Lifting heavy objects is a common activity in many industries, from construction to manufacturing. However, it’s important to understand the tensile load that occurs on slings during the lifting process. A sling is a device made of chains, ropes, or webbing that is used to secure and lift objects. The tensile load on the sling refers to the force that is applied to the sling as it lifts the load, and it’s an important consideration in lifting to ensure the safety of the load and everyone involved in the lifting process.
The amount of tensile load that a sling can handle depends on several factors, including the weight of the load, the length of the sling, and the angle of the sling relative to the load. When lifting a load, the tensile load on the sling increases as the load becomes heavier or as the angle of the sling becomes steeper. The length of the sling also affects the tensile load, as longer slings have a greater bending moment, which can increase the tensile load.
To ensure the safety of the lifting process, it’s essential to ensure that the sling is rated for the weight of the load and the angle of the sling. Sling ratings are determined based on the sling material, length, and configuration, and it’s important to use the appropriate sling for the load being lifted. Using a sling that is not rated for the weight of the load or that has been damaged or worn can cause the sling to fail, resulting in serious injury or death.
Proper rigging techniques are also essential for minimizing tensile load on slings during lifting. Rigging includes the use of shackles, hooks, and other devices to secure the load to the sling. Rigging must be done correctly to prevent the load from shifting during lifting, which can increase tensile load and cause the load to fall.
Regular inspections and maintenance of slings are also crucial for safe lifting. Sling inspections should be done before each use and after any incidents that could damage the sling, such as impact, overheating, or chemical exposure. Slings that show signs of wear, such as cuts, abrasions, or broken fibers, should be removed from service and replaced immediately.
The Load Angle Factor (LAF) or Tension Factor (TF) is a term used in lifting operations to calculate the increase in tension on a lifting sling or device caused by the angle between the sling or device and the load being lifted. The LAF/TF is a dimensionless number that is used in combination with the weight of the load and the breaking strength of the lifting device to determine the safe working load (SWL) of the device or sling.
The LAF/TF is determined using trigonometry, specifically the sine function. The formula for calculating the LAF/TF is:
LAF/TF = 1 / sin(θ)
- θ is the included angle between the lifting device or sling and the vertical.
As the angle between the lifting device or sling and the vertical increases, the LAF/TF decreases. This means that the tension on the lifting device or sling increases as the angle between the lifting device or sling and the load being lifted becomes more acute.
For example, if the angle between the lifting sling and the load is 30 degrees, the LAF/TF is calculated as follows:
LAF/TF = 1 / sin(30°) LAF/TF = 2.00
This means that the tension on the lifting sling will be twice the weight of the load being lifted at a 30-degree angle.
Formula for sling tenson load
(Weight ÷ No. of legs) × LAF
Understanding the LAF/TF is essential for safe lifting practices, as it allows the safe working load of the lifting device or sling to be determined based on the angle of the lift. When lifting a load, it’s important to ensure that the lifting device or sling is rated for the weight of the load, as well as the angle of the lift, to prevent overloading and failure of the equipment. Proper rigging and lifting techniques, regular inspections of the lifting equipment, and proper training for workers involved in lifting operations are also essential for safe lifting practices in the workplace.
In conclusion, understanding the tensile load on slings during lifting is essential for ensuring the safety of the lifting process. It’s important to use the appropriate sling for the weight of the load and the angle of the sling, and to use proper rigging techniques to minimize tensile load. Regular inspections and maintenance of slings are also crucial for safe lifting. By following these guidelines, we can ensure safe lifting and prevent accidents and injuries in the workplace.