The invention relates to a hoisting hook assembly comprising a block with a hoisting element which consists of a shaft with attaching parts for the load ropes, which shaft is capable of rotation about a vertical axis and is supported in the block. Such an object is known in several variations and is used for hoisting large and medium large objects.
Very heavy and large-sized loads such as drilling platforms or their parts have as a rule a rectangular form. It is then usual to work with four load ropes, which ropes are fastened near the four angular points. Sometimes eight load ropes with attaching parts are used on the two long sides. Each rope ends in a loop or sling, and in the case of four ropes being used, around each of the four hooks of the hoisting element one of the slings is tied.
It is evident that the distribution of the load over the four load ropes depends entirely on the correct lengths of the four ropes. If the four taut ropes do not meet in one point, the load will, theoretically, be carried by two diagonally opposite load ropes. The elastic elongation of the ropes provides a very limited adaptation, but the latter is unreliable and, moreover, cannot be truly verified. Therefore, it is possible that that two load ropes might substantially carry the whole load. The strength and hence also the thickness of the load ropes should therefore be chosen carefully, which in the case of the very heavy loads referred to above leads to great difficulties.