A portable crane falls, injuring an electrician. This case demonstrates how important it is to understand correct operation of equipment before using it.

When a young electrical contractor decided to pursue group relamping as a niche business, he had high hopes for success. On this typical job, a local automotive dealership hired him to replace both incandescent and high-intensity lamps. But to complete this job effectively, he needed the right equipment.

The contractor, who held a master electrician's license, initially purchased a section of rolling staging to replace the lamps in the festoon-type fixtures. By using portable staging, he found a safe, cost-efficient method of group relamping an extensive array of incandescent lamps mounted on a steel cable 10 ft above the cars. This procedure went smoothly.

His next task proved to be much more challenging. The job required him to replace the high-intensity lamps located on tall poles. First, the contractor had to find a means to reach the lamps. A local tool rental company advertised a portable boom crane that appeared to meet his requirements. He viewed the lift at the rental company storage yard, and rented the unit. To reach the lamps, he stepped into the crane's bucket and elevated himself 40 ft in the air. Then suddenly, he felt himself plummeting to the ground in a free fall. As a result of the crane's collapse, he suffered severe injuries.

After the electrician's fall, his attorney retained my forensic team to conduct a safety analysis. An inspection of the machinery revealed two sections that elevate the bucket to a height of 44 ft. At the time of this incident, the lift remained elevated at approximately 40 ft. The two sections connect by a so-called "knuckle joint." Four metal support legs extending from the corners of the crane's base stabilized the elevated lift. We found one of these support legs separated from the base. Inside the bucket, there are operating controls: one switch controls the elevation of the upper extended arm that contains the bucket and operator; another controls the operation of the lower arm that extends the height of the lift. Another switch controlled the left and right horizontal movement of the bucket. After reviewing the manufacturer's literature, we noted the equipment had a built-in bubble level system. We discovered this was not functional when the electrician rented the lift.

We inspected one of the support legs that separated from the crane's base with the help of an expert in metallurgy. It lay on the ground several feet from its original position on the base. We concluded the crane had tipped over to one side toward the bucket, allowing the bucket to fall until it contacted the ground. We found a large structural member of another supporting leg badly bent and the rectangular footplate on the separated support leg dented.

We observed cracks in the welds used to fabricate the support legs. The metallurgist concluded "the cracks appeared to be old and not caused by the subject accident." Based on our discoveries, we concluded the crane became unbalanced -- thus tipping over to one side toward the bucket causing the bucket and occupant to drop to the ground. Obviously, an operational balance warning system on the crane could have prevented this accident.

Next, we evaluated the probability of harm and documented the gravity of risk. We quantified what precautions the electrician, manufacturer, and tool rental company took to determine responsibility for the accident.

In every sense, the electrician was the injured party. When he rented the tool, he assumed it was safe and adequate for its intended purpose. He had no reason to believe using this crane would put him in danger.

The manufacturer provided a balance warning system and had a definitive operator's manual. We concluded the manufacturer was also not responsible for the accident. The tool rental company, however, did not offer the renter any such manual. It also did not provide the electrician with any type of training. What's worse, it painted over all of the safety warnings the manufacturer originally placed on the unit.

Since weight and balance are critical in this type of work, we took a look at the equipment's limitations. We determined the electrician's weight with tools and lamps weighed 20% less than the 200-lb rating of the crane. Therefore, he operated the crane consistent with its intended purpose.

Our report documented that the tool rental company was negligent when it rented the crane. Why? It failed to: provide a balance alarm system; properly instruct/train the renter; warn of potential hazards including weight/balance and wind; provide a user's manual; and offer the user with "setup" instructions.

What's the lesson here? Anyone whose job requires him or her to work at elevated surfaces must use caution as well as common sense. No height is always safe. Manufacturers even cover the stepladder, which elevates a person only 8 ft, with danger warnings. Ironically, this crane, which could lift a person five times that distance, had an obscure warning sign covered with paint along with other defects.

Had the rental agency reviewed OSHA 20 Part 1926.550 (a) (5), it would have known the minimum standard of care applicable to those who provide cranes: "...a competent person shall inspect all machinery and equipment prior to each use, and during use, to make sure it is in safe operating condition. Any deficiencies shall be repaired, or defective parts replaced, before continued use."

Because tool rental companies fill a necessary service, they must perform adequate preventive maintenance each time someone returns a tool. They should also provide proper instruction on the correct use of the tool. If they don't offer such literature, ask for it. And if you're considering renting a special piece of equipment, use the "buyer beware" attitude; just to be safe.

Pritzker is Chairman Emeritus of George Slack & Pritzker, Plainville, Mass./Punta Gurda, Fla. Pritzker, a past president of the National Society of Professional Engineers, is a joint founder and the second president of the National Academy of Forensic Engineers.