Working load limit

Performance Criteria (Working Load Limit) — Tiedown assemblies (including chains, wire rope, steel strapping, synthetic... 

The aggregate working load limit of tiedowns used to seciire an article or group of articles against movement must be at least one-half times the weight of the article or group of articles. 

One-half the working load limit of each tiedown that goes from an anchor point on the vehicle to an anchor point on an article of cargo ... 

Working Load Limit — The working load limits of a tiedown may be determined by using either the tiedown manufacturer s markings or by using working load limit tables. 

The working load limits listed in the tables are to be used when the tiedown material is not marked by the manufacturer with the working load limit. 

The following tables show the working load limits for common sizes and types of tiedown devices. 

Working load limit (WLL) The maximum load that may be applied to a component of a cargo securement system during normal service. The WLL is usually assigned by the manufacturer of the component. 

If a lift is vertical (i.e. the lifting hook on one end and the load vertically below on the other end), the total load that may be lifted is that marked on the sling. However, if the method of lifting differs, the working load limit (WLL) will alter as shown in Table 19.1. The figures relate to a sling with a 1 tonne (1000 kg) SWL. 

Table 19.2 shows the working load limits for a variety of chain slings whose links are made from 10 mm diameter material and operating at various angles. 

Generally taken as the maximum load that an item of equipment (e.g., crane) may raise, lower, or suspend under particular service conditions and arrangements. Each individual type of equipment has its own specific safe working load limits. 

Employers must not use allow steel-chain slings with loads in excess of the rated capacities (i.e., working load limits) indicated on the sling by permanently affixed and legible identification markings prescribed by the manufacturer. 

Alloy steel chain slings must not be loaded beyond working load limit — 1926.251 (b)(4) — Aug. 4, 2000... 

A. Section 1926.251(a)(2) states that rigging equipment shall not be loaded in excess of its recommended safe working load, as prescribed in Tables H-1 through H-20... (also, 1926.251 (b)(4) states that the rated capacity for alloy steel chain slings shall conform to the values in Table H-1). Table H-1 prescribes rated capacities (working load limits) for alloy steel chain only. Therefore, the standard mandates that only alloy steel chain be used, and that such chain meet the Table H-1 rated capacities. 

Rated capacity or working load limit—The maximum working load permitted. 

Natural fiber and synthetic fiber rope slings, except for wet frozen slings, may be used in a temperature range from minimum 20°F to plus 180°F without decreasing the work load limit. For operations outside this temperature range and for wet frozen ropes, the sling manufacturer s recommendations should be followed. 

The working load limit is determined by the marking that is on the device, or by using the table in 393.108 if the device is not marked. However, in Canada, unmarked devices cannot be counted toward the aggregate working load limit (they do not recognize the U. S. table and do not provide one of their own). 

How the tie-down is being used also impacts its working load limit. If the device is being used as an indirect tie-down, which involves the tie-down ends being attached to opposite sides of the vehicle, then 100 percent of the marked or determined working load limit can be counted toward the aggregate working load limit. 

In case of lifts of standard packaging structures where the technical safety seeks to take into account the load to be lifted, the frame type and frequency of handling that type of packer, as well as other conditions exist, whether such will be transported to the offshore or onshore in order to verify if the packer is adequate and properly choosing the type of sling more advisable to their movement (synthetic, steel cables or chains) as well as their tension capacity (Working Load Limit—WLL, or Safe Working Load—SWL) or even shackle (dee/bow shackles or other) and the use or master links (DNV, 2006, 2.7-1 and 2.7-3 Gunnebo Industrier, 2001). 

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