Free fall is prohibited. The use of machines having live booms is prohibited. A jib, boom extension, or similar attachment may not be used to hoist a personnel platform. Except where the electrical distribution, transmission, and service lines have been deenergized and visibly grounded at the point of work or where insulating barriers not a part of or an attachment to the cranes and hoists have been erected to prevent physical contact with the lines, cranes and hoists shall be operated proximate to, under, over, by, or near powerlines only in accordance with the following: For a line rated 50 kilovolts or below, the minimum clearance between the line and any part of the crane, hoist, or load shall be 10 feet; For a line rated over 50 kilovolts, the minimum clearance between the line and any part of the crane, hoist, or load shall be either 10 feet plus 0.4 inch for each 1.0 kilovolt over 50 kilovolts or twice the length of the line insulator, but never less than 10 feet. Hoisting of the personnel platform shall be performed in a slow, controlled, cautious manner with no sudden movements of the crane, hoist, or the platform. Load lines shall be capable of supporting, without failure, at least double the current safety factor for the specific type of crane being used by applying the 50 percent derating of the crane and hoist capacity. Load and boom hoist drum brakes, swing brakes, and locking devices, such as pawls or dogs, shall be engaged when the occupied personnel platform is in a stationary working position. Mobile cranes shall comply with the following: Only the main boom shall be used to hoist a personnel platform; The crane shall be uniformly level within 1 percent of level grade and located on firm footing; All pneumatic tired cranes used to lift or lower personnel platforms shall be equipped with outriggers or stabilizers; All outriggers or stabilizers, or both, shall be fully extended and set; Carrier wheels within the boundary of the outriggers shall be relieved of their weight; On a crawler crane, the track shall be fully extended. The total weight of the loaded personnel platform and related rigging may not exceed 50 percent of the rated capacity for the radius and configuration of the crane.