Bucket Trucks and Insulated Aerial Devices
We are investigating electrical injuries and deaths of linemen resulting from their use of the upper control handles of aerial work platforms of insulated aerial devices (or bucket trucks). These injuries and deaths are occurring because the upper controls for these aerial work platforms are not electrically insulated or isolated and the metal components in the upper boom area (including the jib bracket) are not covered or otherwise protected from electrical contact with a power line.
Linemen cannot wear their rubber gloves 100% of the time and they often assume that they are safe so long as they remain within the insulated aerial work platform (or bucket) of their bucket truck. Moreover, many linemen are unaware that the metal components in the upper boom area (including the material handling components) may be inadvertently connected to the metal controls for their insulated aerial work platform.
TYPICAL ACCIDENT SCENARIO
The linemen we represent are from all across the United States. Their injuries (or deaths) typically occur when exposed metal in the upper boom area, such as the jib bracket, contacts an energized power line. Because electrical continuity can exist between a metal component in the upper boom area and the upper controls for the bucket, electrical current can pass from the energized power line through the boom and into the upper controls for the bucket. If the lineman has one hand on the controls of his bucket and his other hand is holding a grounded object, such as a guy wire or new conductor which is being installed on a power line pole, the resulting circuit can be devastating to the lineman.
One of our clients was a lineman in the process of adding a third phase (or conductor) to a power line pole. He was standing within the bucket of a bucket truck. He had one hand on the metal control handle for the bucket, and in his other hand he was holding a metal wire which was being fed to him from a spool on the ground. He was wearing leather work gloves, but not rubber insulated gloves. The bucket was elevated and his boom was near the power lines.
As this lineman used his control handle to guide his bucket closer to the power line pole, he sustained a severe electrical shock. He eventually required amputation of both of his arms. It appears that an electrical current from the power line traveled through the truck’s boom, into the metal control handle that this lineman was operating, out his other hand, and down the metal wire to the spool on the ground.
Another lineman (whose family we now represent) was electrocuted in a similar manner when he was merely installing a guy wire on a new power line pole. In both of these instances, as well as the others we are investigating, the linemen and linewomen were unaware that their control handles were not electrically isolated or electrically insulated.
BUCKET TRUCK ACCIDENT STUDIES BY INDEPENDENT ORGANIZATIONS
In 1969, the Public Utilities Section of the National Safety Congress warned the public utilities industry of the hazard represented by upper boom continuity (the ability for current to travel from metal at the upper boom to the upper controls of the bucket). They pointed out that there were already (in 1969) bucket trucks on the market with “much less exposure of metal and less metal inside the boom.” They indicated that exposed metal at the upper boom should be covered to prevent accidents.
In 1990, the National Safety Council published the results of a survey they conducted of aerial device accidents. They concluded that 12% of electrical contact accidents are “boom contact” accidents. The National Safety Council had already published the results of a study in 1984 where they pointed out that serious electrical contact accidents had occurred when conductive hoses were used in place of non-conductive hoses.
BUCKET TRUCK ACCIDENT STUDIES BY INDUSTRY
In the mid-1970’s, Pitman Manufacturing Company, the makers of the Pitman Hotstik insulated aerial device, conducted a study which revealed a number of incidents where an individual was injured in a Pitman Hotstik when they touched an energized control handle. As a result of these incidents, Pitman embarked on a comprehensive nationwide program to retrofit their trucks. As a result of their retrofit, the incidents stopped occurring. It appears that Pitman’s retrofit fixed the problem.
In response to a series of reports of similar occurrences involving Altec bucket trucks, Altec Industries, Inc. issued the following Safety Bulletin on August 21, 2000:
ELECTRICAL CONTINUITY HAZARD
Always wear insulated protective equipment, use conductor cover-ups, and maintain required clearances when in the vicinity of energized conductors.
Aerial devices and digger derricks with insulated booms can only isolate the operator from grounding through the boom and vehicle. They cannot provide protection against phase-to-phase or phase-to-ground contacts occurring at the boom-tip, above the insulated boom sections.
Boom-tips of aerial devices and digger derricks, of necessity, must contain metal components. Metal conducts electricity. Moreover, under certain circumstances, and to varying degrees, electricity will track across or through non-metallic components (fiberglass covers and structures, hoses, etc.). Electricity can even arc through air. Thus, the boom-tip of an aerial device or a digger derrick must be considered conductive!
If any part of the boom-tip contacts an energized conductor, the entire boom-tip, including the control handle, must be considered energized.
If any part of the boom-tip contacts a grounded object, the entire boom-tip, including the control handle, must be considered grounded.
Hydraulic fluid is flammable. If electricity flows through the boom-tip, it can cause the hydraulic fluid to burn or to explode. Contact by any part of the boom-tip with an energized conductor while the boom-tip also is in contact with another energized source or a grounded object can cause the hydraulic fluid at the boom-tip to burn or explode.
These are among the reasons aerial devices and digger derricks are never considered primary protection for the operator from electrical contact. An operator’s primary protection comes through use of protective equipment (insulated gloves, insulated sleeves, conductor cover-ups) and maintenance of appropriate clearances.
Do not rely on the boom-tip of an aerial device or digger derrick to protect you from an energized conductor or a ground. It cannot do so. Rely, instead, on the only things that can protect you, use of appropriate protective equipment and maintenance of appropriate clearances.
The incidents which we are primarily investigating involve Altec bucket trucks manufactured by Altec Industries, Inc. headquartered in Birmingham, Alabama. Although this hazard was identified in the 1960s and 1970s, Altec, until recently, still produced bucket trucks with uninsulated upper controls which allowed for electrical continuity from parts of the upper boom to the upper controls. Altec Industries, Inc. has recently developed a boom-tip cover kit to retrofit its insulated aerial devices in the field. These new boom-tip covers provide expanded protection against electrical hazards in the event that contact is made between an uncovered energized power line and the metal components in the upper boom area. Altec Industries, Inc. is including in some of its boom-tip cover kits non-conductive metal components to replace some of the electrically connected metal components in the upper boom area. In addition, Altec is manufacturing some of its new aerial devices with an insulated handle control. Unfortunately, too many insulated aerial devices remain in the field that have not been retrofitted. They are being operated by linemen who are unaware that their platform controls are neither isolated nor insulated.