publication Nov-Dec 2019 Issue with Phakamisa on the cover.

Lifting Africa Nov-Dec 2019  

The Lifting Africa Publication Nov-Dec 2019 Issue with Phakamisa on the cover.

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