When lifting various objects, to prevent tilting, overturning, deformation, or damage, it is essential to correctly select the tie-off points based on the object's shape characteristics and center of gravity. This ensures sufficient stability during the lifting process to avoid accidents. The tie-off points for heavy objects refer to the points where the lifting rope comes into contact with the heavy object, concentrating the force. When lifting heavy objects with a single rope, the tie-off point should align with the center of gravity on a vertical line; when using two or more ropes, the rope intersection (hook position) should also align with the center of gravity on a vertical line.
1. The trial lift method is used to select the tie-down points. In general lifting operations, there's no need to calculate the exact center of gravity of the object; instead, an estimated position of the center of gravity is used, and the low-point trial lift method is employed to gradually locate the center of gravity and determine the tie-down position for the lifting point.
2. Objects with attachment points (such as lifting ears or rings) should use the original design's lifting points. Packaging equipment typically has clear attachment point markings, and the diagonal angles of the base plate can also be used for lifting and binding. These are all attachment points.
3. For objects without fixed points, the lifting slings can be secured at four points on either side of the center of gravity. The specific binding points should then be determined based on the particularities of the object being lifted, ensuring that the hook is aligned with the object's center of gravity on a single vertical line.
When lifting slender members (such as utility poles) horizontally, the lifting point should be positioned at equal distances from the center of gravity at both ends, with the hook passing through the center of gravity. For two lifting points, the distance from the end is 0.2l (where l is the length of the object). For three lifting points, one is centered, and the other two are 0.13l from the ends. With four lifting points, the two at the ends are 0.095l from the ends, and the middle lifting point is spaced 0.27l apart. This setup minimizes deformation of the heavy object, ensures even distribution of forces on the lifting ropes, and prevents damage to the object and the ropes.
When vertically lifting slender rods, the lifting point should be set at 0.3l from the lifting end. During the lift, the hook should move towards the support point to maintain the rope vertical, avoiding dragging and potential collisions.
When lifting square objects, the four ropes should be positioned symmetrically around the four sides of the center of gravity.
7. When precision in machinery and equipment installation is high, to ensure safe and smooth assembly, the use of auxiliary lifting points with simple lifting equipment to adjust the required position of the components is recommended. Typically, hand winches are commonly used to adjust the position of the body.
