16.5.1 Working Load Limit
Consideration must be given to the WLL of the sling for the particular service conditions so as to ensure that no part of the sling is overloaded by the method of use. The following should be considered:
The WLL of a webbing sling is based on the minimum breaking load of the sewn webbing component and is calculated on the basis of a factor of safety, which is specified in the applicable national legislation or standard. The terminal fittings of a webbing sling may well be rated at a different factor of safety. It is important to ensure that the webbing and fittings are matched on the basis of their working load limits and not their factors of safety.
Colour coding is often used in standards to relate the WLL of the sewn webbing component . However, standards prior to these permitted, but did not require colour coding. As a result many manufacturers adopted their own systems of colour coding, which were not universal. Care must therefore be exercised in the case of older slings, but in any event reliance should not be placed on the colour code to establish the WLL of the made up sling and reference shall always be made to the label.
The use of colour codes and protective treatments which are coloured limit the ability to de-rate slings for use in adverse conditions. When selecting slings where an increased factor of safety is required for a particular application, this should be achieved by selecting a sling of appropriately larger capacity and providing the operative with written instructions to ensure the correct capacity is selected. The nature of the materials used for flat woven webbing slings also limit their use in certain conditions, such as high temperature, severe abrasion and some chemical environments, for which de-rating is not appropriate.