Rigging Safe Operating Procedures

Equipment Operator Basic - Beginning construction equipment operators manual
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Figure 13-48.—Fleet angle of winch. in figure 13-48. The distance from the drum to the sheave is the controlling factor in the fleet angle. When you are using vehicle-mounted winches, the vehicle should be placed in a position which permits the operator to watch the load being hoisted. A winch is most effective when the pull is exerted on the bare drum of the winch. When a winch is rated at capacity, the rating applies only as the first layer of cable is wound onto the drum. The winch capacity is reduced as each layer of cable is wound onto the drum because of the change in leverage, resulting from the increased diameter of the drum. The capacity of the winch maybe reduced by as much as 50 percent when the last layer is being wound onto the drum. Ground Angle If the hoisting line leaves the drum at an angle upward from the ground, the resulting pull on the winch will tend to lift it off the ground. In this case, a leading block must be placed in the system at some distance from the drum to change the direction of the hoisting line to a horizontal or downward pull. The hoisting line should be overwound or underwound on the drum as may be necessary to avoid a reverse bend. Fleet Angle The drum of the winch is placed so that a line from the last block passing through the center of the drum is at right angles to the axis of the drum. The angle between this line and the hoisting line as it winds on the drum is call the fleet angle. As the hoisting line is wound in on the drum, it moves from one flange to the other, so the fleet angle changes during the hoisting process. The fleet angle should not be permitted to exceed 2 degrees and should be kept below this if possible. A 1 1/2-degree maximum angle is satisfactory and will be obtained if the distance from the drum to the first sheave is 40 inches for each inch from the center of the drum flange. The wider the drum of the hoist, the greater the lead distance must be in placing the winch. RIGGING SAFE OPERATING PROCEDURES All personnel involved with the use of rigging gear should be thoroughly instructed and trained to comply with the following practices: 1. Wire rope slings must not be used with loads that exceed the rated capacities outlined in enclosure (2) of the COMSECOND/COMTHIRDNCBINST 11200.11. Slings not included in the enclosure must be used only according to the manufacturer’s recommendation. 2. Determine the weight of a load before attempting any lift. 3. Select a sling with sufficient capacity rating. 4. Examine all hardware, equipment, tackle, and slings before using them and destroy all defective components. 5. Use the proper hitch. 6. Guide loads with a tag line when practical. 7. When using multiple-leg slings, select the longest sling practical to reduce the stress on the individual sling legs. 8. Attach the sling securely to the load. 9. Pad or protect any sharp corners or edges the sling may come in contact with to prevent chaffing. 10. Keep the slings free of kinks, loops, or twists. 11. Keep hands and fingers from between the sling and the load. 12. To avoid placing shock on the loading slings, you should start the lift slowly. 13. Keep the slings well lubricated to prevent corrosion. 14. Do not pull the slings from under a load when the load is resting on the slings; block the load up to remove the slings. 13-27

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