Licensed Professional Engineers
FORENSIC CLUES #2
A newsletter dedicated to keeping attorneys informed of the technical side of product liability cases.
Issue 2: Vol. 1 November 2003
Electrocutions Due to Inadvertent Contact with High Voltage Power LinesBy John L. Ryan
Figure 1: Power lines are responsible for the deaths of over 500 people annually
Every year, approximately 500 people are either killed or permanently maimed when the equipment they are using or touching accidentally comes in contact with high voltage power lines, energizing the entire lift. Accidents occur with cranes, aerial lifts, and television broadcasting trucks.
Accidental contact with high voltage power lines is invariably due to a mistake on the part of a person. Some power lines are never seen, some are forgotten about, and sometimes the distance to the power line is misjudged. The end result is the same – part of a lift comes in contact with an energized power line, creating a giant deadly circuit.
So is that where it ends? Is it simply human error and nothing can be done about it?
According to the Accident Prevention Manual by the National Safety Council the elimination of the hazard is the first priority in the design of a safe product. With some products, the hazard cannot be designed away. High-voltage power lines are an example of this. The second design priority is to neutralize the hazard with fixed guards, automatic-stop devices, or other protective devices. Lift manufacturers have failed to meet this design requirement, and people are dying because of it.
Power Line Detection Devices (Proximity Alarm)
One solution to the problem of high wire electrocution is to equip the lift trucks with a device which detects electromagnetic fields and can warn the operator when the boom of a truck becomes close to a hot wire.
Figure 2: The Sigalarm
The Sigalarm is a safety system used for detecting the electrostatic field of any AC power line. It provides audible and visual warning signals to alert the operator and ground personnel when the boom comes in proximity of an energized high voltage line. This device can prevent accidental collisions with a power line that workers may have not even been aware was a threat. It also protects workers who simply misjudge the distance to a power line, due to bright skies, distractions, or perception errors.
The Sigalarm is in use today all across the country. There has never been an electrocution on a lift equipped with a Sigalarm.This technology is not new or exclusive. The DELSAR AC Hot Stick and the Zircon Multiscanner Pro SL are two other field detector devices.
Insulated safety links are back-up devices that prevent the flow of current down the hoist cable and protect the individual guiding the load if a power line is struck.
Boom Insulating Device
Another type of insulating safety device is a boom-insulating device. This is a cage constructed of nonconductive materials which fits over the end of a boom.
What the Standards Say
OSHA 1926.550(a)15 states “For lines rated 50 kV. or below, minimum clearance between the lines and any part of the crane or load shall be 10 feet.”
Figure 3: Linemen too close to power lines
Department of Energy Technical Reference
“Proximity warning devices should be installed on all aerial devices where possible to warn of potential contact with overhead electrical wires…“
Electrocution due to contact with lift equipment and high-voltage power lines is a serious, preventable problem. Lift manufacturers are aware of the problem and most are not doing anything about it. Lawsuits have successfully been brought against lift manufacturers because this is a problem that can be fixed – there are solutions which are available today that have a 100 percent success rate.