Boom Contact With an Overhead Distribution Line
A 50-ton telescopic-boom crane is setting a 3,000 lb steel beam at a substation when the boom tip contacts a 12.5 kV overhead distribution line. The operator is in the cab, the outriggers are fully extended, and no fire is visible. The crane’s tires are on dry gravel. A ground worker shouts and starts running toward the crane to help. The operator feels a slight tingling in the controls and sees arcing at the boom tip. The load is suspended about 10 ft above the ground. The utility has not been called. The site’s emergency plan says to call 911 and the utility, but the operator’s cell phone is in the cab. The operator’s hand is on the swing joystick. The operator must decide whether to stay in the cab, exit, or move the crane.
1. What are the operator’s immediate actions while the boom remains in contact with the line?
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The operator should stay in the cab, keep hands off metal parts, and avoid completing a path to ground. The cab is the safest place while the crane is energized and there is no fire. The operator should warn the ground worker away with the horn and voice, and signal others to stay clear. No one should touch the crane, the load, or the rigging. The operator should not move the crane unless directed by the utility or unless there is an immediate fire or other life-threatening condition; moving the boom can change the contact and cause a surge or recontact. The operator should call 911 and the utility as soon as it is safe to do so, and keep the area clear until the line is de-energized.
2. Under what conditions should the operator leave the cab, and how should the operator exit?
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The operator should leave the cab only if there is fire, the cab is becoming unsafe, or the utility directs an evacuation. If leaving, the operator should not step down normally, because that can create a path from the crane to ground. The correct method is to jump clear with feet together, land without touching the crane and ground at the same time, and then shuffle or hop away with feet close together until well clear of the crane. The operator should not return to the crane and should keep others away. If there is no fire and the line remains energized, staying in the cab and waiting for the utility is generally safer.
3. What post-incident actions and notifications are required?
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After the utility de-energizes the line and the area is made safe, the operator and site personnel should barricade the area, account for personnel, and report the incident to the employer, the utility, and emergency services as required. The crane should be removed from service and inspected by a qualified person for electrical damage, structural damage, and function of controls and safety devices before any return to work. The incident should be documented, including the boom position, line voltage, duration of contact, and any injuries. The crane should not be restarted or moved until the utility confirms de-energization and a qualified inspection is completed.