Crane Application
Crane Application
considered when evaluating rigging configurations.
In field conditions, sling angles are often adjusted to accommodate obstructions, limited headroom, or fixed lifting points. These adjustments change how forces are distributed, even when the load weight remains constant. A configuration that appears stable may introduce significantly higher stress into the rigging system than expected based on rated capacity alone.
Hitch selection further influences performance. Choker hitches reduce effective capacity due to the way the sling is bent and loaded. In typical applications, a choker hitch may only achieve approximately 75 to 80 % of the single-leg capacity, and improper positioning can reduce this further. If the choke angle is not properly set or the sling is not seated correctly, capacity can be reduced significantly, and the load may shift during lifting.
Multi-leg sling systems introduce additional variability. Load sharing depends on equal sling length, consistent spacing, and correct alignment with the center of gravity. When one leg is shorter or positioned closer to the center of gravity, it carries a greater portion of the load.
In some configurations, load distribution can be highly uneven. For example, a sling attached at approximately 25 % of the distance from the center of gravity may carry as much as 75 % of the load, while other legs remain lightly loaded. This uneven distribution increases localized stress and reduces the margin between applied force and allowable capacity.
Rated load itself is based on a design factor, which provides a margin between working load and breaking strength. For many slings, this factor is typically in the range of five to one, depending on sling type, meaning the rated load is significantly lower than the ultimate strength of the material. Improper rigging can quickly reduce this margin.
Loads Under Lift
Load behavior during lifting is governed by the center of gravity, which determines how the load will align when suspended. As the load is
30 l Equipment Guide- October 2026
To properly rig and balance a load, a test lift allows verification of stability.
lifted, it will move until equilibrium is reached beneath the lifting point. If rigging is not positioned correctly relative to this center, the load will shift during lifting, redistributing forces across the sling legs.
Differences in attachment point location, sling length, or spacing influence how load is shared once the system stabilizes. These variations may not be obvious during setup, yet they become critical once the load is fully suspended. In multi-leg configurations, even small inconsistencies
can result in one leg carrying a disproportionate share of the load.
Dynamic conditions introduce additional forces beyond static calculations. Sudden lifting, stopping, or changes in direction create transient forces that increase stress within the system. These forces can exceed calculated values and contribute to wear in slings, hardware, and crane components. Over time, repeated exposure to dynamic loading reduces service life and affects reliability.
Maintaining control during lifting