Every industry has its common terminology, and in lifting, a great deal of it will crop up in manuals, brochures, articles, reports and websites. It is, of course, the essential parlance that is necessary for the occupation, but sometimes it can be the source of a certain amount of confusion. A good example is a terminology-related question that our technical team is frequently asked: what’s the correct term to describe the lifting capacity of lifting equipment: Safe Working Load, Working Load Limit or Rated Capacity?
In short, the answer to this is that they are all correct and the choice of which to use really depends on the use of the equipment.
To explain in a little further detail, according to LEEA’s COPSULE (Code of Practice for Safe Use of Lifting Equipment), The Working Load Limit (WLL), or maximum working load as defined in the Supply of Machinery legislation, is the load value assigned to the ‘maximum’ Safe Working Load (SWL) under ideal conditions and in most cases the WLL and the SWL will be the same.
However, depending upon the conditions of use, it may be necessary for the competent person to reduce this to a lower SWL and it is in these cases that the WLL or rated capacity and SWL will differ.
If the risk assessment of the intended lifting operation indicates that such reduction may be required, it is essential that the user exchanges this information with the designer, manufacturer or supplier at the time of ordering so that the correct SWL may be attributed to the equipment and documentation.
Without such a declaration, the manufacturer or supplier will assume that the application is suitable for equipment rated with the SWL equal to the WLL.
If the equipment is in service or the user has not declared this information to the manufacturer, then the user is responsible for determining and marking the appropriate SWL.
One example of where it may be necessary to reduce the WLL to a lower SWL.is when undertaking hazardous duties. These could be, for example, environmental conditions such as extremes of temperature, high windspeeds or lifting procedures such as a likelihood of shock loading or inaccuracy of weight. When such circumstances arise, it is essential that safer systems should be put in place to prevent normally rated equipment from being used to its full capacity.
While it is the responsibility of the user to take such steps, the following advice should be considered. For specific installations where the equipment is fixed permanently in position, the equipment maybe marked with the reduced SWL for that specific duty. For specific installations where the equipment is portable, a competent person should provide written instructions to the operative/end user which includes an instruction to use a normally rated piece of equipment (ie, SWL = WLL) but of appropriately higher capacity, thus achieving the same effective reduction. For an industry, or a definable section of it, where the majority of tasks require equipment having a reduced working load, then all the equipment should have a reduced working load, ie, that corresponding to the most hazardous duty.
While WLL, SWL and rated capacity are common terms that anybody in lifting will come across, with the former two often referred to solely by their acronyms, it is all too easy to assume an understanding of the terms without being fully clear. But, in the Lifting Industry, misunderstandings can create risk. So, hopefully, this article will give a little extra clarity to this particular terminology issue.
