Web slings are highly useful for lifting loads within a shop setting, as they provide balance and control for loads that cannot be lifted from a single point. However, improper use of web slings can cause the destruction of equipment or lifted objects, or worse, result in the injury or death of workers. If you utilize web slings in your work, even occasionally, you need to understand how to properly evaluate and inspect them as well as how to rig them safely to prevent accidents:
How to conduct an inspection of web slings
Web slings are made of a variety of materials, but the most common choices are nylon and polyester. Both of these are strong fibers and resist breakage. However, web slings can be damaged or wear over time. That is why it is important to inspect all slings you intend to use on the job daily. Below are several key inspection points that should be observed:
Check for a manufacturer's label - Any web sling you wish to use must contain a clear, legible label attached to the sling by the factory. The label should contain information about the manufacturer of the sling, its length, material, and vertical load rating. The label may also contain other information, including load ratings under various configurations. If the label is missing from the sling or is impossible to read, then the sling must be removed from service.
Remove knots from the slings - Slings are occasionally found tied together, or an overhand knot is often tied in the middle of the sling. Always remove knots of any size or shape from the sling before using.
Look for disfigurement - Another problem faced by some is damage done to the fibers in the sling. These fibers are resistant to many dangers, but even the strongest web sling can be damaged by acids, bases, and flammable substances. Other hazards to web slings include cuts and abrasions. Always discard any web slings that are damaged that exceeds light, superficial staining.
Be alert for signs of aging and deterioration - Whenever looking over web slings, be sure to observe any signs of fraying, tattering, crushing or loosening of fiber strands. Keep in mind that such problems indicate the web sling is probably nearing the end of its useful lifespan and should be discarded.
How to make sure the safe working limit of a web sling is not exceeded
After you have inspected the web slings you wish to use, the next step is to ensure they are capable of safely handling the forces exerted on them during lifting. Fortunately, making this determination involves a few simple calculations; below is how to make them:
1. Gather basic information about the slings and load size - You will need to know the following parameters to use in your calculations:
Vertical load rating - This is found on the tags of web slings, sometimes designated as the 90-degree load rating.
Weight of the object to be lifted - Be sure to match units of measurement with the load rating (for example, pounds to pounds or kilograms to kilograms).
Length of the web slings - Measure the length of the slings to be used, from the hoist hook to the attachment points on the object to be lifted.
Height of the hook - The last measurement is the distance between the hoist hook and the top of the object to be lifted.
2. Perform the first step in the calculation - After you have gathered all the relevant variables, you can start putting it all together. To start, simply divide the length of each web sling by the height of the hook. For example, for a sling that is 10 feet in length, and a height hook of 8 feet, this calculation will yield 1.25. Write this result down, as you will need it in the next calculation.
3. Perform the final step in the calculation - Once you have finished the first calculation, you are ready to complete the last calculation. To do this, multiply the result from the first step by ½ of the object's weight. Continuing the example above for a 5,000 pound object, this would mean you would need to multiply 1.25 times 5,000 divided by 2, which equals 3,125 pounds. This last number is the amount of force placed upon each web sling.
4. Compare the vertical load rating with the amount of force placed upon the web sling - After you have arrived at the amount of force that your slings will endure, simply compare the vertical load rating to determine if the arrangement is safe. For example, if the force placed upon each sling is 3,125 pounds, and the web slings you wish to use are rated for 2,000 pounds apiece, then you clearly need to use stronger slings.
For more tips and information, contact a company that rents out web slings and overhead cranes, like American Equipment Inc.
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