7.5.2 Capacity

The capacity of the winch to be selected will depend on the maximum load to be lifted and the rigging method to be employed. If the rigging arrangement calls for a single fall of rope, then the SWL of the winch must be at least equal to the maximum load to be lifted. However, if the rigging arrangement utilizes multiple sheaves or blocks, the load will be proportionally shared between the falls of rope. For example, if there are two falls of rope, the load in the rope will be half the total load to be lifted; if there are three falls of rope the load in the rope will be one third the total load to be lifted and so on. (See Figure 7.5.2-1 ) In such cases, the SWL of the winch should be at least equal to the load in the rope plus an allowance for the effects of friction. Although the effects of friction will vary, dependent on the type of sheave and bearings, it is normal to assume that this will be 8% per sheave.