Slack can develop in a wire rope when the load on it unexpectedly slows or stops.
If a load is reapplied to a slack rope, a shock load will result when the slack runs out. One accident involved slack in a slope hoist rope which allowed a mantrip to run away and break the hoist rope due to shock loading. In a separate incident, a slack rope condition developed in a wire rope attached to the counterweight of a crane boom. The counterweight dropped suddenly breaking the rope due to shock loading. Fatal injuries resulted when the counterweight swung down and pinned a worker against the back end of the crane.