‘Basket Down’ on a Structural Beam (Part 1)
People keep discussing about the ‘Basket’ methods of slinging. Since there is not a specific definition, the assumption is that it does not matter where and in which direction the basket slinging is carried out. However, there is a big difference in a physical way. When comparing slinging a structural steel beam at 25 meter elevated over the arena floor or slinging a truss when the structure is lying on the arena floor.
The choice of basket sling lengths can differ when applying to a low or a high beam within the roof structure. Such a decision can be motivated from the ease of the loadout than being more quick and safe. Apart from that, it should be clear that permanently installed steel baskets, being part of a house steel system, can be assembled based on other criteria.
The truss can be used as a ‘secondary beam’, placed in position being ratcheted on the venue beams. This can be found in low venues to avoid the loss of height in the bridle apex and to eliminate the horizontal forces that are applied to the venue beams as a result of bridles.
The easy and safe application of the basket sling to the beam / truss requires a sling set-up with an additional shackle or hook, that is used to close the basket, while leaving all components connected. The sling itself can be a wire rope or soft steel, but the endless polyester round slings (spansets) are pretty much becoming obsolete, because of national or local fire regulations and/or high temperature (fixtures, pyro, lasers) hazards.
Fig. 1: Basket variations: A) with an extra shackle, or ‘working shackle’; B) with a hook fixed to the sling, Ba) hook on the wire rope, Bb) hook on the soft steel.
Note: In this diagram the corner protection material (burlap, slab of thick rubber or a ‘beambo’) is left out.
The basket with the additional shackle has different names, like slave-, side-, or working-shackle. It is a classic rock-n-roll way of doing it. However that set-up is gradually being replaced by the type of Pro-Basket Slings that are predominantly being used to do baskets only. The slings are standard equipped with a hook at one end and a regular oversized thimble at the other end of the sling. Sometimes people prefer to have that thimble to be fitted with a Master-link, instead of a shackle. The sling body itself often is a standard type 6 strand wire rope. These are also known as click-baskets or quick-baskets.
Fig. 2: ‘Bridle Baskets on the Beam’: Shown are the ‘click’ type of baskets, that use a shackle in the termination opposite of the hook.
Some people are a bit hesitant in using this click-basket method, because their national regulations will require that all components must have a closed character. The standard type of latch in a standard type of hook is not considered to be closed. Even the standard type of screw pin shackles are not considered as closed and mousing of the shackle pin can be a requirement.
Some others will argue that in slack chain situations the latch or the hook might get undone. That point is only correct when it is below the lifting machinery set-up, but when applied to a roof beam there will always be gravity pulling with a force of between ca. 15 to 25 daN (the chain self-weight) and eventually ca. 75 daN (chain + chain motor).
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