TECHNICAL INFO
3 Basic Hitches
A sling is used to link a lifting hook to its load. The entire lifting capacity of the sling may be used, but cannot be surpassed. To keep the load from rotating, a tagline is used.
Choker Hitch Capacity Adjustment
Sling safety can never be over-emphasized. These basic safety steps should also be observed:
Determining Lifting Load Capacity of a Sling
As the horizontal angle of a sling decreases, the load on each leg increases. The effect is the same whether a single sling is used as a basket, or two slings are used with each in a straight pull, as with a 2-legged bridle.
Ordering Slings
Although many slings may be considered standard merchandise, many of hte lifting devices described in the Handbook are custom made after receipt of the order to specific dimensions and customer requirements.
Sling Safety
Sling safety can never be over-emphasized. These basic safety steps should also be observed.
3 Basic Hitches
Straight
Straight: A sling is used to link a lifting hook to its load. The entire lifting capacity of the sling may be used, but cannot be surpassed. To keep the load from rotating, a tagline is used. When a spreader bar or more than one leg is used, the entire assembly must be balanced equally among the slings.
Choker
Choker: A hitch whereby the sling wraps around or "chokes" a load. The diameter of the load is critical in determining the capacity of this hitch. Choker hitches have reduced capacity compared to straight or basket-type hitches. The "choke" must be tight and secure prior to the lift.
Basket
Basket: A "cradle" -style hitch where the fittings or eyes are attached to the lifting device such as a crane hook. The effect is to increase capacity from a straight lift and provide greater load bearing and stability to a lift.
Choker Hitch Rated Capacity Adjustment
For slings in choker hitch when angle of choke is less than 120 degrees.
When a choker hitch is drawn tight at an angle of less than 120 degrees, the Choker Hitch Rated Capacity shown in the sling Rated Capacity Tables must be reduced to allow for loss of Rated Capacity. In controlled tests, where the angle was less then 120 degrees, the sling body should always fail at the point of choke when pulled to destruction. Allowance for this phenomenon must be made anytime a choker hitch is used to shift, turn, or control a load, or when the pull is against the choke in a multi-leg lift.
Determining Lifting Load Capacity of a Sling
As the horizontal angle of a sling decreases, the load on each leg increases. The effect is the same whether a single sling is used as a basket, or two slings are used with each in a straight pull, as with a 2-legged bridle.
Anytime pull is exerted at an angle on a leg - or legs - of a sling, the load per leg can be determined by using the data in the table at right. Proceed as follows to calculate this load - and determine the rated capacity required of the sling, or slings, needed for a lift.
Divide the total load to be lifted by the number of legs to be used. This provides the load per leg if the lift were being made with all legs lifting vertically.
Determine the angle between the legs of the sling and the horizontal.
MULTIPLY the load per leg (as computed in No. 1) by the Load Factor for the leg angle being used (from the table at right) - to compute the actual load on each leg for this lift and angle. The angle load must NOT exceed the rated sling capacity.
Thus in drawing #3, (sling angle at 30 degrees): 1000 / 2 = 500 (Load Per Leg is a vertical lift)
500 x 1.154 = 577 lbs. = ACTUAL LOAD on each leg at the 60 degree included angle being used.
In drawing #4 (sling angle at 45 degrees): 1000 / 2 =500 (Load Per Leg if a vertical lift)
500 x 1.414 = 707 lbs. = ACTUAL LOAD on each leg at the 45 degree horizontal angle being used.
Angle of Bridles
The horizontal angle of bridles with 3 or more legs is measured the same as the horiztontal slign angle of 2-legged hitches. In this case where a bridle designed with tdifferent leg lengths results in horizontal angles, the leg with the smallest horizontal angle will carry the greatest load. Therefore, the smallest horizontal angle is used in calculating actual leg load and evaluating the rated capacity of the sling proposed.
Ordering Slings
Although many slings may be considered standard merchandise, many of hte lifting devices described in the Handbook are custom made after receipt of the order to specific dimensions and customer requirements. Therefore it is essential that each order provide the following information to guide manufacturing:
All orders must specify:
- Sling Type Number and Stock Number as given in this catalog.
- Length of sling, measured as shown below.
- Width of sling body.
- Webbing material-Nylon or Polyester.
- Description and placement of any wear pads.
- Protective coating, if an optional coating is desired.
- Description of end fittings for slings where a choice of fittings is offered.
Sling Safety
Sling safety can never be over-emphasized. These basic safety steps should also be observed:
- NEVER exceed rated capacites.
- Horizontal sling angles less than 30 degrees should NEVER be used.
- Failure to follow the care, use, and inspection of a sling could result in severe personal injury or even death.