Sling Load Capacity and Sling Angles The load capacity of the sling is determined by its weakest...

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

Transcript of Sling Load Capacity and Sling Angles The load capacity of the sling is determined by its weakest...

Page 1: Sling Load Capacity and Sling Angles The load capacity of the sling is determined by its weakest component. The load capacity of the sling is determined.

Sling Load Capacity and Sling Angles The load capacity of the sling is determined by its The load capacity of the sling is determined by its

weakest component. weakest component.

Never overload a sling. Never overload a sling. 

Remember, as you change the angle of the slings from 90 Remember, as you change the angle of the slings from 90 degrees to 30 degrees the sling capacity decreases. degrees to 30 degrees the sling capacity decreases.

90 degrees

45 degrees

30 degrees

Highest CapacityHighest Capacity

(strongest)(strongest)

Less Capacity Less Capacity

(weaker) (weaker)

Least Capacity Least Capacity

(weakest) (weakest)

Page 2: Sling Load Capacity and Sling Angles The load capacity of the sling is determined by its weakest component. The load capacity of the sling is determined.

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 This is the angle of concern (the sling to the horizontal lift) on both sides.the horizontal lift) on both sides.

Page 3: Sling Load Capacity and Sling Angles The load capacity of the sling is determined by its weakest component. The load capacity of the sling is determined.

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 feetMeasured Height (H): 10 feetLoad Multiplier (LM) =L/H=12/10 = 1.2Load 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).

Page 4: Sling Load Capacity and Sling Angles The load capacity of the sling is determined by its weakest component. The load capacity of the sling is determined.

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 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

Page 5: Sling Load Capacity and Sling Angles The load capacity of the sling is determined by its weakest component. The load capacity of the sling is determined.

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:

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(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.)

ImportantImportant: Remember that the capacity of a sling depends on the type of hitch being : Remember that the capacity of a sling depends on the type of hitch being used: Choker hitch of a typical 20000lbs rated sling is used: Choker hitch of a typical 20000lbs rated sling is 9200 lbs9200 lbs. (trainer – explain . (trainer – explain with the current slings used at your location).with the current slings used at your location).

Page 6: Sling Load Capacity and Sling Angles The load capacity of the sling is determined by its weakest component. The load capacity of the sling is determined.

Safe Practices Never shock load slings. Never shock load slings. Example - Never use slings to pull Example - Never use slings to pull

trucks out of mud on a jobsite. trucks out of mud on a jobsite.

Keep loads balanced to prevent Keep loads balanced to prevent overloading slings.overloading slings.

Always lift loads straight up. If Always lift loads straight up. If an operator does not have the an operator does not have the hook and crane squarely above hook and crane squarely above the load, then make sure the the load, then make sure the operator moves the hook and operator moves the hook and crane directly above the center of crane directly above the center of the load. the load.

   Never rest a load on a sling, or Never rest a load on a sling, or

pinch a sling between the load pinch a sling between the load and the floor.and the floor.

A sling should not be pulled A sling should not be pulled from under a load when the from under a load when the load is resting on the sling.load is resting on the sling.

Make sure the hook is always Make sure the hook is always over the center of gravity of over the center of gravity of the load before lifting it.the load before lifting it.

Do not apply a load to a Do not apply a load to a twisted, knotted or kinked twisted, knotted or kinked sling.sling.

Never lift material when high Never lift material when high winds or electrical storms are winds or electrical storms are present. Never use straps that present. Never use straps that have ice on them. have ice on them.

Page 7: Sling Load Capacity and Sling Angles The load capacity of the sling is determined by its weakest component. The load capacity of the sling is determined.

Safe Practices1. 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 communicatingwith 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.

Page 8: Sling Load Capacity and Sling Angles The load capacity of the sling is determined by its weakest component. The load capacity of the sling is determined.

Safe Practices Hands and fingers Hands and fingers

shall not be placed shall not be placed between the sling and between the sling and the load while the the load while the sling is being sling is being tightened around the tightened around the load.load.

A sling shall not be A sling shall not be pulled from under a pulled from under a load when the load is load when the load is resting on the sling.resting on the sling.

Never shorten a sling Never shorten a sling with knots, bolts or with knots, bolts or other makeshift other makeshift devices. devices.

  

Page 9: Sling Load Capacity and Sling Angles The load capacity of the sling is determined by its weakest component. The load capacity of the sling is determined.

Standard Universal Hand Signals

Page 10: Sling Load Capacity and Sling Angles The load capacity of the sling is determined by its weakest component. The load capacity of the sling is determined.

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.

Page 11: Sling Load Capacity and Sling Angles The load capacity of the sling is determined by its weakest component. The load capacity of the sling is determined.

In Conclusion

Select the right sling for the job.Select the right sling for the job. Inspect slings prior to use, removing from Inspect slings prior to use, removing from

service any in question.service any in question. Remember the effect of sling angles on load Remember the effect of sling angles on load

capacities.capacities. Know the crane hand signals and how to Know the crane hand signals and how to

safely communicate with the crane operator. safely communicate with the crane operator. Properly store slings when finished to avoid Properly store slings when finished to avoid

damage.damage.

Page 12: Sling Load Capacity and Sling Angles The load capacity of the sling is determined by its weakest component. The load capacity of the sling is determined.

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