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Grabbing and magnet duty should only be allowed if permitted and recommended by the cranes Columbus manufacturer. The weight of the grab and contents, or the weight of the magnet and load, should be less than the corresponding safe working load in normal service by an amount specified by the manufacturer. Where two or more cranes are required to raise a single load, one appointed competent person must supervise the whole operation. It is recommended that the SWL of each crone for the required jib length and operating radius should be at least 25% in excess of the calculated share of the load to be handled by each crane during the tandem lift. The complexities of this type of operation should be clearly appreciated and all necessary steps should be taken to ensure that neither machine takes more than its calculated share of the load, that neither machine becomes out of level and that the hoist ropes remain vertical throughout the lift. Tower cranes must not be used for multiple lifting. Cranes mounted on barges and pontoons. Where lifting operations need to be carried out over water, land based cranes may sometimes be mounted on floating vessels such as barges or pontoons. Cranes operating in such circumstances will be subject to significantly different loading conditions than in the case of land based lifting activities. It is important that, before cranes columbus are put to work on a barge or pontoon, the following are strictly complied with: After determining the length of the jib, maximum working radius and maximum load, the manufacturer should provide the maximum heel at which it is safe for the lifting appliance to operate. A competent person must make stability calculations to state the position and weight of ballast and to determine that the craft will not heel more than that specified by the manufacturer. Calculations should also be made for the load over the sides, forward and stern. Where proprietary pontoons, e.g. Uniflote, are used, tables for calculating the heel under different systems of loading are available from the manufacturers. The mounting of a lifting appliance on a barge is a major modification affecting the stability of the machine and the assembly. This necessitates a thorough examination to be carried out, including testing where identified by the competent person as being appropriate. After the appliance has been positioned on the craft, the load/radius information must be adjusted to the calculated heel. A load/radius curve must be plotted to determine the loads which can be safely applied at specific radii, so that the safe load indicator can be adjusted lo be true at the maximum heel, (i.e. jib over the side). In order to maintain stability, it is important that no unauthorized loads are placed on the vessel and that free surface liquid, e.g. water; does not accumulate. Different types of cranes are sued for different purposes and should be given particular attention to each crane. Reading the reviews provided by the author is one of the best ways to gain necessary information on columbus crane renting.
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