rated capacity of sling
The rated capacity of a sling varies depending upon the type of sling, the size of a sling, and the type of hitch. The American Society of Mechanical Engineers (ASME) requires that all wire rope slings be tagged with the name or trademark of the manufacturer, the rated capacity for specific configurations and the diameter of size of the sling. Under no circumstances shall a slings rated capacity be exceeded.
Selection
The rated capacity of a sling and what it means to you.
The rated capacity of a sling varies depending upon the type of sling, the size of a sling, and the type of hitch. The American Society of Mechanical Engineers (ASME) requires that all wire rope slings be tagged with the name or trademark of the manufacturer, the rated capacity for specific configurations and the diameter of size of the sling. Under no circumstances shall a slings rated capacity be exceeded. The user should maintain this identification so that it is legible during the life of the sling. All persons using the sling should read the tag and understand the information on it. The rated capacity of a wire rope sling si based upon the Minimum Breaking Force (MBF) of the wire rope used in the sling, and other factors that affect the overall strength of the sling, including:
- Attachment or splicing efficiency.
- Design factor (5 is standard).
- Number of parts of rope in the sling.
- Type of hitch (straight pull, choker hitch or basket hitch).
- Diameter around which the body of the sling is bent (D/d ratio).
- Number of legs.
- Diameter of the pin (or hook) over which the eye of the sling is rigged.
- Angle at which the sling is used.
Design Factor
The rated capacities for wire rope slings are based on a design factor of 5 per ASME B30.9. The design factor and other factors are used to calculate the rated capacities. Design factors have established that allow the sling to give efficient service to the user.
D/d Ratios
When a sling is rigged as a basket the diameter of the bend where the sling contacts the load can affect the slings lifting capacity. How much the lifting capacity is affected can be calculated by dividing the diameter of the bed where the rope contacts the load (represented by "D") by the diameter of the bend ("D") is 10 and the component rope diameter ("d") is 1/2 , the D/d Ratio is 10 ÷ 1/2 or 20.
When D/d ratios smaller than those shown in the table below (or those shown in the footnotes below Rated Capacity Tables) are used, the rated capacity of the sling must be decreased.
