Do you have enough?
The term ‘hook height’ is used to describe the vertical distance from the ground to the highest point that the crane hook can go. While most people involved in heavy lift and cargo loading operations will be familiar with the phrase, it is also important to know what factors affect the required hook height of the lift.
When it comes to loading project cargo with a crane, getting this distance wrong could be the difference between being able to successfully complete the lift or not.
The required hook height for a lift will change when the below circumstances are considered:
1) Position of the lift points: this can impact the available hook height in conjunction with the rigging height. Knowing where the lift points are on the cargo is essential in determining the required hook height.
2) Lift Rigging: the height of the rigging between the hook and cargo lifting points is added to the height of the lift points, with the total then subtracted from the hook height. Therefore, the rigging arrangement will influence the required hook height.
3) Lift Height: During the lift, we must recognise the height to which the cargo needs to be lifted to. For example, to clear a hatch coaming or similar obstacle. This will also influence the required hook height.
4) Lift Radius: When using mobile cranes for lifting cargo, we need to carefully consider the available hook height for the total lift weight at the various radii of the lift. As the mobile crane lowers its jib (increasing radius) the available hook height decreases as a function of the boom length and radius of interest. Thus, we need to check the hook height at the following radii: initial lift, over an obstacle, and set down.
It should be noted that although you can get a crane capable of lifting a particular weight at the required radius, it may not have the available hook height when these four points are considered. In this case, a larger crane may be necessary.
When discussing your lifting requirements with your designated ‘Appointed Person’, make sure they are given all the relevant information with respect to lifting radii, obstructions, height of lift points and lift rigging requirements. Early engagement with a suitable lifting specialist will help to ensure you have the right crane with the available hook height to perform the lift.
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