A method for determining the position of the center of gravity of a bulky cargo for safe reloading on a ship

Abstract

Based on the analysis of the equilibrium equations of a two-link suspension system for bulky cargo, two methods for determining the position of the center of gravity of this cargo are proposed. The essence of the methods consists in double suspension of this system and measuring the angles of its deviation in the suspended equilibrium position. In this case, the difference in the angles of deviation of the system between suspensions is provided either by changing the height of the primary suspension (the length of the primary slings), or by changing the ratio of the masses of the traverse and the load.  A comparative analysis of the accuracy and practical feasibility of both methods is carried out. It is shown that when carrying out cargo operations in a port or on a ship, a method in which the difference in the angles of deviation of the system between suspensions is carried out by changing the length of the primary slings (the height of the primary suspension) is practically feasible and more accurate.

The work emphasizes that an important condition for ensuring the stability of the system when hanging and preventing overturning of the load is that the primary slings (connecting the hook and the traverse) must be of such length that the suspended load can virtually be inscribed inside the pyramid (safety pyramid) formed by the traverse and these slings. It is also shown that the length of the secondary slings (connecting the traverse and the load) does not matter, but they must be of equal length and parallel to each other, which will ensure their vertical position after hanging the system. The heavier the traverse (in comparison with the weight of the suspended cargo), the higher the safety pyramid, and therefore the more stable the cargo suspension system as a whole becomes. On the other hand, the longer the primary slings (the higher the safety pyramid), the smaller the angles of deviation of the traverse (and the system as a whole) from the initial position when suspended.  To demonstrate the possibilities of the proposed new method for determining the position of the cargo center, a numerical example of its implementation is given.