Sling Load Capacity and Sling Angles The load capacity of the sling is determined by its weakest component. Never overload a sling.  Remember, as you change the angle of the slings from 90 degrees to 30 degrees the sling capacity decreases. Highest Capacity (strongest) Less Capacity (weaker) Least Capacity (weakest) 45 degrees 90 degrees 30 degrees

Affects of Sling Angles Rated capacities are affected by the angle of the lift (sling to load) measured to the horizontal when used with a choker hitch. An angle of thirty degrees should never be exceeded. This is the angle of concern (the sling to the horizontal lift) on both sides.

Sling Angle Capacities If you don't know the angle: Attach the slings Apply lift until the slings are taut and the load is ALMOST ready to leave the ground (BUT DO NOT LIFT THE LOAD OFF THE GROUND!!) Measure the length of the sling between the lift point and the load Measure the height between the lift point and the load (see below)    When you know the actual weight of the load (use material weight sheets), and you need to calculate the appropriate rated capacity (based on the sling angle) of the sling to lift the load, follow the instructions below: (This example uses a measured length of 12 feet and a measured height of 10 feet.) Measured Length (L): 12 feet Measured Height (H): 10 feet Load Multiplier (LM) =L/H=12/10 = 1.2 Load weight: 6000 lbs. Necessary Rated Capacity of sling = Load Weight x LM = 6000 X 1.2 = 7200 lbs. (compare this to the slings rating in a choker hitch).

Sling Angle Chart (if you know the angle of the sling to the lift) This is typically on sling labels. This is used to determine the safe lifting capacity of a sling according to the angle and weight of material being lifted. This chart will be used as a reference on the following slide. Angle in Degrees from Horizontal Angle Factor 90 1.000 55 .819 85 .996 50 .766 80 .985 45 .707 75 .966 40 .643 70 .940 35 .574 65 .906 30 .500 60 .866

How to determine if a 20,000 lbs How to determine if a 20,000 lbs. capacity sling can safely lift a load at a specific angle using material that weighs 6,000lbs: Important: Remember that the capacity of a sling depends on the type of hitch being used: Choker hitch of a typical 20000lbs rated sling is 9200 lbs. (trainer – explain with the current slings used at your location). With 20 ft. slings, typically 12ft. material is lifted with approximately 60 degrees of angle to the load when the slings are 1ft from the end of the material. Using the chart from the previous slide, we determine: (capacity of sling using choker method) x (angle factor from previous slide) = true capacity 9200 lbs. x 0.866 = 7967 lbs. (true capacity) Since we always use two slings, we double the above capacity 7967 x 2 = 15934 lbs. Even using 30 degrees of angle (worst case scenario for angle): 9200 lbs. x 0.500 = 4600 lbs. (true capacity) Again, since we always use two slings, we double the above capacity (4600lbs. x 2 = 9200 lbs.)

Safe Practices Never shock load slings. Example - Never use slings to pull trucks out of mud on a jobsite. Keep loads balanced to prevent overloading slings. Always lift loads straight up. If an operator does not have the hook and crane squarely above the load, then make sure the operator moves the hook and crane directly above the center of the load.   Never rest a load on a sling, or pinch a sling between the load and the floor. A sling should not be pulled from under a load when the load is resting on the sling. Make sure the hook is always over the center of gravity of the load before lifting it. Do not apply a load to a twisted, knotted or kinked sling. Never lift material when high winds or electrical storms are present. Never use straps that have ice on them.

Safe Practices 1. Avoid all pinch points: - Keep feet from under material being hoisted or set. - Hands should be removed from slings when being hoisted. - Never stand under the load when it is being hoisted. - Never stand under the travel path of the material. Clear all other workers from under the travel path of the crane and material. 2. Only one employee should be communicating with the operator at a time. 3. Stand clear of the load (including swing) when it is lifted at ground level. 4. High visibility gloves are preferred when signaling to an operator.

Safe Practices Hands and fingers shall not be placed between the sling and the load while the sling is being tightened around the load. A sling shall not be pulled from under a load when the load is resting on the sling. Never shorten a sling with knots, bolts or other makeshift devices.  

Standard Universal Hand Signals

Wallet Card – Contains Basic Hand Signals for Quick Reference The operator, signal person, and rigger must be familiar with standard hand signals and must discuss the hand signals for safe communication prior to lifting material.

In Conclusion Select the right sling for the job. Inspect slings prior to use, removing from service any in question. Remember the effect of sling angles on load capacities. Know the crane hand signals and how to safely communicate with the crane operator. Properly store slings when finished to avoid damage.

References 29 CFR 1926.251 ANSI 30.2 ASME B30.9-2006 IPT’s Crane and Rigging Handbook – 2005 Ronald G. Garby NCCO Rigger Reference Booklet